MEDICAL    SCHOOL 


The  Lucy  M.  wanzer  Library 


With  the  Respects  of 

A.   L.  BANCROFT  &  COMPANY, 

San  Francisco,  Cal. 


A  TEEATISE- 


6- 


HUMAN  PHYSIOLOGY; 


DESIGNED  FOR  THE  USE  OF 


STUDENTS  AND  PRACTITIONERS  OF  MEDICINE. 


BY 

JOHN  C.  DALTON,  M.D., 

PROFESSOR  OP  PHYSIOLOGY  AND  HYGIENE  IN  THE  COLLEGE  OP  PHYSICIANS  AND  SURGEONS, 

NEW  YORK;  MEMBER  OF  THE  NEW  YORK  ACADEMY  OF  MEDICINE ;  OF  THE  NEW  YORK 

PATHOLOGICAL  SOCIETY  ;  OF  THE  AMERICAN  ACADEMY  OF  ARTS  AND  SCIENCES. 

BOSTON;  OF  THE  BIOLOGICAL  DEPARTMENT  OF  THE  ACADEMY  OF 

NATURAL  SCIENCES,  PHILADELPHIA;  AND  OF  THE  NATIONAL 

ACADEMY  OF  SCIENCES  OF  THE  UNITED  STATES  OF  AMERICA. 


SIXTH  EDITION, 

REVISED    AND    ENLARGED. 
WITH 

THREE  HUNDRED  AND  SIXTEEN   ILLUSTRATIONS. 


PHILADELPHIA: 
HE^EY     0.     LEA 
1875. 


Entered,  according  to  Act  of  Congress,  in  the  year  1875,  by 

HENRY    C.    LEA, 
in  the  Office  of  the  Librarian  of  Congress  at  Washington.     All  rights  reserved. 


PHILADELPHIA: 

COLLINS,   PRINTER, 

70f>  Jayne  Street. 


TO   MY    FATHER, 

JOHN  C.  DALTON,  M.D., 

IN 

HOMAGE  OF  HIS  LONG  AND  SUCCESSFUL  DEVOTION 

TO  THE 

SCIENCE  AND  AET  OF  MEDICINE, 

AND  IN 
GRATEFDL  RECOLLECTION  OP  HIS  PROFESSIONAL  PRECEPTS  AND  EXAMPLE, 

n  9  aim* 


IS  RESPECTFULLY  AND  AFFECTIONATELY 


INSCRIBED. 


271". 


PREFACE. 


IN  the  present  edition  of  this  book,  while  every  part  has  received 
a  careful  revision,  the  original  plan  of  arrangement  has  been  changed 
only  so  far  as  was  necessary  for  the  introduction  of  new  material.  Al- 
though the  whole  field  of  physiology  has  been  cultivated,  of  late  years, 
with  unusual  industry  and  success,  perhaps  the  most  important  advances 
have  been  made  in  the  two  departments  of  Physiological  Chemistry  and 
the  Nervous  System.  The  number  and  classification  of  the  proximate 
principles,  more  especially,  and  their  relation  to  each  other  in  the  pro- 
cess of  nutrition,  have  become,  in  many  respects,  better  understood 
than  formerly ;  though  it  is  evident  that  this  fundamental  part  of 
physiology  is  to  receive,  in  the  future,  modifications  and  additions  of 
the  most  valuable  kind. 

In  nearly  every  division  of  physiological  study,  a  prominent  feature 
of  recent  progress  has  been  the  increased  attention  paid  to  quantitative 
investigation.  The  conviction  has  apparently  become  general  that, 
in  physiology  as  well  as  in  other  natural  sciences,  the  knowledge 
gained  by  any  method  of  study  is  essentially  imperfect  until  its  re- 
sults can  be  stated  in  figures.  The  chemical  characters  of  an  ingre- 
dient or  product  of  the  animal  system  are  hardly  more  important  than 
its  quantity;  and  for  determining  its  physiological  relation  to  other 
substances,  of  similar  or  different  kinds,  the  knowledge  of  its  quantity 
is  absolutely  indispensable.  Investigations  of  this  sort,  in  respect  to 
the  living  body,  are  surrounded  with  difficulties  ;  but  the  results  ob- 
tained are  steadily  increasing  in  precision  and  extent,  and  already  foiun 
a  most  important  element  in  the  study  of  physiology. 

In  a  text-book  like  the  present,  it  is  desirable  that  the  reader  should 
not  be  misled  by  having  all  the  frequent  changes  of  opinion,  or  sub- 
stitutions of  theory,  presented  as  discoveries  in  physiological  science. 
Any  faithfully  observed  facts,  however  unexpected  or  peculiar,  are  of 
course  at  once  invested  with  a  permanent  value.  But  the  theoretical 
explanations,  by  which  they  are  sometimes  accompanied,  are  not  of  the 
same  importance.  They  often  represent  only  a  scheme  of  probabilities 

(v) 


VI         ,  PKEFACE. 

existing  in  the  mind  of  the  author,  and  may  be  altered  at  any  time  to 
suit  the  requirements  of  more  extended  observation.  In  rendering  an 
account,  therefore,  of  the  state  of  knowledge  upon  any  physiological 
subject,  the  student  should  be  informed,  not  only  of  the  results  now  in 
our  possession,  but  also  of  the  means  of  investigation  by  which  they 
have  been  attained.  He  is  thus  enabled  to  distinguish  between  what 
is  positive  in  physiological  doctrines,  and  what  is  hypothetical ;  and 
when  further  discoveries  are  made,  which  lead  to  changes  of  opinion, 
he  is  not  confused  or  disappointed  at  apparent  contradictions  between 
the  new  views  and  the  old.  This  method  requires  a  certain  amount  of 
detail  in  the  statement  of  facts;  but  its  advantages  are  ample  compen- 
sation for  the  necessary  expenditure  of  time  and  space. 

The  additions  and  alterations  in  the  text,  requisite  to  present  con- 
cisely the  growth  of  positive  physiological  knowledge,  have  resulted, 
in  spite  of  the  author's  earnest  efforts  at  condensation,  in  an  increase 
of  fully  fifty  per  cent,  in  the  matter  of  the  work.  A  change,  however, 
in  the  typographical  arrangement  has  accommodated  these  additions 
without  undue  enlargement  in  the  bulk  of  the  volume. 

The  new  chemical  notation  and  nomenclature  are  introduced  into  the 
present  edition,  as  having  now  so  generally  taken  the  place  of  the  old, 
that  no  confusion  need  result  from  the  change.  The  centigrade  system 
of  measurements  for  length,  volume,  and  weight,  is  also  adopted,  these 
measurements  being  at  present  almost  universally  employed  in  original 
physiological  investigations  and  their  published  accounts.  Tempera- 
tures are  given  in  degrees  of  the  centigrade  scale,  usually  accompanied 
by  the  corresponding  degrees  of  Fahrenheit's  scale,  inclosed  in  brackets. 

NEW  YOKK,  September,  1875. 


CONTENTS. 


INTRODUCTION. 

PAGE 

Definition  of  Physiology — Organization  of  living  bodies — Functions — Mode 
of  study  in  physiology — Experiments — Their  results,  direct  and  indirect — 
Vital  phenomena — Their  various  kinds — Division  of  the  subject  .  25-32 


SECTION   I. 
NUTEITION. 

CHAPTER    I. 

PROXIMATE   PRINCIPLES   IN   GENERAL. 

Definition  of  proximate  principles — Their  mode  of  extraction — Their  propor- 
tions in  the  animal  tissues  and  fluids — Their  classification  .  .  33-39 

CHAPTER    II. 

INORGANIC   PROXIMATE    PRINCIPLES. 

Nature  and  source  of  the  inorganic  proximate  principles — Water — Lime 
phosphate — Lime  carbonate — Magnesium  phosphate — Sodium  chloride — 
Potassium  chloride — Sodium  and  potassium  phosphates — Sodium  and  po- 
tassium carbonates — Sodium  and  potassium  sulphates — Use  and  final  dis- 
charge of  the  inorganic  proximate  principles 40-54 

CHAPTER    III. 

HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 

Source  and  general  character  of  the  hydrocarbonaceous  proximate  principles — 
Starch — Its  reactions — Its  production  in  vegetables — Its  transformation 
in  the  digestive  process — Glycogen — Sugar — Glucose — Its  reactions — Fer- 
mentation— Lactose — Saccharose — The  Fats — Their  reactions — Stearine — 
Palmitine — Oleine — Condition  of  the  fats  in  organized  tissues  and  fluids — 
Their  production  in  vegetables — Their  decomposition  in  the  body — Choles- 
terine — Origin  and  destination  of  the  hydrocarbonaceous  proximate  princi- 
ples    55-78 

(  vii  } 


Vlll  CONTENTS. 

CHAPTER    IV. 

ALBUMINOUS    MATTERS. 

PAOK 

Composition  and  general  characters  of  the  albuminous  matters — Hygrosco- 
picity — Coagulation — Catalysis — Putrefaction — Production  of  albuminous 
matters — Fibrine — Albumen — Albuminose — Gascine  —  Ptyaline — Pepsine 
— Pancreatine — Mucosine — Myosine — Collagen — Chondrine — Elasticine — 
Keratine — Alteration  and  discharge  of  the  albuminous  matters  .  79-93 

CHAPTER    V. 

COLORING    MATTERS. 

General  characters  of  the  coloring  matters — Hemoglobine — Melanine — Bili- 
rubine — Biliverdine — Urochrome — Luteine — Chlorophylle  .  .  94-101 

CHAPTER    VI. 

CRYSTALLIZABLE    NITROGENOUS    MATTERS. 

General  characters  of  the  crystallizable  nitrogenous  matters — Lecithine — 
Cerebrinc — Leucine — Sodium  glycocholate — Sodium  taurocholate — Crca- 
tine — Creatinine — Urea — Sodium  urate — Sodium  hippurate  .  .  102-112 

CHAPTER    VII. 

FOOD. 

Inorganic  ingredients  of  the  food — Non-nitrogenous  organic  ingredients  of 
the  food — Nitrogenous  ingredients  of  the  food — Composition  of  different 
articles  of  food — Milk — Bread  —  Meat  —  Eggs — Vegetables  —  Eequisite 
quantity  of  food  and  of  its  different  ingredients — Results  of  the  assimilation 
and  metamorphosis  of  the  food 113-130 

CHAPTER    VIII. 

DIGESTION. 

Nature  of  the  digestive  process — Digestive  apparatus — Mastication — The  ^ 
saliva — Salivary  glands — Physical  properties  and  composition  of  the  saliva 
— Its  modes  of  secretion — Its  daily  quantity — Its  physiological  action — 
The  gastric  juice  and  stomach  digestion — Mucous  membrane  of  the  sto- 
mach— Physical  qualities  and  composition  of  the  gastric  juice— Its  mode 
of  secretion — Its  daily  quantity — Its  physiological  action — The  pancreatic 
juice — Structure  of  the  pancreas — Physical  character  and  composition  of 
the  pancreatic  juice — Its  physiological  properties — The  intestinal  juice — 
Brunner's  glands — Follicles  of  Lieberkiihn — Mode  of  obtaining  the  intes- 
tinal juice — Its  composition  and  properties — The  large  intestine  and  its 
contents — Excretine — Stercorine  .......  131-188 

CHAPTER    IX. 

ABSORPTION. 

Intestinal  villi — Closed  follicles  of  the  small  intestine — Absorption  by  the 
villi — Absorption  by  the  bloodvessels — Absorption  by  the  lacteals — Pas- 
sage of  absorbed  materials  into  the  circulation — Renovation  of  the  blood 
by  digestion  and  absorption  ........  189-200 


CONTENTS.  IX 

CHAPTER    X. 

THE    BILE. 

FAG  1C 

Structure  of  the  liver — Physical  and  chemical  characters  of  the  bile — Its 
fluorescence — Its  spectrum — Its  composition  —  Pettenkofer's  test  for  the 
biliary  salts — Mode  of  secretion  of  the  bile — Its  daily  quantity — Decompo- 
sition of  the  biliary  matters  in  the  intesjtine — Physiological  function  and 
destination  of  the  bile .  201-227 

CHAPTER    XI. 

PRODUCTION    OF    GLYCOGEN    AND    GLUCOSE    IN    THE    LIVER. 

Glycogen — Its  origin  and  mode  of  formation— Its  transformation  into  sugar — 
Rapidity  of  formation  of  sugar  in  the  liver — Its  accumulation  after  death — 
Its  proportion  in  the  liver-tissue  during  life — Absorption  and  final  disap- 
pearance of  the  liver-sugar — Its  discharge  by  the  urine — Diabetes — Va- 
rious causes  of  diabetes  .........  228-242 

CHAPTER    XII. 

THE    BLOOD. 

Physical  characters  of  the  blood — Red  globules — Their  size,  form,  and  reac- 
tions— Their  composition — Spectrum  of  blood — Yarieties  of  the  red  glo- 
bules in  different  classes  of  animals — Diagnosis  of  blood,  and  distinction 
between  that  of  man  and  animals — White  globules  of  the  blood — Amoeboid 
movements  of  the  white  globules — Plasma  of  the  blood — Coagulation  of 
the  blood— Quantity  of  blood  in  the  body 243-269 

CHA  PTER    XIII. 

RESPIRATION. 

Nature  of  respiration — Respiration  in  vegetables — Organs  of  respiration — 
Movements  of  respiration — Inspiration — Expiration — Respiratory  move- 
ments of  the  glottis — Frequency  of  respiration — Quantity  of  air  used  in 
respiration — Changes  of  the  air  in  respiration— Diminution  of  oxygen — In- 
crease of  carbonic  acid — Relation  between  the  oxygen  absorbed  and  the 
carbonic  acid  given  off— Exhalation  of  watery  vapor — Exhalation  of  or- 
ganic matter — Vitiation  of  the  air  by  respiration — Changes  in  the  blood 
by  respiration — Absorption  of  oxygen — Discharge  of  carbonic  acid — Source 
of  the  carbonic  acid  of  the  blood 270-299 

CHAPTER   XIV. 

ANIMAL    HEAT. 

Temperature  of  the  animal  body — Differences  of  temperature  in  different 
classes — Quantity  of  heat  produced  in  the  body — Normal  variations  of 
temperature  during  life — Mode  of  production  of  animal  heat — Local  pro- 
duction of  heat  in  the  different  organs — Equalization  of  temperature  by 
the  circulation — Regulation  of  the  animal  temperature — Resistance  of  the 
body  to  cold — Resistance  of  the  body  to  heat — The  perspiration  .  300-317 


X  CONTENTS. 

CHAPTER    XV. 

THE    CIRCULATION. 

PAGE 

Apparatus  of  circulation — The  heart — Sounds,  movement,  and  impulse  of  the 
heart — Rhythm  of  the  heart's  action — The  arteries — Distension  of  the  arte- 
ries by  the  heart's  action — Arterial  pulse — The  sphygmograph — Dicrotic 
pulse — The  arterial  pressure — Rapidity  of  the  arterial  current — The  veins 
— Movement  of  the  blood  through  the  veins — Rapidity  of  the  venous  circu- 
lation— The  capillaries — Movement  of  the  blood  through  the  capillaries — 
Physical  cause  of  the  capillary  circulation — General  rapidity  of  the  circu- 
lation— Local  variations  in  the  capillary  circulation  .  .  .  318-353 

CHAPTER    XYI. 

THE    LYMPHATIC    SYSTEM. 

Structure  and  arrangement  of  the  lymphatic  system — Origin  and  course  of* 
the  lymphatic  vessels  -The  lymphatic  glands — Transudation  and  absorp- 
tion by  animal  tissues — Endosmosis  and  exosmosis — Absorption  and  transu- 
dation  in  the  living  body — Lymph  and  chyle — Composition  of  the  lymph 
— The  lymph  globules — Movement  of  fluids  in  the  lymphatic  system — Daily 
quantity  of  lymph  and  chyle — Internal  renovation  of  the  animal  fluids  354-373 

CHAPTER    XVII. 

THE    URINE. 

General  character  of  the  urine — Its  physical  properties — Variations  in  quan- 
tity, density,  and  acidity — Ingredients  of  the  urine — Urea — Creatinine — 
Sodium  and  potassium  urates — Sodium  biphosphate — Alkaline  phosphates 
— Earthy  phosphates — Sodium  and  potassium  chlorides — Sodium  and  po- 
tassium sulphates — Reactions  of  the  urine — Heat — Acids — Alkalies — Mine- 
ral salts — Abnormal  ingredients  of  the  urine — Glucose — Biliary  matters — 
Medicinal  substances — Albumen — Deposits  in  the  urine — Deposits  of  the 
urates — Uric  acid — Blood — Mucus — Pus  —  Decomposition  of  the  urine — 
Acid  fermentation — Alkaline  fermentation — Renovation  of  the  body  in  the 
nutritive  process 374-397 


SECTION    II. 
THE    NERVOUS    SYSTEM. 

CHAPTER    I. 

GENERAL    STRUCTURE    AND    FUNCTIONS    OF    THE    NERVOUS   SYSTEM. 

Mode  of  action  of  the  nervous  system — Its  structure — Nerve  fibres — Tubular 
sheath — Medullary  layer — Axis  cylinder — Course  and  relation  of  the  nerve 
fibres  —  Their  peripheral  termination  —  Physiological  properties  of  the 
nerve  fibres — Nerve  cells — Their  relation  with  nerve  fibres — Their  physio- 
logical properties — Reflex  action  of  the  nervous  system  .  .  .  399-416 


CONTENTS.  XI 

CHAPTER    II. 

NERVOUS    IRRITABILITY,    AND    ITS    MODE    OF    ACTION. 

PAGE 

Nature  of  nervous  irritability — Irritability  of  sensitive  fibres — Irritability  of 
motor  fibres— Identity  of  action  in  sensitive  and  motor  nerve  fibres — Ra- 
pidity of  transmission  of  the  nerve  force — Methods  of  determining  its  rate 
of  transmission — Rate  of  transmission  in  the  motor  nerves — In  the  sensitive 
nerves — In  the  spinal  cord — Rapidity  of  nervous  action  in  the  brain — Va- 
riation of  nervous  rapidity  in  different  individuals  ....  417-431 

CHAPTER    III. 

GENERAL  ARRANGEMENT  OF  THE  VARIOUS  PARTS  OF  THE  NERVOUS 

SYSTEM. 

Two  divisions  of  the  nervous  system — Ganglionic  system — Cerebro-spinal 
system— Spinal  cord— Brain— Brain  of  fish— Of  reptiles— Of  birds— Of 
quadrupeds — Of  man — Medulla  oblongata — Olivary  bodies— Tuber  annu- 
lare— Crura  cerebri— Cerebral  ganglia— Connection  of  the  different  parts 
of  the  cerebro-spinal  system 432-442 

CHAPTER    IV. 

THE    SPINAL    CORD. 

General  structure  of  the  spinal  cord — Arrangement  of  its  gray  and  white  sub- 
stance—Gray substance  of  the  cord — White  substance  of  the  cord — Con- 
nection of  the  spinal  nerve  roots  with  the  spinal  cord — Transmission  of 
motor  and  sensitive  impulses  in  the  spinal  nerves  and  nerve  roots — In  the 
spinal  cord — Sensitive  and  excitable  parts  of  the  spinal  cord — Channels 
for  sensation  and  motion  in  the  spinal  cord — Crossed  action  of  the  spinal 
cord — Decussation  of  the  motor  tracts — Decussation  of  the  sensitive  tracts 
— Various  forms  of  paralysis  from  lesions  of  the  cerebro-spinal  axis — Para- 
plegia— Hemiplegia — Reflex  action  of  the  spinal  cord  .  .  .  443-470 

CHAPTER   V. 

THE  BRAIN. 

General  structure  of  the  brain — The  hemispheres — Cerebral  convolutions — 
Physiological  properties  of  the  hemispheres — Intellectual  faculties — Special 
seat  of  articulate  and  written  language — Special  centres  of  motion  in  the 
hemispheres — The  cerebral  ganglia — The  cerebellum — Physiological  pro- 
perties of  the  cerebellum — The  tuber  annulare — Physiological  properties  of 
the  tuber  annulare — Medulla  oblongata — Physiological  properties  of  the 
medulla — Its  action  as  a  nervous  centre — Its  influence  on  respiration — On 
deglutition — On  phonation — On  articulation  .....  471-510 

CHAPTER   VI. 

THE    CRANIAL    NERVES. 

Classification  of  the  cranial  nerves — Olfactory  nerves — Optic — Oculomo- 
torius — Patheticus — Trigeminus — Abducens  —  Facial — Auditory — Glosso- 
pharyngeal — Pneumogastric  —  Spinal  accessory — Hypoglossal  —  General 
arrangement  and  mode  of  origin  of  the  cranial  nerves  .  .  .  511-581 


Xll  CONTENTS. 

CHAPTER    VII. 

THE    SYMPATHETIC    SYSTEM. 

PAGE 

Nerves  and  ganglia  of  the  sympathetic  system — Their  anatomical  arrange- 
ment— Their  physiological  properties — Their  influence  on  motion  and 
sensibility — Their  connection  with  the  special  senses — With  the  circula- 
tion—With reflex  action 582-592 

CHAPTER    VIII. 

THE   SENSES. 

General  sensibility — Sensations  of  touch — Of  temperature — Of  pain — Sense 
of  taste — Its  necessary  conditions — Sense  of  smell — Its  necessary  conditions 
— Sense  of  sight — Organ  of  vision — Physiological  conditions  of  the  sense 
of  sight — Field  of  vision — Line  of  direct  vision — Point  of  distinct  vision — 
Accommodation  of  the  eye  for  vision  at  different  distances — Apparent  posi- 
tion of  objects  and  binocular  vision — Point  of  fixation — Appreciation  of 
solidity  and  projection — General  laws  of  visual  perception — Persistence  of 
luminous  impressions — Negative  images — Sense  of  hearing — Organ  of  hear- 
ing— Tympanum  and  chain  of  bones — Their  physiological  action — Labyrinth 
— Its  physiological  action — Office  of  the  semicircular  canals — Cochlea — 
Organ  of  Corti — Physiological  action  of  the  cochlea — Production  and  per- 
ception of  musical  notes 593-666 


SECTION    III. 
REPRODUCTION. 

CHAPTER    I. 

THE    NATURE    OF    REPRODUCTION,    AND    THE    ORIGIN    OP    PLANTS    AND 

ANIMALS. 

Changes  of  structure  and  function  in  living  organisms — Their  disappearance 
—Their  reproduction — Reproduction  by  generation— Spontaneous  genera- 
tion— Entozoa — Infusoria — Bacteria — Influence  of  heat  on  the  production 
of  bacteria  .  .  .  ' 667-681 

CHAPTER    II. 

SEXUAL    GENERATION    AND    THE    MODE    OF    ITS    ACCOMPLISHMENT. 

Male  and  female  sexes — Generative  apparatus  of  flowering  plants — Genera- 
tive apparatus  of  animals — Ovaries  and  testicles — Distinction  between  the 
sexes — Accessory  organs  of  generation  ......  682-684 


CONTENTS.  Xlll 

CHAPTER    III. 

THE    EGG   AND    THE    FEMALE    ORGANS   OF    GENERATION. 

PAGE 

Constitution  of  the  egg — Yitelline  membrane — Vitellus — Ovaries  and  Ovi- 
ducts— Action  of  the  oviducts  and  female  generative  passages — In  the  frog 
— In  the  fowl — Uterus  and  Fallopian  tubes  in  quadrupeds — In  the  human 
species 685-694 

CHAPTER    IV. 

THE    SEMINAL    FLUID    AND    THE    MALE    ORGANS    OF    GENERATION. 

The  spermatozoa — Their  anatomical  characters — Their  movement — Forma- 
tion of  the  spermatozoa — Accessory  male  organs  of  generation — Necessary 
conditions  of  fecundation  by  the  seminal  fluid — Union  of  the  sexes  .  695-702 

CHAPTER    V. 

PERIODICAL    OVULATION    AND    THE    FUNCTION    OF    MENSTRUATION. 

Periodical  ovulation — Original  existence  of  eggs — In  ovipara — In  vivipara — 
Complete  development  of  the  ovarian  egg — Condition  of  puberty — Ripen- 
ing and  discharge  of  the  ovarian  egg — OEstruation — Menstruation — Its 
appearance  and  periodicity — Phenomena  of  menstruation — Ovulation  at 
the  menstrual  period 703-712 

CHAPTER    YI. 

THE    CORPUS   LUTEUM,    AND    ITS    CONNECTION   WITH    MENSTRUATION 
AND   PREGNANCY. 

Origin  of  the  corpus  luteum — Corpus  luteum  of  menstruation — Hemorrhage 
into  the  Graafian  follicle — Hypertrophy  of  the  vesicular  membrane — De- 
colorization  of  the  clot — Yellow  coloration  of  the  convoluted  wall — Atrophy 
and  disappearance  of  the  corpus  luteum  of  menstruation — Corpus  luteum 
of  pregnancy — Its  growth  and  duration — Its  disappearance  after  delivery — 
Distinguishing  marks  of  the  corpus  luteum,  in  menstruation  and  pregnancy 

713-720 

CHAPTER    VII. 

DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 

Changes  in  the  egg  before  leaving  the  ovary — Deposit  of  albuminous  layers 
in  the  Fallopian  tube — Segmentation  of  the  vitellus — Blastoderm,  or  ger- 
minal membrane — External  and  internal  blastodermic  layers — Formation 
of  organs  in  the  embryo — Embryonic  spot — Area  pellucida — Primitive 
trace — Medullary  groove — Medullary  canal — Dorsal  plates — Abdominal 
plates — Chorda  dorsalis — Changes  of  form  in  the  frog's  embryo — Growth  of 
the  limbs — Disappearance  of  the  tail — Transformation  of  the  tadpole  into 
the  frog 721-728 


XIV  CONTENTS. 

CHAPTER    VIII. 

FORMATION    OF    THE    EMBRYO   IN    THE    FOWL'S    EGG. 

PAGE 

Development  of  the  chick — The  yolk  and  the  cicatricula — Formation  of  the 
blastoderm — Folds  of  the  blastoderm — Position  of  the  embryo  in  the  egg — 
Division  of  the  blastodermic  layers — Outer  and  inner  lamina}  of  the  blasto- 
derm— Primitive  vertebrae — Formation  of  the  spinal  column  and  its  mus- 
cles    729-737 

CHAPTER    IX. 

DEVELOPMENT    OF   ACCESSORY    ORGANS   IN    THE    IMPREGNATED    EGG. 
UMBILICAL   VESICLE,    AMNION,    AND   ALLANTOIS. 

Nature  and  function  of  the  accessory  embryonic  organs — Umbilical  vesicle — 
Amnion — Allantois — Physiological  action  of  the  allantois — Exhalation  of 
water  in  the  fowl's  egg — Respiration  and  absorption  of  nourishment  by  the 
allantois — Escape  of  the  chick  at  maturity  from  the  egg-shell  .  .  738-744 

CHAPTER    X. 

DEVELOPMENT    OF    THE    IMPREGNATED   EGG  AND   ITS    MEMBRANES   IN 
THE    HUMAN    SPECIES.       AMNION    AND    CHORION. 

Membranous  envelopes  of  the  human  foetus — Amnion — Its  enlargement — 
Amniotic  fluid — Chorion — Early  formation  of  the  chorion — Villosities  of 
the  chorion — Development  of  bloodvessels  of  the  chorion — Partial  disappear- 
ance of  its  villosities — Their  further  development  at  the  situation  of  the 
placenta 745.749 

CHAPTER    XI. 

DEVELOPMENT    OF    THE    DECIDUAL    MEMBRANE,    AND    ATTACHMENT    OF 
THE    EGG    TO    THE    UTERUS. 

Mucous  membrane  of  the  unimpregnated  uterus — Uterine  tubules — Decidua 
vera — Hypertrophy  of  the  uterine  mucous  membrane  after  impregnation — 
Decidua  reflexa — Enclosure  of  egg  by  the  decidua  reflexa — Attachment  of 
the  egg  to  the  uterine  mucous  membrane — Corresponding  development  of 
the  chorion  and  decidua 750-754 

CHAPTER    XII. 

THE    PLACENTA. 

Source  of  nourishment  for  the  foetus  in  man  and  mammalians — Relations  of 
the  allantois  and  uterine  mucous  membrane — In  the  pig — In  ruminating 
animals — In  carnivora — In  man — Vascular  tufts  of  the  placenta — Vascular 
sinuses  of  the  decidua — Relation  between  the  two — Physiological  action  of 
the  placenta 755-762 


CONTENTS.  XV 


CHAPTER    XIII. 

DISCHARGE   OP   THE   FCETUS   AND   PLACENTA.      REGENERATION   OF   THE 
UTERINE    TISSUES. 

PAGE 

Enlargement  of  the  uterus  during  pregnancy — Formation  of  the  umbilical 
cord — Its  elongation  and  twisting — Disappearance  of  the  umbilical  vesicle 
Contact  of  the  decidua  vera  and  reflexa — Separation  and  discharge  of  the 
foetus  and  placenta — Hemorrhage  at  the  time  of  delivery— Its  arrest  by 
contraction  of  the  uterus — Regeneration  of  the  uterine  tissues  after  de- 
livery   763-768 

CHAPTER    XIY. 

DEVELOPMENT   OP   THE    NERVOUS    SYSTEM,    ORGANS   OP   SENSE,  SKELETON, 

AND    LIMBS. 

Cerebro-spinal  axis — Cerebral  vesicles — Their  division — Hemispheres — Optic 
thalami — Tubercula  quadrigemina  —  Cerebellum  —  Medulla  oblongata — 
Organs  of  special  sense — Ossification  of  the  skeleton — Formation  of  the 
limbs— The  integument .  769—774 


CHAPTER    X  Y. 

DEVELOPMENT  OP  THE  ALIMENTARY  CANAL  AND  ITS  APPENDAGES, 

Formation  of  the  intestinal  canal — Stomach — Small  intestine — Large  intes- 
tine— Convolutions  of  the  intestine — Anus — Imperforate  anus — Caput  coli 
Appendix  vermiformis — Congenital  umbilical  hernia — Meconium — Liver — 
Lungs,  thoracic  cavity  and  diaphragm — Urinary  bladder  and  urethra — De- 
velopment of  the  mouth  and  face 775-783 

CHAPTER    XYI. 

DEVELOPMENT   OP   THE   WOLFFIAN    BODIES,  KIDNEYS,   AND    INTERNAL 
ORGANS   OF    GENERATION. 

Embryonic  urinary  apparatus — Wolffian  bodies — Their  structure — The  kid- 
neys— Internal  organs  of  generation — Fallopian  tubes  and  vasa  deferentia 
— Descent  of  the  testicles — Tunica  vaginalis  testis — Congenital  inguinal 
hernia — Female  organs  of  generation — Descent  of  the  ovaries — Formation 
of  the  uterus,  round  ligaments  and  broad  ligaments — Condition  of  the  uterus 
and  ovaries  at  birth 784-790 

CHAPTER    XYII. 

DEVELOPMENT  OP  THE  VASCULAR  SYSTEM. 

Successive  forms  of  the  circulatory  system — Yitelline  circulation — Omphalo- 
mesenteric  vessels — Placental  circulation — Umbilical  arteries  and  vein — 
Adult  circulation — Development  of  the  arterial  system — Development  of  the 
venous  system — The  hepatic  circulation  and  ductus  venosus — The  heart 
and  ductus  arteriosus — Foramen  ovale — Eustachian  valve — Crossing  of 
blood-currents  in  the  foetal  heart — Changes  in  the  circulation  at  birth  791-808 


XVi  CONTENTS. 

CHAPTER    XVIII, 

DEVELOPMENT    OF    THE    BODY    AFTER   BIRTH. 

PAGB 

Condition  of  the  newly-born  infant — Its  weight — Establishment  of  respira- 
tion— Condition  of  the  nervous  system — Relative  weight  of  the  internal 
organs  in  the  foetus  at  term  and  the  adult — Separation  of  the  umbilical 
cord  and  cicatrization  of  the  umbilicus — Exfoliation  of  the  cuticle  and  hairs 
— Appearance  of  the  first  set  of  teeth — Appearance  of  the  second  or  per- 
manent set — Period  of  puberty,  and  complete  ossification  of  the  skeleton 

809-811 


LIST  OF  ILLUSTRATIONS. 


FIG.  PAGE 

1.  Fibula  tied  in  a  knot,  after  maceration  in  dilute  acid      .  .  .45 

2.  Grains  of  potato  starch    .....  ,56 

3.  Starch  grains  of  Bermuda  arrowroot       .  .  .  .  .57 

4.  Starch  grains  of  wheat  flour         .  .  ...  .  .57 

-  5.  Starch  grains  of  Indian  corn         ......         58 

6.  Saccharomyces  cerevisiae,  in  its  quiescent  condition  .  .         65 

7.  Saccharomyces  cerevisiae,  during  active  germination  .             .  .66 

8.  Stearine,  crystallized  from  a  warm  solution  in  oleine  .             .  .70 

9.  Oleaginous  principles  of  human  fat          .  71 

10.  Human  adipose  tissue       .            .                         .  72 

11.  Chyle,  from  thoracic  duct  of  the  dog        .  73 

12.  Globules  of  cow's  milk      ....                         ...  73 

13.  Cells  of  costal  cartilages,  human               .....  74 

14.  Hepatic  cells,  human        .......  74 

15.  Uriniferous  tubules  of  the  dog      ......  75 

16.  Muscular  fibres  of  human  uterus,  three  weeks  after  parturition              .  75 

17.  Cholesterine,  from  an  encysted  tumor      .....  77 

18.  Cells  of  Bacterium  termo  .......  83 

19.  Hemoglobine  crystals,  from  human  blood             .             .             (Funke)  95 

20.  Hemoglobine  crystals,  from  dog-faced  baboon     .            .           (Preyer)  96 

21.  Sodium  glycocholate,  from  ox-bile            .            .                         .             .  105 

22.  Sodium  taurocholate,  from  alcoholic  extract  of  dog's  bile  .  .106 

23.  Creatine,  crystallized  from  hot  water      .             .             .        (Lehmann)  107 

24.  Creatinine,  crystallized  from  hot  water  .            .            .        (Lehmann)  107 

25.  Urea,  crystallized  by  slow  evaporation  .            .             .        (Lehmann)  109 

26.  Alimentary  canal  of  fowl               ......  132 

27.  Compound  stomach  of  ox             .            .            .            .            .            .  133 

28.  Human  alimentary  canal               ......  134 

29.  Skull  of  rattlesnake          ...                         .          (Eichard)  136 

30.  Skull  of  polar  bear            .                                     ....  137 

31.  Skull  of  the  horse              .......  137 

32.  Molar  tooth  of  the  horse  ;  grinding  surface         ....  137 

33.  Human  teeth         ........  138 

34.  Lobule  of  parotid  gland    .....         (Wagner)  139 

35.  Salivary  tubes ;  from  a  muciparous  gland            .             .          (Kolliker)  139 

36.  Glandular  follicles  and  cells  ;  from  submaxillary  gland  .    (Heidenhain)  140 

37.  Section  of  submaxillary  gland ;  from  the  dog      .             .         (Kolliker)  140 

38.  Buccal  and  glandular  epithelium  ;  deposited  from  saliva            .             .  141 

39.  Gastric  mucous  membrane ;  viewed  from  above  .             .             .             .  152 

40.  Gastric  mucous  membrane  ;  in  vertical  section    ....  152 

2  (  xvii  ) 


XV111 


LIST    OF    ILLUSTRATIONS. 


PIG. 

41.  Mucous  membrane  of  pig's  stomach  ;  vertical  section 

42.  Gastric  follicles,  from  pig's  stomach ;  pyloric  portion 

43.  Gastric  follicles,  from  pig's  stomach  ;  cardiac  portion     . 

44.  Gastric  follicles,  from  pig's  stomach  ;  middle  portion 

45.  Gastric  follicle,  from  human  stomach  ;  cardiac  portion   , 

46.  Portion  of  human  pancreas  and  duodenum 

47.  Longitudinal  section  of  wall  of  duodenum 

48.  Entire  Brunner's  gland     ..... 

49.  Portion  of  one  of  Brunner's  glands 

50.  Follicles  of  Lieberkuhn     .... 

51.  Loop  of  small  intestine,  isolated  by  compressors 

52.  Contents  of  stomach,  during  digestion  of  meat    . 

53.  Contents  of  duodenum,  during  digestion  of  meat 

54.  Contents  of  middle  portion  of  small  intestine 

55.  Contents  of  last  quarter  of  small  intestine 

56.  An  intestinal  villus          .  .  . 

57.  Peyer's  patch,  from  the  ileum      .... 

58.  A  closed  follicle  of  Peyer's  patch  ;  from  the  pig 

59.  Chyle,  from  thoracic  duct  of  the  dog 

60.  Intestinal  epithelium  ;  from  the  dog,  fasting 

61.  Intestinal  epithelium ;  from  the  dog,  during  digestion    . 

62.  Capillary  bloodvessels  of  the  intestinal  villi 

63.  Panizza's  experiment,  on  absorption  from  the  intestine  . 

64.  Lacteals  and  lymphatics,  during  digestion 

65.  Hepatic  lobule,  in  transverse  section 

66.  Glandular  hepatic  cells     ..... 

67.  Biliary  canals  and  ducts  ;  from  the  frog's  liver   . 

68.  Hepatic  lobule,  transverse  section  ;  from  rabbit's  liver  , 

69.  Spectrum  of  green  bile     .  .  .  .  . 

70.  Spectrum  of  chlorophylle  .... 

71.  Spectrum  of  Pettenkofer's  test,  with  biliary  salts,  in  watery  solution 

72.  Spectrum  of  Pettenkofer's  test,  with  biliary  salts,  in  alcoholic  solution 

73.  Spectrum  of  Pettenkofer's  test,  with  albumen     . 

74.  Crystalline  and  resinous  biliary  substances 

75.  Duodenal  fistula    ...... 

76.  Human  blood-globules       ..... 

77.  Red  globules  of  the  blood,  seen  beyond  the  focus 

78.  Red  globules  of  the  blood,  seen  within  the  focus 

79.  Red  globules  of  the  blood,  adhering  together 

80.  Red  globules  of  the  blood,  shrunken  and  crenated 

81.  Red  globules  of  the  blood,  swollen  by  imbibition 

82.  Spectrum  of  hemoglobine,  in  aerated  blood 

83.  Spectrum  of  reduced  hemoglobine 

84.  Blood-globules  of  the  frog  .... 

85.  White  globules  of  the  blood,  altered  by  acetic  acid 

86.  Changes  in  form  of  a  white  globule  of  the  blood 

87.  Coagulated  fibrine  .... 

88.  Bowl  of  recently  coagulated  blood          .  . 

89.  Bowl  of  coagulated  blood,  after  twelve  hours 

90.  Head  and  gills  of  Menobranchus 

91.  Lung  of  frog         .  .  .  .  . 

92.  Human  larynx,  trachea,  bronchi,  and  lungs 


PAGE 

153 

153 

.        . 

154 

.        . 

154 

(Kolliker) 

155 

(Bernard) 

172 

(Bernard) 

180 

-  (Frey) 

180 

. 

180 

181 

.  (Colin) 

182 

185 

. 

186 

t 

186 

186 

(Leydig) 

189 

(Boehm) 

190. 

. 

190 

. 

192 

. 

193 

f 

193 

(Kolliker) 

194 

. 

195 

198 

202 

. 

202 

(Eberth) 

203 

(Genth) 

204 

. 

208 

210 

>lution 

213 

c  solution 

214 

. 

215 

217 

. 

217 

. 

244 

244 

245 

.. 

245 

. 

246 

. 

247 

. 

248 

250 

252 

255 

256 

„ 

258 

, 

261 

261 

272 

272 

. 

273 

LIST    OF    ILLUSTRATIONS.  XIX 

FIG-  PAGE 

93.  Single  lobule  of  human  lung      ......  274 

94.  Capillary  bloodvessels  in  the  pulmonary  vesicles          .            .  (Frey)  274 

95.  Diagram  illustrating  the  movements  of  respiration       .             .            .  275 

96.  Human  larynx,  in  its  post-mortem  condition      .  .  .  .278 

97.  Human  larynx,  with  the  glottis  opened             ....  278 

98.  Human  larynx,  posterior  view    ......  278 

99.  Diagram  of  the  circulation  in  mammalians        .  .  .  .319 

100.  Human  heart,  anterior  view       .  .  .  .  .  .319 

101.  Human  heart,  posterior  view     ......  319 

102.  Eight  auricle  and  ventricle ;  ventricular  valves  open,  arterial  valves 

closed    .........  320 

103.  Bight  auricle  and  ventricle  ;  ventricular  valves  closed,  arterial  valves 

open      .........  321 

104.  Course  of  the  blood  through  the  heart   .  .  .  .  .321 

105.  Production  of  valvular  sound  by  fibrous  tension             .             .             .  323 

106.  Bullock's  heart,  anterior  view  ;  showing  superficial  fibres          .             .  325 

107.  Converging  spiral  fibres  at  the  heart's  apex       .  .  .  .325 

108.  Transverse  section  of  the  bullock's  heart  in  cadaveric  rigidity              .  328 

109.  Left  ventricle  of  bullock's  heart ;  showing  deep  fibres               .             .  328 

110.  Curvatures  of  an  artery  in  pulsation      .  .  .  .  .332 

111.  Curves  of  pulsation,  in  an  elastic  tube  .....  333 

112.  Trace  of  the  radial  pulse,  taken  by  sphygmograph        .            .            .  334 

113. ) 

jj^  f  Variations  of  the  radial  pulse,  under  the  influence  of  temperature 

115]  )                                                                                                       (Marey)  335 

116.  Dicrotic  pulse,  in  typhoid  pneumonia     .            .            .            (Marey)  336 

117.  Dicrotic  pulse,  in  typhoid  fever              .            .             .            (Marey)  336 

118.  Chaveau's  instrument,  for  measuring  rapidity  of  arterial  current         .  339 

119.  Vein,  with  valves  open               ......  342 

120.  Vein,  with  valves  closed             ......  342 

121.  Small  artery,  breaking  up  into  capillaries         ....  344 

122.  Capillary  bloodvessel      .....         (Kolliker)  345 

123.  Capillary  plexus,  from  web  of  frog's  foot           ....  346 

124.  Capillary  circulation,  in  web  of  frog's  foot         ....  347 

125.  Diagram  of  the  circulation         ......  353 

126.  Lymphatic  vessels  and  glands,  of  the  head,  neck,  and  thorax  (Mascagni)  357 

127.  Section  of  a  lymphatic  gland     ....         (Kolliker)  358 

128.  Longitudinal  section  through  a  mesenteric  gland          .         (Kolliker)  358 

129.  Crystals  of  uric  acid  ;  deposited  from  urine      ....  385 

130.  Ferment-apparatus,  for  saccharine  urine  .  .  .  .387 

131.  Crystalline  masses  of  sodium  urate  ;  deposited  from  urine        .             .  391 

132.  Crystals  of  lime  oxalate  ;  deposited  from  urine              .             .             .  394 

133.  Crystals  of  ammonio-magnesian  phosphate  ;  deposited  from  urine       .  396 

134.  Nerve  fibres,  from  the  sciatic  nerve       .....  401 

135.  Nerve  fibres,  from  white  substance  of  the  brain            .            .            .  402 

136.  Division  of  a  nervous  branch  into  fibres            ....  405 

137.  Inosculation  of  nerves    .......  405 

138.  Division  of  nerve  fibres               ....         (Kolliker)  407 

139.  Terminal  bulb  of  a  sensitive  nerve         ....  (Frey)  408 

140.  Tactile  corpuscles,  from  tongue  of  the  sparrow              .  .          (Ihlder)  408 

141.  Termination  of  a  nerve  fibre,  in  muscle              .             .    .       (Rouget)  409 

142.  Nerve  cells,  from  the  medulla  oblongata            .            .              (Dean)  413 


XX  LIST    OF    ILLUSTRATIONS. 

FIG.  PAGE 

143.  Frog's  leg,  showing  galvanization  of  the  muscles          ..            .            .  419 

144.  Frog's  leg,  showing  galvanization  of  the  nerve              .             .             .  419 

145.  Frog's  legs  connected,  showing  action  of  direct  and  inverse  currents    .  421 

146.  Diagram  of  registering  apparatus          .....  427 

147.  The  brain  and  spinal  cord,  in  profile      .....  433 

148.  Transverse  section  of  the  spinal  cord     .....  434 

149.  Brain  of  alligator  .  .  .  .  .  .  .436 

150.  Brain  of  pigeon  ........  437 

151.  Brain  of  rabbit  .  .  .  .  .  .  .437 

152.  Medulla  oblongata  and  base  of  the  brain           .            .      (Hirschfeld)  439 

153.  Medulla  oblongata,  tuber  annulare,  and  crura  cerebri        (Hirschfeld)  440 

154.  Diagrammatic  section  of  the  human  brain        .            .            .            .  441 

155.  Transverse  section  of  the  spinal  cord    .....  444 

156.  Fissures  and  convolutions  of  the  human  brain  ....  472 

157.  Horizontal  section  of  the  human  brain              ....  476 

158.  Vertical  section  of  a  cerebral  convolution        .            .             (Henle)  478 

159.  Portraits  of  idiotic  children       ......  482 

160.  Pigeon,  after  removal  of  the  cerebral  hemispheres        .            ..           .  483 

161.  Brain  of  the  dog ;  viewed  from  above   .            .            .            .            .  489 

162.  Brain  of  the  dog ;  viewed  in  profile       .....  489 

163.  Section  of  the  cerebellum  and  medulla  oblongata        .             (Henle)  493 

164.  Brain  of  healthy  pigeon,  profile  view    .....  497 

165.  Brain  of  operated  pigeon,  profile  view               ....  497 

166.  Brain  of  healthy  pigeon,  posterior  view            ....  497 

167.  Brain  of  operated  pigeon,  posterior  view           ....  497 

168.  Transverse  section  of  medulla  oblongata           .             .             (Henle)  504 

169.  Section  of  cerebral  hemisphere,  showing  olfactory  tubercle      (Henle)  514 

170.  Brain  of  the  cod,  showing  optic  nerves              ....  519 

171.  Brain  of  the  fowl,  showing  optic  nerves            ....  519 

172.  Course  of  the  optic  nerves,  in  man        .....  520 

173.  Nucleus  of  the  trigerninus  nerve             .             .             .              (Henle)  527 

174.  Diagram  of  the  fifth  nerve,  and  its  distribution            .            .            .  528 

175.  Nucleus  of  the  abducens  and  facial  nerves        .            .             (Henle)  538 

176.  Diagram  of  the  facial  nerve,  and  its  distribution           .            .            .  541 

177.  Portrait  of  facial  paralysis         ......  544 

178.  Facial  nerve  and  connections,  in  the  aqueduct  of  Fallopius      .            .  548 

179.  Ninth,  tenth,  and  eleventh  cranial  nerves  .            .             (Hirschfeld)  558 

180.  Section  of  medulla  oblongata,  through  lower   part  of   olivary  body 

(Henle)  575 

181.  Section  of  medulla  oblongata,  through  middle  root  of  olivary  body 

(Henle)  576 

182.  Section  of  medulla  oblongata,  through  hypoglossal  nerve  root   (Henle)  577 

183.  Sections  of  tuber  annulare,  medulla  oblongata,  and  spinal  cord             .  580 

184.  Ganglia  and  nerves  of  the  sympathetic  system              .            .            .  584 

185.  Cat,  after  section  of  the  right  sympathetic       ....  588 

186.  Tactile  corpuscle  of  the  human  skin      .             .             .         (Kolliker)  594 

187.  Diagram  of  tongue,  with  nerves  and  papillae     ....  601 

188.  Distribution  of  nerves  in  the  nasal  passages      .             .             ...  605 

189.  Horizontal  section  of  the  right  eyeball  .  .  .  .608 

190.  Vision  without  a  lens     .......  614 

191.  Vision  with  a  lens           .......  614 

192.  Indistinct  image,  from  excessive  refraction        ....  615 


LIST    OF    ILLUSTRATIONS.  XXI 

PIG.  PAGE 

193.  Indistinct  image,  from  deficient  refraction                      .            .            .  615 

194.  Rods  and  cones,  of  human  retina            .            .            .         (Schultze)  618 

195.  Surface  of  the  retina,  showing  ends  of  rods  and  cones         (Helmholtz)  619 

196.  Diagram,  for  showing  blind  spot  of  the  retina  .            .     (Helmholtz)  621 

197.  Section  of  the  retina,  through  macula  lutea  and  fovea  .        (Schultze)  624 

198.  Section  of  the  eyeball,  showing  direct  and  indirect  vision        .            .  629 

199.  Catoptric  images  in  the  eye        ....     (Helmholtz)  632 

200.  Change  of  position  in  catoptric  images  during  accommodation 

(Helmholtz)  633 

201.  Vision  for  distant  objects          .  .  .  .  .  .633 

202.  Yision  for  near  objects   .......  633 

203.  Emmetropic  eye,  in  vision  at  long  distances      .            .           (Wundt)  636 

204.  Myopic  eye,  in  vision  at  long  distances              .            .           (Wundt)  636 

205.  Single  and  double  vision,  at  different  distances             .            .            .  639 

206.  Skull,  as  seen  by  the  left  eye     .  .  .  .  .  .641 

207.  Skull,  as  seen  by  the  right  eye  ......  641 

208.  Eood's  apparatus,  for  measuring  duration  of  electric  spark       .            .  644 

209.  Ossicles  of  the  human  ear           ....        (Rudinger)  650 

210.  Ossicles  of  the  ear,  in  situ          ....       (Rudinger)  651 

211.  Bony  labyrinth  of  the  human  ear          .....  655 

212.  Bony  cochlea  of  the  human  ear              .             .            .    (Cruveilhier)  660 

213.  Organ  of  Corti  .  .  .  .  .  .  .662 

214.  Cysticercus  cellulosae      .....         (Davaine)  673 

215.  Taenia  solium      ........  674 

216.  Trichina  spiralis ;  encysted        ......  675 

217.  Infusoria,  of  various  kinds          .            .              (Ehrenberg  and  Stein)  676 

218.  Stylonychia  mytilus ;  unimpregnated  and  impregnated               (Stein)  679 

219.  Cells  of  Bacterium  termo           ......  680 

220.  Blossom  of  Ipomoea  purpurea  ;  showing  sexual  apparatus        .            .  682 

221.  Single  articulation  of  Taenia  crassicollis            ....  683 

222.  Human  ovum      ........  685 

223.  Human  ovum,  ruptured  by  pressure      .....  686 

224.  Female  generative  organs  of  frog          .            .            .            .  687 

225.  Mature  frog's  eggs         ......             .  688 

226.  Female  generative  organs  of  fowl          .....  690 

227.  Diagram  of  the  fowl's  egg         ......  691 

228.  Uterus  and  ovaries  of  the  sow  ....                         .  692 

229.  Generative  organs  of  the  human  female            ....  693 

230.  Spermatozoa       ........  696 

231.  Graafian  follicle,  near  the  period  of  rupture     ....  707 

232.  Ovary  with  Graafian  follicle  ruptured    .....  707 

233.  Human  Graafian  follicle,  ruptured  during  menstruation                         .  714 

234.  Corpus  luteum  of  menstruation,  three  weeks  old                       .             .  715 

235.  Corpus  luteum  of  menstruation,  four  weeks  old            .            .             .  716 

236.  Corpus  luteum  of  menstruation,  nine  weeks  old            ...  716 

237.  Corpus  luteum  of  pregnancy,  two  months  old   .            .            .            .  718 

238.  Corpus  luteum  of  pregnancy,  four  months  old  .            .            .            .  718 

239.  Corpus  luteum  of  pregnancy,  at  term    .....  719 

240.  Segmentation  of  the  vitellus      .            .            .            .            .            .  722 

241.  Impregnated  egg,  with  embryonic  spot              ....  724 

242.  Impregnated  egg,  in  an  early  stage  of  development      .  •           .            .  725 

243.  Impregnated  egg,  at  a  more  advanced  period    ....  725 


XX11  LIST    OF    ILLUSTRATIONS. 

FIG.  PAGE 

244.  Frog's  egg,  in  an  early  stage  of  development     ....  726 

245.  Frog's  egg,  in  process  of  development    .            .            .            .             .  726 

246.  Frog's  egg,  farther  advanced     ......  726 

247.  Tadpole,  fully  developed                                                                           .  727 

248.  Tadpole,  with  limbs  beginning  to  be  formed      .  .  .  .728 

249.  Perfect  frog         .......  728 

250.  Section  of  the  blastoderm           .             .            .    (Foster  and  Balfour)  730 

251.  Blastoderm,  separating  into  laminae        ....    (His)  735 

252.  Chick-embryo,  in  different  stages  of  development          .            .    (His)  736 

253.  Egg  of  fish,  with  umbilical  vesicle         .....  738 

254.  Human  embryo,  with  umbilical  vesicle  .....  739 

255.  Fecundated  egg,  showing  formation  of  the  amnion        .            .            .  740 

256.  Fecundated  egg,  farther  advanced          .....  741 

257.  Fecundated  egg,  with  allantois  nearly  complete            .            .            .  741 

258.  Fecundated  egg,  with  allantois  fully  formed      ....  742 

259.  Human  embryo  and  envelopes ;  end  of  first  month        .             .            .  745 

260.  Human  embryo  and  envelopes ;  end  of  third  month      .            .            .  745 

261.  Compound  villosity  of  the  chorion          .....  747 

262.  Extremity  of  a  villosity  of  the  chorion  .....  748 

263.  Uterine  mucous  membrane ;  unimpregnated  uterus       .            .            .  750 

264.  Uterine  tubules ;  unimpregnated  uterus             ....  750 

265.  Impregnated  uterus  ;  formation  of  decidua  vera             .             .             .  752 

266.  Impregnated  uterus ;  formation  of  decidua  reflexa        .            .             .  752 

267.  Impregnated  uterus;  egg  inclosed  by  decidua  rcflexa    .            .            .  752 

268.  Impregnated  uterus  ;  connection  of  egg  and  decidua     .            .            .  753 
269-.  Pregnant  uterus  ;  formation  of  the  placenta      ....  754 

270.  FcEtal  pig,  with  its  membranes  ......  755 

271.  Cotyledon,  from  pregnant  cow's  uterus  .            .                         .            .  756 

272.  Extremity  of  a  fcetal  tuft,  from  human  placenta            .            .            .  757 

273.  Extremity  of  a  fcetal  tuft,  injected        .  .  .  .  .758 

274.  Diagram  of  the  placenta,  in  vertical  section      ....  759 

275.  Human  embryo  and  its  membranes        .....  763 

276.  Pregnant  human  uterus,  at  the  seventh  month              .             .            .  764 

277.  Muscular  fibres  of  the  unimpregnated  uterus     .                                      .  767 

278.  Muscular  fibres  of  the  uterus,  ten  days  after  parturition           .             .  767 

279.  Muscular  fibres  of  the  uterus,  three  weeks  after  parturition     .            .  768 

280.  Formation  of  the  cerebro-spinal  axis      .            .            .             .             .  769 

281.  Formation  of  the  cerebral  vesicles          .....  770 

282.  Foetal  pig,  showing  brain  and  spinal  cord          ....  770 

283.  Fcetal  pig,  farther  advanced       .  .  .  .  .  .770 

284.  Head  of  foetal  pig,  showing  hemispheres,  cerebellum,  and  medulla  oblon- 

gata       .........  770 

285.  Brain  of  adult  pig  .  .  .  .  .  .  .771 

286.  Human  embryo,  one  month  old  .            .            .            .            .             .  774 

287.  Formation  of  the  alimentary  canal          .....  775 

288.  Foetal  pig,  showing  umbilical  hernia      .....  777 

289.  Human  embryo,  showing  development  of  the  face         .            .            .  781 

290.  Head  of  human  embryo,  about  the  sixth  week              .             .            .  782 

291.  Head  of  human  embryo,  at  end  of  second  month          .            .            ,  782 

292.  Fcetal  pig,  showing  Wolffian  bodies       .....  784 

293.  Fcetal  pig,  showing  Wolffian  bodies  and  kidneys          .            .            .  785 

294.  Internal  organs  of  generation,  in  the  fcetal  pig             .            .            .  786 


LIST    OF    ILLUSTRATIONS.  XX111 


295.  Internal  organs  of  generation,  in  the  total  pig,  farther  advanced         .  787 

296.  Formation  of  tunica  vaginalis  testis        .             .             .                      •    .  788 

297.  Congenital  inguinal  hernia          ......  788 

298.  Egg  of  fish,  showing  vitelline  circulation           ....  791 

299.  Diagram  of  the  embryo,  with  umbilical  vesicle  and  allantois  .             .  793 

300.  Diagram  of  the  embryo,  showing  the  placental  circulation        .  .794 

301.  Venous  system,  in  its  earliest  condition              ....  797 

302.  Venous  system,  farther  advanced           .....  798 

303.  Venous  system,  more  fully  developed    .....  798 

304.  Venous  system,  adult  condition              .             .            ...             .  799 

305.  Early  form  of  the  hepatic  circulation     .....  799 

306.  Hepatic  circulation,  farther  advanced    .....  800 

307.  Hepatic  circulation,  in  latter  part  of  foetal  life  .  .  .801 

308.  Hepatic  circulation,  adult  condition       .....  801 

309.  Foetal  heart,  earliest  form          ......  802 

310.  Fcetal  heart,  bent  upon  itself     ......  802 

311.  Foetal  heart,  divided  into  right  and  left  cavities            .            .             .  802 

312.  Foetal  heart,  farther  advanced    ...  802 

313.  Heart  of  infant   .....  .803 

314.  Heart  of  human  foetus,  at  sixth  month  .            .                         .  804 

315.  Diagram  of  foetal  circulation  through  the  heart            .             ,             .  805 

316.  Diagram  of  adult  circulation  through  the  heart            .            .            .  808 


HUMAN  PHYSIOLOGY. 


INTEODUCTIOlSr. 

THE  study  of  Physiology* embraces  all  the  active  phenomena  pre- 
sented by  living  beings — such  as  growth,  reproduction,  movement, 
sensation,  the  chemical  changes  manifested  in  the  body  during  life,  as 
well  as  its  action  upon  external  substances  and  its  dependence  upon 
external  conditions. 

Living  bodies  are  distinguished,  as  regards  their  structure,  from 
those  of  the  inorganic  world  mainly  by  the  fact  that  they  are  organized  ; 
that  is,  they  are  composed  of  a  number  of  different  parts,  or  organs, 
connected  with  each  other  and  mutually  dependent.  In  all  the  higher 
orders,  both  of  animals  and  plants,  these  various  organs  belonging  to 
the  same  body  are  quite  numerous,  and  are  very  different  from  each 
other  both  in  their  structure  and  properties. 

In  an  animal,  for  example,  there  is  an  external  integument  covering 
the  surface  of  the  body,  bones  which  form  a  framework  for  the  protection 
and  attachment  of  other  parts,  muscles  by  which  the  limbs  are  put  in 
motion,  an  alimentary  canal  for  the  digestion  of  the  food,  and  various 
glands  for  the  secretion  of  the  animal  fluids.  In  a  plant  there  are  roots 
which  absorb  the  ingredients  of  the  soil,  leaves  which  elaborate  the 
vegetable  juices,  and  the  various  parts  of  the  blossom  which  are  con- 
cerned in  the  production  of  the  fruit.  Thus  each  different  organ  has  a 
special  structure,  and  plays  a  distinct  part  in  the  living  organism. 

The  peculiar  action  or  result  accomplished  in  this  way  l>y  a  particular 
organ  is  called  its  function.  There  are,  therefore,  a  variety  of  functions 
going  on  in  the  living  body,  each  one  as  distinct  as  the  organ  by  which 
it  is  performed.  But  no  one  of  them  is  entirely  independent  of  the  rest. 
The  circulation  of  the  blood,  which  is  carried  on  by  the  organs  of  the 
vascular  system,  requires  that  the  blood  should  be  incessantly  renovated 
by  the  process  of  respiration  in  order  that  it  may  continue  undisturbed  ; 
and  the  circulation  is  in  its  turn  necessary  to  the  functions  of  secretion 
and  nutrition,  for  which  it  supplies  the  necessary  material  to  all  parts 
of  the  body.  Thus  all  the  different  functions  are  in  a  state  of  mutual 
dependence,  and  the  life  of  the  whole  body  is  a  result  of  the  simultaneous 
and  harmonious  action  of  its  different  parts. 

3  (  25  ) 


26  INTRODUCTION. 

The  only  method  by  which  physiology  can  be  studied  is  the  observa- 
tion of  nature.  The  phenomena  presented  by  living  creatures  are  only 
to  be  learned  by  direct  examination,  and  cannot  be  inferred,  by  any 
process  of  reasoning,  from  any  other  facts  of  a  different  character. 
Even  a  knowledge  of  the  minute  structure  of  a  part,  however  exact, 
cannot  furnish  any  information  as  to  its  active  properties  or  function ; 
and  these  properties  can  be  learned  only  by  examining  the  organ  when 
it  is  in  a  state  of  activity.  Thus  the  muscular  fibre  and  the  nervous 
fibre  present  certain  well-defined  characters  of  minute  structure  which 
are  easily  distinguished  by  anatomical  examination,  but  which  could 
not  teach  us  anything  of  their  physiological  properties ;  while  direct 
experiment  shows  that  the  muscular  fibre  is  contractile  and  the  nervous 
fibre  excitable  or  sensitive. 

Since  the  vital  phenomena  of  the  entire  body  result  from  the  com- 
bined activity  of  its  different  parts,  th«se  different  parts  should  be 
studied  by  themselves  in  order  to  ascertain  their  particular  properties. 
This  can  be  done  by  examination  and  experiment  for  each  part  while  it 
still  retains  its  vital  powers.  Experience  shows  that  after  the  circula- 
tion has  ceased,  and  consciousness  and  volition  have  disappeared,  many 
minute  portions  of  the  body  continue  for  a  time  capable  of  manifesting 
their  physiological  action.  Thus  a  muscular  fibre,  separated  from  the 
remaining  tissues,  may  still  be  made  to  contract  under  the  appropriate 
stimulus;  and  a  nerve,  though  cut  off  from  its  connection  with  the 
brain,  may  also  be  called  into  activity  by  mechanical  or  electrical 
irritation.  This  is  because  each  part  retains  its  physiological  powers 
so  long  as  it  retains  its  peculiar  structure  and  constitution.  The 
general  functions  of  the  body,  such  as  the  circulation,  digestion,  and 
respiration,  have  for  their  object  to  provide  for  the  nutrition  of  the 
tissues  and  organs,  and  thus  maintain  their  natural  constitution  unim- 
paired. Their  cessation,  accordingly,  does  not  instantly  destroy  the 
vitality  of  particular  parts,  but  only  after  a  sufficient  time  has  elapsed 
to  alter  or  impair  their  natural  constitution.  The  time  during  which 
the  vital  powers  may  thus  be  retained  varies*  for  different  parts.  Thus 
the  muscular  fibre  is  capable  of  manifesting  its  excitability,  as  a  general 
rule,  longer  than  the  nervous  fibre,  and  the  nervous  fibre  longer  than 
the  gray  matter  of  a  nervous  ganglion.  There  is,  also,  a  difference  in 
the  same  part  shown  by  different  kinds  of  animals.  The  excitability  of 
both  nervous  and  muscular  tissues  continues  longer  in  the  cold-blooded 
than  in  the  warm-blooded  animals,  and  in  the  quadrupeds  longer  than  in 
birds.  In  every  instance,  of  course,  the  examination  of  such  an  isolated 
part  of  the  body  should  be  made  while  it  still  preserves  its  physiological 
properties. 

On  the  other  hand,  the  functions  of  entire  organs,  or  the  general 
functions  of  the  body  as  a  whole,  can  only  be  studied  with  success 
while  life  is  going  on.  The  anatomical  relations  of  the  various  organs 
may  be  learned  by  dissection  after  death ;  but  their  vital  actions  are 
not  to  be  ascertained  in  this  way,  because  they  have  ceased  and  cannot 


INTRODUCTION.  27 

again  be  put  in  operation.  The  most  important  facts  have  often 
remained  long  unknown  or  misunderstood  for  this  reason.  The  earlier 
anatomists  supposed  that,  the  arteries  were  tubes  for  the  circulation  of 
air,  because  they  appeared  empty  when  opened  after  death.  It  was 
only  when  Galen  exposed  the  artery  of  a  living  animal,  and,  opening  it 
between  two  ligatures,  showed  it  to  be  full  of  blood,  that  the  true  func- 
tion of  these  vessels  was  ascertained.  The  lacteal  and  lymphatic  vessels 
were  discovered  in  the  seventeenth  century ;  but  from  their  small  size, 
and  the  small  amount  of  fluid  contained  in  them,  the  circulation  in  the 
lymphatic  system  was  thought  to  be  very  limited  in  quantity.  Two 
hundred  years  afterward,  when  the  experiment  was  performed  of 
introducing  a  canula  into  the  thoracic  duct  of  the  living  animal  and 
continuing  the  observation  while  digestion  and  absorption  were  going 
on,  the  experimenters  obtained,  in  horses  and  oxen,  from  fifty  to  one 
hundred  pounds  of  lymph  and  chyle  during  twenty-four  hours ;  thus 
demonstrating  the  existence  of  a  vital  activity  much  greater  than  could 
have  been  suspected  from  any  examination  of  the  dead  bod}^. 

The  observation  of  the  physiological  actions  during  life  usually  re- 
quires the  employment  of  certain  contrivances  and  manipulations  in 
order  to  arrive  at  accurate  results.  Even  the  more  superficial  phe- 
nomena, such  as  the  changes  in  the  air  produced  by  respiration,  can 
only  be  studied  with  precision  *by  the  aid  of  artificial  means  for  meas- 
uring and  examining  the  various  gases  absorbed  or  discharged.  The 
processes  going  on  in  the  internal  organs  are  more  especially  concealed 
from  view,  and,  therefore,  need  for  their  study  the  use  of  instruments 
and  operations  in  order  to  bring  them  under  observation.  It  is  accord- 
ingly necessary,  in  the  large  majority  of  cases,  to  resort  to  experiment* 
upon  animals  in  the  study  of  physiology,  and  all  the  important 
knowledge  thus  far  gained  has  been  acquired  in  this  way.  But  as  the 
physiology  of  the  human  species  is  the  main  object  of  our  study,  and 
as  each  different  species  of  animals  presents  certain  peculiarities  which 
distinguish  it  from  others,  it  becomes  essential  to  know  how  far  we  can 
apply  the  results  derived  from  experiment  upon  one  species  to  the 
physiology  of  the  others,  or  to  that  of  the  human  body  itself. 

All  animals  present  certain  general  phenomena  in  common,  namely, 
those  of  nutrition,  secretion,  absorption,  movement,  and  reproduc- 
tion. The  vertebrate  animals,  to  which  class  man  belongs,,  are  fur- 
thermore constructed  upon  the  same  general  plan  of  organization,  and 
their  corresponding  organs  are  evidently  the  same  in  character.  The 
different  parts  of  their  nervous  and  vascular  systems,  their  digestive 
apparatus,  their  organs  of  locomotion,  of  secretion,  excretion,  and 
reproduction,  have  the  same  relative  position,  and  can  be  easily  recog- 
nized and  compared  with  each  other.  The  ingredients  of  their  solids 
and  fluids  have  the  same  or  a  similar  chemical  constitution,  and  play  a 
corresponding  part  in  the  vital  processes.  The  coloring  matter  of  the 
blood  is  identical  in  all  of  them ;  they  all  absorb  oxygen  and  exhale 
carbonic  acid  with  more  or  less  activity ;  and  many  or  most  of  their 


28  INTRODUCTION. 

secretions  and  excretions  have  the  same  physiological  character.  The 
whole  value  of  physiological  experiment,  as  applied  to  different  species, 
depends  upon  this  general  resemblance  between  them,  both  of  structure 
and  function. 

On  the  other  hand,  the  differences  between  species  of  vertebrate  ani- 
mals consist  only  in  the  relative  size  and  development  of  particular 
parts,  and  consequently  in  the  relative  importance  of  particular  func- 
tions. The  intestine,  for  example,  is  longer  and  more  complicated  in 
the  herbivorous  animals,  shorter  and  simpler  in  the  carnivora.  The 
muscles  of  the  external  ear  are  slightly  developed  and  powerless  in  the 
human  subject,  large  and  active  in  many  of  the  inferior  species.  Fish 
and  reptiles  produce  but  little  animal  heat,  and  are,  therefore,  called 
cold-blooded  animals ;  birds  and  quadrupeds  generate  it  in  abundance, 
and  are  therefore  called  warm-blooded.  The  differences  between  them 
are,  therefore,  almost  invariably  differences  in  degree  and  not  in  kind. 

Consequently  the  simple  and  direct  result  of  an  experiment  in  different 
animals  is  the  same,  or  varies  only  in  degree.  If  we  deprive  an  animal 
of  oxygen,  whatever  the  species  may  be,  it  produces  death  invariably  and 
in  the  same  way,  because  in  all  this  element  is  essential  to  the  nourish- 
ment of  the  tissues.  But  death  will  take  place  rapidly  in  birds  or 
quadrupeds,  more  slowly  in  reptiles,  because  the  vital  changes  are  more 
active  in  the  former  than  in  the  latter.  Division  of  the  spinal  cord  in 
all  cases  produces  immediate  paralysis  of  sensation  and  voluntary 
motion  in  the  parts  below,  showing  that  the  sensitive  and  motor  fibres 
follow  in  all  the  same  route  and  possess  the  same  nervous  endowments. 
Experiments  accordingly  of  the  same  kind,  performed  upon  different 
animals,  have  a  direct  result  which  is  the  same  in  character. 

But  experiments  have  often  also  certain  indirect  or  secondary  results, 
dependent  upon  the  relative  importance  of  associated  organs,  and  these 
vary  considerably  in  different  kinds  of  animals.  Thus  division  or  dis- 
ease of  the  facial  nerve  in  all  instances  causes  a  direct  paralysis  of  the 
muscles  of  the  face.  In  the  human  subject  this  produces  only  a  loss  of 
expression,  with  some  inconvenience  in  the  retention  of  fluids  by  the 
mouth.  But  in  the  horse  it  is  followed  by  a  partial  suffocation,  because 
in  him  the  expansion  of  the  nostrils  is  an  important  part  of  the  move- 
ments of  respiration.  While  the  direct  effect  of  an  experiment,  there- 
fore, is  always  the  same,  its  indirect  effect  varies  with  the  comparative 
development  of  different  parts.  It  is  evident,  however,  that  this  varia- 
tion does  not  impair  the  value  of  experiment  as  a  means  of  study,  but, 
on  the  contrary,  enlarges  its  usefulness  and  leads  to  the  acquisition  of 
greater  knowledge  by  its  means. 

The  physiological  actions  of  living  beings  are,  of  course,  dependent 
upon  natural  causes,  and  are  to  be  studied  in  a  similar  manner  with 
other  natural  phenomena,  such  as  those  of  magnetism,  gravitation, 
chemical  affinity,  and  the  like.  In  all  these  cases,  we  observe  the 
character  of  the  phenomenon,  the  conditions  upon  which  it  depends, 
the  mechanism  of  its  production,  and  the  quantities  of  force  or  material 


INTRODUCTION.  29 

expended  in  its  manifestation.  The  study  of  physiology,  therefore, 
requires  a  certain  knowledge  of  the  chemical  and  physical  reactions 
presented  in  the  outer  world,  in  order  that  the  observer  may  be  able  to 
appreciate  the  peculiarities  of  similar  phenomena  as  they  occur  in  the 
living  body.  As  all  animated  beings  are  closely  dependent  on  external 
conditions  for  the  maintenance  of  their  vitality,  it  is  evident  that  the 
study  of  their  vital  actions  cannot  be  disconnected  from  that  of  external 
natural  phenomena.  The  pressure  and  tension  of  the  atmosphere,  for 
example,  as  well  as  its  chemical  constitution,  are  directly  connected  with 
the  process  of  respiration ;  and  the  circulation  of  the  blood  through  the 
vessels  exhibits  the  physical  phenomena  of  an  incompressible  fluid  flow- 
ing through  elastic  tubes. 

By  the  term  vital  phenomena,  accordingly,  we  mean  those  phenomena 
which  are  manifested  in  the  living  body,  and  which  are  characteristic  of 
its  functions.  At  the  same  time  many  of  them  do  not  differ  in  character 
from  those  of  the  outside  world,  but  only  in  the  peculiarity  of  their 
conditions  and  their  results. 

Some  of  these  phenomena  are  physical  or  mechanical  in  their  charac- 
ter ;  as,  for  example,  the  play  of  the  articulating  surfaces  upon  each 
other,  the  balancing  of  the  spinal  column  with  its  appendages,  the  action 
of  the  elastic  ligaments.  Nevertheless,  these  phenomena,  though  strictly 
physical  in  character,  are  often  entirely  peculiar  and  different  from  those 
seen  elsewhere,  because  the  mechanism  of  their  production  is  peculiar  in 
its  details.  Thus  the  human  Voice  and  its  modulations  are  produced  in 
the  larynx,  in  accordance  with  the  general  physical  laws  of  sound ;  but 
the  arrangement  of  the  elastic  and  movable  vocal  chords,  and  their 
relations  with  the  columns  of  air  above  and  below,  the  moist  and  flexi- 
ble mucous  membrane,  and  the  contractile  muscles  outside,  are  of  such 
a  special  character  that  the  entire  apparatus,  as  well  as  the  sounds  pro- 
duced by  it,  is  peculiar ;  and  its  action  cannot  be  properly  compared 
with  that  of  any  other  known  musical  instrument. 

In  the  same  manner,  the  movements  of  the  heart  are  so  complicated 
and  remarkable  that  they  cannot  be  comprehended,  even  by  one  who  is 
acquainted  with  the  anatoniy  of  the  organ,  without  a  direct  examination. 
This  is  not  because  there  is  anything  essentially  obscure  or  mysterious 
in  their  nature,  for  they  are  purely  mechanical  in  character ;  but  because 
their  conditions  are  so  peculiar,  owing  to  the  tortuous  course  of  the 
muscular  fibres,  their  arrangement  in  interlacing  layers,  their  attach- 
ments and  relations,  that  their  combined  action  produces  an  effect  alto- 
gether peculiar,  and  one  which  is  not  similar  to  anything  outside  the 
living  body. 

A  very  large  and  important  class  of  the  vital  phenomena  are  those  of 
a  chemical  character.  It  is  one  of  the  characteristics  of  living  bodies 
that  a  succession  of  chemical  actions,  combinations,  and  decompositions, 
is  constantly  going  on  in  their  interior.  It  is  one  of  the  necessary  con- 
ditions of  the  existence  of  every  animal  and  every  vegetable,  that  it 
should  constantly  absorb  various  substances  from  without,  which  under- 


30  INTRODUCTION. 

go  different  chemical  alterations  in  its  interior,  and  are  finally  discharged 
from  it  under  other  forms.  If  these  changes  be  prevented  from  taking 
place,  life  is  immediately  extinguished.  Thus  animals  constantly  absorb, 
on  the  one  hand,  water,  oxygen,  salts,  albumen,  oil,  sugar,  etc.,  and  give 
up,  on  the  other  hand,  to  the  surrounding  media,  carbonic  acid,  water, 
creatine,  the  urates,  urea,  and  the  like  ;  while  between  these  two  extreme 
points,  of  absorption  and  exhalation,  there  take  place  a  multitude  of 
different  transformations  which  are  essential  to  the  continuance  of  life. 

Some  of  these  chemical  actions  are  the  same  with  those  which  are 
seen  outside  the  body ;  but  most  of  them  are  peculiar,  and  do  not  take 
place  anywhere  else.  This,  again,  is  not  because  there  is  anything  excep- 
tional in  their  nature,  but  because  the  conditions  necessary  for  their 
accomplishment  exist  in  the  body,  and  do  not  exist  elsewhere.  All 
chemical  phenomena  are  liable  to  be  modified  by  surrounding  conditions. 
Many  reactions  which  will  take  place  at  a  high  temperature  will  not 
take  place  at  a  low  temperature,  and  vice  versa.  Some  will  take  place 
in  the  light,  but  not  in  the  dark  ;  others  will  take  place  in  the  dark,  but 
not  in  the  light.  Because  a  chemical  reaction,  therefore,  takes  place 
under  one  set  of  conditions,  we  cannot  be  at  all  sure  that  it  will  take 
place  under  others  which  are  different. 

The  chemical  conditions  of  the  living  body  are  exceedingly  compli- 
cated. In  the  animal  solids  and  fluids,  there  are  many  substances 
mingled  together  in  varying  quantities,  which  modify  or  interfere  with 
each  other's  reactions.  New  substances  are  constantly  entering  by 
absorption,  and  old  ones  leaving  by  exhalation;  while  the  circulating 
fluids  are  incessantly  passing  from  one  part  of  the  body  to  another, 
and  coming  in  contact  with  different  organs  of  different  texture  and 
composition.  All  these  conditions  are  peculiar,  and  so  modif}^  the 
chemical  actions  taking  place  in  the  body  that  they  are  often  unlike 
those  met  with  elsewhere. 

If  starch  and  iodine  be  mingled  together  in  a  watery  solution,  they 
unite  with  each  other,  and  strike  a  deep  blue  color;  but  if  they  be 
mingled  in  the  blood,  no  such  reaction  takes  place,  because  it  is  pre- 
vented by  the  presence  of  certain  organic  substances  which  interfere 
with  it. 

If  dead  animal  matter  be  exposed  to  warmth,  air,  and  moisture,  it 
putrefies;  but  if  introduced  into  the  living  stomach,  this  process  is  pre- 
vented, because  the  fluids  of  the  stomach  cause  the  animal  substance  to 
undergo  a  peculiar  transformation  (digestion),  after  which  the  blood- 
vessels immediately  remove  it  by  absorption.  There  are  also  certain 
substances  which  make  their  appearance  in  the  living  body  of  animals 
or  vegetables,  and  which  are  not  found  elsewhere ;  such  as  fibrine,  albu- 
men, caseine,  the  biliary  salts,  hemoglobine,  chlorophyll,  morphine,  etc. 
These  substances  cannot  be  manufactured  artificially,  simply  because 
we  are  unable  to  imitate  the  necessary  conditions.  They  require  for 
their  production  the  presence  of  a  living  organism. 

The  chemical  phenomena  of  the  living  body  are,  therefore,  not  different 


INTRODUCTION.  31 

in  their  nature  from  any  other  chemical  phenomena;  but  they  are  often 
different  in  their  conditions  and  in  their  results,  and  are  consequently 
peculiar  and  characteristic. 

Another  set  of  vital  phenomena  are  those  whiph  are  manifested  in  the 
processes  of  reproduction  and  development.  They  are  entirely  distinct 
from  any  phenomena  which  are  exhibited  by  matter  not  endowed  with 
life.  An  inorganic  substance,  even  when  it  has  a  definite  form,  as,  for 
example,  a  crystal  of  fluor  spar,  has  no  particular  relation  to  any  similar 
form  which  has  preceded,  or  any  other  which  is  to  follow  it.  On  the 
other  hand,  every  animal  and  every  vegetable  owes  its  origin  to  pre- 
ceding animals  or  vegetables  of  the  same  kind;  and  the  manner  in 
which  this  production  takes  place,  and  the  different  forms  through 
which  the  new  body  successively  passes  in  the  course  of  its  develop- 
ment, constitute  the  phenomena  of  reproduction.  These  phenomena 
are  mostly  dependent  on  the  chemical  processes  of  nutrition  and  growth, 
which  take  place  in  a  particular  direction  and  in  a  particular  manner ; 
but  their  results,  namely,  the  production  of  a  connected  series  of  different 
forms,  constitute  a  separate  class  of  phenomena,  which  cannot  be  ex- 
plained in  any  manner  by  the  preceding,  and  require,  therefore,  to  be 
studied  by  themselves. 

Another  set  of  vital  phenomena  are  those  which  belong  to  the  nervous 
system.  These,  like  the  processes  of  reproduction  and  development, 
depend  on  the  chemical  changes  of  nutrition  and  growth.  That  is  to 
say,  if  the  nutritive  processes  did  not  go  on  in  a  healthy  manner  and 
maintain  the  nervous  system  in  a  healthy  condition,  the  peculiar  phe- 
nomena which  are  characteristic  of  it  could  not  take  place.  The  nutri- 
tive processes  are  necessary  conditions  of  the  nervous  phenomena.  But 
there  is  no  other  connection  between  them ;  and  the  nervous  phenomena 
themselves  are  distinct  from  all  others,  both  in  their  nature  and  in  the 
mode  in  which  they  are  to  be  studied. 

The  study  of  Physiology  is  naturally  divided  into  three  distinct  Sec- 
tions : — 

I.  The  first  of  these  includes  everything  which  relates  to  the  NUTRI- 
TION of  the  body  in  its  widest  sense.  It  comprises  the  history  of  the 
proximate  principles,  their  source,  the  manner  of  their  production,  the 
proportions  in  which  they  exist  in  different  kinds  of  food  and  drink,  the 
processes  of  digestion  and  absorption,  and  the  constitution  of  the  circu- 
lating fluids ;  then,  the  physical  phenomena  of  the  circulation  and  the 
forces  by  which  it  is  accomplished ;  the  changes  which  the  blood  under- 
goes in  different  parts  of  the  body ;  all  the  phenomena,  both  physical 
and  chemical,  of  respiration;  those  of  secretion  and  excretion,  and  the 
character  and  destination  of  the  secreted  and  excreted  fluids.  All  these 
processes  have  reference  to  a  common  object,  namely,  the  preservation  of 
the  normal  structure  and  organization  of  the  individual.  Their  results 
cprnprise  the  phenomena  of  internal  growth  and  nutrition,  which  are 
common  to  the  animal  and  vegetable  kingdoms;  and  they  are  accord- 
ingly known  by  the  name  of  the  vegetative  functions. 


32  INTRODUCTION. 

II.  The  second  Section,  in  the  natural  order  of  study,  is  devoted  to 
the  phenomena  of  the  NERVOUS  SYSTEM.     These  phenomena  are  not 
exhibited  by  vegetables,  but  belong  exclusively  to  animal  organizations. 
They  bring  the  animal  body  into  relation  with  the  external  world,  and 
preserve  it  from  external  dangers,  by  means  of  sensation,  movement, 
consciousness,  and  volition.     They  are  more  particularly  distinguished 
by  the  name  of  the  animal  functions. 

III.  Lastly  comes  the  study  of  the  entire  process  of  REPRODUCTION. 
Its  phenomena,  again,  with  certain  modifications,  are  met  with  in  both 
animals  and  vegetables ;  and  might,  therefore,  with  some  propriety,  be 
included  under  the  head  of  vegetative  functions.     But  their  distinguish- 
ing peculiarity  is,  that  they  have  for  their  object  the  production  of  new 
organisms,  which  take  the  place  of  the  old  and  remain  after  they  have 
disappeared.     These  phenomena  do  not,  therefore,  relate  to  the  preserva- 
tion of  the  individual,  but  to  that  of  the  species ;  and  any  study  which 
concerns  the  species  comes  properly  after  we  have  finished  everything 
relating  to  the  individual. 


SECTION  I. 
NUTRITION. 


CHAPTEE    I. 

PROXIMATE  PRINCIPLES  IN   GENERAL. 

THE  study  of  NUTRITION  begins  naturally  with  that  of  the  proximate 
principles,  or  the  substances  entering  into  the  composition  of  the  dif- 
ferent parts  of  the  body,  and  the  different  kinds  of  food.  In  examining 
the  body,  the  anatomist  finds  that  it  is  composed,  first,  of  various  parts, 
which  are  easily  recognized  by  the  eye,  and  which  occupy  distinct  situa- 
tions. In  the  case  of  the  human  body,  for  example,  a  division  is  easily 
made  of  the  entire  frame  into  the  head,  neck,  trunk,  and  extremities. 
Each  of  these  regions,  again,  is  found,  on  examination,  to  contain  several 
distinct  parts,  or  "organs,"  which  require  to  be  separated  from  each 
other  by  dissection,  and  which  are  distinguished  by  their  form,  color, 
texture,  and  consistency.  In  a  single  limb,  for  example,  every  bone  and 
every  muscle  constitutes  a  distinct  organ.  In  the  trunk,  we  have  the 
heart,  the  lungs,  the  liver,  spleen,  kidneys,  spinal  cord,  etc.,  each  of 
which  is  also  a  distinct  organ.  When  a  number  of  organs,  differing  in 
size  and  form,  but  similar  in  texture,  are  found  scattered  throughout 
the  entire  frame,  or  a  large  portion  of  it,  they  form  a  connected  set  or 
order  of  parts,  which  is  called  a  "  system."  Thus,  all  the  muscles  taken 
together  constitute'  the  muscular  system ;  all  the  bones,  the  osseous 
system ;  all  the  arteries,  the  arterial  system.  Several  entirely  different 
organs  may  also  be  connected  with  each  other,  so  that  their  associated 
actions  tend  to  accomplish  a  single  object,  and  they  then  form  an 
"  apparatus."  Thus  the  heart,  arteries,  capillaries,  and  veins,  together, 
form  the  circulatory  apparatus ;  the  stomach,  liver,  pancreas,  intestines, 
etc.,  the  digestive  apparatus.  Every  organ,  again,  on  microscopic  ex- 
amination, is  seen  to  be  made  up  of  minute  bodies,  of  definite  size  and 
figure,  which  are  so  small  as  to  be  invisible  to  the  naked  eye,  and  which, 
after  separation  from  each  other,  cannot  be  further  subdivided  without 
destroying  their  organization.  They  are,  therefore,  called  "  anatomical 
elements."  Thus,  in  the  liver,  there  are  hepatic  cells,  capillary  blood- 
vessels, the  fibres  of  Glisson's  capsule,  and  the  ultimate  filaments  of  the 

(33) 


34  PROXIMATE    PRINCIPLES    IN    GENERAL. 

hepatic  nerves.  Lastly,  two  or  more  kinds  of  anatomical  elements 
interwoven  with  each  other  in  a  particular  manner  form  a  "tissue." 
Adipose  vesicles,  with  capillaries  and  nerve  filaments,  form  adipose 
tissue.  White  fibres,  elastic  fibres,  and  connective-tissue  cells,  with 
capillary  bloodvessels  and  nerve  filaments,  form  connective  tissue.  Thus 
the  solid  parts  of  the  entire  body  are  made  up  of  anatomical  elements, 
tissues,  organs,  systems,  and  apparatuses.  Every  organized  frame,  and 
even  every  apparatus,  every  organ,  and  every  tissue,  is  made  up  of  dif- 
ferent parts,  variously  interwoven  and  connected  with  each  other,  and 
it  is  this  character  which  constitutes  its  organization. 

But  beside  the  above  solid  forms,  there  are  also  certain  fluids,  which 
are  constantly  present  in  various  parts  of  the  body,  and  which,  from 
their  peculiar  constitution,  are  termed  "  animal  fluids."  These  fluids 
are  just  as  much  an  essential  part  of  the  body  as  the  solids.  The  blood 
and  the  lymph,  for  example,  the  pericardial  and  synovial  fluids,  the 
saliva,  which  always  exists  more  or  less  abundantly  in  the  ducts  of  the 
parotid  gland,  the  bile  in  the  biliary  ducts  and  the  gall-bladder :  all 
these  go  to  make  up  the  entire  body,  and  are  quite  as  necessary  to  its 
physiological  structure  as  the  muscles  or  the  nerves.  Now,  if  these 
fluids  be  examined,  they  are  found  to  be  made  up  of  many  different  sub- 
stances, which  are  mingled  together  in  certain  proportions ;  these  pro- 
portions being  constantly  maintained  at  or  about  the  same  standard  by 
the  natural  processes  of  nutrition.  Such  a  fluid  is  termed  an  organized 
fluid.  It  is  organized  by  virtue  of  the  numerous  ingredients  which 
enter  into  its  composition,  and  the  regular  proportions  in  which  these 
ingredients  are  maintained.  Thus  in  the  plasma  of  the  blood,  we  have 
albumen,  fibrine,  water,  chlorides,  carbonates,  and  phosphates.  In  the 
urine,  we  find  water,  urea,  sodium  urate,  creatinine,  coloring  matter,  and 
salts.  These  substances,  which  are  mingled  together  so  as  to  make  up, 
in  each  instance,  by  their  intimate  union,  a  homogeneous  liquid,  are 
called  the  PROXIMATE  PRINCIPLES  of  the  animal  fluid. 

In  the  solids,  furthermore,  even  in  those  parts  which  are  apparently 
homogeneous,  there  is  a  similar  mixture  of  various  ingredients.  In  the 
hard'  substance  of  bone,  for  example,  there  is,  first  water,  which  may  be 
expelled  by  evaporation ;  second,  lime  phosphate  and  carbonate,  which 
may  be  extracted  by  the  proper  solvents  ;  third,  a  peculiar  animal  matter, 
with  which  these  calcareous  salts  are  in  union  ;  and  fourth,  various  other 
saline  substances,  in  special  proportions.  The  muscular  tissue  contains 
water,  sodium  and  potassium  chlorides,  lime  phosphate,  creatine,  vari- 
ous forms  of  albumen,  and  an  animal  matter  termed  myosine.  The 
difference  in  consistency  between  the  solids  and  fluids  does  not,  there- 
fore, indicate  any  radical  difference  in  their  constitution.  Both  are 
equally  made  up  of  proximate  principles,  mingled  together  in  various 
proportions. 

It  is  important  to  understand,  however,  exactly  what  are  proximate 
principles,  and  what  are  not  such;  for  since  these  principles  are  ex- 
tracted from  the  animal  solids  and  fluids,  and  separated  from  each 


PROXIMATE    PRINCIPLES    IN    GENERAL.  35 

other  by  the  help  of  certain  chemical  manipulations,  such  as  evapora- 
tion, solution,  crystallization,  and  the  like,  it  might  be  supposed  that 
every  substance  which  could  be  extracted  from  an  organized  solid  or 
fluid,  by  chemical  means,  should  be  considered  as  a  proximate  princi- 
ple. That,  however,  is  not  the  case.  A  proximate  principle  is  properly 
defined  to  be  any  substance,  whether  simple  or  compound,  chemically 
speaking,  which  exists,  under  its  own  form,  in  the  animal  solid  or  fluid, 
and  which  can  be  extracted  by  means  which  do  not  alter  or  destroy  its 
chemical  properties.  Lime  phosphate,  for  example,  is  a  proximate 
principle  of  bone,  but  phosphoric  acid  is  not  so,  since  it  does  not  exist 
as  such  in  the  bony  tissue,  but  is  produced  only  by  the  decomposition 
of  the  calcareous  matter  ;  still  less  phosphorus,  which  is  obtained  only 
by  the  decomposition  of  the  phosphoric  acid. 

Proximate  principles  may,  in  fact,  be  said  to  exist  in  all  solids  or 
fluids  of  mixed  composition,  and  may  be  extracted  from  them  by  the 
same  means  as  in  the  case  of  the  animal  tissues  or  secretions.  Thus,  in 
a  watery  solution  of  sugar,  we  have  two  proximate  principles,  namely: 
first,  the  water,  and  secondly,  the  sugar.  The  water  may  be  separated 
by  evaporation  and  condensation,  after  which  the  sugar  remains  behind, 
in  a  crystalline  form.  These  two  substances  have,  therefore,  been  sim- 
ply separated  from  each  other  by  the  process  of  evaporation.  They 
have  not  been  decomposed,  nor  their  chemical  properties  altered.  On 
the  other  hand,  the  hydrogen  and  oxygen  of  the  water  were  not  proxi- 
mate principles  of  the  original  solution,  and  did  not  exist  in  it  under 
their  own  forms,  but  only  in  a  state  of  combination;  forming,  in  this 
condition,  a  fluid  substance  (water),  endowed  with  sensible  properties 
entirely  different  from  theirs.  If  we  wish  to  ascertain,  accordingly,  the 
nature  and  properties  of  a  saccharine  solution,  it  will  afford  us  but 
little  satisfaction  to  extract  its  ultimate  chemical  elements;  for  its 
nature  and  properties  depend  not  so  much  on  the  presence  in  it  of  the 
ultimate  elements,  oxygen,  hydrogen,  and  carbon,  as  on  the  particular 
forms  of  combination,  namely,  water  and  sugar,  under  which  they  are 
present. 

It  is  very  essential,  therefore,  that  in  extracting  the  proximate  prin- 
ciples from  the  animal  body,  only  such  means  should  be  adopted  as  will 
isolate  the  substances  already  existing  in  the  tissues  and  fluids,  without 
decomposing  them,  or  altering  their  nature.  A  neglect  of  this  rule 
would  lead  to  erroneous  results  in  the  pursuit  of  physiological  chemis- 
try; for  by  subjecting  the  animal  tissues  to  the  action  of  acids  and 
alkalies,  of  prolonged  boiling,  or  of  too  intense  heat,  we  might  obtain, 
at  the  end  of  the  analysis,  substances  which  would  not  be,  properly 
speaking,  proximate  principles,  but  only  the  remains  of  an  altered  and 
disorganized  material.  Thus,  the  fibrous  tissues,  if  boiled  steadily  for 
thirty-six  hours,  dissolve,  for  the  most  part,  at  the  end  of  that  time, 
in  the  boiling  water;  and  on  cooling  the  whole  solution  solidifies  into  a 
homogeneous,  jelly-like  substance,  which  has  received  the  name  of 
gelatine.  But  this  gelatine  does  not  really  exist  in  the  body  as  a 


36  PROXIMATE    PRINCIPLES    IN    GENERAL. 

proximate  principle,  since  the  fibrous  tissue  which  produces  it  is  not  at 
first  soluble,  even  in  boiling  water,  and  its  ingredients  become  altered 
and  converted  into  a  gelatinous  matter  only  by  prolonged  ebullition. 
So,  again,  an  animal  substance  containing  the  alkaline  acetates  or  lac- 
tates  will,  upon  incineration  in  the  air,  yield  carbonates  of  the  same 
bases,  the  original  acid  having  been  destroyed,  and  replaced  by  car- 
bonic acid.  In  either  case,  the  analysis  of  the  tissue,  so  conducted, 
would  be  a  deceptive  one,  and  useless  for  anatomical  and  physiological 
purposes,  because  its  real  ingredients  have  been  decomposed,  and  re- 
placed by  others,  in  the  process  of  manipulation. 

It  should,  therefore,  be  kept  constantly  in  view,  in  the  examination 
of  an  animal  tissue  or  fluid,  that  the  object  of  the  operation  is  simply 
the  separation  of  its  ingredients  from  each  other,  and  not  their  decom- 
position or  ultimate  analysis.  Only  the  simplest  forms  of  chemical 
manipulation,  if  possible,  should  be  employed.  The  substance  to  be 
examined  should  first  be  subjected  to  evaporation,  in  order  to  extract 
and  estimate  its  water.  This  evaporation  must  be  conducted  at  a  heat 
not  above  100°  (212°  p.),  since  a  higher  temperature  would  destroy  or 
alter  some  of  the  animal  ingredients.  Then,  from  the  dried  residue, 
sodium  chloride,  alkaline  sulphates,  carbonates,  and  phosphates  may  be 
extracted  with  water.  Coloring  matters  may  be  separated  by  alcohol, 
and  oils  may  be  dissolved  out  by  ether.  When  a  chemical  decomposi- 
tion is  unavoidable,  it  must  be  kept  in  sight  and  afterward  corrected. 
Thus  the  sodium  glyko-cholate  of  the  bile  is  separated  from  certain 
other  ingredients  by  precipitating  it  with  plumbic  acetate,  forming  lead 
glyko-cholate;  but  this  is  afterwards  decomposed,  in  its  turn,  by  sodium 
carbonate,  reproducing  the  original  sodium  glyko-cholate.  Sometimes 
it  is  impossible  to  extract  a  proximate  principle  in  an  entirely  unaltered 
form.  Thus  the  fibrine  of  the  blood  can  be  separated  only  by  allowing 
it  to  coagulate ;  and  once  coagulated,  it  is  permanently  altered,  and  no 
longer  presents  its  original  characters  as  an  ingredient  of  the  blood. 
•In  such  instances  as  this,  we  can  only  make  allowance  for  an  unavoid- 
able difficulty,  and  endeavor  by  other  means  to  ascertain  under  what 
form  the  substance  originally  existed  in  the  animal  fluids,  being  careful 
that  the  substance  suffers  no  further  alteration.  By  bearing  in  mind 
the  above  considerations,  we  may  form  a  tolerably  correct  estimate  of 
the  nature  and  quantity  of  all  the  proximate  principles  in  the  tissue  or 
fluid  under  examination. 

The  manner  in  which  the  proximate  principles  are  associated  to- 
gether is  also  deserving  of  notice.  In  every  animal  solid  and  fluid, 
there  is  a  considerable  number  of  proximate  principles  which  are 
present  in  certain  proportions,  and  which  are  so  united  with  each  other 
that  the  mixture  presents  a  homogeneous  appearance.  But  this  union 
is  of  a  complicated  character ;  and  the  presence  of  each  ingredient  de- 
pends, to  a  certain  extent,  upon  that  of  the  others.  Some-  of  them, 
such  as  the  alkaline  carbonates  and  phosphates,  are  in  solution  directly 
in  the  water.  Some,  which  are  insoluble  in  water,  are  retained  in  solu- 


PROXIMATE    PRINCIPLES    IN    GENERAL.  37 

tion  by  the  presence  of  other  soluble  substances.  Thus,  the  insoluble 
lime  phosphate  of  the  urine  is  held  in  solution  by  the  acid  reaction  of 
the  sodium  biphosphate,  which  is  also  present  as  an  ingredient.  In  the 
alkaline  blood-plasma,  on  the  other  hand,  the  lime  phosphate  is  lique- 
fied by  union  with  the  albumen,  which  is  itself  soluble  in  the  water  of 
the  plasma.  The  same  substance  may  be  fluid  in  one  part  of  the  body, 
and  solid  in  another  part.  Thus  in  the  blood  and  secretions  the  water 
is  fluid,  and  holds  in  solution  other  substances,  both  animal  and  mine- 
ral, while  in  the,  bones  and  cartilages  it  is  solid — not  crystallized,  as  in 
ice,  but  amorphous  and  solid,  by  the  fact  of  its  intimate  union  with  the 
animal  and  saline  ingredients,  which  are  abundant  in  quantity,  and 
which  are  themselves  present  in  the  solid  form.  Again,  the  lime  phos- 
phate of  the  blood  is  fluid  by  solution  in  the  albumen;  but  in  the  bones 
it  forms  a  solid  substance  with  the  animal  matter  of  the  osseous  tissue ; 
and  yet  the  union  of  the  two  is  as  intimate  and  homogeneous  in  the 
bones  as  in  the  blood.  A  proximate  principle,  therefore,  never  exists 
alone  in  any  part  of  the  body,  but  is  always  intimately  associated  with 
a  number  of  others,  by  a  kind  of  homogeneous  mixture  or  mutual  solu- 
tion. 

Every  animal  tissue  and  fluid  contains  a  number  of  proximate  prin- 
ciples which  are  present,  as  we  have  already  mentioned,  in  certain 
characteristic  proportions.  Thus,  water  is  present  in  very  large  quan- 
tity in  the  perspiration  and  the  saliva,  but  in  very  small  quantity  in 
the  bones  and  teeth.  Sodium  chloride  is  comparatively  abundant  in 
the  blood  and  deficient  in  the  muscles.  On  the  other  hand,  potassium 
chloride  is  more  abundant  in  the  muscles,  less  so  in  the  blood.  But 
these  proportions  are  nowhere  absolute  or  invariable.  There  is  a  great 
difference,  in  this  respect,  between  the  chemical  composition  of  an  inor- 
ganic substance  and  the  physiological  constitution  of  an  animal  fluid. 
The  former  is  always  constant  and  definite ;  the  latter  always  presents 
certain  variations.  Thus,  water  is  always  composed  of  exactly  the 
same  relative  quantities  of  hydrogen  and  oxygen ;  and  if  these  propor- 
tions be  altered  in  the  least,  it  thereby  ceases  to  be  water,  and  is  con- 
verted into  some  other  substance.  But  in  the  urine,  the  proportions 
of  water,  urea,  urates,  phosphates,  etc.,  vary  within  certain  limits  in 
different  individuals,  and  even  in  the  same  individual,  from  one  hour 
to  another.  This  variation,  which  is  almost  constantly  taking  place, 
within  the  limits  of  health,  is  presented  by  all  the  animal  solids  and 
fluids.  It  is  even  a  necessary  accompaniment  of  the  actions  of  life,  and 
one  of  the  characteristic  phenomena  of  living  beings.  For  all  parts  of 
the  body  are  composed  of  different  ingredients  which  are  supplied  by 
absorption  or  formed  in  the  interior,  and  which  are  constantly  given 
up  again,  under  the  same  or  different  forms,  to  the  surrounding  media 
by  the  unceasing  activity  of  the  vital  processes.  Every  variation,  then, 
in  the  general  condition  of  the  body,  as  a  whole,  is  accompanied  by  a 
corresponding  variation,  more  or  less  pronounced,  in  the  constitution 
of  its  different  parts.  This  constitution  is  consequently  of  a  very  dif- 


38  PROXIMATE    PRINCIPLES    IN    GENERAL. 

ferent  character  from  the  chemical  constitution  of  an  oxide  or  a  salt. 
Whenever,  therefore,  we  meet  with  the  analysis  of  an  animal  fluid,  in 
which  the  relative  quantity  of  its  different  ingredients  is  expressed  in 
numbers,  we  must  understand  that  such  an  analysis  is  always  approxi- 
mative, and  not  absolute. 

The   proximate   principles  are  naturally  divided  into  five  different 


The  first  of  these  classes  comprises  all  the  proximate  principles  which 
are  purely  INORGANIC  in  their  nature.  These  principles  are  derived 
mostly  from  the  exterior.  They  are  found  everywhere,  in  the  inorganic 
world  as  well  as  in  organized  bodies ;  and  they  present  themselves  under 
the  same  forms  and  with  the  same  properties  in  the  interior  of  the 
animal  frame  as  elsewhere.  They  are  crystallizable,  and  they  present 
very  definite  chemical  characters  and  have  a  comparatively  simple  chemi- 
cal constitution.  They  are  compounds,  in  simple  proportions,  of  the 
ultimate  chemical  elements,  hydrogen  and  oxygen,  the  metals  of  the 
alkaline  and  earthy  salts,  sulphur,  phosphorus,  chlorine,  and,  in  general 
terms,  of  the  ingredients  of  mineral  substances.  They  comprise  water, 
which  is  the  most  abundant  of  its  class  in  the  animal  frame,  sodium 
and  potassium  chlorides,  phosphates,  and  sulphates,  alkaline  carbonates, 
the  salts  of  lime  and  magnesia,  together  with  combinations  of  a  few 
other  of  the  metallic  elements  in  minute  quantity. 

The  second  class  of  proximate  principles  consists  of  the  HYDROCAR- 
BONACEOUS  SUBSTANCES  of  organic  origin.  They  are  distinguished  from 
inorganic  matters  first  by  the  fact  of  their  containing  carbon  in  large 
proportion  as  one  of  their  immediate  constituents,  associated  always 
with  hydrogen  and  oxygen,  but  with  no  other  chemical  element.  They 
are  always  either  crystallizable,  or  else  readily  convertible  into  other 
crystallizable  members  of  the  same  group.  Their  chemical  composition 
is  less  simple  than  that  of  inorganic  substances,  but  it  is  still  sufficiently 
definite,  and  their  chemical  characters  are  well  marked  and  easily  recog- 
nizable. They  first  make  their  appearance  in  the  interior  of  organized 
bodies,  and  are  not  found  in  the  inorganic  world,  excepting  as  the 
remains  or  products  of  animal  or  vegetable  life.  To  this  group  belong 
the  several  varieties  of  starch,  sugar,  and  oil. 

The  third  class  comprises  the  ALBUMINOUS,  or  nitrogenized  proximate 
principles.  These  substances  derive  their  name  from  the  albumen  or 
white  of  egg,  which  was  one  of  the  earliest  to  be  studied,  and  which 
was  long  considered  as  a  kind  of  representative  of  the  whole  class. 
They  differ  from  the  substances  of  the  two  preceding  groups,  especially 
in  the  fact  that  they  contain  nitrogen  as  an  ingredient,  in  addition  to 
the  three  elements  of  the  hydrocarbonaceous  matters.  They  are  exclu- 
sively of  organic  origin,  appearing  only  as  ingredients  of  the  living  bod}T. 
Their  chemical  constitution,  furthermore,  is  a  complicated  one — that  is, 
their  four  elements  are  united  with  each  other  in  such  a  way  as  to  form 
compounds  of  a  very  high  atomic  weight.  Their  chemical  characters 


PROXIMATE    PRINCIPLES    IN    GENERAL.  39 

are  not  well  defined,  as  compared  with  those  of  inorganic  substances, 
and  their  most  striking  properties  are  not  such  as  can  be  accounted 
for  by  ordinary  chemical  reactions  or  expressed  in  the  usual  chemical 
phraseology.  Nevertheless,  they  are  of  the  first  importance  as  ingredi- 
ents of  the  organized  frame,  since  they  form  a  large  proportion  of  its 
mass,  and  contribute,  by  their  peculiar  properties,  to  its  most  essential 
and  characteristic  active  phenomena.  They  include  such  substances  as 
albumen,  fibrine,  caseine,  and  myosine. 

The  fourth  class  is  formed  by  the  COLORING  MATTERS.  These  sub- 
stances, upon  which  the  different  tints  of  the  solids  and  fluids  depend, 
are  present,  for  the  most  part,  in  small  quantity,  the  most  abundant 
being  the  red  coloring  matter  of  the  blood. 

Lastly,  in  the  fifth  class  are  comprised  a  group  of  CRYSTALLIZABLE 
NITROGENOUS  MATTERS,  many,  if  not  all,  of  which  are  derived  from  the 
physiological  metamorphosis  of  albuminous  principles.  They  are  found 
in  some  of  the  solid  tissues,  as  the  brain  and  nerves,  in  the  secretions 
of  the  liver,  and  especially  in  the  urine,  where  they  represent  the  pro- 
ducts of  excretion. 


CHAPTEE    II. 

INORGANIC   PROXIMATE    PRINCIPLES. 

THE  inorganic  substances  are  present  in  the  animal  body  in  great 
variety.  Some  of  them,  such  as  water  arid  the  salts  of  lime,  constitute 
also  a  large  proportion  of  the  mass  of  the  tissues  and  fluids  in  which 
they  are  found ;  others  present  themselves  in  comparatively  small 
quantity.  Some  of  them  are  found  universally  in  all  regions  of  the 
body,  while  others  are  met  with  only  in  particular  tissues  or  fluids ;  but 
there  are  hardly  any  which  do  not  appear  at  the  same  time  as  con- 
stituents of  several  different  parts.  As  their  name  indicates,  these 
substances  are  met  with  extensively  in  the  inorganic  world,  and  form  a 
large  part  of  the  crust  of  the  earth.  Notwithstanding,  however,  their 
inorganic  nature,  they  are  also  essential  constituents  of  the  animal 
frame.  They  are  accordingly  necessary  ingredients  of  the  food  and 
drink,  and  no  regimen  would  be  capable  of  supporting  life  indefinitely 
which  did  not  contain  these  materials  in  due  proportion. 

The  group  of  inorganic  proximate  principles  includes  the  following 
substances : — 

Water  ;  Potassium  phosphate  ; 

Sodium  chloride  ;  Potassium  sulphate  ; 

Sodium  phosphate ;  Potassium  carbonate  ; 

Sodium  biphosphate  ;  Lime  phosphate  ; 

Sodium  sulphate ;  Lime  carbonate  ; 

Sodium  carbonate  ;  Magnesium  phosphate  ; 

Potassium  chloride ;  Magnesium  carbonate. 

Beside  the  above-named  proximate  principles  there  are  found,  as 
constant  ingredients  of  the  incombustible  residue  of  various  parts  of 
the  human  body,  iron,  silica,  and  fluorine  ;  but  it  is  not  certainly  known 
in  what  form  of  combination  these  substances  originally  existed  in  the 
animal  solids  and  fluids.  Sometimes,  but  not  always,  there  are  indica- 
tions of  the  presence,  in  minute  quantity,  of  copper,  manganese,  and 
lead,  also  in  some  unknown  forms  of  combination. 

The  most  important  of  the  inorganic  proximate  principles,  considered 
in  regard  to  their  quantity  or  the  part  which  they  play  in  the  vital 
actions,  are  the  following : — 

1.  Water,  H20. 

Water  is  universally  present  in  all  the  tissues  and  fluids  of  the  body. 
It  is  abundant  in  the  blood  and  secretions,  where  its  presence  is  indis- 
(40) 


WATER.  41 

pen  sable  in  order  to  give  them  the  fluidity  which  is  necessary  to  the 
performance  of  their  functions ;  for  it  is  by  the  blood  and  secretions 
that  new  substances  are  introduced  into  the  body,  and  old  ingredients 
discharged.  And  it  is  a  necessary  condition  both  of  the  introduction 
and  discharge  of  substances  naturally  solid,  that  they  assume,  for  the 
time  being,  a  fluid  form ;  water  is  therefore  an  essential  ingredient  of 
the  fluids,  for  it  holds  their  solid  materials  in  solution,  and  enables  them 
to  pass  and  repass  through  the  animal  frame. 

But  water  is  an  ingredient  also  of  the  solids.  For  if  we  take  a  muscle 
or  a  cartilage,  and  expose  it  to  a  gentle  heat  in  dry  air,  it  loses  water 
by  evaporation,  diminishes  in  size  and  weight,  and  becomes  dense  and 
stiff.  Even  the  bones  and  teeth  lose  water  by  evaporation  in  this  way, 
though  in  smaller  quantity.  In  all  these  solid  and  semi-solid  tissues, 
the  water  which  they  contain  is  useful  by  giving  them  the  special  con- 
sistency which  is  characteristic  of  them,  and  which  would  be  lost  without 
it.  Thus  a  tendon,  in  its  natural  condition,  is  white,  glistening,  and 
opaque ;  and  though  very  strong,  perfectly  flexible.  If  its  water  be 
expelled  by  evaporation  it  becomes  yellowish  in  color,  shrivelled,  semi- 
transparent,  inflexible,  and  unfit  for  performing  its  mechanical  functions. 
The  same  thing  is  true  of  the  other  tissues,  such  as  that  of  the  skin,  the 
muscles,  the  cartilages,  and  the  glands. 

The  following  is  a  list,  compiled  by  Robin  and  Yerdeil  from  various 
observers,  showing  the  proportion  of  water  per  thousand  parts,  in  dif- 
ferent solids  and  fluids : — 

QUANTITY  OF  WATER  IN  1000  PARTS  IN 

Teeth       .        .  .  .100  Bile.        .                         .880 

Bones       .         .  .  .130  Milk         .         .         .         .     887 

Cartilage          .  .  .     550  Pancreatic  juice       .         .     900 

Muscles    .         .  .  .750  Urine        .         .         .         .936 

Ligaments        .  .  .     768  Lymph     ....     960 

Brain        ....     789  Gastric  juice     .        .        .     975 

Blood        .         .  .  .795  Perspiration     .         .         .986 

Synovial  fluid  .  .  .     805  Saliva       ....     995 

According  to  the  best  calculations,  water  constitutes,  in  the  human 
subject,  about  seventy  per  cent,  of  the  entire  weight  of  the  body. 

The  water  which  thus  forms  a  part  of  the  animal  frame  is  derived 
mainly  from  without.  It  is  taken  in  the  different  kinds  of  drink,  and 
also  forms  an  abundant  ingredient  in  the  various  articles  of  food.  For 
no  articles  of  food  are  taken  in  an  absolutely  dry  state,  but  all  contain 
a  larger  or  smaller  quantity  of  water,  which  may  readily  be  expelled  by 
evaporation.  The  quantity  of  water,  therefore,  which  is  daily  taken  into 
the  system,  cannot  be  ascertained  in  any  case  by  simply  measuring  the 
quantity  of  drink,  but  its  proportion  in  the  solid  food,  taken  at  the  same 
-time,  must  also  be  determined  by  experiment,  and  this  ascertained 
quantity  added  to  that  which  is  taken  in  with  the  fluids.  By  measuring 
the  quantity  of  fluid  taken  with  the  drink,  and  calculating  in  addition 
4 


42  INORGANIC    PROXIMATE    PRINCIPLES. 

the  proportion  existing  in  the  solid  food,  we  have  found,  in  common 
with  the  results  formerly  obtained  by  Barral,  that,  for  a  healthy  adult 
man,  the  average  quantity  of  water  introduced  into  the  system  is  about 
2000  grammes  per  day. 

There  is  every  reason  to  believe  that  a  certain  quantity  of  water  also 
makes  its  appearance  within  the  body  by  the  liberation  of  its  elements 
from  various  organic  combinations.  This  is  shown  by  the  fact  that  a 
considerable  quantity  of  hydrogen  is  daily  introduced  into  the  system 
as  a  constituent  element  of  the  organic  substances  of  the  food,  while 
only  a  small  part  of  this  quantity  reappears,  under  similar  forms  of 
combination,  in  the  excretions.  The  most  reliable  estimates,  in  this 
respect,  are  as  follows : — 

AVERAGE  DAILY  QUANTITY  OF  HYDROGEN 

Introduced  in  organic  combinations  with  the  food  .  .  .  .40  grammes. 
Discharged  "  "  "  excretions  .  .  .6 

Eesidue  unaccounted  for 34        " 

Thus  not  more  than  fifteen  per  cent,  of  the  quantity  introduced  is 
discharged  in  the  organic  ingredients  of  the  excretions.  But  no  hydro- 
gen is  exhaled  from  the  body  in  a  free  state,  nor  in  notable  quantity  in 
any  other  form  of  inorganic  combination  except  water.  The  surplus 
must,  therefore,  pass  out  as  part  of  the  water  or  watery  vapor  which  is 
constantly  being  discharged  from  various  organs.  The  estimates  given 
above  indicate  that  a  little  over  300  grammes  of  water  are  daily  pro- 
duced in  the  body  in  this  way.  As  we  shall  hereafter  see,  an  important 
class  of  the  organic  ingredients  of  the  food  already  contain  hydrogen 
and  oxygen  in  the  relative  quantities  necessary  to  form  water;  and, 
when  decomposed  in  the  system,  may  readily  yield  these  elements  in  the 
required  proportions. 

Furthermore,  although  it  has  not  yet  been  proved,  in  any  particular 
case,  that  more  water  is  discharged  from  the  system  than  can  be  ac- 
counted for  by  that  introduced,  yet  a  comparison  of  the  average  results 
obtained  by  different  observers,  always  tends  to  show  a  surplus  of  water 
in  the  entire  excretions,  varying  from  200  to  500  grammes  over  and 
above  that  introduced  with  the  food  and  drink.  The  quantity  of  water, 
however,  thus  produced  in  the  body  is  small  in  comparison  with  that 
which  is  introduced  and  discharged  under  its  own  form. 

While  in  the  interior  of  the  living  body,  water  takes  part  in  the  vital 
functions  principally  by  its  physical  properties.  It  is  the  universal 
solvent  for  all  the  ingredients  of  the  animal  fluids,  holding  them  in  solu- 
tion either  by  its  direct  liquefying  power,  or  by  the  aid  of  other  sub- 
stances which  are  themselves  soluble.  It  thus  enables  the  nutritious 
elements  of  the  food  to  find  their  way  into  the  circulating  fluid,  and  to 
penetrate  the  substance  of  the  solid  organs.  It  permeates  the  organized 
membranes  of  the  body  and  brings  into  contact  with  each  other  the  in- 
organic and  organic  materials  of  various  parts,  and  enables  them  to 


LIME    PHOSPHATE.  43 

assume  new  forms  by  their  mutual  reactions.  In  this  way  it  is  subser- 
vient to  all  the  phenomena  of  absorption,  transudation,  exhalation,  and 
even  of  chemical  union  and  decomposition,  which  make  up  the  internal 
nutritive  functions  of  the  animal  frame. 

After  forming  part  of  the  animal  solids  and  fluids,  and  playing  its 
part  in  the  vital  processes  of  the  interior,  the  water  is  again  discharged ; 
for  its  presence  in  the  body,  like  that  of  all  the  other  proximate  princi- 
ples, is  not  permanent,  but  only  temporary.  It  makes  its  exit  from  the 
body  by  four  different  passages :  namely,  in  a  liquid  form  with  the  urine 
and  feces,  and  in  the  form  of  vapor  by  the  lungs  and  skin.  The  actual 
quantity  which  is  expelled  in  each  case  is  not  uniform,  but  varies  accord- 
ing to  circumstances.  Thus,  if  the  kidneys  be  unusually  active,  the 
watery  ingredients  of  the  urine  will  be  temporarily  increased  in  quantity, 
while  the  cutaneous  perspiration  will  be  diminished ;  and  the  state  of 
the  atmosphere  and  the  rapidity  of  respiration  will  influence  for  the 
time  the  amount  of  watery  vapor  exhaled  by  the  lungs  and  skin.  Still 
there  is  a  well-marked  average  relation  between  the  functional  activity 
of  the  various  organs  and  the  daily  quantity  of  their  excreted  fluids.  It 
appears  from  a  comparison  of  the  researches  of  Lavoisier  and  Seguin, 
Valentin,  and  other  observers,  that  the  water  which  is  thus  discharged 
from  the  system  finds  its  way  out  by  these  different  routes  nearly  in  the 
following  proportions : — 

By  exhalation  from  the  lungs 20  per  cent. 

By  the  cutaneous  perspiration        .         ....        30       " 
By  the  urine  and  feces 50       " 

While  only  four  per  cent,  of  the  water  is  expelled  with  the  feces, 
ninety-six  per  cent,  passes  out  by  the  lungs,  the  skin,  and  the  kidneys. 
It  is  evident,  therefore,  that  at  least  the  main  bulk  of  the  water 
taken  in  with  the  food  does  not  simply  pass  through  the  alimentary 
canal,  but  is  taken  up  by  the  mucous  membranes,  enters  the  circulating 
fluid,  and  forms  a  temporary  constituent  of  the  solid  tissues  of  the 
body.  As  it  appears  in  the  secretions  it  also  brings  with  it  various 
ingredients  which  it  has  absorbed  from  the  substance  of  the  glandular 
organs;  and  when  finally  discharged  it  is  mingled  in  the  urine  and  feces 
with  salts  and  excrementitious  matters,  which  it  holds  in  solution,  and 
in  the  cutaneous  and  pulmonary  exhalations,  with  animal  vapors  and 
odoriferous  materials  of  various  kinds.  In  the  perspiration  it  also  con- 
tains mineral  sulphates  and  chlorides,  which  it  leaves  behind  on  evapo- 
ration. 

2.  Lime  Phosphate,  Ca3P408. 

This  substance  exists  as  an  ingredient  of  all  the  animal  solids  and 
fluids  without  exception.  So  far  as  regards  its  mass,  it  is,  next  to 
water,  the  most  important  of  the  inorganic  constituents  of  the  body,  as 
its  entire  quantity  is  far  greater  than  that  of  any  other  of  the  mineral 
salts.  For,  although  it  is  not  especially  abundant  in  the  fluids  and 


44  INORGANIC    PROXIMATE    PRINCIPLES. 

the  softer  tissues,  it  forms  more  than  one-half  the  substance  of  the  bones. 
It  is  estimated  by  Barral,  that  the  osseous  tissues  constitute  6.4  per 
cent,  of  the  entire  mass  of  the  body ;  and  the  lime  phosphate  forms  on 
the  average  from  51  to  58  per  cent,  of  the  substance  of  the  bones.  This 
would  give,  for  a  man  weighing  65  kilogrammes,  or  143  pounds  avoir- 
dupois, 2400  grammes  of  the  calcareous  salt  in  the  whole  body.  Its 
proportion  in  various  tissues  and  fluids  of  the  human  system  is  as 
follows: — 

QUANTITY  OF  LIME  PHOSPHATE  IN  1000  PARTS  IN  THE 

Enamel  of  the  teeth       .       885  Milk  ....      2.72 

Dentine  .         .         .         .643  Blood  ....      0.30 

Bones     .  .        .      576  Bile  ....     0.92 

Cartilages       ...        40  Urine  .         .         .        .0,75 

Notwithstanding,  therefore,  the  large  quantity  of  lime  phosphate  in 
the  body  as  a  whole,  it  is  evident,  from  an  inspection  of  the  preceding 
list,  that  nearly  all  of  it  is  deposited  in  the  more  solid  tissues ;  while  it 
is  present  in  but  slender  proportion  in  the  animal  fluids.  Of  these 
fluids  it  is  the  milk  alone  which  contains  lime  phosphate  in  notable 
quantity,  and  here  it  is  plainly  subservient  to  the  ossification  of  the 
growing  bones  of  the  young  infant,  for  whom  the  milk  is  used  as  food. 
In  the  circulating  fluids,  the  internal  secretions,  and  the  urine,  on  the 
other  hand,  the  calcareous  salt  is  in  small  amount.  Its  importance  in 
the  body  depends  mainly  upon  its  simple  physical  property  of  impart- 
ing rigidity  to  the  solid  tissues,  rather  than  upon  its  active  qualities  in 
the  general  phenomena  of  nutrition. 

In  the  solid  tissues  it  is  associated  with  other  earthy  and  alkaline 
salts,  but  preponderates  largely  over  them  in  amount.  In  the  bones, 
the  quantity  of  lime  phosphate  is  from  5  to  6  times  greater  than  that  of 
all  the  other  mineral  ingredients  taken  together. 

In  the  bones,  teeth,  and  cartilages,  the  lime  phosphate  exists  in  a 
solid  form ;  not,  however,  deposited  mechanically  in  the  osseous  or 
cartilaginous  substance  as  a  granular  powder,  but  intimately  united 
with  the  animal  matter  of  the  tissues,  like  coloring  matter  in  colored 
glass,  the  union  of  the  two  forming  a  homogeneous  material.  It  is  not, 
on  the  other  hand,  so  combined  with  the  animal  matter  as  to  lose  its 
identity  and  constitute  a  new  chemical  substance,  as  where  hydrogen 
combines  with  oxygen  to  form  water ;  but  rather  as  salt  unites  with 
water  in  a  saline  solution,  both  substances  retaining  their  original  charac- 
ter and  composition,  though  so  intimately  associated  that  they  cannot 
be  separated  by  mechanical  means.  The  lime  phosphate,  therefore,  may 
be  extracted  from  a  bone  by  maceration  in  dilute  muriatic  acid,  leaving 
behind  the  animal  substance,  which  still  retains  the  original  form  of  the 
bone  or  cartilage. 

In  all  the  solid  tissues  the  lime  phosphate  is  useful  by  giving  to 
them  their  proper  consistence  and  solidity.  For  example,  in  the  ena- 
mel of  the  teeth,  the  hardest  tissue  of  the  body,  it  predominates  very 


LIME    PHOSPHATE. 


45 


Fig.  1. 


much  over  the  animal  matter,  and  is  present  in  greater  abundance  there 
than  in  any  other  part  of  the  frame.  In  the  dentine,  a  softer  tissue,  it 
is  in  somewhat  smaller  quantity,  and  in  the  bones  smaller  still ;  though 
in  the  bones  it  continues  to  form  more  than  one-half  the  entire  mass 
of  the  osseous  tissue.  The  importance  of  this  substance,  in  com- 
municating to  bones  their  natural  stiffness  and  consistency,  may  be 
readily  shown  by  the  alteration  which  they  suffer  from  its  removal.  If 
a  long  bone  be  macerated  in  dilute  muriatic  acid,  the 
earthy  salt,  as  already  mentioned,  is  dissolved  out, 
after  which  the  bone  loses  its  rigidity,  and  may  be 
bent  or  twisted  in  any  direction  without  breaking. 

(Fig.  1.) 

In  the  formation  of  the  bony  skeleton,  during  foetal 
life,  infancy,  and  childhood,  the  cartilaginous  sub- 
stance previously  existing  is  replaced  by  osseous 
matter,  which  contains  a  larger  proportion  of  calcare- 
ous salts ;  while  the  anatomical  texture  of  the  parts  is 
also  changed,  giving  rise  to  the  characteristic  forms 
of  bony  tissue.  This  progressive  consolidation  of  the 
framework  of  the  body  is  known  as  the  process  of 
"ossification."  In  some  instances  this  process  is 
defective,  owing  to  partial  failure  in  the  powers  of 
assimilation;  and  as  the  rigidity  of  the  skeleton,  ac- 
cordingly, does  not  increase  as  it  should  do  in  propor- 
tion to  the  weight  of  the  body  and  to  muscular  action, 
the  bones  become  gradually  bent  and  deformed,  some- 
times to  an  extraordinary  degree.  This  affection  has 
received  the  name  of  Rachitis. 

A  somewhat  similar  result  is  produced  by  a  morbid 
softening  of  the  bones,  which  sometimes  comes  on  in 
adult  life,  known  as  Osteomalakia.  In  this  disease 
the  bony  fabric,  after  its  formation,  becomes  altered 
in  texture  and  composition ;  and,  the  new  substance  which  takes  its 
place  being  deficient  in  calcareous  matter,  a  progressive  yielding  and 
deformity  of  the  skeleton  takes  place,  like  that  which  happens  in  cases 
of  rachitis. 

In  the  plasma  of  the  blood  the  lime  phosphate,  though  insoluble  in 
simple  alkaline  watery  liquids,  is  held  in  solution  by  its  union  with  the 
albuminous  ingredients.  It  has  been  shown  by  Fokker  that  the  earthy 
phosphates  added  to  white  of  egg  unite  with  the  albuminous  matter  and 
become  soluble  in  considerable  proportion.  This  explains  the  presence 
of  lime  phosphate  in  a  liquid  form  both  in  the  blood  and  in  the  milk, 
both  fluids  which  have  an  alkaline  reaction.  In  the  urine,  on  the  other 
hand,  it  is  held  in  solution  by  the  presence  of  the  acid  sodium  biphos- 
phate.  Accordingly,  whenever  the  urine  is  rendered  alkaline  by  the 
addition  of  soda  or  potassa,  the  earthy  phosphates  are  precipitated  in 
the  form  of  a  white  turbidity. 


FIBULA  TIED 
IN  A  KNOT,  after 
maceration  in  a  di- 
lute acid.  (From  a 
specimen  in  the  mu- 
seum of  the  College 
of  Physicians  and 
Surgeons.) 


4(5  INOKGANIC    PKOXIMATE    PRINCIPLES. 

The  source  of  the  lime  phosphate  of  the  animal  solids  and  fluids  is  in 
the  food.  This  substance  exists  in  nearly  every  animal  and  vegetable 
alimentary  matter  in  common  use.  It  is  found  not  only  in  muscular 
flesh,  eggs,  and  milk,  and  in  all  the  cereal  grains,  as  wheat,  rye,  oats, 
barley,  maize,  and  rice,  but  also  in  peas  and  beans,  the  nutritive  tubers 
and  roots,  as  potatoes,  beets,  turnips,  and  carrots,  and  even  in  the 
juicy  fruits,  such  as  the  apple,  pear,  plum,  and  cherry. 

After  forming  for  a  time  a  constituent  part  of  the  body,  the  lime 
phosphate  is  again  discharged  with  the  excretions,  but  very  slowly  and 
in  small  amount.  According  to  the  observations  of  Neubauer  and 
Beneke  about  0.4  gramme,  on  the  average,  is  daily  expelled  with  the 
urine.  A  slightly  larger  quantity  is  also  found  in  the  feces,  but  this 
may  be  only  the  residue  derived  from  the  undigested  portion  of  the  food. 
Only  traces  of  it  are  to  be  detected  in  the  perspiration.  As  so  large  a 
quantity  of  this  salt,  therefore,  is  contained  in  the  body,  while  so  small 
a  proportion  is  expelled  daily  with  the  excretions,  it  is  evidently  to  be 
regarded  as  one  of  the  more  permanent  constituents  of  the  frame ;  being 
comparatively  inactive  in  the  process  of  internal  metamorphosis,  and 
serving  for  the  most  part  as  a  physical  ingredient  of  the  solid  tissues. 

3.  Lime  Carbonate,  CaC03. 

Lime  carbonate  is  to  be  found  in  the  bones,  the  teeth,  the  blood,  the 
lymph  and  chyle,  the  saliva,  and  sometimes  in  the  urine.  In  all  these 
situations  it  is  normally  in  much  smaller  proportion  than  the  calcareous 
phosphate  with  which  it  is  associated.  In  the  bones,  however,  it  is  next 
in  importance  to  the  lime  phosphate,  being  on  the  average  one-seventh 
as  abundant  as  that  salt,  and  much  more  so  than  any  of  the  remaining 
mineral  ingredients.  In  the  animal  fluids  its  solubility  is  accounted  for 
by  the  presence  of  the  alkaline  chlorides  or  by  that  of  free  carbonic  acid. 

4.  Magnesium  Phosphate,  MgHP04. 

Magnesium  phosphate  was  formerly  associated  with  the  corresponding 
lime  salt  under  the  name  of  the  earthy  phosphates,  owing  to  certain 
resemblances  in  their  chemical  relations.  Like  the  lime  phosphate,  which 
it  everywhere  accompanies,  it  is  present  in  all  the  tissues  and  fluids  of 
the  body,  though  this  substance  is  for  the  most  part  in  the  smaller 
quantity  of  the  two.  Thus  in  the  bones  the  lime  phosphate  is  in  the 
proportion  of  516  parts  per  thousand,  while  the  magnesium  phosphate 
forms  only  12.5  parts.  In  the  blood  the  calcareous  salt  amounts  to  0.30 
part  per  thousand,  the  magnesium  salt  to  0.22  part ;  and  in  the  milk 
there  are  2.72  parts  of  lime  phosphate  to  0.53  part  of  magnesium  phos- 
phate. On  the  other  hand,  the  salts  of  magnesium  have  been  found  to 
be  in  larger  quantity  than  those  of  lime  in  the  muscles,  and  nearly  twice 
as  abundant  in  the  substance  of  the  brain. 

The  magnesium  phosphate  is  discharged,  by  the  urine,  in  the  average 
daily  quantity  of  0.6  gramme.  The  average  amount  of  both  the  earthy 


SODIUM    CHLORIDE.  47 

phosphates,  taken  together,  is  accordingly  about  1  gramme  per  da}^ ; 
the  magnesian  salt  being  rather  the  more  abundant  of  the  two. 

Both  the  magnesium  phosphate  and  carbonate,  of  which  latter  salt 
traces  occur  in  the  blood,  appear  to  have  similar  physiological  relations 
with  the  corresponding  salts  of  lime,  and  almost  the  same  things  may  be 
said  in  regard  to  their  union  with  the  substance  of  the  more  solid  tissues 
and  their  mode  of  solubility  in  the  animal  fluids. 

5,  Sodium  Chloride,  NaCl. 

This  is  undoubtedly  the  most  important  of  the  mineral  constituents 
of  the  body,  so  far  as  regards  its  general  distribution  and  the  active  part 
which  it  takes  in  the  internal  phenomena  of  nutrition.  It  is  the  most 
abundant  of  all,  next  to  the  lime  phosphate,  and  it  is  universally  pre- 
sent in  all  the  animal  tissues  and  fluids.  Its  entire  quantity  in  the 
human  body  is  estimated  by  Dr.  Lankester  at  110  grammes,  or  nearly 
one-quarter  of  a  pound  avoirdupois.  In  the  blood  it  is  rather  more 
abundant  than  all  the  other  mineral  ingredients  taken  together.  Its 
proportion  in  the  various  parts  of  the  body  is  as  follows : — 

QUANTITY  OF  SODIUM  CHLORIDE  IN  1000  PARTS  IN  THE 

Bones       ....     7.02  Saliva      ....  1.53 

Blood      ....     3.36  Milk        ....  0.30 

Bile         ....     3.18  Lymph     ....  5.00 

Gastric  juice  .        .        .     1.70  Sebaceous  matter    .  *      .  5.00 

Perspiration    .         .         .     2.23  Urine       ....  5.50 

One  of  the  most  important  characters  of  this  suit  in  the  living  body 
is  undoubted!}'  its  property  of  regulating  the  phenomena  of  endosmosis 
and  exosmosis,  or  the  transudation  of  nutritive  fluids  through  the  organic 
membranes.  This  property  is  shared  more  or  less  by  the  other  mineral 
ingredients  of  the  blood,  but  is  more  important  in  the  case  of  sodium 
chloride,  owing  to  its  preponderance  in  quantity  as  compared  with  the  rest. 

Since  this  substance  is  present  in  all  parts  of  the  body,  it  is  also  an 
important  ingredient  of  the  food.  It  occurs,  of  course,  in  all  animal 
food,  as  a  natural  ingredient  of  the  corresponding  tissues.  In  muscular 
flesh,  however,  it  is  very  much  less  abundant  than  potassium  chloride, 
while,  on  the  other  hand,  it  is  more  abundant  in  the  blood.  It  is  present 
also  in  various  articles  of  vegetable  food. 

According  to  Boussingault,  it  exists  in  the  following  proportions  in 
certain  vegetable  substances: — 

PROPORTION  OF  SODIUM  CHLORIDE  IN  1000  PARTS  IN 

Potatoes          .        .        .     0.43  Oats        ....  0.11 

Beets       ....     0.66  Peas        ....  0.09 

Turnips   ....     0.28  Beans      ....  0.06 

Cabbage          .         .         .     0.40  Meadow  hay   .         .         .  3.28 

The  relative  quantity  of  sodium  chloride  taken  in  animal  and  vegetable 
food  has  not  been  determined.  In  regard  to  the  demand  for  this  salt, 


48  INORGANIC    PROXIMATE    PRINCIPLES. 

however,  there  is  a  striking  difference  between  the  carnivorous  and 
many  herbivorous  animals.  The  carnivora  receive  a  fully  sufficient 
supply  with  their  natural  food,  and  invariably  show  a  repugnance  to 
salt  itself,  as  well  as  to  salted  meats.  On  the  other  hand,  the  horse, 
and  more  especially  the  ruminating  animals,  have  an  instinctive  desire 
for  salt,  and  greedily  devour  it,  wh.en  offered  to  them,  in  addition  to 
that  naturally  contained  in  the  vegetable  matters  of  their  food.  It  is 
well  known  with  what  avidity  the  cattle,  sheep,  and  all  kinds  of  deer 
frequent  the  saline  springs  or  "  salt  licks"  of  the  United  States ;  and  it 
is  shown  by  common  experience  that  a  liberal  supply  of  salt  is  important 
for  the  healthy  nutrition  and  development  of  these  animals  in  the 
domesticated  condition. 

The  same  fact  has  been  demonstrated  in  a  more  exact  manner  by  the 
experiments  of  Boussingault  on  the  ox.1  This  observer  made  a  series 
of  comparative  investigations  upon  the  growth  of  two  sets  of  bullocks 
selected  from  animals  of  the  same  age  and  vigor,  and  supplied  equally 
with  an  abundance  of  ordinary  nutritious  food,  those  of  one  set,  how- 
ever, receiving  in  addition  each  34  grammes  of  salt  per  day.  At  the 
end  of  six  months  the  difference  in  the  aspect  of  the  animals  of  the  two 
sets  began  to  be  distinctly  evident,  and  became  more  marked  as  time 
went  on.  The  experiment  lasted  for  a  year,  and  at  the  end  of  that  time 
both  sets  of  animals  had  on  the  average  equally  increased  in  weight ; 
but  those  fed  with  ordinary  food  alone  presented  a  rough  and  tangled 
hide  and  a  dull,  inexcitable  disposition,  while  in  those  which  had  re- 
ceived the  additional  ration  of  salt  the  hide  was  smooth  and  glistening 
and  the  general  appearance  was  vigorous  and  animated.  While  these 
animals,  therefore,  may  subsist  for  a  time  without  inconvenience  upon 
the  salt  naturally  contained  in  their  food,  an  additional  quantity  is 
required  to  maintain  the  system  in  good  condition  for  an  indefinite 
period. 

There  is  a  similar  necessity  for  salt  as  an  addition  to  the  food  of  the 
human  species.  No  other  substance  is  so  universally  used  as  a  condi- 
ment by  all  races  and  conditions  of  men.  This  custom  does  not  depend 
simply  on  a  fancy  for  gratifying  the  palate,  but  is  based  upon  an  in- 
stinctive demand  of  the  system  for  a  substance  which  is  necessarj^  for 
the  full  performance  of  its  functions.  Beside  its  other  properties,  it  no 
doubt  acts  in  a  favorable  manner  by  exciting  the  digestive  fluids,  and 
assisting  in  this  way  the  solution  of  the  food.  For  food  which  is  taste- 
less, however  nutritious  it  may  be  in  other  respects,  is  taken  with 
reluctance  and  digested  with  difficulty ;  while  the  attractive  flavor  which 
is  developed  by  cooking,  and  by  the  addition  of  salt  and  other  condiments 
in  proper  proportion,  excites  the  secretion  of  the  saliva  and  gastric  juice, 
and  facilitates  consequently  the  whole  process  of  digestion.  The  sodium 
chloride  is  then  taken  up  by  absorption  from  the  intestine,  and  is  de- 
posited in  various  quantities  m  different  parts  of  the  body. 

1  Cliimie  Agricole.     Paris,  1854,  p.  251. 


SODIUM    AND    POTASSIUM    PHOSPHATES.  49 

Notwithstanding  various  surmises  which  have  been  presented  from 
time  to  time  with  regard  to  its  possible  decomposition  and  the  re-com- 
bination of  its  elements  in  the  body,  we  have  no  certain  knowledge  of 
such  changes  taking  place  in  the  sodium  chloride  while  forming  a  con- 
stituent of  the  animal  frame.  It  passes  from  the  alimentary  canal  to 
the  blood,  from  the  blood  to  the  tissues,  and  is  finally  discharged  with 
the  urine,  mucus,  and  cutaneous  perspiration,  in  solution  in  the  water 
of  these  fluids.  Under  ordinary  circumstances,  by  far  the  largest  pro- 
portion passes  out  by  the  kidneys.  The  quantity  of  sodium  chloride 
thus  discharged  with  the  excretions  by  an  adult  man  is  about  15 
grammes  per  day  j1  of  which  13  grammes  are  contained  in  the  urine,  and 
2  grammes  in  the  perspiration.  Thus,  of  all  the  sodium  chloride  con- 
tained in  the  body,  considerably  more  than  ten  per  cent,  passes  through 
the  system  in  twenty-four  hours.  This  fact  plainly  indicates  the  activity 
and  importance  of  this  salt  in  the  daily  internal  changes  of  nutrition. 

6,  Potassium  Chloride,  KC1. 

This  substance  is  found  in  very  many  if  not  all  of  the  animal  tissues 
and  fluids,  accompanying  the  sodium  chloride,  many  of  the  properties 
of  which  it  shares,  and  with  which  it  is  closely  related  in  its  physiological 
characters.  It  is  especially  abundant,  as  compared  with  the  sodium 
chloride,  in  the  muscles  and  in  the  milk,  less  so  in  the  blood,  the  gastric 
juice,  the  urine,  and  the  perspiration.  Both  salts  are  neutral  in  reaction, 
and  are  retained  in  the  liquid  form  in  the  blood  and  secretions  by  solution 
in  the  water  of  these  fluids.  The  potassium  chloride  is  introduced  as 
an  ingredient  of  both  animal  and  vegetable  food,  and  is  discharged  with 
the  mucus,  the  urine,  and  the  perspiration. 

7.  Sodium  and  Potassium  Phosphates,  Na2HP04  and  K2HP04. 

These  substances,  associated  under  the  name  of  the  alkaline  phos- 
phates, are  of  the  greatest  importance  as  ingredients  of  the  animal  body. 
They  exist  universally  in  all  its  solids  and  fluids,  and  in  the  latter  are 
present  in  the  liquid  form  by  means  of  their  ready  solubility  in  water. 
No  doubt  they  are  useful  in  a  variety  of  ways,  but  at  least  one  of  their 
most  important  characters  is  their  property  of  exhibiting  an  alkaline 
reaction.  This  reaction  is  essential  to  a  large  number  of  the  vital  pro- 
cesses taking  place  in  the  interior,  and  is  present,  without  exception,  in 
all  the  animal  fluids  which  are  actually  contained  in  the  circulatory 
system,  or  in  the  closed  cavities  of  the  body.  An  acid  reaction,  on  the 
other  hand,  is  found  only  in  a  very  few  of  the  organic  fluids  which  are 
either  employed  in  the  process  of  digestion  or  are  discharged  externally. 

The  following  list  shows  the  comparative  frequency  of  alkaline  and 
acid  reactions  in  the  animal  fluids  : — 

1  Neubauer  und  Vogel-,  Analyse  des  Hams,  Wiesbaden,  1872,  p.  54.  Beneke, 
Pathologic  des  Stoffwechsels,  Berlin,  1874,  p.  322. 


50  INORGANIC    PROXIMATE    PRINCIPLES. 

FLUIDS  WITH  AN  ALKALINE  REACTION.          FLUIDS  WITH  AN  ACID  REACTION. 

1.  Blood-plasma.  1.  Gastric  juice. 

2.  Lymph.  2.  Perspiration. 

3.  Aqueous  humor.  3.  Mucus  of  the  vagina. 

4.  Cephalo-rachidian  fluid.  4.  Urine. 

5.  Pericardial  fluid. 

6.  Synovia. 

7.  Fluids   of  the   living   muscular 

tissue. 

8.  Mucus  in  general. 

9.  Milk. 

10.  Spermatic  fluid. 

11.  Tears. 

12.  Saliva. 

13.  Pancreatic  juice. 

14.  Intestinal  juice. 

If  we  take  into  account  the  carbonic  acid  exhaled  with  the  breath, 
we  see  therefore  that,  while  in  general  an  alkaline  condition  is  charac- 
teristic of  the  internal  fluids,  the  products  of  excretion,  on  the  contrary, 
present  universally  an  acid  reaction. 

Of  all  the  internal  fluids  the  most  essential  is  the  plasma  of  the  blood, 
since  it  affords  the  materials  of  nutrition  to  the  entire  system  ;  and  its 
alkaline  reaction,  which  is  distinctly  marked,  has  been  found  to  be  in- 
variably present,  not  only  in  the  human  subject,  but  also  in  every  species 
of  animal  in  which  it  has  been  examined.  This  reaction  of  the  blood  is 
moreover  necessary  to  life,  since  Bernard  has  shown1  that  if  an  injection 
of  dilute  acetic  or  lactic  acid  be  made  into  the  veins  of  the  living  animal 
death  always  results  before  the  point  of  neutralization  has  been  reached. 

The  alkaline  reaction  of  the  blood-plasma  gives  to  this  fluid  its  extra- 
ordinary capacity  for  dissolving  carbonic  acid.  According  to  Liebig, 
water  which  holds  in  solution  one  per  cent,  of  sodium  phosphate  is 
enabled  to  absorb  and  retain  twice  its  usual  proportion  of  carbonic  acid; 
and  the  other  alkaline  salts,  as  is  well  known,  have  a  similar  dissolving 
action  upon  this  gas.  Consequently  the  blood  as  it  circulates  among 
the  tissues  rapidly  absorbs  from  them  the  carbonic  acid  which  has  been 
formed  in  their  substance,  and  incessantly  carries  it  away  to  be  elimi- 
nated by  the  lungs.  This  important  property  of  the  circulating  fluid 
depends  upon  its  alkaline  reaction. 

The  alkalescence  of  the  blood  is  due  in  great  measure  to  the  alkaline 
phosphates,  which  are  present  in  human  blood  in  the  proportion  of  0.6 T 
per  thousand  parts.  A  peculiar  relation,  however,  exists  in  this  respect, 
for  different  classes  of  animals,  between  the  alkaline  phosphates  and  the 
alkaline  carbonates,  which  are  to  be  mentioned  hereafter.  Both  these 
groups  of  salts  have,  when  in  solution,  an  alkaline  reaction ;  and  both 
contribute  to  the  alkalescence  of  the  blood  in  man  and  animals.  But  in 
the  carnivorous  animals  it  is  the  phosphates  which  preponderate,  while 

1  Liquides  de  1'Organisme.     Paris,  1859,  tome  i.  p.  412. 


SODIUM    AND    POTASSIUM    CARBONATES.  51 

in  the  herbivora  the  carbonates  are  the  more  abundant  of  the  two.  In 
animals  fed  at  the  same  time  upon  both  animal  and  vegetable  food  the 
two  kinds  of  salts  are  found  to  be  present  in  nearly  equal  proportion, 
and  in  the  same  animal  either  the  phosphates  or  the  carbonates  may 
be  made  to  predominate  by  increasing  the  relative  quantity  of  animal 
or  vegetable  food  respectively.  This  is  readily  understood  when  we 
remember  that  muscular  flesh  and  the  animal  tissues  generally  are  com- 
paratively abundant  in  phosphates,  while  vegetable  matters,  as  we  shall 
hereafter  see,  abound  also  in  salts  of  the  organic  acids,  which  give 
rise  by  their  decomposition  in  the  system  to  carbonates  of  the  same 
bases. 

The  alkaline  phosphates  are  taken  in  with  the  food,  as  they  exist 
widely  in  both  animal  and  vegetable  matters.  They  circulate  with  the 
animal  fluids,  and  are  finally  excreted  with  the  perspiration,  the  mucus, 
and  the  urine.  In  the  urine  a  portion  of  the  alkaline  sodium  phosphate 
is  replaced  by  the  acid  sodium  biphosphate,  which  gives  to  this  fluid  its 
property  of  reddening  blue  litmus  paper,  although  it  contains  no  free 
acid.  The  manner  in  which  this  change  is  supposed  to  take  place  is  the 
following.  A  nitrogenous  organic  acid  of  new  formation,  namely,  uric 
acid,  makes  its  appearance  in  the  system,  and  is  excreted  by  the  urine. 
It  exists,  however,  in  this  fluid  only  in  the  form  of  combination,  as 
sodium  urate.  It  is,  therefore,  believed  to  combine,  at  the  time  of  its 
formation,  with  a  portion  of  the  sodium  which  forms  the  base  of  the 
sodium  phosphate;  and  the  remainder  of  this  salt,  converted  into  a 
biphosphate,  is  then  eliminated  by  the  urine,  which  thus  acquires  an 
acid  reaction. 

There  is  evidence  that  phosphoric  acid  is  also  generated  in  the  inte- 
rior of  the  body  by  oxidation.  A  substance  to  be  described  hereafter, 
containing  phosphorus  in  the  form  of  organic  combination,  exists  in 
various  parts  of  the  system,  especially  in  the  blood  and  in  the  tissue  of 
the  brain  and  nerves,  and  is  taken  with  certain  kinds  of  food ;  but  no 
such  substance  is  to  be  met  with  in  the  excretions.  In  the  fluids  dis- 
charged from  the  body  phosphorus  exists  only  in  the  form  of  the  phos- 
phatic  salts.  It  is,  therefore,  without  doubt  oxidized  in  the  internal 
transformation  of  the  organic  substances,  thus  becoming  phosphoric 
acid,  which  in  turn  unites  with  the  alkaline  bases  to  form  neutral  or  acid 
phosphates.  In  this  way  a  certain  portion  of  the  superabundant  acid 
is  produced,  which  gives  rise  to  the  acid  reaction  of  the  excreted  fluids. 

The  sodium  and  potassium  phosphates,  including  the  acid  biphosphate, 
are  discharged  with  the  urine  to  the  amount  of  about  4.5  grammes  per 
day. 

8.  Sodium  and  Potassium  Carbonates,  Na2C03  and  E^CO.,. 
The  alkaline  carbonates,  as  mentioned  above,  are  associated  with  the 
phosphates  in  all  the  more  important  fluids  of  the  body.     They  are 
readily  soluble,  and  assist  in  producing  the  necessary  alkalescence  of 
the  blood  and  secretions. 


52  INORGANIC    PROXIMATE    PRINCIPLES. 

The  alkaline  carbonates  are  partly  introduced  as  such  with  the  food, 
but  are  to  a  great  extent  formed  within  the  body  by  the  decomposition 
of  other  salts  contained  in  the  substance  of  certain  fruits  and  vegetables. 
Various  of  these  fruits  and  vegetables,  such  as  apples,  cherries,  grapes, 
potatoes,  carrots,  and  the  like,  contain  malates,  tartrates,  and  citrates 
of  the  alkaline  bases.  It  has,  furthermore,  been  often  observed  that 
after  the  use  of  acescent  fruits  and  vegetables  containing  the  above  salts, 
the  urine  becomes  alkaline  in  reaction  from  the  presence  of  the  alkaline 
carbonates.  Lehmann1  found,  by  experiments  upon  his  own  person, 
that  within  thirteen  minutes  after  taking  15.5  grammes  of  sodium  lactate, 
the  urine  had  an  alkaline  reaction.  He  also  observed  that,  if  a  solution 
of  this  substance  were  injected  into  the  jugular  vein  of  a  dog,  the  urine 
became  alkaline  at  the  end  of  five,  or,  at  the  latest,  of  twelve  minutes. 
The  conversion  of  these  salts  into  carbonates  takes  place,  therefore,  not 
in  the  intestine,  but  in  the  blood.  The  same  observer  found  that,  in 
many  persons  living  on  a  mixed  diet,  the  urine  became  alkaline  in  two 
or  three  hours  after  swallowing  0.65  gramme  of  sodium  acetate. 

The  organic  acid  in  these  cases  is  decomposed  and  oxidized  with  the 
production  of  carbonic  acid  and  water ;  and  the  original  salts  are  thus 
replaced  by  the  alkaline  carbonates,  which  appear  in  the  urine  and  tem- 
porarily modify  its  reaction  in  the  manner  above  described. 

A  preponderance  of  vegetable  food,  accordingly,  influences  the  quan- 
tity of  the  alkaline  carbonates  in  the  system,  and  consequently  the  reac- 
tion of  the  excretions.  As  a  rule,  the  urine  of  man  and  of  the  carnivo- 
rous animals  is  clear  and  acid,  while  that  of  the  herbivora  is  alkaline 
and  turbid  with  calcareous  deposits.  This  turbid  and  alkaline  urine 
will  often  effervesce  with  acids,  showing  the  presence  of  carbonates  in 
considerable  quantity.  Bernard  has  shown  that  this  difference  depends 
upon  the  alimentation  of  the  animal,  and  that  although  in  carnivorous 
and  herbivorous  animals  under  ordinary  conditions  the  urine  is  respec- 
tively acid  and  alkaline,  if  they  be  both  deprived  of  food  for  a  few  days 
the  urine  becomes  acid  in  both,  since  they  are  then,  in  each  instance, 
living  upon  their  own  tissues.  Furthermore,  a  rabbit,  whose  urine  is 
turbid  and  alkaline  while  feeding  on  fresh  vegetables,  if  kept  upon  a  diet 
of  animal  food,  soon  produces  an  excretion  which  is  clear  and  acid.  The 
reverse  effect  is  produced  upon  a  dog  by  changing  his  food  from  meat 
to  vegetable  matters.  Finally,  it  is  also  shown2  that  the  urine  of  the 
young  calf  while  living  on  the  milk  of  the  mother  is  clear  and  acid ;  but 
after  the  animal  has  been  weaned  and  feeds  upon  vegetable  matter,  its 
urine  becomes  alkaline  and  turbid,  like  that  of  the  adult  animal. 

9.  Sodium  and  Potassium  Sulphates,  S04Na2  and  S04K2. 
The  sulphates  are  also  to  be  regarded  as  constant  ingredients  of  the 
body,  as  they  are  found  in  several  of  the  animal  fluids,  including  the 

1  Physiological  Chemistry.     Cavendish  edition.     London,  1851,  vol.  i.  p.  97. 

2  Milne  Edwards,  Legons  sur  la  Physiologie.    Paris,  1862,  tome  vii.  p.  471. 


SODIUM    AND    POTASSIUM    SULPHATES.  53 

blood,  the  lymph,  the  aqueous  humor,  milk,  saliva,  mucus,  the  perspira- 
tion, and  the  urine.  They  are  usually,  however,  in  small  quantity,  as 
compared  with  other  saline  matters.  In  the  blood  and  the  lymph,  they 
are  much  less  abundant  than  either  the  chlorides,  phosphates,  or  car- 
bonates. In  the  milk  and  the  saliva,  there  is  hardly  more  than  a  trace 
of  them ;  and  they  have  not  been  found  at  all  in  the  bones,  the  gastric 
juice,  the  bile,  or  the  pancreatic  juice.  They  are  most  abundant  in  the 
urine,  where  they  amount  to  rather  more  than  one-half  the  quantity  of  the 
phosphates,  and  they  are  found  also,  in  small  proportion,  in  the  feces. 

The  sulphates  are  introduced  into  the  body,  to  some  extent,  with  the 
food  and  drink.  They  are  to  be  found,  in  minute  quantity,  in  muscular 
flesh  and  in  the  yolk  of  egg.  They  exist  also  in  certain  vegetable  pro- 
ducts, such  as  the  cereal  grains,  fruits,  and  tuberous  roots,  where  they  are 
much  less  abundant  than  the  phosphates,  though  often  more  so  than  the 
chlorides.  Spring  and  river  water,  as  used  for  drink,  usually  contains 
sulphates,  including  sulphate  of  lime,  varying  in  amount,  according  to 
the  tables  given  by  Payen,1  from  .003  to  .06  per  thousand  parts.  In 
the  water  of  the  Croton  River,  with  which  the  city  of  New  York  is  sup- 
plied, they  amount,  as  shown  by  the  analyses  of  Prof.  Chandler,2  to  a 
little  more  than  .007  per  thousand  parts. 

Beside  the  sulphates,  however,  introduced  with  the  food  and  drink,  a 
certain  amount  of  sulphuric  acid  originates  within  the  body  by  oxida- 
tion, in  a  mode  analogous  to  that  already  described  for  phosphoric  acid. 
The  albuminous  substances,  which  form  so  important  a  part  of  the  solid 
food,  contain  sulphur  as  one  of  their  constituent  elements,  and  a  con- 
siderable quantity  of  this  substance  is  accordingly  introduced  daily  into 
the  system  in  the  form  of  organic  combination.  The  entire  quantity  of 
sulphur,  thus  forming  part  of  the  organic  matters  of  the  body  of  a  man 
of  medium  size,  amounts,  according  to  Payen,3  to  about  110  grammes ; 
and  at  least  1  gramme  must  be  taken  daity  with  the  albuminous  ingre- 
dients of  the  food.  A  portion  of  these  substances  is  expelled  by  the 
daily  exfoliation  of  the  hair,  nails,  and  epidermis;  but  no  such  sul- 
phurous organic  compound  is  discharged  by  the  urine  and  feces  except 
in  insignificant  quantity.  On  the  other  hand,  the  sulphates  are  compar- 
atively abundant  in  the  excretions.  While  they  are  to  be  found  in  the 
blood  only  in  the  proportion  of  0.28  per  thousand,  they  exist  in  the 
urine  in  the  proportion  of  from  3.00  to  7.00  parts  per  thousand,4  and  are 
discharged  by  this  channel  to  the  amount  of  about  4  grammes  per  day. 

These  facts  indicate  that  a  notable  quantity  of  sulphuric  acid  is  con- 
stantly formed  in  the  body,  during  the  decomposition  of  albuminous 
matters,  by  oxidation  of  their  sulphur.  This  is  confirmed  by  the  fact 
that  the  quantity  of  sulphuric  acid  in  the  sulphates  eliminated  by  the 
kidneys  is  perceptibly  increased  by  the  use  of  a  flesh  diet,  and  also  by 

1  Substances  Alimentaires.     Paris,  1865,  p.  436. 

2  Lecture  on  Water.     Transactions  of  the  American  Institute  for  1870-71. 
8  Substances  Alimentaires.     Paris,  1865,  p.  68. 

4  Robin,  LeQons  sur  les  Humeurs.     Paris,  1874,  p.  770. 


54  INORGANIC    PROXIMATE    PRINCIPLES. 

the  administration  of  sulphur  or  a  sulphuret.1  Dr.  Parkes  estimates 
the  quantity  of  sulphuric  acid  thus  produced  in  the  system  as  about 
double  that  taken  in  the  form  of  sulphates  with  the  food  and  drink.  It 
unites  at  once  with  the  alkaline  bases,  displacing  the  weaker  acids  with 
which  they  were  previously  combined,  and  thus  contributes  indirectly 
to  the  general  acid  reaction  of  the  excreted  fluids. 

The  foregoing  substances  constitute  the  most  important  of  the  in- 
organic proximate  principles  of  the  animal  body.  They  are  distin- 
guished, as  a  class,  by  their  comparatively  simple  chemical  composition, 
by  their  external  origin,  and  by  the  part  which  they  take  in  the  constitu- 
tion and  nourishment  of  the  animal  frame  They  are  derived  for  the 
most  part  from  without,  being  taken  directly  from  the  materials  of  the 
inorganic  world.  There  are  some  exceptions  to  this  rule;  as  in  the 
case  of  the  alkaline  carbonates  formed  in  the  body  by  decomposition  of 
the  salts  of  the  vegetable  acids ;  and  of  the  sodium  biphosphate  pro- 
duced from  the  neutral  phosphate,  by  the  action  of  an  organic  acid  of 
internal  origin.  The  greater  part,  however,  of  the  proximate  principles 
belonging  to  this  class  are  introduced  with  the  food,  and  taken  up 
by  the  animal  tissues  and  fluids,  in  the  form  under  which  they  exist 
in  external  nature.  The  lime  carbonate  of  the  bones,  for  example,  and 
the  sodium  chloride  of  the  blood  and  the  tissues,  are  the  same  sub- 
stances as  those  met  with  in  calcareous  rocks,  or  in  solution  in  sea 
water. 

In  the  process  of  internal  nutrition  they  are  also  exempt,  as  a  general 
rule,  from  any  marked  chemical  changes.  Some  of  them,  such  as  the 
lime  and  magnesium  phosphates,  are  mostly  deposited  in  the  solid  parts, 
and  are  renewed  very  slowly,  contributing  principally  to  the  physical 
properties  of  the  tissues,  and  taking  a  comparatively  small  share  in  the 
actions  of  repair  and  waste.  Others,  such  as  water  and  the  alkaline 
chlorides,  are  introduced  and  discharged  daily  in  considerable  abund- 
ance, passing  rapidly  through  the  system,  and  playing  an  important 
part  in  the  phenomena  of  solution  and  transudation.  Others  still,  such 
as  the  alkaline  phosphates  and  sulphates,  are  partly  formed  in  the  body 
by  the  process  of  oxidation,  and  appear  in  the  urine  as  a  residue  from 
the  decomposition  of  other  proximate  principles. 

Principally,  however,  the  inorganic  substances  are  reabsorbed  by  the 
blood  from  the  tissues  in  which  they  were  deposited,  and  discharged 
unchanged  with  the  excretions.  The  importance  of  this  character  will 
become  fully  manifest  when  we  see  how  different  are  the  relations 
exhibited  by  the  proximate  principles  of  other  groups.  The  inorganic 
substances  do  not,  for  the  most  part,  participate  directly  in  the  chemical 
changes  going  on  in  the  body ;  but  rather  serve  by  their  presence  to 
enable  those  changes  to  be  accomplished,  in  the  other  ingredients  of  the 
animal  frame,  which  are  necessary  to  the  process  of  nutrition. 

1  Neubauer  und  Vogel,  Analyse  des  Hams.     Wiesbaden,  1872,  pp.  356,  357. 


CHAPTBE  III. 

HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 

THE  proximate  principles  belonging  to  this  class  are  distinguished 
from  the  preceding  by  their  organic  origin.  They  appear  as  products 
of  the  nutritive  actions  of  organized  beings,  and  are  not  introduced 
ready  formed  from  the  inorganic  world.  They  exist  both  in  vegetables 
and  in  animals.  In  the  former  they  are  produced  entirely  as  new  com- 
binations, under  the  influence  of  the  vegetative  process ;  and  even  in 
animals,  which  feed  upon  vegetables  or  upon  other  animals,  they  are  so 
modified  by  digestion  and  assimilation  that  they  present  themselves,  as 
final  constituents  of  the  body,  under  new  and  specific  forms.  They  all 
consist  of  carbon,  hydrogen,  and  oxygen,  of  which  carbon  is  present  by 
weight  in  especially  large  proportion,  forming  from  44  to  84  per  cent, 
of  the  entire  substance.  Owing  to  the  absence  of  nitrogen,  which  is  an 
important  element  in  organic  substances  of  the  following  class,  they  are 
sometimes  known  as  the  "non-nitrogenous"  proximate  principles.  They 
are  naturally  divided  into  two  principal  groups,  namely:  the  carbo- 
hydrates, or  substances  containing  carbon,  together  with  hydrogen  and 
oxygen  in  the  proportions  to  form  water ;  and  the  fatty  matters,  in 
which  the  proportions  of  carbon  and  hydrogen  are  both  increased,  while 
that  of  oxygen  is  considerably  diminished.  The  group  of  the  carbo- 
hydrates includes  starch,  glycogen,  and  sugar. 

I.  Starch,  C6H1005. 

Starch  is  most  abundantly  diffused  throughout  the  vegetable  kingdom, 
and  exists,  for  at  least  a  certain  period  of  vegetative  life,  in  every  plant 
which  has  yet  been  examined  for  it.  It  occurs  especially  in  seeds,  in 
the  cot3'ledons  of  the  young  plant,  in  roots,  tubers,  and  bulbs,  in  the 
pith  of  stems,  and  sometimes  in  the  bark.  It  is  very  abundant  in  corn, 
wheat,  rye,  oats,  and  rice,  in  the  parenchyma  of  the  potato,  in  peas  and 
beans,  and  in  most  vegetable  substances  used  as  food.  It  constitutes 
almost  entirely  the  different  preparations  known  as  sago,  tapioca,  arrow- 
root, and  maizena,  which  are  nothing  more  than  varieties  of  starch, 
extracted  from  different  species  of  plants. 

The  following  list,  compiled  mainly  from  the  tables  of  Payen,1  shows 
the  percentage  of  starch  occurring  in  various  kinds  of  food  : — 

1  Substances  Alimentaires.    Paris,  1865. 

(55) 


56       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 


QUANTITY  OF  STARCH  IN  100  PARTS  IN 


Wheat  . 
Rye 

Oats       . 
Barley   . 
Indian  corn 
Rice 


57.88 
64.65 
60.59 
66.43 
67.55 
88.65 


Potatoes 
Sweet  potatoes 
Peas 
Beans     . 
Flaxseed 
Chocolate  nut 


20.00 
16.05 
37.30 
33.00 
23.40 
11.00 


When  purified  from  foreign  substances  starch  is  a  white,  glistening 
powder,  which  gives  rise  to  a  peculiar  crackling  sensation  if  rubbed 
between  the  fingers.  It  consists  of  minute  granules  of  very  firm  con- 
sistency and  definite  shape,  presenting  certain  peculiarities,  of  both  form 
and  size,  by  which  its  varieties,  derived  from  different  sources,  may  be 
distinguished  from  each  other.  The  young  starch  granules,  when  first 
produced  in  the  tissues  of  the  plant,  are  exceedingly  small,  round,  and 
perfectly  homogeneous ;  but  they  afterward  increase  in  size,  and,  as  their 
growth  is  irregular,  they  become  ovoid,  pear-shaped,  lenticular,  or 
polygonal  in  form.  They  also  show  under  the  microscope  a  definite 
structure,  each  granule  being  composed  of  a  series  of  layers,  disposed 
one  over  the  other,  giving  rise  to  the  appearance  of  concentric  markings, 
which  are  very  characteristic  of  most  varieties  of  starch  grains,  after 
they  have  attained  a  certain  size.  The  markings  are  arranged  round  a 
single  point,  usually  more  or  less  eccentric  in  position,  which  is  called 
the  hilum. 

The  successive  layers  of  which  the  starch  granule  is  composed  differ 
from  each  other  mainly  in  their  consistency,  being  alternately  harder 

and  softer  in  comparison  with 
each  other;  and  this  difference 
in  density  produces  a  corres- 
ponding difference  in  the  refrac- 
tive power  of  the  layers,  and 
consequently  an  appearance  of 
concentric  striation. 

Each  starch  granule,  further- 
more, consists  of  two  sub- 
stances, intimately  mingled  in 
every  part  of  its  mass,  which  re- 
semble each  other  completely  in 
chemicalcomposition,  but  differ 
greatly  in  solubility.  These 
two  substances  are,  1st,  granu- 
lose,  which  may  be  extracted 

GRAINS  OP  POTATO  STABCH.  f™m  the  starch  S™™   ^  b°U- 

ing  water ;    and  2d,  cellulose, 

which  remains  undissolved.  The  granulose  is  usually  much  the  more 
abundant  of  the  two,  but  the  cellulose  has  so  marked  a  consistency  that 
it  retains  the  form  and  apparent  laminated  structure  of  the  starch  grain. 


STARCH. 


57 


Fig.  3. 


STARCH  GRAIUS  OF  BERMUDA  ARROW- 
ROOT. 


after  extraction  of  the  granulose,  though  it  may  be  reduced  to  five  or 
six  per  cent,  of  its  original  weight. 

The  starch  grains  of  the  potato  (Fig.  2)  vary  considerabl}7  in  size. 
The  smallest  have  a  diameter  of  2.5  inmm.,1  the  largest  62.5  mmm. 
They  are  irregularly  pear-shaped 
in  form,  and  their  concentric 
markings  are  very  distinct.  The 
starch  obtained  from  the  potato, 
however  carefully  prepared,  re- 
tains in  connection  with  it  traces 
of  an  odoriferous  principle  which 
makes  it  less  valuable  for  culi- 
nary purposes  than  many  other 
varieties. 

The  starch  granules  of  arrow- 
root (Fig.  3)  are  generally 
smaller  and  more  uniform  in 
size,  than  those  of  the  potato. 
They  vary  from  12.5  mmm.  to 
50  mmm.  in  diameter.  They  are 
elongated  and  cylindrical  in 
form,  and  the  concentric  mark- 
ings are  less  distinct  than  in  the  preceding  variety.  The  hilum  has  here 
sometimes  the  form  of  a  circular  pore,  and  sometimes  that  of  a  trans- 
verse fissure  or  slit. 

The  grains  of  wheat  starch 
(Fig.  4)  are  still  smaller  than 
those  of  arrowroot.  They  vary 
from  2.5  mmm.  to  35  mmm. 
in  diameter.  They  are  nearly 
circular  in  form,  with  a  round 
or  transverse  hilum,  but  with- 
out any  distinct  appearance  of 
lamination.  Many  of  them  are 
flattened  or  compressed  later- 
ally, so  that  they  present  a 
broad  surface  in  one  position, 
and  a  narrow  edge  when  viewed 
in  the  opposite  direction. 

The  starch  grains  of  Indian 
corn  (Fig.  5)  are  of  nearly  the 
same  size  with  those  of  wheat 
flour.  They  are  somewhat  more  irregular  and  angular  in  shape  ;  and 

1  The  sign  mmm.  stands  for  micro-millimetre  ;  that  is,  the  one-thousandth  part 
of  a  millimetre.     A  millimetre  is  very  nearly  equivalent  to  one  twenty-fifth  of  an 


Fig.  4. 


STARCH  GRAINS  OP  WHEAT  FLOTTR. 


inch  ;  and  a  micro-millimetre,  accordingly,  is  about 
5 


of  an  inch. 


HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 


Fig.  5. 


STARCH  GRAINS  OF  INDIAN  CORN. 


are  often  marked  with  crossed  or  radiating  lines,  as  if  from  partial 
fracture. 

Starch  derived  from  all  these  different  sources  has  essentially  the 
same  chemical  composition,  and  may  be  recognized  b}"  the  same  tests. 

It  is  insoluble  in  cold  water,  but 
if  it  be  treated  with  about 
twenty  times  its  weight  of  boil- 
ing water  its  granules  swell, 
become  gelatinous  and  amor- 
phous, combine  with  a  certain 
proportion  of  water,  and  fuse 
into  a  thick  opaline  liquid,  which 
is  thinner  or  thicker  according 
to  the  quantity  of  water  present. 
After  that  they  cannot  be  made 
to  resume  their  original  form, 
but  on  cooling  they  solidify  into 
a  nearly  homogeneous  paste, 
retaining  the  water  in  union  with 
the  starchy  matter.  The  starch 
is  then  said  to  be  amorphous  or 
•*'  hydrated."  By  this  process 

it  is  not  essentially  altered  in  its  chemical  properties,  but  only  in 
its  physical  condition.  If  starch  be  treated  with  100  or  150  parts  of 
boiling  water,  it  makes  an  opaline  liquid  which  does  not  gelatinize  ;  but 
on  standing,  the  imperfectly  liquefied  portions,  containing  the  insoluble 
cellulose,  subside  to  the  bottom  as  a  turbid  deposit,  while  the  soluble 
starch  remains  above,  forming  a  clear,  colorless,  and  perfectly  fluid  solu- 
tion. 

Starch  is  especially  distinguished  by  its  property  of  striking  a  blue 
color  by  contact  with  iodine.  This  reaction  will  take  place  even  when 
the  starch  is  in  the  raw  condition,  and  starch  granules  may  be  readily 
recognized  under  the  microscope  by  this  means.  It  is  still  more  prompt 
when  the  starch  is  hydrated  and  especially  when  it  is  in  solution. 
A  very  minute  quantity  of  tincture  of  iodine  added  to  a  solution  of 
starch  will  cause  the  whole  to  assume  at  once  a  very  deep  and  rich  blue 
color,  which  may  be  largely  diluted  without  losing  its  characteristic 
tinge.  The  mixture  of  the  two  substances,  however,  must,  in  the  first 
place,  be  made  at  a  moderate  temperature.  If  the  solution  be  hot,  no 
visible  reaction  will  occur ;  and  even  after  it  has  taken  place  if  heat  be 
applied  the  blue  color  will  disappear,  to  return  again  after  cooling  down 
to  the  original  temperature.  Secondly,  the  iodine  must  be  in  a  free 
state.  If  it  be  used  in  the  form  of  a  soluble  iodide,  it  will  produce 
no  effect,  since  the  starch  has  not  sufficient  affinity  for  it  to  withdraw 
it  from  its  union  with  other  matters.  No  third  substance,  furthermore, 
must  be  present  in  the  mixture,  which  would  be  capable  of  combining 
with  the  iodine  and  thus  preventing  its  action  upon  the  starch.  All  the 


STARCH.  59 

animal  fluids  more  especially,  such  as  the  serum  of  blood,  saliva,  mucus, 
urine,  contain  ingredients  which  prevent  the  reaction  of  starch  with 
iodine,  and  may  even  dissipate  the  blue  color  after  it  has  been  once  pro- 
duced. These  substances,  therefore,  must  be  removed  from  the  fluid 
before  the  application  of  the  test,  or  else  the  iodine  must  be  added  in 
sufficient  excess  to  allow  a  surplus  for  action  upon  the  starch.  With 
these  precautions  it  forms  a  striking  and  valuable  test. 

Starch  has  the  property  of  being  changed,  under  certain  conditions, 
into  two  other  substances. 

1.  If  subjected  to  torrefaction,  that  is,  a  dry  heat  of  about  210°  (about 
4000  F.),  it  is  converted  into  Dextrine,  a  gummy  substance  freely  solu- 
ble in  water,  so  called  from  the  fact  that  in  solution  it  rotates  the  plane 
of  the  polarized  ray  toward  the  right.1     Dextrine  has  the  same  chemical 
composition  with  starch,  namely  C6H1005,  but  its  properties  are  changed, 
and  it  will  no  longer  produce  a  blue  color   with   iodine.      The   same 
transformation  is  very  quickly  accomplished  by  boiling  starch  with  a 
dilute   acid;   the  opaline  arid   gelatinous  solution   becoming  in  a  few 
minutes  clear  and  liquid,  and  losing  at  the  same  time  its  power  of 
reaction  with  iodine.      Finalty,  in  the  germination  of  starchy  seeds, 
like  the  cereal  grains,  a  nitrogenous   substance   is  produced   termed 
"  diastase ;"  and  this  has  the  power,  when  supplied  with  moisture  at  a 
moderate  temperature,  of  effecting  the  transformation  of  the  starch  into 
soluble  dextrine. 

2.  Starch  may  be  converted  into  Sugar.    When  a  starch  solution  or 
a  thin  starch  paste  is  boiled  with  a  dilute  acid,  it  is  rapidly  changed, 
as  already  mentioned,  into  dextrine.     If  the  boiling  be  continued  for 
several  hours  it  is  still  further  transformed  into  sugar  ;  and  at  last  the 
whole  of  it  passes  over  into  the  saccharine  condition.     This  also  hap- 
pens in  the  process  of  germination  and  growth  in  plants,  where  sugar 
makes  its  appearance  under  influence  of  the  diastase,  and  at  the  expense 
of  the  starch,  as  soon  as  moisture  and  warmth  are  supplied  in   the 
requisite  degree.      This    is   the   usual   source'  of  sugar   in   vegetable 

1  A  ray  of  light  which  has  passer!  through  certain  crystalline  bodies,  such  as  a 
"  Nicol's  prism"  of  Iceland  spar,  is  found  to  be  polarized  ;  that  is,  it  has  acquired 
opposite  and  complementary  properties  in  two  different  directions.  For  if  it  be 
received  by  a  second  similar  prism,  which  is  equally  transparent  in  all  positions 
to  ordinary  light,  the  polarized  ray  will  pass  through  it  only  when  the  prin- 
cipal section  of  the  second  prism  is  parallel  with  that  of  the  first ;  but  when  the 
second  prism  is  turned  round  90°,  the  light  is  entirely  arrested.  Now  if  certain 
organic  substances  in  solution  be  placed  between  the  two  prisms,  it  is  found  that 
they  have  the  effect  of  changing  the  angle  at  which  the  second  prism  must  stand 
in  order  to  arrest  or  transmit  the  light  from  the  first.  In  other  words,  the  plane 
of  polarization  of  the  polarized  ray  has  been  deviated  or  rotated  by  passing 
through  the  organic  liquid.  Some  substances  deviate  in  this  way  the  plane  of 
polarization  toward  the  right,  others  toward  the  left.  The  specific  rotatory 
power  of  each  is  estimated  for  a  solution  of  standard  strength  and  quantity,  for 
yellow  light,  and  is  indicated  in  degrees  of  the  circle.  The  specific  rotatory  power 
of  dextrine  is  118°. 


60       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 

juices,  the  starch  previously  stored  up  being  at  some  period  of  growth 
changed  into  sugar  by  the  molecular  actions  going  on  in  the  vegetable 
fabric.  Finally,  various  nitrogenous  animal  substances  produce  the 
same  effect.  The  contact  of  human  saliva  or  the  intestinal  juices  at  a 
temperature  of  37.5°  (10(P  F.)  rapidly  transforms  hydrated  starch  into 
sugar. 

A  special  interest  attaches  to  starch  from  the  fact  that  it  is  the  first 
organic  substance  produced,  in  the  process  of  vegetation,  from  inor- 
ganic materials.  The  animal  body  is  incapable  of  forming  organic 
matter,  and  must  therefore  be  supplied  with  these  substances  in  the 
food.  But  vegetables  have  the  power  of  combining  inorganic  ele- 
ments in  such  a  way  as  to  produce  a  new  class  of  bodies,  peculiar  to 
the  organic  world,  and  capable  of  serving  for  the  nutrition  of  animals. 
This  is  shown  by  numerous  experiments,  in  which  seeds  or  young 
plants,  artificially  cultivated  in  a  soil  of  clean  sand,  and  moistened  only 
with  solutions  of  various  mineral  salts,1  have  germinated,  grown,  and 
fructified,  increasing,  many  times  over,  the  quantity  of  organic  material 
which  they  contained  at  the  beginning. 

This  production  of  organic  matter  takes  place  in  the  green  tissues, 
principally  in  the  leaves,  of  growing  plants,  under  the  influence  of 
the  solar  light ;  and  the  first  substance  which  makes  its  appearance 
under  these  conditions  is  nearly  always  starch.  It  is  produced  from 
two  inorganic  matters  absorbed  from  without,  namely,  carbonic  acid 
and  water,  which  are  deoxidized  by  the  green  vegetable  tissues,  their 
elements  being  re-combined,  to  form  a  carbo-hydrate.  This  is  proved 
by  the  fact  that  oxygen  is  exhaled,  during  the  vegetative  process,  in 
the  same  or  nearly  the  same  proportion  as  that  in  which  it  existed 
originally  in  the  carbonic  acid ;  and  the  new  substance  produced  con- 
tains hydrogen  and  oxygen  in  the  relative  proportions  to  form  water. 
The  production  of  starch  in  growing  vegetables  is  therefore  repre- 
sented by  the  following  formula : — 

Carbonic  acid.        Water.  Starch. 

(C6012    +   H1005)  -  012  =  CCH1005. 

The  starch  thus  formed  in  the  leaves  of  plants  is  afterward  trans- 
formed into  other  vegetable  substances  belonging  to  the  group  of  the 
carbo-hydrates,  such  as  dextrine,  sugar,  and  cellulose,  and  used  for  the 
further  nutrition  of  the  plant.  When  abundantly  deposited  in  special 
organs,  such  as  the  starchy  seeds  of  wheat  or  Indian  corn,  or  the  tubers 
of  the  potato,  it  constitutes  a  reserve  material  of  nutrition,  to  be  after- 
ward dissolved  and  employed  for  the  purposes  of  germination  and 
growth.  It  is  from  such  natural  deposits  of  reserve,  in  the  vegetable 
fabric,  that  starch  is  obtained  in  quantity  to  serve  as  food  for  animals 
or  man. 

1  Mayer,  Lehrbuch  der  Agrikultur-Chemie.  Heidelberg,  1871,  Band  i. 
p.  10. 


GLYCOGEN. —  SUGAR.  61 

When  taken  into  the  alimentary  canal,  starch  is  rapidly  transformed 
into  sugar  by  the  action  of  the  digestive  fluids ;  and  in  this  form  is 
absorbed  into  the  circulation. 

II.  Glycogen,  C6H1005. 

This  is  an  amylaceous  substance  of  animal  origin,  corresponding  in 
character  with  starch  derived  from  the  vegetable  world.  It  is  found  in 
the  livers  of  all  vertebrate  animals  in  the  healthy  condition,  and  in  the 
muscles  and  integument  of  the  embryo  of  mammalia  at  an  early  period 
of  development.  It  has  also  been  discovered  in  the  oyster  and  the 
cockle-shell.  Glycogen,  so  called  from  its  property  of  producing  sugar 
or  glucose,  has  the  same  chemical  composition  as  starch,  and  agrees 
with  it  in  all  its  essential  characters,  except  that  it  is  readily  soluble 
in  water,  and,  when  treated  with  iodine,  yields  a  violet-red  instead  of 
a  blue  color.  Its  watery  solution  is  opalescent,  and  deviates  the  plane 
of  polarization  strongly  to  the  right,  its  specific  power  of  rotation  for 
yellow  light  being  about  130°.  By  boiling  with  a  dilute  acid  it  is 
changed  first  into  dextrine  and  afterward  into  sugar.  It  also  under- 
goes the  saccharine  transformation  when  in  solution  at  the  temperature 
of  the  living  body  by  contact  with  saliva,  the  intestinal  juices,  the  sub- 
stance of  the  liver,  or  the  serum  of  the  blood.  It  is  the  source  of  the 
sugar  produced  in  the  animal  body,  as  starch  is  the  source  of  that 
formed  in  vegetables. 

Both  starch  and  glycogen,  accordingly,  are  to  be  regarded  as  tempo- 
rary products,  destined  to  undergo  further  transformation  before  being 
used  for  the  purposes  of  nutrition.  In  vegetables,  the  starch  which. 
is  abundantly  stored  up  at  one  period  in  the  cellular  tissues  is  after- 
ward liquefied  and  altered  into  other  substances;  and  although  it 
enters  so  largely  into  the  composition  of  the  vegetable  food  of  ani- 
malSj  it  is  converted  into  sugar  during  digestion  in  the  alimentary 
canal. 

III.  Sugar. 

The  proximate  principles  designated  under  this  name  include  a  va- 
riety of  substances  which  have  certain  well-marked  characters,  and  are 
of  frequent  occurrence  in  both  animal  and  vegetable  juices.  They  are 
crystallizable  and  soluble  in  water,  and  have,  when  in  solution,  a 
distinctly  sweet  taste,  which,  in  some  varieties,  is  very  highly  de- 
veloped. They  are  all  decomposed  by  being  heated  with  sulphuric 
acid;  their  hydrogen  and  oxygen  being  driven  off,  while  the  carbon 
remains  behind  as  a  jet-black  deposit.  In  this  condition  they  are  said 
to  be  carbonized.  The  proportions  in  which  they  occur  in  various  arti- 
cles of  food,  according  to  the  tables  of  Pay  en,.  Yon  Bibra,  and  a  few 
other  observers,  are  as  follows:. — 


62       HYDROOARBONACEOUS    PROXIMATE    PRINCIPLES. 

QUANTITY  OF  SUGAR  IN  100  PARTS  IN 

Cherries         .        .  .  18.12  Wheat  flour  .  .  .  2.33 

Apricots        .        .  .  16.48  Rye  flour       .  .  .  3.46 

Peaches         .        .  .  11.61  Barley  meal  .  .  .  3.04 

Pears     ....  11.52  Oatmeal        .  .  .  2.19 

Juices  of  sugar-cane  .  18.00  Indian  corn  meal  .  .  3.71 

Sweet  potatoes      .  .  10.20  Cow's  milk     .  .  .  5.20 

Beet  roofs     .        .  .  8.00  Goat's  milk    .  .  .5.80 

Parsnips        .         .  .  4.50  Beefs  liver     .  .  .  1.79 

The  three  principal  varieties  of  this  substance  which  are  most  impor- 
tant in  a  physiological  point  of  view  are  glucose,  cane  sugar,  and  milk 
sugar. 

Glucose,  CGH1206. 

Glucose,  also  called  grape  sugar  from  its  abundance  in  the  juices  of 
the  ripe  grape,  may  be  considered  as  the  most  marked  and  representa- 
tive variety  of  the  saccharine  substances.  It  occurs  more  frequently 
than  any  other  in  the  animal  fluids,  being  found  in  the  juices  of  the 
liver,  in  the  chyle,  the  blood,  and  the  lymph.  In  diabetes  it  is  abund- 
antly excreted  with  the  urine.  It  is  also  found  in  the  juices  of  many 
plants,  in  various  sweet  fruits,  and  in  honey,  where  it  is  associated  with 
certain  other  varieties.  It  is  freely  soluble  in  water.  Its  solution  has 
a  moderately  sweet  taste,  and  deviates  the  plane  of  polarization  toward 
the  right  53.5°. 

It  is  this  form  of  sugar  which  is  produced  from  starch  by  boiling  with 
dilute  acids,  by  the  action  of  the  digestive  fluids  of  the  alimentary  canal, 
and  in  the  plant  during  the  process  of  vegetation.  The  change  consists 
in  the  assumption  by  starch  of  the  elements  of  water  in  due  proportion, 
the  new  substance  thus  produced  being  still  a  carbo-hydrate.  The 
transformation  of  starch  into  glucose  is  therefore  represented  as 
follows : — 

Starch.       Water.        Glucose. 

C6H1005  +  H20  =  C6HW06- 

Glucose  may  be  recognized  in  solution  by  various  well-marked  tests. 
First,  the  action  of  alkalies  at  a  boiling  temperature.  If  a  solution  of 
glucose  be  treated  with  a  solution  of  potassium  hydrate  and  heat  applied, 
the  sugar  is  decomposed  and  the  liquid  assumes,  first,  a  yellowish  and 
then  a  brown  color,  which  becomes  deeper  in  proportion  to  the  amount 
of  glucose  and  alkali  existing  in  the  solution.  This  is  not  a  certain  test 
for  the  presence  of  glucose,  as  some  other  organic  matters  are  discolored 
in  a  similar  way  by  the  strong  alkalies  ;  but  it  will  serve  to  distinguish 
it  from  certain  varieties  of  sugar,  which  do  not  possess  this  property. 

Secondly,  the  test  most  commonly  employed  for  detecting  glucose 
depends  upon  its  power  of  reducing  the  salts  of  copper  in  a  boiling 
alkaline  solution.  This  test,  which  is  known  as  "  Trommer's  test,"  is 
applied  in  the  following  manner:  A  very  small  quantity  of  copper 
sulphate  in  solution  should  be  added  to  the  suspected  liquid,  and  the 


SUGAR.  63 

mixture  then  rendered  distinctly  alkaline  by  the  addition  of  potassium 
hydrate.  The  whole  solution  then  takes  a  deep-blue  color.  On  boiling 
the  mixture,  if  sugar  be  present,  the  copper  suboxide  is  thrown  down  as 
an  opaque  red,  j^ellow,  or  orange-colored  deposit ;  otherwise  no  change 
of  color  takes  place.  In  this  reaction  the  sugar,  which  is  oxidized  at  a 
high  temperature  under  the  influence  of  the  alkali,  takes  a  portion  of 
its  oxygen  from  the  copper  in  the  copper  salt,  and  thus  reduces  it  to 
the  form  of  an  insoluble  suboxide. 

Some  precautions  are  necessary  in  the  use  of  this  test.  As  a  general 
rule,  only  a  small  quantity  of  the  copper  sulphate  should  be  added  to 
the  liquid  under  examination,  just  sufficient  to  give  to  the  whole  a  dis- 
tinct blue  tinge  after  the  addition  of  the  alkali.  If  the  copper  salt  be 
used  in  excess,  the  sugar  in  solution  may  not  be  sufficient  to  reduce  the 
whole  of  it ;  and  that  which  remains  as  a  blue  sulphate  may  mask  the 
yellow  color  of  that  which  is  thrown  down  as  a  deposit.  This  diffi- 
culty may  be  removed  by  due  care  in  the  proportion  of  the  ingre- 
dients. 

Furthermore,  there  are  some  albuminous  substances  which  have  the 
power  of  interfering  with  Trommer's  test,  and  prevent  the  reduction  of 
the  copper  even  when  sugar  is  present.  Certain  animal  matters,  to  be 
more  particularly  described  hereafter,  which  are  liable  to  be  held  in  solu- 
tion in  the  gastric  juice  and  in  the  blood,  have  this  effect. 

The  ordinary  ingredients  of  the  urine  also  interfere  with  the  complete 
reaction  of  Trommer's  test,  by  holding  the  copper  oxide  in  solution,  so 
that  no  precipitate  takes  place  when  glucose  is  present,  although  the 
liquid  turns  yellow  on  boiling.  A  very  large  proportion  of  glucose  may 
be  added  to  fresh  urine  without  giving  rise  to  a  pulverulent  precipitate 
on  the  application  of  Trommer's  test;  notwithstanding  that,  if  dis- 
solved in  water,  it  will  react  in  the  proportion  of  one  part  in  10,000. 
That  the  interference  of  urine  with  Trommer's  test  depends  on  its 
retaining  in  solution  the  reduced  copper  oxide,  and  not  upon  its  pre- 
venting deoxidation,  is  indicated  by  the  fact  that  the  color  of  the 
mixture  changes,  as  usual,  from  blue  to  yellow  although  no  precipitate 
takes  place ;  and  also  by  the  experiments  of  Dr.  Fowler,1  who  has  shown 
that  if  the  precipitate  resulting  from  Trommer's  test  with  a  watery  solu- 
tion of  glucose  be  added  to  boiling  urine,  it  is  at  once  redissolved.  The 
same  observer  has  devised  a  method  of  applying  the  test  successfully 
notwithstanding  the  interference  of  the  urine.  A  certain  quantity  of 
urine  can,  of  course,  only  dissolve  a  certain  amount  of  copper  oxide ; 
and  if  the  copper  sulphate  solution  be  added  to  a  specimen  of  saccharine 
urine  in  large  proportion,  the  excess  will  be  precipitated  and  show  itself 
as  a  deposit.  A  copper  sulphate  solution,  made  in  the  proportion  of  1 
part  copper  sulphate  to  T.5  parts  of  water,  and  added  to  saccharine  urine 
to  the  amount  of  one-half  or  one-third  its  bulk  will  generally  be  suffi- 
cient to  produce  a  satisfactory  reaction. 

1  New  York  Medical  Journal,  June,  1874,  p.  632. 


6i       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 

All  sources  of  error  of  this  kind,  due  to  the  presence  of  extraneous 
substances,  may  be  avoided  in  delicate  examinations,  by  treating  the 
suspected  fluid  with  animal  charcoal,  or  by  evaporating  it  to  dryness, 
extracting  the  dry  residue  with  alcohol,  and  then  dissolving  the  dried 
alcoholic  extract  in  water,  before  the  application  of  the  test.  Either  of 
these  processes  will  remove  the  substances  which  interfere  with  the 
action  of  Trommer's  test,  and  will  leave  the  glucose  by  itself  in  the 
watery  solution. 

A  more  delicate  form  of  the  copper  test  for  glucose  is  in  the  employ- 
ment of  "  Fehling's  liquor,"  which  is  an  alkaline  solution  of  a  double 
copper  and  potassium  tartrate.  It  is  made  as  follows  : — 

Take — Pure  crystallized  copper  sulphate 40  grammes. 

Neutral  potassium  tartrate 160        " 

A  solution  of  sodium  hydrate  of  the  specific  gravity  1.12  .     650        " 

The  neutral  potassium  tartrate,  dissolved  in  a  little  water,  is  first 
mixed  with  the  solution  of  sodium  hydrate.  Then  the  copper  sulphate, 
dissolved  in  160  cubic  centimetres  of  water,  is  gradually  added  to  the 
alkaline  liquor,  which  assumes  a  clear,  deep  blue  color.  The  whole  is 
finally  diluted  with  water  to  the  volume  of  1154.4  cubic  centimetres. 
If  one  drop  of  this  liquid  be  added  to  one  cubic  centimetre  of  a  saccha- 
rine solution  and  heat  applied,  it  will  detect  one-fifteenth  of  a  milli- 
gramme of  glucose  by  the  reduction  o£  the  copper  oxide.  One  advan- 
tage of  Fehling's  liquor  as  a  test  is  that  the  quantity  of  copper  salt 
contained  in  a  given  volume  is  accurately  known,  and  consequently  not 
only  the  presence  but  alsd  the  amount  of  glucose  in  any  solution  may 
be  determined  by  the  quantity  of  test  liquid  which  it  decomposes  at  a 
boiling  temperature.  One  cubic  centimetre  of  Fehling's  liquor  is 
exactly  decolorized  by  •%  J^th  of  a  gramme  of  glucose. 

One  inconvenience  connected  with  this  test  is  that  Fehling's  liquor  by 
exposure  to  the  air  and  light  undergoes  an  alteration,  in  which  some  of 
its  tartaric  acid  disappears  and  is  replaced  by  carbonic  acid.  In  this 
condition  it  will  partially  precipitate  on  boiling,  even  without  the  pres- 
ence of  sugar.  To  guard  against  this,  it  should  be  kept  in  bottles  which 
are  quite  full  and  protected  from  the  light ;  and,  in  every  case  where  a 
suspected  fluid  is  to  be  examined  for  sugar,  a  small  portion' of  the  test- 
liquor  should  be  previously  boiled  by  itself,  in  order  to  be  sure  that  it 
has  not  undergone  spontaneous  decomposition.  Although  by  exposure 
to  the  air  and  light  at  a  summer  temperature,  Fehling's  liquor  may  become 
altered  at  the  end  of  a  week,  yet  if  protected  from  the  light,  in  carefully 
closed  and  full  bottles,  it  can  be  kept  unchanged  for  two  or  three  years. 

Thirdly,  the  most  marked  and  distinctive  property  of  glucose,  in  a 
physiological  sense,  is  its  capacity  for  fermentation.  If  a  watery  solu- 
tion of  pure  glucose  be  left  to  itself,  even  exposed  to  the  air,  no  remark- 
able change  takes  place  in  it.  But  if  a  small  quantity  of  beer-yeast  be 
added  and  the  mixture  kept  at  a  temperature  of  about  25°  (77°  F.),  after 
a  short  time  it  becomes  turbid.  It  then  develops  an  abundance  of 


SUGAR. 


65 


carbonic  acid,  which  is  partly  dissolved  in  the  liquid  and  partly  rises 
in  the  form  of  gas  bubbles  to  its  surface.  It  is  this  circumstance  which 
has  given  to  the  process  the  name  of  "  fermentation"  or  boiling.  At  the 
same  time  the  sugar  is  gradually  destroyed  and  alcohol  appears  in  its 
place.  Finally  the  whole  of  the  glucose  is  decomposed,  having  been 
converted  principally  into  alcohol,  C2H60,  and  carbonic  acid,  CO.,. 
Then  the  fermentation  stops  and  the  liquid  becomes  clear,  its  turbid  con- 
tents subsiding  to  the  bottom  as  a  whitish  layer.  This  layer  is  itself 
found  to  consist  of  yeast,  which  has  increased  in  quantity  over  that 
originally  added,  and  is  itself  capable  of  exciting  fermentation  in  another 
saccharine  liquid. 

If,  instead  of  a  solution  of  pure  glucose,  we  employ  the  expressed 
juices  of  certain  fruits,  like  those  of  the  grape,  which  contain  nitro- 
genous albuminoid  matters  in  addition  to  glucose,  fermentation  begins 
after  a  certain  period  of  exposure  to  the  air,  and  goes  on  with  the  same 
phenomena  and  results  as  before.  This  is  the  natural  source  of  all  the 
vinous  and  alcoholic  fluids  used  by  man ;  namely,  the  fermentation  of 
some  fluid  containing  glucose  or  a  similar  saccharine  substance. 

The  alcoholic  fermentation  of  glucose  is  due  to  the  vegetative 
action  of  a  microscopic  fungus,  known  as  Saccharomyces.  This  plant 
consists  entirely  of  cells  which 

multiply  by  a  process  of  bud-  Fig.  6. 

ding,  but  do  not  produce  fila- 
ments, nor  any  compound  ve- 
getable fabric.  The  species 
which  is  present  in  beer-yeast 
is  the  "  Saccharomyces  cerevi- 
sise."  Its  cells  are  usually 
rounded  in  form,  sometimes 
oval  (Fig.  6).  They  vary  in 
size,  but  the  greater  number 
have  an  average  diameter  of  10 
mmm.  They  have  a  very  thin 
investing  integument,  which 
incloses  a  finely  granular  semi- 
solid  substance,  often  with  one 
or  two  rounded  cavities  or 
vacuoles  filled  with  fluid.  The 
cells  are  mostly  isolated,  but 
occasionally  two  of  them  may 

be  seen  adhering  to  each  other.  There  is  also  a  small  amount  of  inter- 
cellular liquid,  containing  albuminous  matter  and  various  mineral  salts. 
When  a  little  of  the  yeast  is  added  to  a  solution  containing  glucose, 
the  cells  of  the  yeast-plant  after  a  short  time  begin  to  multiply  by  bud- 
ding. The  buds  increase  rapidly  in  size,  and,  when  the  young  cell  has 
nearly  attained  the  size  of  its  parent,  it  usually  separates  and  begins  an 


SACCHAROMYCES  OEREVISI^E,  in  its 
quiescent  condition ;  from  deposit  of  beer- 
yeast,  after  fermentation. 


66       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 


SACCHAEOMYCES  OBRKVISI^E  during  active 
germination.  From  fermenting  saccharine  solu- 
tion. 


Fig.  7.  independent  existence.     While 

in  this  active  condition  the 
cells  are  mostly  oval  in  form, 
and  have  an  average  diameter 
of  only  a  little  more  than  8  mmm. 
Often  two  and  three  are  seen 
connected  together,  forming 
moniliform  chains.  It  is  by 
the  active  growth  and  develop- 
ment of  the  cells  during  this 
process  that  the  glucose  of  the 
solution  is  decomposed,  and 
alcohol  and  carbonic  acid  pro- 
duced in  its  place.  Another 
species  of  saccharomyces  forms 
the  fungus  of  bread-yeast,  and 
a  third  the  ferment  of  grape- 
juice  by  which  it  is  made  to  un- 
dergo the  vinous  fermentation. 

When  fermentation  is  used  as  a  test,  a  little  beer-yeast  is  added  to 
the  supposed  saccharine  fluid,  and  the  mixture  kept  at  the  temperature 
of  about  25°  (77°  P.).  The  gas  which  is  given  off  during  the  process 
is  collected  and  examined,  and  the  remaining  fluid  is  purified  by  distil- 
lation. If  the  gas  be  found  to  be  carbonic  acid,  and  if  the  distilled 
liquid  contain  alcohol,  there  can  be  no  doubt  that  a  fermentable  sugar 
was  originally  present  in  the  solution.  Glucose  undergoes  fermenta- 
tion more  readily  and  completely  than  most  other  varieties  of  sugar. 

Lactose,  C12H24012,  or  Sugar  of  Milk. 

This  is  the  variety  of  sugar  which  is  found  in  milk,  the  only  fluid  in 
which  it  is  known  to  occur.  It  is  less  freely  soluble  than  glucose,  and 
its  sweet  taste  is  less  marked.  In  watery  solution  it  rotates  the  plane 
of  polarization  to  the  right  58°.20.  In  chemical  composition  it  is 
isomeric  with  glucose,  which  it  resembles  in  several  of  its  reactions, 
namely,  in  being  decomposed  and  turned  brown  by  boiling  alkalies,  in 
readily  reducing  the  copper-oxide  in  Trommer's  and  Fehling's  tests, 
and  in  undergoing  the  alcoholic  fermentation  under  the  influence  of 
yeast.  It  enters  into  fermentation,  however,  very  slowly,  as  compared 
with  glucose,  and  the  process  is  usually  incomplete.  If  fermentation 
go  on  in  the  milk  itself,  or  in  the  presence  of  other  ingredients  of  the 
milk,  a  part  of  the  sugar  is  converted  into  lactic  acid,  C3H603,  also  a 
carbo-hydrate.  By  boiling  for  ^ome  time  with  dilute  sulphuric  or 
hydrochloric  acid,  lactose  becomes  readily  and  completely  fermentable. 
This  sugar  forms  an  important  element  in  the  food  of  the  young 
infant,  being  a  constant  ingredient  of  the  milk.  It  is  not  known 
from  what  substance  it  is  formed  in  the  tissues  of  the  mammary  gland ; 


SUGAR.  67 

but  it  is  evidently  a  reserve  material,  intended  for  the  nutrition  of  the 
infant,  and  not  for  consumption  in  the  body  of  the  parent. 

Saccharose,  012H220U,  or  Cane  Sugar. 

This  variety,  the  oldest  known  species  of  sugar,  is  derived  from  the 
juices  of  the  sugar  cane,  where  it  exists  in  great  abundance.  It 
solidifies  on  cooling  from  a  hot  concentrated  solution  in  the  well- 
known  white  granular  crystalline  masses,  the  form  in  which  it  is 
generally  used  for  culinary  purposes.  If  crystallized  more  slowly,  it 
furnishes  large,  colorless,  prismatic  crystals,  in  which  form  it  is  known 
as  "  rock  candy"  or  ki  sugar  candy."  This  sugar  is  also  manufactured 
from  the  juices  of  the  beet-root,  and,  imperfectly  purified,  from  those  of 
the  sorghum  and  the  sugar-maple.  It  exists  to  some  extent  in  the 
green  stems  of  Indian  corn,  in  sweet  potatoes,  in  parsnips,  turnips,  and 
carrots,  and  in  the  spring  juices  of  the  birch  and  walnut  trees.  Honey 
is  a  mixture. of  glucose  and  saccharose,  together  with  various  other 
substances. 

Cane  sugar  originates  from  glucose,  in  the  process  of  vegetation,  by 
a  change  the  reverse  of  that  by  which  glucose  itself  is  formed  from 
starch,  that  is,  by  the  loss  of  oxygen  and  hydrogen  in  the  proportions 
to  form  water.  A  comparison  of  the  chemical  composition  of  the  two 
substances  will  show  the  manner  in  which  the  transformation  takes 
place,  namely : — 

Glucose.          "Water.       Cane  sugar. 

2(C6H1206)  -  H20  =  C12H22On. 

Saccharose  is  the  most  soluble  of  all  the  sugars,  and  has  the  strongest 
sweet  taste.  It  rotates  the  plane  of  polarization  to  the  right  73°. 8 4. 
It  differs  in  its  reactions  from  glucose  by  the  fact  that  it  is  not  turned 
brown  by  boiling  with  an  alkali,  and  does  not  reduce  the  copper-oxide 
in  Trommer's  test,  or  does  so  very  slowly  and  imperfectly.  It  may  be 
converted  into  glucose,  however,  by  a  few  seconds'  boiling  with  a  trace 
of  dilute  mineral  acid,  and  will  then  react  promptly  both  with  boiling 
alkalies  and  with  Trommer's  test.  Cane  sugar  is  not  immediately 
fermentable,  but  by  contact  with  yeast  it  is  after  a  time  changed  into 
glucose,  and  finally  enters  into  fermentation.  As  it  occurs  in  the 
tissues  of  the  living  vegetable,  it  is  regarded  as  a  reserve  material, 
which  is  subsequently  reconverted  into  glucose  for  the  purposes  of 
nutrition.1  When  taken  as  food,  it  is  transformed  into  glucose  by  the 
intestinal  fluids  in  the  digestive  process. 

Sugar  and  starch,  accordingly,  in  all  their  varieties,  are  closely  allied 
to  each  other,  both  in  their  chemical  and  physiological  relations.  Their 
proportions  of  hydrogen  and  oxygen  are  such  as  to  have  given  them,  as 
a  class,  a  distinct  name,  and  their  mutual  convertibility  in  the  process 
of  vegetation  has  been  shown  by  abundant  investigations.  Starch  and 
sugar,  in  the  living  plant,  represent  the  same  nutritive  material  under 

1  Mayer,  Agrikultur-Chemie,  Band  i.  p.  122. 


63       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 

two  different  conditions ;  starch  being  the  substance  in  the  form  of  a 
solid  deposit,  and  glucose  in  the  form  of  solution  and  activity.1  In 
the  animal  body,  the  glycogen  of  the  liver  is  converted  into  soluble 
glucose,  and  thus  enters  the  circulation  before  it  takes  an  active  part 
in  the  nutritive  operations;  and  vegetable  starch,  when  taken  as  food, 
undergoes  the  same  transformation  in  the  intestinal  canal.  Finally 
these  substances,  from  whatever  source  they  may  be  derived,  are  com- 
pletely decomposed  in  the  interior  of  the  system,  and  do  not  reappear, 
in  any  notable  quantity,  in  the  excreted  fluids  of  the  body. 

IV.  Fats. 

The  fatty  matters,  or  fixed  oils,  are  distinguished  from  the  preceding 
group,  so  far  as  regards  their  chemical  composition,  by  the  fact  that  they 
do  not  contain  hydrogen  and  oxygen  in  the  proportions  to  form  water, 
the  oxygen  being  present  in  smaller  quantity ;  and  also  by  their  large 
proportion  of  carbon,  which  preponderates  much,  by  weight,  over  the 
other  two  elements.  This  fact  is  probably  connected  with  the  strongly 
marked  inflammability  which  constitutes  one  of  their  most  useful  pro- 
perties, the  oils  being  decomposed  at  a  temperature  of  300°  (570°  F.), 
and  burning  with  a  bright  flame.  The  peculiarly  smooth  consistency 
of  the  oleaginous  matters  is  also  one  of  their  distinguishing  features, 
and  enables  them  to  be  employed  as  lubricating  substances,  to  diminish 
the  friction  between  opposite  surfaces. 

The  fats  are  all  insoluble  in  water,  slightly  soluble  in  alcohol,  and 
freely  soluble  in  ether,  which  is  accordingly  used  with  advantage  in 
extracting  them  from  their  admixture  with  other  organic  matters. 
They  are  also  readily  soluble  in  each  other.  They  exhibit  no  rotatory 
action  upon  polarized  light.  They  are  all  fluid  at  a  high  temperature, 
and  crystallize  on  being  cooled  down  to  the  requisite  point ;  the  precise 
degree  at  which  crystallization  takes  place  varying  for  the  different 
kinds  of  fats. 

The  fats  are  not  only  insoluble  in  water,  but  they  refuse  to  mix  with 
it,  even  after  prolonged  mechanical  agitation ;  and  as  soon  as  the  two 
fluids  are  left  at  rest  they  separate  from  each  other,  the  water  remain- 
ing below,  and  the  oil  rising  to  the  surface,  where  it  collects  as  a  dis- 
tinct layer.  But  if  the  watery  fluid  contain  a  trace  of  free  alkali,  the 
oil  is  broken  up  into  minute  particles,  which  are  disseminated  uni- 
formly throughout  the  fluid  and  held  in  permanent  suspension.  Such 
a  fluid  is  called  an  emulsion,  and  presents  an  opaque  white  color,  owing 
to  the  intimate  mixture  of  watery  and  oleaginous  particles  having 
different  refractive  powers.  In  an  emulsion,  the  oil  does  not  suffer  any 
chemical  modification,  but  is  simply  broken  up  into  a  state  of  minute 
dissemination.  It  can  be  recovered,  with  all  its  original  characters, 
by  evaporating  the  watery  fluid  and  extracting  the  oil  from  the  dry 
residue  by  means  of  ether.  Oil  may  also  be  emulsioned  by  contact 

1  Sachs,  Trait£  do  Botauique.     Puris,  1874,  p.  840. 


FATS.  69 

with  certain  nitrogenous  organic  matters  of  an  albuminous  nature. 
White  of  egg,  or  the  serum  of  blood,  exerts  this  effect  in  an  energetic 
manner,  and  the  fatty  substances  of  milk  are  held  in  suspension  by  its 
liquid  albuminous  ingredients. 

Another  characteristic  of  the  true  fatty  substances  is  their  property 
of  saponification,  that  is,  of  forming  soaps  when  subjected  to  certain 
chemical  influences.  If  either  of  the  natural  fats  be  boiled  for  a  con- 
siderable time  in  the  watery  solution  of  a  free  alkali,  it  is  decomposed, 
with  the  production  of  two  new  bodies—first,  glycerine  (C3H803),  a  neu- 
tral fluid  substance  which  is  soluble  in  water;  and  secondly,  a  fatty 
acid  which  combines  with  the  alkali  and  forms  a  soap.  An  analogous 
change  is  thought  to  take  place  with  a  portion  of  the  fatty  matters  in 
the  animal  fluids. 

The  fats  are  derived  from  both  the  animal  and  the  vegetable  world. 
They  are  present  in  many  of  the  solids  and  fluids  of  the  living  body, 
and  are  found  also  in  many  varieties  of  vegetable  food.  The  following 
list  gives  the  proportion  of  fat  in  various  alimentary  substances,  accord- 
ing to  the  tables  of  Payen  : — 

QUANTITY  OF  FAT  IN  100  PARTS  IN 

Wheat         .        .        .  2.10  Beef's  flesh  (average) .  5.19 

Indian  corn .         .         .  8.80  Calf's  liver .  .  .  5.58 

Potatoes      .         .         .  0.11  Mackerel      .  .  .  6.76 

Beans  ....  2.50  Salmon         .  .  .  4.85 

Peas    ....  2.10  Oysters        .  .  .  1.51 

Sweet  almonds     .  24.28  Cow's  milk  .  .  .  3.70 

Chocolate  nut      .         .  49.00  Fowl's  egg  .  .  .  7.00 

Beside  entering  as  an  ingredient  into  the  above  articles,  fat  is  often 
taken  with  the  food  in  a  pure,  or  nearly  pure  form,  as  butter,  olive  oil, 
or  the  various  kinds  of  adipose  tissue. 

Fat  is  produced  in  the  vegetable  tissues,  perhaps  to  some  extent 
directly  from  carbonic  acid  and  water,  but  certainly  in  considerable 
quantity  by  transformation  of  the  starch  originally  formed.1  It  is  from 
this  source  that  the  fat  so  abundantly  stored  up  in  oily  seeds  and  fruits 
is  mainly  derived;  and  in  this  situation  it  is  retained  until  required  for 
the  purposes  of  germination  and  growth.  It  is  accumulated  in  some 
seeds  and  fruits  in  remarkable  quantity,  particularly  in  those  of  the 
sweet  and  bitter  almond,  the  chocolate  tree,  hemp,  flax,  ricinus  com- 
munis,  and  Croton  tiglium,  where  it  exists  in  the  proportions  of  from 
24  to  60  per  cent. 

The  three  most  important  varieties  of  fat  are  those  known  as  Stearins, 
Palmitine,  and  Oleine.  They  resemble  each  other  in  their  general 
characters,  and  differ  mainly  in  their  degree  of  fluidity  at  correspond- 
ing temperatures ;  stearine  solidifying  the  most  readily  of  the  three, 
while  oleine  remains  fluid  at  a  lower  temperature  than  either  of  the 
others. 

1  Mayer,  Agrikultur-Chemie,  Band  i.  pp.  84,  85. 


TO       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 

Stearine,  C57H1100C, 

So  called  from  the  readiness  with  which  it  assumes  the  solid  form,  is  a 
main  ingredient  of  the  more  consistent  fats.  It  liquefies,  when  pure,  at 
about  60°  (1400  p.^  an(j  again  solidifies  when  the  temperature  falls  to 

or  a  little  below  this  point.    It 

•Fig-  8-  crystallizes,  on  cooling  from  a 

warm  solution  in  oleine,  in  fine 
radiating  needles  which  often 
follow  a  wavy  or  curvilinear 
direction.  It  is  rather  less 
freely  soluble  in  alcohol  and 
ether  than  the  other  fatty  sub- 
stances. 


Palmitine,  C51H9806, 
Was  first  recognized  as  an  in- 
gredient of  palm  oil,  a  semi- 
solid  fat  obtained  from  the 
seed  of  an  African  palm.  It 
crystallizes,  on  cooling  from  its 
concentrated  alcoholic  or  ethe- 

STEABiNE,cryBtallizedJrom  a  warm  solution  in      real    solution,  in    the    form    of 

slender    needles.     It    liquefies 

about  the  temperature  of  46°  (115°  F.).     It  is  found  in  considerable 
abundance  in  a  variety  of  animal  and  vegetable  fats. 

Oleine,  C57H10406. 

As  its  name  indicates,  this  is  the  representative  ingredient  of  the  oils, 
or  liquid  fatty  substances.  When  pure  it  is  transparent  and  colorless. 
It  retains  its  fluidity  at  all  ordinary  temperatures,  and  even  below  the 
freezing  point  of  water.  It  readily  dissolves  both  stearine  and  palmi- 
tine,  its  solvent  power  for  these  substances  increasing  writh  the  elevation 
of  the  temperature. 

None  of  these  oleaginous  substances  occur  naturally  in  an  isolated 
form,  but  they  are  mingled  together  in  varying  proportions  in  all  the 
ordinary  animal  and  vegetable  fats  and  oils.  The  consistency  of  the 
mixtures  varies  with  the  relative  quantity  of  their  different  fatty  ingre- 
dients. Thus  the  more  solid  fats,  such  as  suet  and  tallow,  consist 
largely  of  stearine ;  the  softer  fats,  as  lard,  butter,  and  the  ingredients 
of  human  adipose  tissue,  contain  a  greater  abundance  of  palmitine; 
while  the  liquid  fats,  like  the  fish  oils,  olive  oil,  and  nut  oil,  are 
composed  mainly  of  oleine.  As  a  general  rule,  in  the  bodies  of  the 
warm-blooded  animals  these  mixtures  are  fluid,  or  very  nearly  so,  in 
consistency ;  for,  although  both  stearine  and  palmitine,  when  pure,  are 
solid  at  the  ordinary  temperature  of  the  body,  they  are  held  in  solu- 
tion during  life  by  the  oleine  with  which  they  are  associated.  After 


FATS. 


71 


OLEAGINOUS  PBINCIPLES  OP  HUMAN 
FAT.  Steariiie  and  Palmitine  crystallized ;  Ole- 
ine  fluid. 


death,  as  the   body   cools,  the  Fig.  9. 

stearine  and  pafmitine  some- 
times separate  in  a  crystalline 
form,  since  the  oleine  can  no 
longer  hold  in  solution  so  large 
a  quantity  as  it  had  dissolved  at 
a  higher  temperature.  (Fig.  9.) 

When  in  a  fluid  state,  the  fatty 
substances  present  themselves  in 
the  form  of  drops  or  globules, 
which  vary  greatly  in  size,  but 
which  may  be  readily  recog- 
nized by  their  optical  proper- 
ties. They  are  circular  in  shape, 
with  a  sharp  well-defined  out- 
line. They  often  have  a  faint 
amber  color,  which  is  distinctly 
marked  in  the  larger  globules, 
less  so  in  the  smaller.  As  they 

have  a  higher  refractive  power  than  the  watery  fluids  in  which  they  are 
immersed,  they  act  under  the  microscope  as  double  convex  lenses,  and 
concentrate  the  light  transmitted  through  them,  at  a  point  above  the 
level  of  the  liquid.  Consequently,  they  present  the  appearance  of  a 
bright  centre  surrounded  by  a  dark  border.  If  the  lens  of  the  micro- 
scope be  lifted  farther  away,  the  centre  of  the  globule  becomes  brighter, 
and  its  borders  darker.  These  characters  will  usually  be  sufficient  to 
distinguish  them  from  other  fluid  globules  of  less  refractive  power. 

The  oleaginous  matters  present  a  striking  peculiarity  in  regard  to  the 
form  under  which  they  occur  in  the  living  body,  and  one  which  distin- 
guishes them  from  other  ingredients  of  the  animal  solids  and  fluids. 
The  remaining  proximate  principles  of  different  groups  are  intimately 
associated  together  by  molecular  union,  so  as  to  form  either  clear  solu- 
tions or  homogeneous  solids.  Thus  the  saccharine  matters  of  the  blood 
or  the  milk  are  in  solution  in  water,  in  company  with  the  albumen,  the 
lime  phosphate,  sodium  chloride,  and  the  like ;  all  of  them  equally  dis- 
tributed throughout  the  general  mass  of  the  fluid.  In  the  bones  and 
cartilages,  the  animal  matters  and  the  calcareous  salts  are  in  similarly 
intimate  union  with  each  other ;  and  in  every  other  part  of  the  body  the 
animal  and  inorganic  ingredients  are  united  in  a  similar  way.  But  it  is 
different  with  the  fats.  For,  while  the  three  principal  varieties  of 
oleaginous  matter  are  united  with  each  other,  they  are  not  united,  as  a 
general  rule,  with  proximate  principles  of  other  kinds  ;  that  is,  with 
water,  saline  substances,  sugar,  or  albumen.  The  fats  are  soluble  to  a 
certain  extent  in  the  ingredients  of  the  bile,  and  they  are  found  in  small 
quantity,  in  the  saponified  condition,  in  the  plasma  of  the  blood,  as 
sodium  stearate,  palmitate,  or  oleate.  But  in  by  far  the  larger  propor- 


72        HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 


tion  of  cases,  instead  of  forming  a  homogeneous  solid  or  fluid  with  the 
other  proximate  principles,  the  oleaginous  matters  are*  found  in  distinct 
masses  or  globules,  suspended  in  the  serous  fluids,  interposed  in  the 
interstices  between  the  anatomical  elements,  included  in  the  interior  of 
cells,  or  deposited  in  the  substance  of  fibres  or  membranes.  Even  in 
the  vegetable  tissues,  oil  is  always  deposited  in  distinct  drops  or 
granules. 

Owing  to  this  fact,  the  oils  can  be  easily  extracted  from  the  organized 
tissues  by  the  employment  of  mechanical  processes.  The  tissues,  animal 
or  vegetable,  are  cut  into  small  pieces  and  subjected  to  pressure,  by 
which  the  oil  is  forced  out  from  the  parts  in  which  it  was  entangled, 
and  separated,  sometimes  without  further  manipulation,  in  a  state  of 
comparative  purity.  A  moderately  elevated  temperature  facilitates  the 
operation  by  increasing  the  fluidity  of  the  oleaginous  matter ;  but  no 
chemical  agency  is  required  for  its  separation.  Under  the  microscope, 
oil-drops  and  granules  can  be  readily  distinguished  from  the  remaining 
parts  of  a  tissue,  and  may  also  be  recognized  by  the  dissolving  action 
of  ether,  which  acts  upon  them,  for  the  most  part,  without  attacking 
the  other  proximate  principles. 

Oils  are  found,  in  the  animal  body,  most  abundantly  in  the  adipose 
tissue.  Here  they  are  contained  in  the  interior  of  the  adipose  vesicles, 
the  cavities  of  which  they  completely  fill,  in  a  state  of  health.  These 
vesicles  are  transparent,  and  have  a  partly  angular  form,  owing  to  their 
mutual  compression.  (Fig.  10.)  They  vary  in  diameter,  in  the  human  sub- 
ject, from  28  mmm.  to  125  mmm.,  and  are  composed  of  a  thin,  structure- 
less animal  membrane,  forming 

Fig-  10.  a  closed  sac.  in  the  interior  of 

which  the  oily  matter  is  con- 
tained. The  oil,  accordingly, 
is  simply  included  mechani- 
cally in  the  interior  of  the 
vesicles.  Sometimes,  when 
emaciation  is  going  on,  the  oil 
partially  disappears  from  the 
cavity  of  the  adipose  vesicle, 
and  its  place  is  taken  by  a 
watery  serum  ;  but  the  serous 
and  oily  fluids  remain  distinct, 
and  occupy  different  parts  of 
the  cavity  of  the  vesicle. 

In  the  chyle,  the  oleaginous 
matter  is  in  a  state  of  emul- 
sion or  suspension  in  the  form 
of  minute  particles  in  a  serous  fluid.  Its  subdivision  is  here  more  com- 
plete, and  its  molecules  more  minute,  than  anywhere  else  in  the  body. 
It  presents  the  appearance  of  a  fine  granular  dust,  which  has  been  known 
by  the  name  of  the  "  molecular  base  of  the  chyle."  A  few  of  these 


HUMAN  ADIPOSK  TISSUE. 


FATS. 


73 


CHYLE,  from  commencement  of  Thoracic  Duct, 
from  the  Dog. 


granules  are  to  be  seen  which  Fig.  H- 

measure  2.5  mmm.  in  diameter ; 
but  they  are  generally  much 
less  than  this,  and  the  greater 
part  are  so  small  that  they  can- 
not be  accurately  measured. 
(Fig.  11.)  For  the  same  reason 
they  do  not  present  the  bril- 
liant centre  and  dark  border  of 
the  larger  oil-globules  ;  but  ap- 
pear by  transmitted  light  only 
as  minute  dark  granules.  The 
white  color  and  opacity  of  the 
chyle,  as  of  all  other  fatty  emul- 
sions, depend  upon  this  mole- 
cular condition  of  the  oily  in- 
oredients.  The  albumen  and 

O 

salts,   which   are    in    intimate 

union  with  each  other,  and  dissolved  in  the  water,  would  alone  make  a 
colorless  and  transparent  fluid;  but  the  oily  matters,  suspended  in 
distinct  particles,  with  a  different  refractive  power  from  that  of  the 
serous  fluid,  interfere"  with  its  transparency,  and  give  to  the  mixture 
the  white  color  and  opaque  appearance  which  are  characteristic  of  emul- 
sions. The  oleaginous  nature 
of  these  particles  is  readily 
shown  by  their  solubility  in 
ether. 

In  the  milk,  the  oily  matter 
occurs  in  larger  masses  than  in 
the  chyle.  In  cow's  milk  (Fig. 
12),  the  oil-drops,  or  "milk- 
globules,"  are  not  quite  fluid, 
but  have  a  pasty  consistency, 
owing  to  the  large  quantity  of 
palmitine  which  they  contain,  in 
proportion  to  the  oleine.  When 
forcibly  amalgamated  with  each 
other  and  collected  into  a  mass 
by  prolonged  beating  or  churn- 
ing, they  constitute  butter.  In 
cow's  milk,  the  globules  vary 

somewhat  in  size,  but  their  average  diameter  is  6  mmm.  They  are 
suspended  in  the  serous  fluid  of  the  milk,  and  by  heating  may  be  more 
perfectly  liquefied,  and  made  to  assume  a  circular  form. 

In  the  cells  of  the  laryngeal,  tracheal,  and  costal  cartilages  (Fig.  13) 
there  is  always  more  or  less  fat  deposited  in  the  form  of  rounded  glo- 
bules, somewhat  similar  to  those  of  the  milk. 
6 


Fig.  12. 


GLOBULES 


Cow's  MILK. 


74       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 


Fig.  13. 


CELLS  OF  COSTAL  CARTILAGES,  containing 
oil-globules.    Human. 

Fig.  14. 


In  the  glandular  cells  of  the  liver,  oil  occurs  constantly,  in  a  slate  of 
health.  It  is  here  deposited  in  the  substance  of  the  cell  (Fig.  14), 

generally  in  smaller  globules 
than  the  preceding.  In  some 
cases  of  disease,  it  accumulates 
in  excessive  quantity,  and  pro- 
duces the  state  known  as  fatty 
degeneration  of  the  liver.  This 
is  consequently  only  an  exag- 
gerated condition  of  that  which 
normally  exists  in  health. 

In  the  carnivorous  animals 
oil  exists  in  considerable  quan- 
tity in  the  convoluted  portion 
of  the  uriniferous  tubules.  (Fig. 
15.)  It  is  here  in  the  form  of 
granules  and  rounded  drops, 
which  sometimes  appear  to  fill 
nearly  the  whole  calibre  of  the 
tubules. 

It  is  found  also  in  the  secret- 
ing cells  of  the  sebaceous  and 
other  glandules,  deposited  in 
the  same  manner  as  in  those  of 
the  liver,  but  in  smaller  quan- 
tity. It  exists,  beside,  in  large 
proportion,  in  a  granular  form, 
in  the  secretion  of  the  seba- 
ceous glandules. 

It  occurs  abundantly  in  the 
marrow  of  the  bones,  both  un- 
der the  form  of  free  oil-globules 
and  inclosed  in  the  vesicles  of 
adipose  tissue,  and  is  found  in 
considerable  quantity  in  the 
substance  of  the  yellow  wall  of 
the  corpus  luteum. 

It  occurs  also  in  the  form  of 

granules  and  oil-drops  in  the  muscular  fibres  of  the  uterus  (Fig.  16), 
in  which  it  begins  to  be  deposited  soon  after  delivery,  and  where  it 
continues  to  be  present  during  the  whole  period  of  the  resorption  or 
involution  of  this  organ. 

In  all  these  instances^  the  oleaginous  matters  remain  distinct  in  form 
and  situation  from  the  other  ingredients  of  the  tissues,  and  are  only 
mechanically  entangled  among  the  fibres  and  cells,  or  imbedded  in  their 
interior. 


HEPATIC  CELLS.    Human. 


FATS. 


75 


Fig.  15. 


TJRTNIFEROUS    TUBULES    OF    DOG,    from    COr- 

tical  portion  of  kidney. 


Fig.   16. 


A  large  part  of  the  fat  which  is  found  in  the  animal  body  may  be 
accounted  for  by  that  which  is  taken  in  with  the  food,  since  oily  matter 
occurs  in  both  animal  and  vege- 
table substances.  Fat  is,  how- 
ever, formed  in  the  body  from 
other  organic  substances,  inde- 
pendently of  what  is  intro- 
duced with  the  food.  This 
important  fact  has  been  defi- 
nitely ascertained  by  the  ex- 
periments of  MM.  Dumas  and 
Milne-Edwards  on  bees,1  M. 
Persoz  on  geese,3  and  finally 
by  those  of  M.  Boussingault 
on  geese,  ducks,  and  pigs.3  The 
observers  first  ascertained  the 
quantity  of  fat  existing  in  the 
whole  body  at  the  commence- 
ment of  the  experiment.  The 
animals  were  then  subjected  to 
a  definite  nutritious  regimen, 
in  which  the  quantity  of  fatty 
matter  was  duly  ascertained  by 
analysis.  The  experiments 
lasted  for  a  period  varying,  in 
different  instances,  from  thirty- 
one  days  to  eight  months; 
after  which  the  animals  were 
killed  and  all  their  tissues  ex- 
amined. The  result  of  these 
investigations  showed  that  con- 
siderably more  fat  had  been 
accumulated  by  the  animal 
during  the  course  of  the  expe- 
riment than  could  be  accounted 
for  by  that  which  existed  in 
the  food ;  and  placed  it  beyond 
a  doubt  that  oleaginous  sub- 
stances may  be,  and  actually 

are,  formed  in  the  interior  of  the  animal  body  by  the  decomposition  or 
metamorphosis  of  other  proximate  principles. 

There  is  reason  to  believe  that  fat  is  produced  in  this  way,  under  the 
influence  of  the  vital  process,  from  the  transformation  of  starchy  and 
saccharine  substances.  In  the  first  place,  as  we  have  already  seen,  there 


MUSCULAR    FIBRES    OF    HUMAN    UTERUS 
three  weeks  after  parturition. 


1  Annales  de  Chira.  et  de  Phys.,  3d  series,  vol.  xiv.  p.  400.  2  Ibid.,  p.  408. 

3  Chimie  Agricole.     Paris,  1854. 


76       HYDROCARBONACEOUS    PROXIMATE    PRINCIPLES. 

is  no  clonbt  that  fat  is  produced  from  starch  and  glucose  in  vegetables 
during  a  certain  period  of  their  growth.  The  oily  seeds  of  certain 
plants  while  still  immature  contain  starch  ;  but  as  they  ripen,  the  starch 
diminishes  or  disappears  and  oil  takes  its  place.1 

It  is  also  a  matter  of  common  observation  that  articles  of  food,  con- 
sisting largely  of  starch  or  sugar,  or  of  both,  are  especially  apt  to  be 
fattening,  both  for  man  and  animals  and  in  sugar  growing  countries, 
during  the  short  season  occupied  in  extracting  and  preparing  the  sugar, 
the  horses  and  cattle,  as  well  as  the  laborers  emplo3red  on  the  plantation, 
all  of  whom  partake  freely  of  the  saccharine  juices,  grow  remarkably 
fat,  and  again  lose  their  superabundant  flesh  when  the  season  is  past. 
It  is  not  known,  however,  whether  the  saccharine  matters  in  these  in- 
stances are  directly  converted  into  fat,  or  whether  they  pass  through  a 
series  of  intermediate  changes  which  furnish  the  materials  for  its  forma- 
tion. The  abundant  accumulation  of  fat  in  certain  regions  of  the  body 
and  its  absence  in  others,  and  more  particularly  its  constant  occurrence 
in  situations  to  which  it  could  not  have  been  transported  by  the  blood, 
as  the  interior  of  the  cells  of  the  costal  cartilages,  make  it  probable  that 
oily  matter  is  often  formed  from  the  metamorphosis  of  other  proximate 
principles,  upon  the  very  spot  where  it  makes  its  appearance  in  the 
solid  tissues.  Cases  of  hereditary  obesity,  and  of  obesity  occurring 
only  after  a  definite  period  of  life,  indicate  also  that  the  excessive  depo- 
sition of  fat  may  be  due  to  internal  causes  dependent  on  the  special 
condition  of  the  bodily  system. 

In  the  female  during  lactation,  a  large  part  of  the  oily  matter  intro- 
duced with  the  food,  or  formed  in  the  body,  is  discharged  with  the  milk, 
and  goes  to  the  support  of  the  infant.  But  in  the  female  in  the  inter- 
vals of  lactation,  and  in  the  male  at  all  times,  the  oily  matters  almost 
entirely  disappear  by  decomposition  in  the  interior  of  the  body ;  since 
the  small  quantity  which  is  discharged  with  the  sebaceous  matter  by 
the  skin  bears  only  an  insignificant  proportion  to  that  which  is  intro- 
duced daily  with  the  food. 

Beside  the  fats  proper  there  is  also  contained  in  the  body  the  fol- 
lowing substance,  which  resembles  fat  in  the  general  features  of  its 
chemical  composition,  and  in  some  of  its  reactions,  but  differs  from 
them  in  three  important  particulars,  namely :  1st,  in  being  volatile  at  a 
high  temperature ;  2d,  in  exerting  a  rotatory  action  on  polarized  light ; 
and  3d,  in  the  fact  that  it  cannot  be  transformed,  by  the  action  of  alka- 
line solutions,  into  glycerine  and  a  fatty  acid — that  is,  it  is  not  saponi- 
fiable. 

Cholesterine,  C26H440, 

So  called  from  its  being  often  precipitated  as  a  solid  deposit  from  the 
bile,  in  which  form  it  was  first  discovered.  Cholesterine  is  an  ingredient 
in  the  blood-plasma  and  the  blood-globules,  in  the  bile,  in  the  sebaceous 

1  Prof.  S.  W.  Johnson,  How  Crops  Grow.    New  York,  p.  94. 


CHOLESTERINE. 


77 


Fig.  17. 


matter  of  the  skin,  the  liver,  the  spleen,  the  crystalline  lens,  and  espe- 
cially in  the  nerves,  spinal  cord,  and  brain,  in  which  last  it  has  been 
found  by  Flint1  in  the  proportion  on  the  average  of  about  one  part  per 
thousand.     Recent  observations  have  shown  that  it  is  also  a  constituent  / 
of  various  articles  of  food,  such  as  the  yolk  of  egg,  and  even  of  many  1 
vegetable  products,  as  peas,  beans,3  olives,  almonds,  and  Indian  corn.3    J 

Cholesterine  is  a  cry stalliz able  substance,  insoluble  in  water,  freely 
soluble  in  ether,  chloroform,  boiling  alcohol,  and  the  volatile  and  fatty 
oils.  It  is  partially  soluble  in 
watery  solutions  of  the  biliary 
salts  and  of  the  saponified  fats. 
It  is  deposited  from  its  alco- 
holic or  ethereal  solution  in 
the  form  of  very  thin,  color- 
less, transparent,  rhomboidal 
plates,  portions  of  which  are 
often  cut  out  by  lines  of  cleav- 
age parallel  to  the  edges  of  the 
crystal.  They  frequently  occur 
deposited  in  layers,  in  which 
the  outlines  of  the  subjacent 
crystals  show  very  distinctly 
through  the  substance  of 
those  placed  above.  It  is 
often  found,  in  a  crystalline 
form,  in  the  fluid  of  hydrocele 
and  other  morbid  exudations,  in  the  contents  of  encysted  tumors,  and 
in  biliary  calculi.  Crystallized  cholesterine  melts  at  145°  (293°  F.)? 
and  distils  unchanged  in  vacuo  at  about  360°  (680°  F.).  Its  solutions 
rotate  the  plane  of  polarization  to  the  left  32°. 

If  cholesterine  be  triturated  with  strong  sulphuric  acid,  and  chloro- 
form added  to  the  mixture,  a  blood-red  color  is  produced,  which  after- 
ward disappears  by  exposure  to  the  air,  passing  gradually  from  red  to 
violet,  blue,  and  green,  the  solution  finally  becoming  colorless. 

Our  knowledge  with  regard  to  the  physiological  relations  of  choleste- 
rine is  less  definite  than  as  to  those  of  the  true  fatty  substances.  Its 
abundant  proportion  in  the  brain  and  nerves,  and  its  association  in  these 
tissues  with  other  important  constituents,  have  led  to  the  opinion  that 
it  is  an  essential  ingredient  of  the  nerve  substance.  Whatever  may  be 
its  source  in  these  organs,  it  is  no  doubt  absorbed  from  the  nervous 
system  by  the  blood,  carried  to  the  liver,  and  thence  discharged  with 

1  American  Journal  of  the  Medical  Sciences,  October,  1862. 

Hoppe-Seyler,  Handbuch  der   Physiologisch-  und  Pathologisch-Chemischen, 
Analyse.     Berlin,  1870,  p.  98. 
3  Hardy,  Principes  de  Chimie  Biologique.     Paris,  1871,  p.  123. 


GHOLBSTERINE,  from  an  Encysted  Tumor. 


78        HYDROCARBONAOEOUS    PROXIMATE    PRINCIPLES. 

the  bile.  According  to  the  observations  of  Prof.  Flint,  Jr.,  on  the  dog,1 
its  quantity  in  the  blood  increases,  while  passing  through  the  brain, 
from  0.52  to  1.09  parts  per  thousand.  Authorities  differ  as  to  whether 
it  is  discharged  with  the  feces,  or  is  transformed  in  the  interior  of  the 
body. 

The  most  important  characteristic,  in  a  physiological  point  of  view, 
of  all  the  proximate  principles  of  the  second  class,  including  the  amyla- 
ceous, saccharine,  and  oily  substances,  relates  to  their  source  and  their 
final  destination.  Not  only  are  they  of  organic  origin,  making  their 
appearance  first  in  the  interior  of  vegetables ;  but  they  are  all  produced 
also,  to  a  certain  extent,  from  other  organic  materials,  in  the  bodies  of 
animals  ;  continuing  to  be  formed  when  no  similar  substances,  or  only 
an  insufficient  quantity  of  them,  have  been  taken  with  the  food.  Fur- 
thermore, when  introduced  with  the  food,  or  formed  in  the  body  and 
deposited  in  the  tissues,  these  substances  are  not  found  in  the  secretions. 
They,  therefore,  for  the  most  part,  disappear  by  decomposition  in  the 
interior  of  the  body.  They  pass  through  a  series  of  changes  by  which 
their  essential  characters  are  destroyed ;  and  they  are  finally  replaced 
in  the  circulation  by  other  substances,  which  are  discharged  with  the 
excreted  fluids. 

1  Physiology  of  Man,  vol.  iii.     New  York,  1870,  pp.  281,  282 


CHAPTEE    IV. 

ALBUMINOUS    MATTEES. 

THE  proximate  principles  belonging  to  this  class  are  very  important, 
not  only  from  their  peculiar  physiological  properties,  but  also  from 
their  comparatively  abundant  quantity  in  the  animal  body.  They  are 
derived  both  from  animal  and  vegetable  sources.  But  in  plants,  as  a 
general  rule,  the  albuminous  matters,  though  constantly  present,  and 
essential  to  the  activity  of  vegetative  life,  are  in  small  quantity  as  com- 
pared with  other  ingredients  of  the  fully  developed  tissues.  In  man  and 
animals,  on  the  other  hand,  they  constitute  by  far  the  larger  part  of  all 
the  solid  constituents  of  the  body.  Everywhere  their  chemical  consti- 
tution, their  physical  characters,  and  the  distinctive  properties  which 
belong  to  them,  show  that  they  have  an  intimate  connection  with  the 
more  active  phenomena  of  living  beings. 

The  first  peculiarity  by  which  they  are  distinguished  from  the  proxi- 
mate principles  of  the  preceding  class,  is  that  they  contain  nitrogen,  in 
addition  to  the  three  elements  belonging  to  other  organic  bodies,  namely, 
carbon,  hydrogen,  and  oxygen.  They  are,  therefore,  sometimes  called 
the  "nitrogenous"  proximate  principles.  But,  as  we  shall  hereafter 
see,  there  are  various  other  substances,  of  a  crystallizable  nature,  also 
containing  nitrogen,  which  are  produced  in  the  body,  and  which  are  of  a 
different  character  from  the  albuminous  matters. 

The  albuminous  matters  are  not  crystallizable.  They  always,  when 
pure,  assume  an  amorphous  condition,  in  which  they  are  sometimes 
solid,  as  in  the  bones ;  sometimes  fluid,  as  in  the  plasma  of  the  blood ; 
and  sometimes  semi-solid  in  consistency,  or  midway  between  the  solid 
and  fluid  condition,  as  in  the  muscles  and  the  substance  of  the 
glandular  organs.  Even  in  the  fluids,  the  albuminous  matters,  when 
present  in  considerable  quantity,  as  in  the  blood-plasma,  the  pancreatic 
juice,  or  the  subrnaxillary  saliva,  give  to  the  solution  a  peculiar 
viscid  or  mucilaginous  consistency.  This  consistency  is  more  marked, 
in  proportion  to  the  abundance  of  the  organic  ingredients.  The 
albuminous  matters,  in  solution,  all  rotate  the  plane  of  polarization 
toward  the  left.  The  precise  chemical  constitution  of  these  substances 
has  not  been  in  all  cases  determined.  The  apparent  variation  in  the 
exact  proportion  of  their  ultimate  elements  in  different  instances  is 
probably  due  to  the  readiness  with  which  they  become  modified  in  the 
processes  of  nutrition,  many  of  them  passing  into  each  other  under  the 
influence  of  digestion  and  assimilation.  There  are,  no  doubt,  a  great 
variety  of  these  matters  existing  in  the  body,  only  a  certain  number  of 


80  ALBUMINOUS    MATTERS. 

which  have  as  yet  been  so  distinctly  recognized  as  to  receive  specific 
names.  Many  of  them,  perhaps  all,  contain  a  small  amount  of  sulphur 
in  addition  to  their  carbon,  hydrogen,  oxygen,  and  nitrogen.  Their 
chemical  relation  to  other  substances  has  not  been  found  sufficiently 
definite,  in  any  case,  to  establish  the  formula  for  their  atomic  constitu- 
tion. The  average  proportion,  however,  by  weight,  of  their  constituent 
elements,  according  to  the  tables  of  Hoppe-Seyler1  and  Fremy,  is  as 
follows : — 

AVERAGE  COMPOSITION  OF  ALBUMINOUS  MATTERS. 

Carbon 52.0 

Hydrogen         ......  6.9 

Nitrogen 15.6 

Oxygen 24.0 

Sulphur  .......          1.5 

100.0 

One  of  the  simpler  physical  characters  of  the  albuminous  substances 
is  that  they  are  hygroscopic.  '  As  met  with  in  different  parts  of  the  body, 
they  present  different  degrees  of  consistency ;  some  being  nearly  solid, 
others  more  or  less  fluid.  But  on  being  subjected  to  evaporation  they 
all  lose  water,  and  may  finally  be  reduced  to  the  perfectly  solid  form. 
If  after  this  desiccation  they  be  exposed  to  the  contact  of  moisture, 
they  again  absorb  water,  swell,  and  regain  their  original  mass  and  con- 
sistency. This  phenomenon  is  different  from  that  of  capillary  attrac- 
tion, by  which  some  inorganic  substances  or  tissues  become  moistened 
when  exposed  to  the  contact  of  water ;  for  in  the  latter  case  the  water 
is  simply  entangled  mechanically  in  the  meshes  and  pores  of  the  inorganic 
body,  while  that  which  is  absorbed  by  the  albuminous  matter  is  actually 
united  with  its  substance,  and  diffused  equally  throughout  its  entire 
mass.  Every  albuminous  matter  is  naturally  united  in  this  way  with  a 
certain  quantity  of  water,  some  with  more,  some  with  less.  Thus  the 
albumen  of  the  blood  is  in  union  with  so  much  water  that  it  has  the 
fluid  form,  while  the  corresponding  substance  of  cartilage  contains  less 
and  is  of  a  firmer  consistency.  The  quantity  of  water  contained  in  each 
albuminous  substance  may  be  diminished  by  artificial  desiccation,  or  by 
a  deficient  supply ;  but  it  cannot  be  increased  beyond  a  certain  amount. 
Thus,  if  the  albumen  of  the  blood  and  the  albuminous  matter  of  carti- 
lage be  both  reduced  by  evaporation  to  a  similar  degree  of  dryness,  and 
then  placed  in  water,  the  albumen  will  absorb  so  much  as  again  to  be- 
come fluid,  but  the  cartilaginous  substance  only  so  much  as  to  regain 
its  usual  nearly  solid  consistency.  Even  where  the  organic  substance, 
therefore,  as  in  the  case  of  albumen,  becomes  fluid  under  these  cir- 
cumstances, it  is  not  precisely  by  its  solution  in  water,  but  only  by  its 
reabsorption  of  that  quantity  of  fluid  with  which  it  was  naturally 
associated. 

1  Handbuch  der  Physiologisch-  und  Pathologisch-Chemischen  Analyse.  Berlin, 
1870. 


ALBUMINOUS    MATTERS.  81 

Another  characteristic  feature  of  the  proximate  principles  of  this 
group  is  their  property  of  coagulation.  Those  which  are  naturally  fluid 
suddenly  assume,  under  certain  conditions,  a  solid  or  semi-solid  consist- 
ency. They  are  then  said  to  be  coagulated ;  and,  when  once  coagulated, 
they  cannot  usually  be  made  to  resume  their  original  condition.  This 
property  of  coagulability  is  not  only  a  marked  quality  of  the  albu- 
minous matters  as  a  class,  but  it  often  serves  to  distinguish  them 
from  each  other  by  the  different  special  conditions  under  which  it  is 
manifested  by  each  one.  Thus  the  substance  producing  fibrine  coagulates 
spontaneously  on  being  withdrawn  from  the  bloodvessels ;  albumen,  on 
being  subjected  to  the  temperature  of  boiling  water ;  caseine,  on  being 
placed  in  contact  with  an  acid.  When  an  albuminous  substance  thus 
coagulates,  the  change  which  takes  place  is  a  peculiar  one,  and  differs 
from  that  by  which  a  mineral  salt  is  precipitated  from  its  watery  solu- 
tion. The  albuminous  matter,  in  coagulating,  appears  to  assume  a 
special  condition,  and  to  permanently  change  its  properties;  but,  in 
passing  into  the  solid  form,  it  still  retains ^all  the  water  with  which  it 
was  previously  united.  Albumen,  when  coagulated,  retains  the  same 
quantity  of  water  in  union  with  it  which  it  held  before.  After  coagu- 
lation, this  water  may  be  driven  off  by  evaporation,  in  the  same  manner 
as  previously ;  and  on  being  once  more  exposed  to  moisture,  the  organic 
matter  will  again  absorb  the  same  quantity,  though  it  will  not  assume 
the  liquid  form.  The  coagulated  substance  may  sometimes  be  dissolved 
by  certain  chemical  agents,  as  the  caustic  alkalies ;  but  it  is  not  by 
this  means  restored  to  its  original  condition.  It  rather  suffers  a  still 
further  alteration. 

In  many  instances  we  are  obliged  to  resort  to  coagulation  in  order 
to  separate  an  albuminous  substance  from  the  other  proximate  princi- 
ples with  which  it  is  associated.  This  is  the  case,  for  example,  with 
the  fibrine  of  the  blood,  which  is  obtained  in  the  form  of  flocculi,  by 
beating  freshly-drawn  blood  with  a  bundle  of  rods.  But  when  separated 
in  this  way,  it  is  already  in  an  unnatural  condition,  and  no  longer 
represents  exactly  the  original  fluid  fibrine  as  it  existed  in  the  circulating 
blood.  Nevertheless,  this  is  the  only  mode  in  which  it  can  be  examined, 
as  there  are  no  means  of  bringing  it  back  to  its  previous  condition. 

Another  important  property  of  the  albuminous  matters  is  that  they 
excite,  in  other  proximate  principles  and  in  each  other,  those  peculiar 
indirect  chemical  changes  which  have  been  termed  catalyses  or  catalytic 
transformations.  That  is  to  say,  they  produce  the  changes  referred  to, 
not  directly,  by  combining  with  the  substance  which  suffers  alteration, 
or  with  any  of  its  ingredients ;  but  simply  by  their  presence,  which 
induces  the  chemical  change  in  an  indirect  manner.  We  do  not  under- 
stand the  manner  in  which  these  changes  are  accomplished,  but  the 
influence  thus  exerted  by  the  albuminous  matters  is  a  very  marked  one, 
and  is  of  great  importance  in  many  of  the  acts  of  animal  and  vegetable 
nutrition.  A  comparatively  small  quantity  of  the  catalytic  body  is 
often  capable  of  inducing  a  palpable  change  in  a  large  quantity  of 


82  ALBUMINOUS    MATTEKS. 

another  substance.  The  action  of  vegetable  diastase  in  converting 
starch  into  dextrine  and  glucose  is  a  process  of  this  nature ;  and  it  is 
found  that  one  part  of  diastase  is  capable  of  effecting  the  transformation 
of  2000  parts  of  starch.  The  albuminous  ingredients  of  the  saliva,  of 
the  pancreatic  and  intestinal  juices,  exert  a  similar  action  on  hyd rated 
starch.  The  whole  process  of  digestion  and  assimilation  is  in  great 
part  made  up  of  a  series  of  such  catalytic  changes,  in  which  the 
nutritious  matters  undergo  their  requisite  transformations,  by  contact 
with  special  albuminous  ingredients  of  the  blood,  the  tissues,  or  the 
secretions. 

At  a  temperature  of  300°  (570°  F.)  or  over,  the  albuminous  matters, 
like  other  organic  substances,  are  destroyed  and  decomposed  into 
gaseous  products.  But  if  subjected  for  a  certain  time  to  a  temperature 
of  about  125°  (257°  F.)?  they  undergo  a  change  in  addition  to  their 
coagulation,  by  which  a  distinct  and  agreeable  flavor  is  developed,  and 
by  which  they  become  suitable  for  use  as  human  food.  It  is  this  change 
which  is  produced  in  the  process  of  cooking,  and  the  peculiar  flavor 
which  results  always  depends  upon  the  presence  of  a  certain  quantity 
of  albuminous  matter  in  the  substance  employed.  If  the  temperature 
at  which  the  cooking  process  is  carried  on  be  too  low,  the  characteristic 
flavors  are  not  developed;  if  it  be  too  high,  they  are  destroyed  and 
replaced  by  empyreumatic  odors,  from  the  combustion  or  decomposition 
of  the  ingredients  of  the  food. 

Lastly,  the  albuminous  matters  are  distinguished  by  the  property  of 
putrefaction.  This  is  a  process  by  which  dead  animal  substances, 
when  exposed  to  the  atmosphere  at  a  moderately  warm  temperature, 
gradually  soften  and  liquefy  and  are  finally  decomposed,  with  the  pro- 
duction of  certain  fetid  and  unwholesome  gases,  among  which  are 
hydrogen  sulphide  and  carbide,  usually  with  more  or  less  carbonic  acid, 
nitrogen,  and  ammoniacal  vapors.  The  mixture  of  these  emanations 
causes  an  odor  which  is  easily  recognized  as  a  "putrefactive  odor;" 
and  wherever  such  emanations  are  perceived,  it  is  an  indication  that 
some  substance  containing  albuminous  matters  is  undergoing  decom- 
position. As  these  albuminous  matters  are  more  abundant  in  the 
tissues  and  fluids  of  animals  than  in  those  of  vegetables,  the  phenomena 
of  putrefaction  are  also  most  distinctly  marked  in  the  decay  of  animal 
substances.  But  they  will  take  place  in  both,  under  the  requisite  con- 
ditions. A  solution  of  nitrogenous  vegetable  matters  will  present  all 
the  essential  characters  of  putrefaction,  though  not  developed  with  the 
same  degree  of  intensity  as  in  fluids  of  animal  origin. 

In  order  that  putrefaction  may  take  place  certain  special  conditions 
are  necessary.  In  the  first  place  it  requires  the  access  of  atmospheric 
air,  or  of  some  fluid  containing  oxygen.  If  the  putrescible  substance 
be  first  boiled  so  as  to  expel  all  the  free  oxygen  contained  in  its  fluids, 
and  if  then,  while  the  boiling  is  going  on,  it  be  inclosed  in  a  hermetically 
sealed  vessel,  no  putrefaction  takes  place,  but  the  substance  remains 
unaltered  for  an  indefinite  time.  It  is  by  this  means  that  cooked  meats 


ALBUMINOUS    MATTERS. 


83 


are  preserved  in  sealed  cans,  for  use  upon  long  voyages  or  expeditions 
at  a  distance  from  the  usual  base  of  supplies.  So  long  as  the  cans  are 
kept  perfectly  closed,  their  contents  remain  sound.  After  they  are 
opened  and  the  air  admitted  to  their  interior,  the  food  must  be  used  at 
once,  otherwise  it  will  begin  to  putrefy  after  the  usual  interval  of  time. 

Another  essential  condition  for  putrefaction  is  the  presence  of 
moisture.  Albuminous  substances  which  are  reduced  to  a  perfectly 
dry  state  do  not  undergo  decomposition ;  and  in  some  regions,  where  a 
high  temperature  and  a  dry  atmosphere  favor  the  rapid  desiccation  of 
organic  substances,  this  fact  is  also  utilized  for  the  preservation  of 
meats.  Immediately  after  the  animal  is  killed,  the  flesh  is  cut  into  thin 
strips  and  hung  up  to  dry  in  the  air,  and,  desiccation  being  completed 
before  putrefaction  has  commenced,  the  food  thus  prepared  is  preserved 
for  an  indefinite  time. 

The  third  requisite  for  putrefaction  is  a  moderately  elevated  tempe- 
rature. It  goes  on  most  rapidly  between  25°  and  35°  (^7°  to  95°  F.). 
Below  25°  it  gradually  diminishes  in  activity,  and  ceases  altogether 
about  the  freezing  point  of  water.  Meats,  therefore,  which  are  kept 
frozen  or  closely  packed  in  ice  do  not  putrefy.  The  process  is  also 
suspended  in  all  albuminous  matters  exposed  to  winter  weather  at  the 
freezing  point.  The  carcass  of  an  extinct  mammoth  has  even  been 
found  imbedded  in  ice  in  Northern  Siberia,  which  was  in  such  a  state 
of  preservation  that  its  flesh  was  used  for  food  by  dogs  and  other 
animals.1  A  temperature  much  above  35°  is  also  unfavorable  to  the 
putrefactive  change,  and  it  is  completely  arrested  by  a  heat  approaching 
that  of  boiling  water. 


The  process  of  putrefaction 
is  accompl  ished  by  the  growth 
and  multiplication  of  a  micro- 
scopic vegetable  organism, 
somewhat  analogous  to  that 
by  which  fermentation  is  ex- 
cited in  saccharine  fluids. 
If  any  clear  solution  con- 
taining animal  or  vegeta- 
ble albuminous  matters  be 
exposed  to  the  air  at  a 
moderate  temperature,  after 
a  short  time  it  becomes  tur- 
bid. This  turbidity  is  due  to 
the  development  of  minute 
vegetable  cells,  of  very  sim- 
ple organization,  which  mul- 
tiply with  great  rapidity  in 


Fig.  18. 


CELLS  OF  BACTERIUM  TEBMO;   from  a 
putrefying  infusion. 


1  M6moires  de  1' Academic  Imperiale  des  Sciences  de  St.  Petersbourg,  tome  5, 
p.  440. 


84  ALBUMINOUS    MATTERS. 

the  decomposing  liquid,  and  produce  in  it,  by  their  vegetative  activity, 
the  changes  of  putrefaction.  These  cells  belong  to  the  genus  "  Bacteri- 
um," so  called  from  their  simple  rod-like  form ;  and  the  species  which 
is  invariably  to  be  found  in  putrefying  infusions  is  known  by  the 
name  of  Bacterium  termo.  The  cells  are  of  an  oblong  form,  and 
average  3  mmm.  in  length  by  0.6  mmm.  in  thickness.  They  are  usually 
double,  consisting  of  two  single  cells  placed  end  to  end.  While  actively 
growing  in  a  putrefying  infusion,  they  are  in  constant  process  of  mul- 
tiplication, by  which  their  numbers  are  rapidly  increased.  The  multi- 
plication takes  place  by  spontaneous  division  of  the  cell,  by  a  trans- 
verse partition  which  grows  across  its  middle.  After  a  time  the  two 
cells,  thus  formed  out  of  a  single  one,  separate  from  each  other,  and 
each  repeats  the  process  for  itself. 

One  of  the  most  remarkable  characters  of  the  bacterium  cells  is 
their  active  spontaneous  movement.  During  a  certain  period  of  their 
development  they  are  in  incessant  and  rapid  motion  by  means  of  a 
conical  rotation  about  their  longitudinal  axis,  by  which  they  are  trans- 
ported in  various  directions  through  the  fluid  in  which  they  are  contained. 
This  motion  is  often  so  rapid  that  it  can  hardly  be  followed  by  the  eye ; 
in  other  instances  it  is  so  slow  that  its  mechanism  may  be  distinguished 
by  careful  examination.  The  movement  and  mutiplication  of  the  bac- 
terium cells  go  on  while  putrefaction  continues.  After  all  the  albumin- 
ous ingredients  of  the  infusion  have  been  decomposed,  the  liquid  again 
becomes  clear,  and  the  bacterium  cells  subside  to  the  bottom  in  a  quies- 
cent whitish  layer.  A  small  portion  of  this  layer  will  readily  excite 
putrefaction,  if  added  to  another  albuminous  liquid. 

As  the  bacterium  cells  effect  the  decomposition  of  albuminous  matters 
by  their  own  vegetative  activity,  it  is  for  this  reason  that  putrefaction 
is  limited  by  certain  special  conditions,  already  mentioned.  Bacteria 
belong  to  the  group  of  colorless  cryptogamic  vegetables.  Like  other 
plants  of  this  kind,  they  assimilate  directly  organic  substances  ready 
formed,  and  at  the  same  time  absorb  oxygen  and  exhale  carbonic 
acid,  after  the  manner  of  animals.  Consequently  oxygen  is  one  of  the 
substances  essential  to  their  growth ;  and,  as  putrefaction  takes  place 
only  by  means  of  their  vital  activit}r,  ox}^gen  or  atmospheric  air  must 
be  present  in  order  to  allow  putrefaction  to  go  on.  Furthermore  the 
presence  of  moisture  is  necessary  to  their  growth,  as  it  is  to  that  of  all 
other  plants  ;  and  a  substance  thoroughly  dried  cannot  putrefy,  since  no 
vegetative  development  is  possible  in  the  total  absence  of  moisture.  A 
certain  degree  of  warmth  is  also  essential  to  the  continued  growth  of 
these  bodies.  Their  development  is  suspended  by  a  freezing  tempera- 
ture, and  their  vitality  is  destroyed  by  prolonged  contact  with  boiling 
water. 

Lastly,  a  certain  amount  of  albuminous  matter  is  necessary  for  the 
nutrition  of  bacteria.  Their  cells  may  remain  indefinitely,  in  a  quies- 
cent condition,  suspended  in  other  fluids  or  even  in  pure  water;  but 
for  their  active  development  and  multiplication  they  require  the  pre- 


FIBRINE.  85 

sence  of  albuminous  matters,  which  appear  to  supply  the  necessary 
material  for  their  growth.  They  decompose  these  substances  therefore 
by  assimilating  their  ingredients  in  the  process  of  vegetable  nutrition, 
and  the  putrefactive  gases  are  the  final  result  of  the  changes  thus  taking 
place,  just  as  alcohol  and  carbonic  acid  are  produced  in  the  fermenta- 
tion of  saccharine  liquids. 

Fermentation  and  putrefaction,  accordingly,  are  analogous  processes, 
in  which  certain  materials  are  decomposed  under  the  influence  of  micro- 
scopic vegetation.  The  former  takes  place  in  saccharine  fluids,  the 
latter  in  those  containing  albuminous  matter;  since  the  yeast-plant 
requires  for  its  growth  a  preponderance  of  non-nitrogenized  hydrocar- 
bonaceous  matter,  while  bacterium  cells  are  nourished  mainly  by  the 
absorption  of  nitrogenous  substances. 

The  following  table  shows  the  proportion  of  albuminous  matter, 
according  to  Payen,  in  different  substances  used  as  food : — 

QUANTITY  OF  ALBUMINOUS  MATTER  IN  100  PARTS  IN 

Beef  flesh  .  .  .  19.50  Wheat  grains     .         .  18.03 

Fowl's  eggs  .  .  12.35  Rye   ....  12.50 

Mackerel    .  .  .  24.31  Oats  ....  14.39 

Salmon      .  .  .  13.58  Indian  corn         .         .  12.50 

Oysters      .  .  .  14.01  Rice  ....  7.55 

Beans  (dry)  .  .  24.40  Potatoes    .         .        .  2.50 

Peas       "  .  .  .  23.80  Sweet  potatoes  .         .  1.50 

The  first  formation  of  albuminous  matter  takes  place  in  vegetables, 
subsequent  to  the  production  of  the  non-nitrogenous  organic  substances, 
starch  and  glucose,  by  the  union  of  these  last  with  nitrogen  derived 
from  the  inorganic  salts.  Green  plants,  which  have  the  power  of  gene- 
rating the  carbohydrates  from  carbonic  acid  and  water,  if  supplied  with 
moisture  containing  nitrates  or  ammonium  salts  in  solution,  are  known 
to  grow  vigorously  and  increase  many  fold  their  contents  of  albuminous 
matter.1  These  salts  must  therefore  have  supplied  the  nitrogen  requisite 
for  the  formation  of  the  nitrogenous  substances.  The  sulphur,  which 
also  enters  into  the  composition  of  these  substances,  is  derived  by  the 
plants  from  a  reduction  of  the  soluble  sulphates  contained  in  the  soil. 

Notwithstanding  the  very  marked  and  important  peculiarities  which 
distinguish  the  albuminous  matters  as  a  group,  there  are  many  of  these 
substances  which  differ  from  each  other  by  a  variety  of  secondary  char- 
acters. It  is  possible  that  some  of  those  now  designated  by  specific 
names  may  really  be  mixtures  of  two  or  more  distinct  substances ;  but 
the  classification  at  present  in  use  expresses  the  distinguishing  marks 
of  the  more  important  varieties,  so  far  as  they  are  yet  known. 

Fibrine. 

Fibrine  is  found  in  the  plasma  of  the  blood,  where  it  exists  in  the 
proportion,  on  the  average,  of  three  parts  per  thousand.  It  is  also 

1  Mayer,  Lehrbuch  der  Agrikultur-Chemie,  Band  i.  pp.  145,  150. 


bb  ALBUMINOUS    MATTERS. 

present  in  small  quantity  in  the  lymph  and  in  the  chyle.  It  is  this  sub- 
stance which  is  distinguished  by  its  property  of  "  spontaneous  coagula- 
tion ;"  that  is,  it  coagulates  on  being  withdrawn  from  the  vascular 
system,  without  the  addition  of  any  physical  or  chemical  reagent.  It 
is  the  coagulating  element  of  the  blood  ;  and  the  power  of  freshly  drawn 
blood  to  form  a  clot  depends  upon  its  presence  as  an  ingredient  of  the 
circulating  fluid.  The  term  fibrine  properly  represents,  hot  the  solid 
clot  obtained  by  coagulation,  but  the  fluid  substance  existing  before- 
hand in  the  blood,  and  which  becomes  solidified  after  its  withdrawal. 
It  is  regarded  by  some  as  generated  by  the  union  of  two  pre-existing 
substances  ;  by  others,  as  produced  from  the  decomposition  of  one.  As 
we  have,  however,  but  little  opportunity  of  studying  it  while  still  forming 
a  part  of  the  fluid  plasma,  our  knowledge  is  mainly  confined  to  its  pro- 
perties in  the  solidified  form.  It  is  obtained  by  stirring  the  freshly 
drawn  blood  with  glass  rods  or  a  bundle  of  twigs,  and  afterward  washing 
the  deposited  clots  with  distilled  water  until  the  adherent  coloring 
matter  is  removed. 

Coagulated  fibrine  is  a  colorless,  tolerably  firm,  extensible,  and 
elastic  substance,  which  has,  under  the  microscope,  a  finely  fibrillated 
texture.  It  is  insoluble  in  water,  but  in  solutions  of  the  caustic  alkalies 
or  the  alkaline  carbonates  it  becomes  gelatinous,  and  is  after  a  time,  by 
the  aid  of  warmth,  partially  dissolved.  Some  of  the  free  acids,  as  hydro- 
chloric, acetic,  lactic,  or  phosphoric  acid,  have  a  similar  effect.  If  it  be 
heated  in  water  or  in  a  neutral  liquid  to  72°  (162°  F.),  it  becomes  con- 
tracted, white,  and  opaque,  and  less  extensible  than  before. 

An  albuminous  matter  very  similar  in  its  physical  properties  to  animal 
fibrine,  exists  in  certain  vegetable  substances,  especially  in  wheat  flour, 
where  it  is  known  as  gluten.  When  freed  from  the  admixture  of  other 
ingredients,  it  is  tenacious,  extensible,  elastic,  insoluble  in  water,  and 
slowly  soluble  in  dilute  alkalies.  Its  property  of  tenacity  and  its 
nitrogenous  character  make  it  an  important  constituent  of  wheat  flour 
in  the  manufacture  of  bread. 

Albumen. 

Albumen  is  found  abundantly  in  the  plasma  of  the  blood,  also  in  the 
lymph,  the  pericardial  and  cephalo-rachidian  fluids,  and  in  very  small 
quantity  in  the  saliva  and  in  the  milk.  It  is  not  spontaneously  coagu- 
lable,  but  coagulates  promptly  when  heated  in  its  liquid  form  to  a 
temperature  of  72°  (162° F.),  and  its  coagulum  is  again  soluble  in  the 
caustic  alkalies.  It  is  also  coagulated  by  contact  with  nitric  or  sul- 
phuric acid,  alcohol,  or  the  metallic  salts.  The  organic  acids,  as  acetic, 
lactic,  or  tartaric  acid,  do  not  affect  it ;  but  if  it  be  first  slightly  acidu- 
lated by  dilute  acetic  acid,  it  may  be  precipitated  by  a  solution  of 
potassium  ferrocyanide.  This  is  one  of  the  most  delicate  tests  for  the 
presence  of  albumen,  but  it  is  usually  recognized  from  its  coagulability 
by  heat  and  nitric  acid.  When  dissolved  in  a  fluid  of  neutral  reaction, 
it  rotates  the  plane  of  polarization  to  the  left  56°. 


ALBUMINOSE.  87 

The  white  of  the  fowl's  egg  is  mainly  composed  of  a  substance  also 
called  albumen,  and  which  corresponds  with  the  albumen  of  blood 
in  its  coagulability  by  heat,  nitric  acid,  alcohol,  and  the  metallic  salts. 
It  is  distinguished  from  the  preceding  mainly  by  its  coagulability  by 
ether,  which  has  no  effect  on  the  albumen  of  blood.  It  rotates  the 
plane  of  polarization  to  the  left  35°.5. 

The  fresh  juices  of  nearly  all  vegetables,  and  especially  the  succulent 
plants,  contain  a  substance  coagulable  by  heat,  which  has  been  called 
vegetable  albumen.  It  may  also  be  obtained  from  the  cereal  grains  by 
extraction  with  water,  and  resembles  in  its  principal  chemical  reactions 
the  albumen  derived  from  animal  sources. 

Albuminose. 

This  substance  is  closely  related  to  albumen  by  its  chemical  composi- 
tion and  its  general  characters.  It  is  not  coagulated,  however,  by  either 
heat,  nitric  acid,  or  acidulated  potassium  ferrocyanide,  but  only  by  the 
metallic  salts  and  alcohol  in  excess.  It  is  also  distinguished  by  its 
ready  diffusibility  through  animal  membranes  or  parchment  paper  ;  while 
albumen,  and  all  other  liquid  albuminous  matters,  pass  through  these 
membranes  either  not  at  all  or  only  with  great  difficulty.  Coagulated 
albumen  and  all  other  digestible  albuminous  matters  are  converted 
into  albuminose  by  the  action  of  gastric  juice.  They  thus  become 
liquefied  and  incapable  of  coagulation  by  heat.  Owing  to  the  origin  of 
these  products  from  the  digestive  act  they  are  designated  by  several 
writers  under  the  name  of  peptones;  and  a  variety  of  them  are  enume- 
rated, but  their  distinctive'  characters  are  not  very  sharply  denned. 
Albuminose  is  found  in  the  fluids  of  the  stomach  and  small  intestine 
during  digestion,  and  exists  also  in  the  blood  in  the  proportion  of  two 
to  three  parts  per  thousand. 

Albuminose  in  solution  has  the  property  of  modifying  certain  well- 
known  chemical  reactions.  It  interferes  especially  with  the  reduction 
of  the  copper  oxide  in  Trommer's  test.  If  a  small  quantity  of  glucose 
be  dissolved  in  gastric  juice  containing  albuminose,  and  Trommer's  test 
applied,  no  peculiarity  is  observed  on  first  dropping  in  the  copper 
sulphate ;  but  on  the  addition  of  potassium  hydrate,  the  mixture  takes 
a  rich  purple  hue,  instead  of  the  clear  blue  tinge  which  is  presented 
under  ordinary  circumstances.  On  boiling,  the  color  changes  to  claret, 
cherry  red,  and  finally  to  a  light  yellow ;  but  no  copper  oxide  is 
deposited,  and  the  fluid  remains  clear.  If  albuminose  be  present  only 
in  small  quantity,  an  incomplete  reduction  of  the  copper  takes  place, 
so  that  the  mixture  becomes  opaline  and  cloudy,  but  still  without  any 
well  marked  deposit.  This  interference  will  take  place  when  sugar  is 
present  in  very  large  proportion.  We  have  found  that  gastric  juice, 
drawn  from  the  dog's  stomach  during  digestion,  may  sometimes  be 
mixed  with  an  equal  volume  of  honey  without  giving  any  deposit  of 
copper  on  the  application  of  Trommer's  test.  If  such  a  mixture,  how- 
ever, be  previously  diluted  with  water,  it  will  often  fail  to  prevent  the 


88  ALBUMINOUS    MATTERS. 

reduction  and  deposit  of  the  copper  oxide.  The  peculiar  action  above 
described  depends  upon  the  presence  of  albuminose,  and  not  upon  that 
of  any  original  ingredient  of  the  gastric  juice  ;  since  it  is  not  exhibited 
by  the  perfectly  clear  and  colorless  juice,  obtained  from  the  empty 
stomach  of  the  fasting  animal  by  irritation  of  the  mucous  membrane 
with  a  glass  rod  or  metallic  catheter ;  while  the  same  fluid,  if  macerated 
for  a  time  with  finely  chopped  meat  at  a  temperature  of  38°  (lOQo  F.), 
will  be  found  to  have  acquired  the  property  in  a  marked  degree.  Gas- 
tric juice,  furthermore,  drawn  from  the  stomach  after  digestion  has 
been  going  on  for  half  an  hour  or  more,  always  contains  a  certain 
quantity  of  albuminose,  and  consequently  interferes,  as  above  described, 
with  Trommer's  test. 

Albuminose,  if  present  in  notable  quantity,  will  also  interfere  with  the 
mutual  reaction  of  starch  and  iodine.  If  gastric  juice,  containing  albu- 
minose, be  mingled  with  an  equal  volume  of  iodine  water,  and  a  solution 
of  starch  be  subsequently  added,  no  blue  color  is  produced ;  though  if 
the  iodine  water  be  added  in  excess,  or  if  the  tincture  of  iodine  be  used 
instead  of  its  aqueous  solution,  the  superabundant  iodine  then  com- 
bines with  the  starch,  and  produces  the  ordinary  blue  color.  This 
property,  like  that  described  above,  is  not  possessed  by  pure,  colorless 
gastric  juice,  taken  from  the  empty  stomach,  but  is  acquired  by  it  on 
being  digested  with  albuminoid  substances. 

Accordingly,  in  testing  for  the  presence  of  glucose  in  fluids  which  are 
liable  to  contain  albuminose  or  other  organic  substances  of  similar 
character,  the  precaution  must  always  be  adopted  of  first  eliminating 
the  albuminous  matters  which  might  interfere  with  the  test.  This  may 
be  done  in  either  of  two  ways  :  first,  by  evaporating  the  fluid  to  dryness 
over  the  water  bath,  and  extracting  the  dry  residue  with  alcohol,  which 
takes  up  the  sugar,  but  leaves  behind  the  albuminous  matters.  The 
alcoholic  solution  may  then  be  filtered  and  evaporated,  and  the  evapo- 
rated residue  dissolved  in  water,  when  it  will  respond  to  Trommer's  test 
if  glucose  be  present.  Or,  secondly,  the  fluid  may  be  treated  with  ani- 
mal charcoal,  which  retains  the  albuminous  matters,  and  allows  the 
glucose  to  pass  through  in  watery  solution. 

Caseine, 

This  is  the  principal  albuminous  ingredient  of  milk,  the  only  animal 
fluid  in  which  it  is  certainly  known  to  exist.  It  is  called  caseine,  be- 
cause, when  solidified,  it  forms  the  substance  of  cheese.  It  is  not 
affected  by  a  boiling  temperature,  but  coagulates  on  the  addition  of  any 
of  the  dilute  acids,  organic  as  well  as  mineral,  and  of  magnesium  sul- 
phate. These  characters  are  sufficient  to  distinguish  it  from  albumen. 
It  is  also  coagulated  by  a  temperature  of  30°  (860F.),'by  contact  with 
gastric  juice,  or  an  infusion  of  rennet,  the  mucous  membrane  of  the 
fourth  stomach  of  the  calf.  In  solution  in  neutral  fluids  it  rotates  the 
plane  of  polarization  to  the  left  80°.  Caseine  is  an  important  article 
of  food,  being  the  principal  nutritious  ingredient  in  preparations  of  milk. 


PTYALINE. — PANCREATINE.  89 

A  nitrogenous  substance,  termed  vegetable  caseine,  exists  abundantly 
in  peas  and  beans,  where  it  is  known  as  "  legumine."  It  is  found 
also  in  small  quantity  in  oats,  in  the  potato,  and  in  the  juices  of  many 
plants.  It  resembles  the  caseine  of  milk  in  not  being  affected  by  a 
boiling  temperature,  and  in  its  coagulability  by  the  organic  acids  and 
magnesium  sulphate. 

Ptyaline 

Is  an  ingredient  of  the  saliva,  to  which  it  communicates  the  property 
of  converting  hydrated  starch  into  glucose.  From  this  circumstance  it 
has  sometimes  been  called  "animal  diastase."  It  differs  from  albumen 
in  many  of  its  characters,  and  is  not  coagulated  by  nitric  acid  nor  by 
potassium  ferrocyanide  in  an  acidulated  solution.  On  the  other  hand, 
it  is  precipitated  by  alcohol  in  excess,  and  by  a  boiling  temperature ; 
but  while,  after  precipitation  by  alcohol,  it  may  be  redissolved  in  water 
with  all  its  original  properties,  the  action  of  heat  produces  in  it  a  per- 
manent alteration,  and  saliva  which  has  once  been  boiled  and  allowed 
to  cool  is  found  to  have  lost  its  power  of  converting  starch.  Ptyaline 
can  also  be  thrown  down  by  adding  to  the  saliva  dilute  phosphoric  acid, 
and  afterward  neutralizing  the  solution  with  lime  water.  The  precipi- 
tate of  lime  phosphate  thus  produced  brings  down  with  it  the  ptyaline, 
which  may  afterward  be  redissolved  in  water,  and  again  separately 
precipitated  by  alcohol.  Ptyaline  does  not  constitute  the  whole  of  the 
organic  ingredients  of  the  saliva,  but  is  mingled  in  the  secretion  with 
other  albuminous  substances. 

Fepsine 

Is  the  albuminous  matter  of  the  gastric  juice,  where  it  is  found  in  the  pro- 
portion of  fifteen  parts  per  thousand.  It  is  this  substance  which  effects 
the  conversion  of  nitrogenous  matters  into  albuminose  in  the  digestive 
process.  It  requires,  however,  in  order  to  exert  this  action,  to  be  dis- 
solved in  an  acidulated  liquid.  It  also  causes  the  coagulation  of  caseine, 
when  first  brought  in  contact  with  that  substance.  It  is  coagulated  by 
a  boiling  temperature,  and  when  once  subjected  to  the  action  of  heat 
loses  permanently  its  digestive  power.  It  is  also  thrown  down  by  alco- 
hol in  excess,  but  may  be  redissolved  in  water  after  removal  of  the 
alcohol.  Pepsine  is  produced  in  the  glandular  follicles  of  the  stomach, 
and  there  mingled  with  the  other  ingredients  of  the  gastric  juice. 

Pancreatine. 

This  is  the  characteristic  ingredient  of  the  pancreatic  juice,  where  it 
is  very  abundant ;  being  present  in  the  proportion  of  a  little  over  ninety 
parts  per  thousand.  It  is  coagulable  by  heat,  nitric  acid,  alcohol,  and 
the  metallic  salts ;  in  these  respects  resembling  albumen.  But  it  is 
also  coagulated  by  magnesium  sulphate,  which  has  no  effect  on  albumen. 
It  is  further  distinguished  by  the  fact  that,  after  precipitation  by  alcohol, 
it  may  be  again  dissolved  in  water,  and  its  solution  exhibits  the  same 
t 


90  ALBUMINOUS    MATTERS. 

albuminous  consistency  which  belongs  to  fresh  pancreatic  juice.  It  has 
the  power  of  emulsifying  fatty  matters  with  great  rapidity  at  the  tem- 
perature of  the  living  body,  and  also  of  saponifying  a  certain  portion  of 
them  by  the  production  of  a  fatty  acid.  It  is  believed  by  some  observers 
that  the  pancreatine  of  pancreatic  juice  is  a  mixture  of  several  sub- 
stances ;  one  of  which,  like  ptyaline,  is  active  in  the  conversion  of  starch, 
while  another  aids  in  the  liquefaction  of  albuminous  matters,  and  a  third 
has  the  property  of  acting  upon  fats. 

Mucosine. 

There  are  a  variety  of  secretions  in  the  body  which  are  designated 
by  the  common  name  of  "  mucus,"  and  which  are  distinguished  by  a 
peculiar  physical  character  of  viscidity.  This  viscid  consistency  is 
given  to  them  by  the  presence  of  a  substance  termed  "  mucosine,"  or,  as 
it  is  called  by  some  writers,  "  mucine."  It  exists  in  all  the  varieties  of 
mucus,  some  of  which,  like  those  of  the  bronchial  tubes  and  intestine, 
are  nearly  fluid,  while  others,  like  that  of  the  cervix  uteri  during  preg- 
nancy, are  gelatinous  and  semi-solid.  It  is  also  present  in  abundant 
proportion  in  the  synovia,  the  bile,  and  the  saliva  of  the  submaxillary 
and  sublingual  glands.  The  secretion  of  the  mucous  follicles  of  the 
mouth  consists  almost  entirely  of  it.  Mucosine  is  not  coagulated  by 
heat,  but  is  thrown  down  by  alcohol  and  by  the  acids,  both  mineral  and 
organic.  It  is  remarkably  unaffected  by  the  metallic  salts,  lead  sub- 
acetate  being  the  only  one  that  produces  a  distinct  coagulation.  In 
some  cases,  as  in  the  bile,  it  is  dissolved  in  the  fluid  ingredients  of  the 
secretion,  from  which  it  may  be  separated  by  the  action  of  alcohol.  In 
others,  as  in  the  urine,  it  is  only  mechanically  suspended,  and  subsides 
as  a  light  deposit  after  a  few  hours'  repose. 

Myosine. 

The  contractile  substance  of  the  striped  muscular  fibres  contains  an 
albuminous  matter  which  after  death  coagulates,  like  the  fibrine  of  the 
blood-plasma ;  at  the  same  time  the  muscles  lose  their  contractility  and 
assume  the  condition  of  cadaveric  rigidity.  The  coagulation  of  this 
substance  is  retarded  by  the  action  of  cold  ;  and  it  has  been  extracted 
by  Kiihne,  from  the  muscular  tissue  of  frogs,  by  the  following  process : 
The  vascular  system  is  first  deprived  of  blood  by  an  injection  of  a  ^  per 
cent,  solution  of  sodium  chloride.  The  muscles,  thoroughly  washed, 
are  then  subjected  for  two  hours  to  a  temperature  of  7°  to  10°  below 
0°  (17OF.)?  reduced  to  a  pulp  in  a  cold  mortar,  and  then  allowed 
gradually  to  thaw  upon  a  filter.  The  filtered  liquid  coagulates  spon- 
taneously at  ordinary  temperatures. 

Coagulated  myosine  is  gelatinous,  and  without  fibrillated  texture. 
It  is  insoluble  in  water  and  in  concentrated  solutions  of  common  salt ; 
but  is  dissolved  by  a  watery  solution  of  salt,  made  in  the  proportion  of 
ten  per  cent,  or  less.  It  is  extracted  from  the  muscles  after  death  by 
bruising  the  muscular  tissue  to  a  pulp  in  a  ten  per  cent,  solution  of 


COLLAGEN.  —  CHONDRINE.  91 

sodium  chloride,  filtering  the  expressed  liquid,  and  then  precipitating 
the  dissolved  myosine  by  dropping  the  clear  solution  into  distilled 
water.  It  may  also  be  precipitated  by  adding  sodium  chloride  in  sub- 
stance, and  thus  increasing  the  strength  of  .the  solution.  Myosine  is, 
distinguished  from  the  fibrine  of  the  blood  by  its  complete  solubility 
in  saline  solutions  of  a  certain  strength,  as  well  as  in  dilute  acids  and 
alkalies.  When  dissolved  in  a  neutral  saline  fluid  it  is  coagulable  by 
heat,  like  the  albumen  of  blood. 

The  preceding  substances  are  all  naturally  liquid,  or  nearly  so,  in  con- 
sistency, and  form  constituent  parts  of  the  various  animal  fluids  and 
juices.  The  following  are  ingredients  of  the  solid  tissues. 

Collagen. 

This  substance  is  very  widely  diffused  in  the  animal  body,  forming 
the  more  or  less  homogeneous  interstitial  mass  of  the  bones,  perios- 
teum, tendons,  ligaments,  fasciae,  and  connective  tissues  generally.  All 
these  tissues,  although  at  first  insoluble,  after  long  ebullition  dissolve 
in  the  boiling  water ;  and  the  substance  thus  dissolved  solidifies  on  cool- 
ing into  a  jelly-like  mass.  This  substance  is  gelatine,  or  the  animal 
principle  of  glue.  Gelatine,  however,  does  not  exist  as  such  in  the 
osseous  and  fibrous  tissues  in  their  natural  condition,  but  is  evidently 
the  result  of  a  transformation  produced  by  long  boiling.  The  original 
body  of  which  these  tissues  are  mainly  composed  is  termed  "collagen ;" 
that  is,  a  substance  which  produces  gelatine  or  glue.  The  conversion 
of  collagen  into  gelatine  is  a  simple  transformation,  and  neither  a  decom- 
position nor  combination,  since  it  is  not  accompanied  by  any  increase  or 
diminution  of  weight. 

The  gelatine  produced  by  the  action  of  boiling  water  on  collagen, 
when  present  in  the  proportion  of  ten  parts  per  thousand,  solidifies  on 
cooling ;  below  this  proportion,  or  if  the  boiling  be  repeated,  it  may 
remain  liquid.  Its  solution  rotates  the  plane  of  polarization  to  the 
left  130°.  It  is  precipitated  by  alcohol  and  by  tannic  acid.  The  last, 
which  is  the  only  acid  by  which  this  substance  is  precipitated,  is  a 
very  sensitive  test  of  its  presence ;  and,  according  to  Hardy,1  will  de- 
tect one  part  of  gelatine  in  5000  parts  of  water.  A  similar  combination 
no  doubt  takes  place,  in  the  process  of  tanning,  between  tannic  acid 
and  the  original  collagen  of  the  fibrous  tissues,  by  which  they  are  ren- 
dered harder,  more  impermeable  to  water,  and  incapable  of  putrefac- 
tion. Gelatine  is  not  affected  by  potassium  ferrocyanide  with  acetic 
acid,  nor  by  lead  subacetate. 

Chondrine. 

The  amorphous  intercellular  substance  of  cartilage  resembles  that 
of  the  bones  and  the  fibrous  tissues  in  being  changed  by  prolonged  boil- 
ing with  water  into  a  substance  which  will  gelatinize  on  cooling.  In 

1  Chimie  Biologique.     Paris,  1871,  p.  282. 


92  ALBUMINOUS    MATTERS. 

the  case  of  the  cartilages,  however,  this  substance  is  termed  chondrine, 
from  the  source  from  which  it  is  derived.  Chondrine  corresponds  with 
gelatine  in  most  of  its  characters,  but  differs  from  it  in  being  precipitated 
from  its  watery  solution  by  both  acetic  acid  and  lead  subacetate.  It 
rotates  the  plane  of  polarization  to  the  left  213°.5. 

Elasticine. 

The  fibres  of  all  the  yellow  elastic  tissues,  as  that  in  the  middle  coat 
of  the  larger  arteries,  the  elastic  ligaments  of  the  spinal  column,  and  the 
ligamentum  nucha3,  mainly  consist  of  a  homogeneous  substance  which 
possesses  all  the  physical  properties  of  the  fibre  itself,  and  is  furthermore 
distinguished  by  its  extremely  refractory  nature  toward  most  chemical 
reagents.  It  is  obtained  by  boiling  the  elastic  fibres  successively  with 
alcohol,  ether,  water,  acetic  acid,  dilute  soda  solution,  and  dilute  hydro- 
chloric acid.  The  elasticine  is  thus  purified  from  other  ingredients,  but 
is  not  itself  soluble  in  either  of  the  above  reagents.  It  is  not  converted 
into  gelatine  even  by  long  boiling  ;  and  it  is  dissolved,  but,  at  the 
same  time,  decomposed,  only  by  the  concentrated  acids  and  alkalies. 
The  slender  elastic  fibres  mingled  with  connective  tissue,  and  the  sarco- 
lemma  of  the  striped  muscular  fibres,  are  probably  composed  of  the 
same  substance. 

Keratine. 

Under  this  name  is  known  the  exceedingly  resisting  and  indestruc- 
tible substance  of  the  hair,  nails,  epidermis,  feathers,  and  all  horny 
tissues.  It  is  unaffected  by  boiling  with  alcohol,  ether,  water,  and  the 
dilute  acids.  By  continuous  boiling  in  a  Papin's  digester  at  150°  (302°  F.) 
it  is  liquefied  and  partly  decomposed.  It  is  distinguished  from  the 
preceding  substance  by  containing  sulphur  as  an  ingredient,  which  is 
not  present  in  elasticine.  Keratine,  accordingly,  when  decomposed  by 
boiling  under  pressure  or  with  concentrated  alkalies,  gives  rise  to  hydro- 
gen sulphide  vapors. 

It  is  evident  that  the  albuminous  substances,  under  different  forms, 
constitute  a  large  and  important  part  of  the  mass  of  the  body ;  and  as 
they  are  during  life  in  a  constant  state  of  active  alteration,  they  require 
for  their  maintenance  an  abundant  supply  of  similar  ingredients  in  the 
food.  All  highly  nutritious  articles  of  diet  contain  more  or  less  of 
these  substances.  According  to  the  estimates  of  Payen,  which  corre- 
spond very  closely  in  their  gross  results  with  our  own  observations,  an 
adult  man  requires  a  daily  supply  of  about  130  grammes  of  albuminous 
matter  to  provide  for  the  wants  of  the  system ;  and  this  quantity  is 
actually  contained  in  the  food  consumed. 

But  although  nitrogenous  matter  is  thus  abundantly  supplied  to  the 
system  from  without,  yet  the  particular  kinds  of  albuminous  substances 
characteristic  of  the  various  tissues  and  fluids  are  formed  within  the 
body  in  the  process  of  digestion  and  assimilation,  by  transformation  of 


ALBUMINOUS    MATTERS.  93 

those  which  are  introduced  with  the  food.  A  large  part  of  the  albu- 
minous matters  of  the  food  are  derived  from  vegetables,  and,  though 
closely  related  to  the  corresponding  animal  substances,  are  not  pre- 
cisely identical  with  them.  Even  the  animal  albuminous  matters  used 
for  food,  as  the  albumen  of  eggs,  the  caseine  of  milk,  and  the  sub- 
stance of  muscular  flesh,  are  usually  taken  in  the  coagulated  form,  and 
suffer  still  further  changes  before  they  become  converted  into  the  albu- 
men of  the  blood.  From  their  subsequent  metamorphoses  in  the  act 
of  nutrition  they  are  transformed  into  the  many  specific  varieties  of 
albuminous  matter  peculiar  to  the  different  tissues  and  fluids. 

Only  a  very  small  proportion  of  these  substances  is  discharged  with 
the  excretions.  The  albuminous  ingredients  of  the  perspiration  and 
sebaceous  matter,  and  the  mucus  of  the  urinary  bladder  and  large  intes- 
tine are  almost  the  only  ones  which  find  an  exit  from  the  body  in  this 
way.  A  minute  quantity  of  albuminous  matter  is  exhaled  in  a  vola- 
tile form  with  the  breath,  and  a  little  also,  in  all  probability,  from  the 
cutaneous  surface.  But  the  entire  quantity  so  discharged  bears  an 
insignificant  proportion  to  that  which  is  daily  introduced  with  the  food. 
The  albuminous  substances,  accordingly,  are  decomposed  in  the  interior 
of  the  body.  They  are  transformed  by  the  process  of  destructive  assi- 
milation, and  their  elements  are  finally  eliminated  and  discharged  under 
other  forms  of  combination. 


CHAPTER  Y. 

COLORING   MATTERS. 

THERE  are  found,  in  various  parts  of  the  animal  body,  a  number  of 
substances  which  are  distinguished  by  imparting  to  the  tissues  and 
fluids  a  distinct  and  characteristic  coloration.  Notwithstanding  the 
evident  physiological  importance  of  these  substances,  and  the  striking 
character  of  their  optical  properties,  they  have  proved  in  many  re- 
spects more  difficult  of  study  than  the  other  proximate  principles  ; 
and  with  regard  to  several  of  them  our  knowledge  is  still  very  imper- 
fect. In  some  instances  this  is  partly  due  to  the  comparatively  small 
quantity  in  which  they  occur,  in  others  to  the  extreme  readiness  with 
which  they  are  decomposed  or  altered  in  the  process  of  separation.  In 
some  cases  it  has  been  found  difficult  to  decide  whether  a  variation  of 
tint  be  due  to  the  different  proportions  of  one  or  more  different  color- 
ing matters  or  to  the  varying  degrees  of  concentration  of  a  single  one. 

The  coloring  matters  are  all  nitrogenous  compounds,  but  differ  in 
essential  particulars  from  the  albuminous  substances.  Those  which 
have  been  most  fully  examined  are  known  to  be  crystallizable  ;  and  it  is 
possible  that  all  of  them  might  be  obtained  in  a  crystalline  form,  could 
they  be  completely  separated  without  decomposition.  The  most  abun- 
dant of  all,  and  that  which  possesses  the  most  important  physiological 
properties,  is  the  red  coloring  matter  of  the  blood.  It  appears  to  be 
analogous  in  many  respects  to  the  green  matter  of  the  leaves  and  leaf- 
like  organs  in  the  vegetable  world.  Each  of  these  two  coloring  matters 
is  the  most  abundant  and  widely  diffused  in  its  own  kingdom,  and  is 
distinguished  by  the  identity  of  its  characters  in  many  different  species 
of  animals  and  plants  respectively ;  and  while  the  red  coloring  matter 
of  the  blood,  on  the  one  hand,  is  the  agent  by  which  oxygen  is  absorbed 
and  distributed  in  the  animal  body,  on  the  other,  it  is  the  green  coloring 
matter  of  plants  by  which  carbonic  acid  and  water  are  decomposed  and 
oxygen  set  free  in  the  act  of  vegetation.  It  is  believed  by  many  ob- 
servers that  all  the  coloring  matters  of  the  animal  body,  at  least  in  man 
and  the  vertebrate  animals,  are  derived  by  transformation  from  the 
coloring  matter  of  the  blood ;  and  although  we  have  no  complete  experi- 
mental evidence  that  this  is  true  in  all  cases,  yet  it  is  evident  that  these 
substances  have  a  close  physiological  relation  with  each  other,  perhaps 
as  distinct  and  real  as  that  which  exists  between  the  various  members 
of  the  albuminous  or  saccharine  groups. 

The  organic  coloring  matters  may  be  conveniently  removed  from 
liquids  containing  them  by  the  action  of  animal  charcoal;  that  is, 
(94) 


HEMOGLOBINE. 


95 


Fig.  19. 


carbon  derived  from  the  imperfect  combustion  of  animal  substances. 
Burned  bones  are  generally  employed  for  this  purpose,  their  combustion 
having  been  carried  on  with  a  scanty  supply  of  air,  so  that  while  the 
hydrogen,  nitrogen,  and  oxygen  are  driven  off  in  the  form  of  gaseous 
combinations,  the  carbon  remains  behind.  If  a  fluid  containing  either 
of  the  coloring  matters  be  mixed  with  a  sufficient  quantity  of  this  char- 
coal and  filtered,  the  filtered  fluid  will  pass  through  colorless.  Albu- 
minous substances  are  also  retained  upon  the  filter  when  treated  with 
animal  charcoal ;  while  glucose  and  other  crystallizable  and  saline  mat- 
ters pass  through  freely  in  solution. 

The  animal  coloring  matters  most  distinctly  recognized  are  those  of 
the  blood,  the  blackish-brown  solid  tissues,  the  bile,  and  the  urine. 

Hemoglobine,  C900H960N154Fe,S30179. 

This  is  the  coloring  matter  of  the  red  globules  of  the  blood,  the  most 
abundant  and  important  of  all  the  substances  belonging  to  this  group. 
It  constitutes  much  the  largest  proportion  of  the  solid  ingredients  of 
the  blood-globules,  amounting  in  all  probability  to  from  25  to  30  per 
cent,  of  their  weight  in  the 
fresh  condition.  It  is  also 
found,  in  much  smaller  quan- 
tity, in  the  substance  of  the 
muscular  tissue,  of  which  it 
forms  the  coloring  principle. 
It  crystallizes  in  well  marked 
forms,  which  vary  somewhat 
in  different  species  of  ani- 
mals; but  are  all,  so  far  as 
accurately  known,  either 
rhombic  or  hexagonal  tables 
or  prisms.  It  is  soluble  in 
water,  in  very  dilute  alcohol, 
and  in  dilute  solutions  of 
albumen,  of  the  alkalies  and 
their  carbonates,  and  of  so- 
dium and  ammonium  phos- 
phates. It  is  insoluble  in 
strong  alcohol,  in  ether,  and 

in  the  volatile  and  fatty  oils.  In  almost  every  condition  it  is  readily 
decomposed.  According  to  Preyer,1  crystals  which  have  been  thoroughly 
dried  at  a  temperature  below  the  freezing  point  become,  after  a  time, 
decomposed,  and  lose  their  color  and  solubility,  even  at  ordinary  tem- 
peratures. A  watery  solution  of  hemoglobine  kept  at  any  temperature 
above  0°  (32°  F.)  becomes  altered  in  the  course  of  twenty-four  hours, 
and  if  heated  to  64°  (147°  F.)  it  is  at  once  decomposed. 


HEMOGLOBINE  CRYSTALS;  from  human  blood. 
(Funke.) 


1  Die  Blutkrystalle.     Jena,  1871,  p.  58. 


96 


COLORING    MATTERS. 


HEMOGLOBINE  CRYSTALS;  from  dog-faced 
baboon.    (Preyer.) 


Hemoglobine,  both  crystallized  and  in  watery  solution,  has  the  clear 
bright  red  color  of  arterial  blood.     It  is  distinguished  beyond  all  other 

known    ingredients    of    the 

Fig.  20.  body,  by  its  capacity  for  ab- 

sorbing oxygen,  which  it 
retains  in  the  form  of  a  loose 
combination.  According  to 
the  average  result  of  various 
experiments  one  gramme  of 
hemoglobine  in  watery  solu- 
tion will  absorb  1.27  cubic 
centimetres  of  oxygen.  The 
oxygen  thus  absorbed  is 
again  given  off  under  the  in- 
fluence of  diminished  pres- 
sure, heat,  or  the  continued 
displacing  action  of  hydro- 
gen or  nitrogen'  gas.  The 
coloring  matter  is  accord- 
ingly known  under  two  dif- 
ferent forms,  namely,  that 
of  "  oxidized"  hemoglobine, 

containing  an  excess  of  loosely  combined  oxygen,  and  that  of  "  reduced" 
hemoglobine,  in  which  the  surplus  oxygen  has  been  removed.  The  color 
of  hemoglobine  varies  according  to  these  two  conditions,  being  bright 
red  in  the  oxidized  form,  and  dark  purple  when  deoxidized.  The 
presence  of  hemoglobine  in  either  one  of  these  two  conditions  is  the 
cause  of  the  color  of  arterial  and  venous  blood. 

A  marked  feature  in  the  chemical  constitution  of  hemoglobine  is  that 
it  contains  iron.  This  fact  is  the  more  important  because  it  is  the  only 
'  substance  in  the  animal  body,  excepting  hair,  which  contains  iron  in 
any  considerable  amount,  and  because  iron  is  also  an  indispensable 
requisite  for  the  formation  of  the  green  coloring  matter  of  plants. 
Experiment  has  shown  that  without  the  presence  of  iron  vegetation 
cannot  go  on ;  and  there  is  every  reason  to  believe  that  iron  is  equally 
essential  to  the  constitution  of  the  animal  coloring  matter,  and  thus 
indirectly  to  the  general  nutrition  of  the  animal  body.  It  is  present 
in  hemoglobine,  in  all  probability,  not  in  the  form  of  a  distinct  oxide, 
but  directly  combined,  like  sulphur,  with  the  carbon,  hydrogen,  nitro- 
gen, and  oxygen  which  form  the  remainder  of  its  substance. 

One  thousand  parts  of  hemoglobine  contain  4.2  parts  of  iron ;  and, 
according  to  the  average  results  obtained  by  different  observers,  healthy 
human  blood  contains,  per  thousand  parts,  123.4  parts  of  hemoglobine, 
and  0.52  part  of  iron.  This  would  give,  for  a  man  weighing  65  kilo- 
j  grammes,  2.82  grammes  of  iron,  as  contained  in  the  blood  of  the  whole 
body. 

The  iron  of  the  hemoglobine  passes  out  of  the  body  by  the  bile  and 


MELANINE.  97 

the  urine,  both  of  which  contain  slight  traces  of  its  presence.  It  is  also 
contained  in  the  hair,  where  it  forms  sometimes  as  much  as  7  per  cent, 
of  the  incombustible  ingredients.  It  is  supplied  to  the  body  in  ample 
abundance  by  ordinary  food,  in  which  it  is  always  present  in  appre- 
ciable amount.  Green  vegetables  of  course  contain  it,  as  an  ingre- 
dient of  their  coloring  matter.  Since  hemoglobine  exists  to  some 
extent  in  muscular  tissue,  it  will  be  present  in  a  more  or  less  altered 
form,  but  still  containing  iron,  in  most  kinds  of  animal  food.  Accord- 
ing to  the  analyses  of  Moleschott,  500  grammes  of  beef  (about  one 
pound  avoirdupois)  will  contain  0.035  gramme  of  iron;  and  iron  is 
also  found  in  even  larger  proportion  in  rye,  barley,  oats,  wheat,  peas, 
and  especially  in  strawberries.  As  the  quantity  of  this  substance  daily 
discharged  in  the  urine  and  with  the  bile  is  so  small,  we  must  regard 
the  greater  portion  of  that  which  passes  through  the  system  as  used 
in  the  growth  of  the  hair ;  and  a  very  moderate  amount  contained  in 
the  food  must  be  sufficient  for  the  daily  requirements  of  nutrition. 

Melanine. 

In  all  the  dark-colored  tissues  of  the  body,  in  the  choroid  coat  of 
the  eyeball,  the  rete  Malpighi  of  the  skin  in  the  black  and  brown  races 
and  in  all  individuals  of  dark  complexion,  in  the  hair,  and  in  the 
substance  of  melanotic  tumors,  there  exists  a  coloring  matter  known 
as  melanine.  When  isolated  or  when  collected  in  compact  masses,  it  is 
of  a  very  dark  blackish-brown  color ;  but  by  its  mixture,  in  different 
proportions,  with  other  colorless  or  ruddy  semitransparent  elements  of 
the  tissues,  it  may  produce  all  the  varying  grades  of  hue,  from  light 
yellowish-brown  to  an  almost  absolute  black.  It  is  deposited  in  the 
substance  of  the  animal  cells  in  the  form  of  minute  granules,  and  is 
usually  more  abundant  in  the  immediate  neighborhood  of  the  nucleus, 
when  one  is  present,  than  near  the  edges  of  the  cell. 

Melanine  has  not  yet  been  obtained  in  a  perfect  crystalline  form,  and 
its  chemical  characters  are  not  completely  determined.  It  is  known, 
however,  to  be  a  nitrogenous  substance.  As  the  average  result  of  vari- 
ous analyses  collected  by  Hoppe-Seyler,1  it  contains,  freed  from  ashes, 
the  following  proportions,  by  weight,  of  carbon,  hydrogen,  nitrogen,  and 
oxygen. 

COMPOSITION  OF  MELANINE. 

Carbon 54.39 

Hydrogen "  5.08 

Nitrogen 11.17 

Oxygen 29.36 


100.00 
According  to  Kiiline2  repeated  observations  show  that  it  also  con- 

1  Handbuch  der  Physiologisch-  und  Pathologisch-Chemischen  Analyse.     Berlin, 
1870,  p.  177. 

2  Lehrbuch  der  Physiologischen  Chemie.     Leipzig,  1868,  pp.  365,  442. 


98  COLORING    MATTERS. 

tains  iron,  which  has  been  found  in  the  proportion  of  2.5  parts  per 
thousand  in  the  incombustible  residue. 

Melanine  is  insoluble  in  water,  alcohol,  ether,  and  solutions  of  the 
organic  and  mineral  acids.  Boiling  solutions  of  potassium  hydrate 
dissolve  it  without  change  of  color,  but  its  color  is  destroyed  by  chlo- 
rine. It  is  regarded  as  derived  from  the  coloring  matter  of  the  blood, 
but  there  is  no  positive  evidence  of  this,  further  than  the  fact  that  it 
contains  iron,  and  that  it  forms  the  coloring  matter  of  the  hair,  in 
which  most  of  the  iron  of  the  blood-globules  is  probably  deposited. 

Bilirubine,  C16HI8N203, 

The  red  or  orange-red  coloring  matter  of  the  bile.  This  substance 
has  been  designated,  by  different  writers,  under  the  various  names  of 
Biliphaein,  Bilifulvine,  Hematoidine,  and  Cholepyrrhine.  It  is  formed 
in  the  substance  of  the  liver,  and  may  be  extracted  from  the  liver- 
cells  in  a  pure  form.  From  these  it  is  taken  up  by  the  biliary 
ducts  and  mingled  with  the  other  ingredients  of  the  bile.  It  is  crystal- 
lizable,  soluble  in  chloroform,  less  so  in  alcohol,  and  slightly  soluble 
in  ether.  It  is  readily  soluble  also  in  alkaline  liquids,  but  quite  insolu- 
ble in  pure  water.  In  the  crystallized  form  its  color  is  red;  in  the 
amorphous  condition,  orange  ;  and  in  solution,  reddish-brown  or  yellow, 
according  to  the  degree  of  concentration.  According  to  Hoppe-Seyler, 
it  gives  a  perceptible  yellow  color  when  viewed  in  a  layer  of  1.5  centi- 
metre's thickness,  even  if  dissolved  in  500,000  times  its  weight  of  fluid. 

Solutions  of  bilirubine  exhibit  a  well-marked  reaction  with  nitroso- 
nitric  acid,  which  is  known  as  "  Gmelin's  bile  test."  If  to  such  a  solu- 
tion we  add  a  small  quantity  of  nitric  acid,  in  which  nitrous  acid  is  also 
present,  a  series  of  colors  is  produced  in  the  following  order :  green, 
blue,  violet,  red,  and  finally  a  dingy  yellow.  These  colors  are  produced 
by  transformation  of  the  bilirubine,  and  represent  successive  degrees 
of  its  oxidation  by  nitric  acid.  The  reaction  is  a  very  sensitive  one, 
and,  according  to  Hoppe-Seyler,  will  produce  a  visible  result  in  solu- 
tions containing  only  one  part  in  70,000. 

Bilirubine  is  generally  regarded  as  derived  from  hemoglobine.  The 
reasons  for  this  opinion  are:  First,  its  reddish  color,  similar,  in  some 
degree,  to  that  of  diluted  blood.  Secondly,  it  has  been  found  in  various 
parts  of  the  body,  in  old  bloody  extravasations,  evidently  produced 
from  an  alteration  of  the  blood  upon  the  spot.  When  found  under 
these  circumstances,  it  was  formerly  known  as  hematoidine.  Thirdly, 
if  hemoglobine,  in  the  living  animal,  be  withdrawn  from  the  blood- 
globules,  and  made  to  assume  a  liquid  form  by  alternately  freezing 
and  thawing  a  portion  of  freshly  drawn  blood,  and  then  re-injected 
into  the  bloodvessels,  this  operation  is  followed  by  a  discharge  of  bili- 
rubine with  the  urine.  If  hemoglobine,  however,  be  normally  trans- 
formed into  bilirubine,  its  iron  and  sulphur  must  enter  into  some  other 
combination,  as  neither  of  these  substances  exists  in  the  coloring  matter 


BILIVERDINE. —  UROCHROME.  99 

of  the  bile.  Bilirubine,  if  exposed  to  the  atmospheric  air  in  alkaline 
solution,  becomes  oxidized  and  assumes  a  green  color,  being  converted 
into  another  closely  related  substance,  namely,  biliverdine. 

Biliverdine,  C16H20N205. 

In  addition  to  bilirubine,  the  bile  contains  also  a  green  coloring 
matter,  namely,  biliverdine;  and  its  varying  tint  in  different  specimens 
depends  on  the  different  proportions  in  which  the  two  substances  are 
present.  In  many  species  of  animals,  as  in  the  ox,  sheep,  rabbit,  and 
vegetable  feeders  generally,  the  bile  presents  a  strong  green  or  greenish 
color,  due  to  the  comparative  abundance  of  biliverdine.  Biliverdine 
is  insoluble  in  water,  ether,  and  chloroform,  readily  soluble  in  dilute 
alkaline  solutions  and  in  alcohol.  It  is  also  soluble  in  glacial  acetic 
acid,  and  is  deposited  from  the  evaporated  solution  in  the  form  of  an 
imperfect  crystallization.  It  is  often  found  in  human  gall-stones,  and 
in  the  dog  is  abundantly  deposited  along  the  edges  of  the  placenta. 

There  is  every  reason  to  believe  that  biliverdine  is  formed  from  bili- 
rubine by  a  process  of  oxidation,  the  elements  of  water  entering  at  the 
same  time  into  combination.  The  nature  of  this  change  is  shown  by 
the  following  formula: 

Bilirubine.  Biliverdine. 

C16H18N203  +  H20  +  0  =  C16H.20N205. 

The  prompt  conversion  of  the  color  of  ruddy  or  reddish-brown  bile 
into  green  by  the  action  of  various  oxidizing  agents,  or  even  by  ex- 
posure to  the  air,  and  the  evident  chemical  relationship  between  the 
two  substances,  leave  no  doubt  that  this  is  the  mode  in  which  bili- 
verdine originates  in  the  animal  body.  Both  bilirubine  and  biliverdine 
are  discharged  with  the  bile  into  the  alimentary  canal,  but  they  become 
undistinguishable  toward  the  lower  end  of  the  small  intestine.  Beyond 
that  point  they  are  replaced  by  the  brown  coloring  matter  of  the  feces, 
and  are  finally  discharged  from  the  body  under  this  form. 

Urochrome. 

The  coloring  matter  of  the  urine  has  been  repeatedly  studied  by 
competent  and  laborious  observers,  but  thus  far  with  only  partial  suc- 
cess. The  substances  which  have  been  extracted  from  the  urine  by 
various  methods,  and  which  have  been  regarded  as  representing,  more 
or  less  exactly,  its  natural  coloring  principle,  are  known  by  the  dif- 
ferent names  of  Urochrome,  Urosine,  Urosacine,  Hemaphaeine,  Uro- 
hematine,  Uroxanthine,  Urobiline,  and  Hydrobilirubine.  They  are  all 
probably  modifications  of  the  same  substance,  variously  altered  by  dif- 
ferent methods  of  extraction,  or  obtained  in  different  grades  of  purity- 
The  fresh,  normal  urine  has  a  light  yellowish  or  amber  color,  while 
specimens  of  unusually  high  specific  gravity,  and  particularly  specimens 
of  febrile  urine,  often  exhibit  a  distinct  reddish  hue.  Normal  urine, 
which,  when  fresh,  is  only  amber-colored,  will  often,  by  exposure  to 
the  air,  acquire  a  jiftge?  tff  iec£^  The  substance  obtained  by  Thudi- 


100  COLORING    MATTERS. 

chum,1  and  called  by  him  urochrome,  is  precipitable  from  the  urine  by 
various  metallic  salts.  It  has  not  yet  been  produced  in  a  crystalline 
form.  It  is  soluble  in  water  and  in  ether,  but  only  slightly  soluble 
in  alcohol.  Its  watery  solution  has  a  yellowish  color,  which,  on  stand- 
ing, becomes  red.  Urohematine  (Harley)  is  nitrogenous  in  composition, 
and  contains  iron.2  It  is  insoluble  in  pure  water,  but  soluble  in  the 
fresh  urine,  as  well  as  in  ether,  chloroform,  and  alcohol.  The  sub- 
stance termed  Urobiline  (Jaffe)  was  so  named  because  supposed  to  be 
derived  from  the  coloring  matters  of  the  bile.  It  is  soluble  in  alcohol, 
ether,  and  chloroform.  Its  solutions  have  a  brownish-yellow  color, 
and,  by  dilution,  become  first  yellow,  and  lastly  faint  rosy-red.  It  was 
found  by  Jaffe5  to  be  present  in  nearly  every  instance  (45  cases)  in 
healthy  human  urine,  where  it  was  recognized,  after  partial  extraction 
and  purification,  by  its  peculiar  optical  (spectroscopic)  properties. 
The  same  observer,  however,  found  that  fresh  urine,  not  subjected  to 
chemical  manipulation,  would  often  present  no  indication  of  urobiline. 
Such  urine,  if  secluded  from  the  atmosphere,  would  remain  light- 
colored,  and  free  from  this  substance ;  but  if  exposed  to  the  air  for  from 
two  to  twelve  hours,  would  become  darker  in  hue,  and  at  the  same  time 
would  show,  by  the  spectroscope,  signs  of  the  presence  of  urobiline. 

It  is  evident,  therefore,  that  the  urine  contains  a  coloring  matter 
which  gives  to  it  in  the  fresh  condition  its  well  known  amber  tint. 
This  substance  is  liable  to  be  changed  under  the  influence  of  oxidation, 
and  to  assume  in  that  condition  a  more  or  less  distinct  red  color. 
Such  a  modification  certainly  takes  place  outside  the  body,  and  it  is 
possible  that  it  may  also  occur  within  the  system,  giving  rise  to  the 
varying  proportions  of  red  in  the  color  of  the  urine  in  different 
healthy  and  diseased  conditions. 

Beside  the  above  named  substances,  there  are  two  other  bodies  of  suf- 
ficient interest  in  general  physiology  to  be  enumerated  in  connection 
with  those  already  described. 

Lnteine. 

This  substance,  as  its  name  indicates,  is  of  a  strongly  marked  yellow 
color.  It  is  extracted  from  the  yolk  of  eggs,  and  from  the  tissue  of  the 
corpus  luteum.  It  exists  also,  according  to  Thudichum,4  in  the  grains 
of  Indian  corn,  in  certain  berries  and  roots,  and  in  the  yellow  stamens 
and  petals  of  a  large  number  of  flowering  plants.  It  is  crystallizable, 
soluble  in  alcohol,  ether,  .chloroform,  and  the  fatty  oils,  but  insoluble  in 
water.  It  is  readily  decomposed  and  decolorized  by  sunshine ;  and  by 
the  action  of  nitric  acid  it  is  first  turned  blue,  and  afterward  decolorized. 

1  British  Medical  Journal,  London,  Nov.  5,  1864. 

2  Harley,  The  Urine  and  its  Derangements.     Philadelphia,  1872,  p.  97. 

3  Archiv    fur    Pathologische   Anatomic    und    Physiologic,    1869,   vol.   xlvii. 
p.  405. 

4  Centralblatt  fur'die'Me.lictnische  W'hsFfosch'afttfn',  78f&;  JK  2. 


CHLOROPHYLLS.  101 

Its  color  is  also  changed  to  blue  or  green  by  other  strong  acids,  but  it 
is  not  affected  by  dilute  solutions  of  the  alkalies.  It  has  not  yet  been 
obtained  in  sufficient  quantity  for  complete  analysis. 

Chlorophylle, 

This  is  the  green  coloring  matter  of  plants.  It  is  more  widely  dif- 
fused than  any  other  coloring  matter  in  the  vegetable  world,  and  it 
apparently  constitutes  exclusively  the  coloring  principle  of  all  the  green 
parts  of  the  higher  plants  without  exception.  Its  exact  chemical  con- 
stitution has  not  been  fully  determined,  but  it  is  considered  to  be  a 
nitrogenous  substance,  and  Mulder  has  given  it  the  formula  C9H(JN04. 
It  is  certain  that  iron  is  essential  to  its  production,  as  plants  artificially 
cultivated  without  the  access  of  this  substance,  grow  up  in  a  blanched 
or  chlorotic  condition ;  and  their  green  color  may  afterward  be  restored 
by  the  supply  of  moisture  containing  a  ferruginous  salt.1 

Chlorophylle  is  of  the  first  importance  in  vegetable  physiology,  as  it 
is  under  the  influence  of  this  substance,  together  with  that  of  the  solar 
light,  that  the  inorganic  ingredients  of  the  soil  and  the  atmosphere  are 
deoxidized  and  combined  in  the  form  of  an  organic  carbo-hydrate.  The 
process  of  vegetation  proper,  that  is,  the  production  and  accumula- 
tion of  organic  material  in  the  form  of  starch,  sugar,  cellulose,  woody 
fibre,  and  the  substance  of  various  vegetable  tissues,  is  inseparably 
dependent  on  the  presence  and  action  of  Chlorophylle.  At  the  same 
time,  in  order  to  produce  this  effect,  the  Chlorophylle  must  constitute  a 
part  of  the  living  vegetable  cell ;  for  the  coloring  matter  alone,  if  ex- 
tracted from  the  chlorophylle-holding  cells,  and  placed  under  all  other 
conditions,  such  as  the  access  of  air,  sunlight,  warmth,  and  moisture, 
known  to  be  essential  to  the  work  of  production,  is  found  to  be  incapable 
of  forming  organic  matter  out  of  water  and  carbonic  acid.  Its  func- 
tion, therefore,  is  not  that  of  a  simple  chemical  reagent,  but  that  of  an 
active  constituent  of  the  living  vegetable  organism. 

Chlorophylle  is  produced,  in  the  interior  of  the  vegetable  cell,  some- 
times as  a  uniformly  diffused  mass.  Usually,  however,  it  is  deposited 
in  the  form  of  distinct  rounded  grains,  frequently  arranged  in  definite 
figures  or  patterns  in  the  cavity  of  the  cell.  It  may  be  extracted  by  the 
action  of  alcohol  or  of  ether,  and  retains  its  green  color  in  solutions  of 
these  substances.  It  disappears  previously  to  the  shedding  of  the  leaves, 
when  they  cease  to  perform  the  act  of  vegetation,  and  is  usually  replaced 
by  a  few  grains  of  red  or  yellowish  color. 

1  Mayer,  Lehrbuch  der  Agrikultur-Chemie,  Band  i.  pp.  51,  265. 


CHAPTER  VI. 

CRYSTALLIZABLE    NITROGENOUS  MATTERS. 

THE  fifth  and  last  group  of  proximate  principles  consists  of  a 
number  of  colorless  substances  which,  like  the  albuminous  matters, 
contain  nitrogen,  but  which  differ  from  them  in  being  readily  crystal- 
lizable.  Many  of  them  are  evidently  derived  from  the  albuminous 
ingredients  of  the  body  by  retrograde  metamorphosis,  being  dis- 
charged from  the  system  as  products  of  excretion.  Others  do  not 
exhibit  this  character,  and  are  found  only  in  the  permanent  tissues  or 
the  internal  fluids  of  the  body.  Several  of  them  are  of  comparatively 
recent  discovery,  and,  although  undoubtedly  of  importance  in  the  con- 
stitution of  the  body,  are  still  somewhat  obscure  in  their  physiological 
relations. 

Lecithine,  C44H90NP09, 

From  Af'xt^oj,  the  yolk  of  egg,  in  which  substance  it  was  first  discovered. 
Lecithine  was  for  some  time  described  under  the  name  of  phosphorized 
fat,  owing  to  the  circumstance  that  one  of  the  products  of  its  de- 
composition is  phosphoglyceric  acid  (C3H9P06).  It  is  not,  however, 
a  fatty  substance,  since  it  contains  nitrogen,  and  in  other  respects 
differs  from  the  fats.  As  mingled  or  combined  with  other  animal  mat- 
ters, it  has  also  been  known  by  the  name  of  "  protagon."  Lecithine  is 
of  very  wide  distribution  in  both  the  animal  and  vegetable  kingdoms, 
occurring  in  the  cereal  grains  and  the  leguminous  seeds,  and,  according 
to  Hoppe-Seyler,  in  the  cellular  juices  of  a  variety  of  plants.  It  is 
found  in  the  blood,  both  in  the  plasma  and  the  globules,  in  the  bile,  the 
spermatic  fluid,  the  yolk  of  egg,  and  particularly  in  the  tissues  of  the 
brain,  spinal  cord,  and  nerves.  In  the  plasma  of  the  blood,  it  is  in  the 
proportion  of  0.4  part  per  thousand,  and  in  the  fresh  substance  of  the 
calf's  brain,  according  to  the  analyses  of  Petrowsky,1  in  the  proportion 
of  31  parts  per  thousand.  Taking  into  account  the  watery  ingredients 
of  the  brain,  lecithine  is  about  equally  abundant  in  the  white  and  gray 
substance ;  but  of  the  solid  matters  alone,  it  constitutes  a  little  less  than 
10  per  cent,  in  the  white  substance,  and  rather  more  than  It  per  cent, 
in  the  gray  substance. 

Lecithine  obtained  from  either  of  these  sources,  if  treated  with  water, 
swells  up  into  a  pasty  mass  and  gives  origin  to  the  remarkable  appearances 
under  the  microscope  known  as  "myeline  forms;"  that  is,  a  great 

1  Archiv  fur  die  gesammte  Physiologie,  1873,  Band  vii.  p.  101. 
(102) 


CRYSTALL1ZABLE    NITROGENOUS    MATTERS.  103 

variety  of  mucilaginous  or  oily  looking  drops  and  filaments,  of  double 
contour,  which  exude  from  the  edges  of  the  mass,  and  remain  separate 
and  insoluble ;  resembling  the  microscopic  forms  produced  under  simi- 
lar circumstances  from  the  "myeline,"  or  medullary  layer  of  nerve 
fibres.  It  is  readily  soluble  in  alcohol,  less  so  in  ether,  and  is  also  solu- 
ble to  some  extent  in  chloroform  and  the  fatty  oils.  It  is  readily 
decomposed  on  standing,  either  in  solution  or  in  a  state  of  watery 
imbibition,  acquiring  an  acid  reaction.  Decomposition  is  also  effected 
by  the  action  of  acids  or  alkalies.  By  boiling  with  baryta  water  it 
suffers  a  characteristic  alteration,  giving  rise  to  the  production  of  two 
new  bodies;  namely,  a  nitrogenous  alkaline  substance  and  phospho- 
gly eerie  acid. 

Lecithine  has  a  special  importance,  not  only  as  an  abundant  ingre- 
dient of  the  nervous  tissue,  but  also  as  being  the  only  organic  combina- 
tion in  the  body  containing  phosphorus.  Considering  the  number  of 
vegetable  and  animal  articles  of  food  in  which  it  is  an  ingredient,  it  is 
evident  that  a  considerable  quantity  must  be  introduced  with  the  nutri- 
ment into  the  system  and  assimilated  by  the  tissues,  particularly  by 
those  of  the  nerves  and  nervous  centres.  But  as  no  known  organic 
combination  of  phosphorus  is  discharged  with  the  excretions,  this  sub- 
stance must  pass  out  of  the  body  as  part  of  the  phosphates  which 
appear  in  the  urine  and  the  perspiration.  On  this  account,  together 
with  the  known  fact  of  the  constant  consumption  of  oxygen  by  the 
animal  body,  it  is  believed  that  the  phosphorus,  introduced  as  an  ingre- 
dient of  organic  materials,  is  converted  by  oxidation  in  the  system 
into  phosphoric  acid,  and  thus  appears  finally  under  the  form  of  phos- 
phatic  salts. 

Cerebrine,  C17H33N03. 

As  its  name  indicates,  this  is  an  ingredient  of  the  brain  and  nerves, 
the  only  healthy  constituents  of  the  body  in  which  it  is  known  to  exist. 
Although  this  substance  has  not  been  obtained  in  a  crystalline  form, 
it  is  placed  among  the  members  of  this  group  because  it  resembles 
them  in  the  general  features  of  its  chemical  composition,  particularly  in 
its  small  proportion  of  nitrogen,  and  also  in  certain  of  its  reactions, 
which  are  entirely  dissimilar  to  those  of  an  albuminous  matter. 

Cerebrine  is  insoluble  in  water,  but  if  moistened  swells  up  slowly 
into  a  pasty  mass.  It  is  insoluble  in  ether  and  in  cold  alcohol. 

It  is  readily  soluble  in  boiling  absolute  alcohol,  from  which  it  is 
again  deposited  on  cooling.  Boiling  with  baryta  water  decomposes  it 
very  slowly  and  incompletely,  and  does  not  produce  phosphoglyceric 
acid,  by  which  means  it  may  be  distinguished  from  lecithine.  If 
strongly  heated  in  the  air,  it  turns  brown,  melts,  and  finally  burns  with 
a  bright  flame. 

It  is  much  more  abundant  in  the  white  than  in  the  gray  substance  of 
the  brain,  forming,  according  to  Petrowsky,  in  the  solid  ingredients  of 
the  white  substance  9.5  per  cent.,  in  those  of  the  gray  substance  but 


104:  CRYSTALLIZABLE    NITROGENOUS    MATTERS. 

little  more  than  0.5  per  cent.  It  is,  therefore,  undoubtedly  a  constitu- 
ent of  the  medullary  layer  of  nerve  fibres. 

Leucine,  C6H13N0.2, 

So  called  from  the  glistening  white  color  of  its  crystals.  It  is  found 
in  the  tissue  of  the  spleen,  the  thymus,  thyroid,  lymphatic,  submaxillary, 
and  parotid  glands,  the  pancreas  and  pancreatic  juice,  the  brain,  liver, 
kidneys,  and  supra-renal  capsules.  In  all  these  situations  it  exists  in 
comparatively  small  quantity,  but  its  exact  proportions  have  not  been 
determined.  '  It  has  not  yet  been  found  in  the  blood  in  a  state  of  health, 
and  has  only  been  met  with  in  the  urine  in  certain  cases  of  disease. 
According  to  Hoppe-Seyler  it  is  one  of  the  products  of  putrefactive 
decomposition  of  albuminous  and  gelatinous  substances.  When  pure, 
it  crystallizes  in  thin  white  laminae,  in  which  form  it  is  readily  solu- 
ble in  water,  less  so  in  alcohol,  and  insoluble  in  ether.  Heated 
slowly  to  170°  (338°  F.)  it  volatilizes  unchanged;  above  this  point  it 
is  decomposed ;  two  of  the  products  of  its  decomposition  being  carbonic 
acid  and  ammonia.  But  little  is  known  with  regard  to  the  normal 
origin  or  physiological  destination  of  this  substance,  its  importance 
being  only  indicated  by  the  number  and  variety  of  the  situations  in 
which  it  is  found. 

Sodium  Glycocholate,  C26H42N06Na. 

This  is  one  of  the  characteristic  ingredients  of  the  bile,  where  it 
sometimes  forms,  according  to  the  observations  of  Jacobsen,  nearly  49 
per  cent,  of  the  dry  residue.  It  is  also  found  in  the  tissue  of  the  liver 
and  in  the  fluids  of  the  upper  part  of  the  intestinal  canal,  into  which 
it  is  discharged  with  the  bile ;  but  it  does  not  exist  in  the  blood  or  in 
the  other  animal  fluids. 

It  is  a  saHne  body,  consisting  of  a  nitrogenous  organic  acid,  glyco- 
cholic  acid  (C26H43N06)  in  combination  with  sodium.  Glycocholic  acid 
is  so  called  because  by  boiling  with  solutions  of  potassium  hydrate  or 
baryta  water,  or  by  continued  boiling  with  dilute  hydrochloric  or 
sulphuric  acids,  it  is  decomposed  with  the  production  of  two  new 
bodies,  namely,  glycine  (C2H6N02),  a  nitrogenous  neutral  substance, 
and  cholic  acid  (C24H4005),  a  non-nitrogenous  organic  acid,  so  called 
because  peculiar  to  the  bile.  This  change  takes  place  with  the  assump- 
tion, by  the  glycocholic  acid,  of  the  elements  of  water,  as  follows : 

Glycocholic  acid.  Glycine.          Cholic  acid. 

C26H43N06  +  H20  =  C2H5N02  +  C24H4005. 

The  two  bodies  thus  formed  do  not,  therefore,  pre-exist  in  the  organic 
acid  of  the  bile,  but  are  produced,  by  the  addition  of  other  elements, 
at  the  time  of  its  decomposition. 

Sodium  glycocholate  is  a  neutral,  crystallizable  substance,  very 
soluble  in  water  and  in  alcohol,  and  insoluble  in  ether.  It  is  accord- 
ingly extracted  from  the  bile  by  the  following  process :  The  bile  is  first 
evaporated  to  dry  ness  over  the  water-bath,  the  dry  residue  extracted 


CRYSTALLIZABLE    NITROGENOUS    MATTERS. 


105 


Fig.  21. 


SODIUM    GLYOOOHOI.ATI!   FROM  OX-BILB, 

after  two  days'  crystallization.  At  the  lower 
part  of  the  figure  the  crystals  are  melting  into 
drops,  from  evaporation  of  the  ether  and  absorp- 
tion of  moisture. 


with  absolute  alcohol,  the  alcoholic  solution  decolorized  with  animal 
charcoal,  and  then  mixed  with  from  8  to  10  times  its  volume  of  ether. 
A  whitish  precipitate  is  thrown 
down  which  soon  collects  into 
little  drops  and  masses,  of  a 
consistency  like  that  of  Canada 
balsam,  whence  the  biliary  salts 
have  been  sometimes  termed  the 
"  resinous"  matters  of  the  bile. 
In  the  course  of  24  hours, 
sometimes  only  after  four  or 
five  days,  the  sodium  glyco- 
cholate  crystallizes  abundantly 
in  the  form  of  hemispherical  or 
star-shaped  masses  of  fine  ra- 
diating acicular  crystals.  These 
crystals  may  be  preserved  in- 
definitely in  the  mixture  of  al- 
cohol and  ether ;  but  if  the  mix- 
ture be  poured  off,  the  cold 
produced  by  evaporation  causes 
a  condensation  of  atmospheric 
moisture  and  a  rapid  melting 

and  solution  of  the  crystals,  which  may  be  seen  under  the  microscope 
liquefying  into  transparent,  rounded,,  oleaginous-looking  drops.  The 
solubility  of  these  drops  in  water  and  their  insolubility  in  ether  will 
readily  distinguish  them  from  oil  globules,  which  they  closely  resemble 
in  their  optical  properties.  Sodium  glycocholate  may  be  precipitated 
from  its  watery  solution  by  both  the  neutral  and  tribasic  lead  acetates. 
Its  alcoholic  solution  rotates  the  plane  of  polarization  toward  the  right 
25°.T. 

Sodium  Taurocholate,  C26H44NS07Na. 

This  is  a  substance  similar  in  many  of  its  properties  to  the  last,  and, 
like  it,  a  peculiar  ingredient  of  the  bile.  Its  organic  acid,  taurocholic 
acid  (C26H43NS07),  is  distinguished  by  containing  an  atom  of  sul- 
phur, owing  perhaps  to  its  having  been  derived  from  the  albuminous 
matters.  If  so,  glycocholic  acid  will  represent  a  product  of  further 
oxidation,  under  which  sulphur,  hydrogen,  and  oxygen  are  given  up  in 
such  proportions  that  the  products  of  elimination  are  sulphuric  acid  and 
water,  as  follows : 

Taurocholic  acid.  Glycocholic  acid. 

C26H45NS07  -  S(HaO)  =  C26H43N06. 

By  boiling  with  dilute  acids  or  alkalies,  or  even  in  water,  taurocholic  acid 
is  decomposed  with  the  formation  of  two  other  bodies,  namely,  taurine 
(C2H.NSO.S),  a  neutral  nitrogenous  substance,  containing  all  the  sulphur, 
so  called  because  first  discovered  in  bullock's  bile,  and  cholic  acid 

8 


106 


CRYSTALLIZABLE    NITROGENOUS    MATTERS. 


Fig.  22. 


(C24H4005),  the  same  body  produced  by  a  similar  process  from  glyco- 
cholic  acid.  The  change  here  also  takes  place  with  the  assumption 
of  the  elements  of  water,  as  follows : 

Taurocholic  acid.  Taurine.  Cholic  acid. 

C26H45NS07  +  H20  =  C2H7NS03  +  C24H4005- 
Sodium  taurocholate,  like  the  preceding  biliary 
salt,  is  soluble  in  water  and  in  alcohol,  and  insoluble 
in  ether.  It  is  extracted  from  the  bile  by  a  similar 
process  to  that  already  described,  and,  after  precipita- 
tion by  ether,  crystallizes  in  slender  needles,  much 
like  those  of  the  glycocholate.  It  may  be  distin- 
guished, however,  and  separated  from  the  last-named 
substance,  when  in  company  with  it,  by  its  reaction 
toward  the  salts  of  lead.  It  is  not  precipitated  from 
its  watery  solution  by  the  neutral,  but  only  by  the 
tribasic  acetate.  If  a  watery  solution,  therefore,  con- 
taining both  salts  be  precipitated  by  neutral  lead  ace- 
tate, the  filtered  fluid  will  contain  the  sodium  tauro- 
cholate alone.  In  alcoholic  solution  it  rotates  the 
plane  of  polarization  toward  the  right  24°.5. 

The  two  biliary  salts  are  associated  in  the  bile  in 
varying  proportions.  Generally  the  glycocholate  may 
be  said  to  preponderate  in  the  bile  of  the  ruminant 
animals,  taurocholate  in  that  of  the  carmvora.  In 
dog's  and  cat's  bile,  the  taurocholate  exists  alone.  In 
human  bile  it  appears  that  both  substances  may  be 
present,  sometimes  one  of  them  being  the  more  abun- 
dant, sometimes  the  other ;  according  to  some  writers  the  taurocholate 
existing  alone  or  in  larger  proportion  (Gorup-Besanez,  Hoppe-Seyler, 
Robin,  Hardy),  according  to  others  the  gtycocholate  (Bischoff,  Lossen, 
RankeJ.  In  the  observations  of  Jacobsen,1  on  a  case  of  biliary  fistula 
in  man,  the  glycocholate  was  shown  to  be  a  constant  ingredient,  while 
the  taurocholate  was  either  absent,  or,  if  present,  varied  in  quantity. 
We  have  also  found  human  bile  to  contain  the  glycocholate  without 
the  presence  of  taurocholate. 

The  biliary  salts  are  formed  in  the  glandular  tissue  of  the  liver  and 
discharged  with  the  bile.  According  to  the  observations  of  Ranke  on 
a  man  with  biliary  fistula,  the  average  quantity  of  the  organic  acids  of 
the  bile  thus  produced,  by  a  man  weighing  65  kilogrammes,  would  be  a 
little  over  15  grammes  per  day.  They  are  not  discharged  with  the  feces, 
but  are  changed  in  the  intestine,  and,  probably,  reabsorbed  under  another 
form  by  the  blood. 

Creatine,  C4H9N302,  from  x^,  flesh. 

This  is  a  neutral  crystallizable  substance,  which  exists  very  generally 
in  the  muscular  tissue,  both  voluntary  and  involuntary,  of  man  and 


SODIUM  TAU- 
ROCHOLATE, from 
alcoholic  extract  of 
dog's  bile,  crystalliz- 
ing at  the  bottom  of 
a  test-tube. 


Kevue  des  Sciences  Medicales,  1874,  vol.  iii.  p.  85. 


CRYSTALLIZABLE    NITROGENOUS    MATTERS. 


107 


CREATINE,  crystallized  from  hot  water. 
(Lehmann.) 


animals;  its  proportion  in  the  human  muscles  being,  according  to 
Neubauer,1  about  two  parts  per  thousand.  It  has  also  been  found 
in  minute  quantity  in  the  blood, 
the  brain,  and  the  kidneys.  It  is 
soluble  in  cold,  very  readily  in  hot 
water,  slightly  soluble  in  alcohol, 
insoluble  in  ether.  From  its  watery 
solution  it  crystallizes  in  the  form 
of  transparent,  colorless,  rhombic 
prisms  of  firm  consistency.  It  is 
decomposed  by  a  temperature  of 
100°  (2120  p.).  By  boiling  in  acid 
solutions,  or  by  long-continued 
boiling  in  water,  it  is  transformed 
into  another  closely  related  sub- 
stance, namely,  creatinine.  If  boil- 
ed with  baryta  water  it  produces, 
among  other  substances,  urea,  car- 
bonic acid,  and  ammonia.  Creatine 
is  regarded  as  a  product  of  metamorphosis  of  the  albuminous  matters, 
especially  of  those  existing  in  muscular  tissue.  It  does  not  appear  in 
the  urine,  but  undergoes  further  transformation  in  the  interior  of  the 
body,  probably  into  the  following  substance. 

Creatinine,  C4H.N30, 

Is  known  to  exist,  with  certainty,  only  in  the  urine.     Although  it  has 
been  occasionally  found  by  some  observers  in  the  muscles,  according  to 
Neubauer  it  is  not  a  normal  ingredient  of  the  tissue,  but  is  produced 
during  the  process  of  extraction, 
under  the  continued  influence  of 
heat  and  moisture,  from  the  previ- 
ously existing  creatine.    C  reatinine 
is  soluble  in  water  and  in  alcohol, 
but  only  slightly  soluble  in  ether. 
It  crystallizes  in  colorless  glitter- 
ing prisms.     In  solutions  it  has  a 
strong   alkaline   reaction,   decom- 
poses   the    combinations   of   am- 
monia,   and   forms   with    various 
acids  neutral  salts. 

The  relation  between  these  two 
bodies  is  such  that  by  different 
chemical  processes  they  may  be 
artificially  converted  into  each 

,,  T     J.U     •    A.  *•  it      i      -i          CREATININE,  crystallized  from  hot  water. 

other.    In  the  interior  of  the  body  (Lehmann.) 


Fig.  24. 


1  Neubauer  und  Vogel,  Analyze  des  Harns,  1872,  p.  20. 


108  CKYSTALLIZABLE    NITROGENOUS    MATTERS. 

the  change  which  takes  place  is  undoubtedly  the  conversion  of  creatine 
into  creatinine,  since  the  former  is  that  which  exists  normally  in  the 
muscles,  while  the  latter  is  an  ingredient  of  the  urine.  In  this  change 
the  elements  of  water  are  eliminated  as  follows : 

Creatine.  Creatinine. 

C4H9N302  —  H20  =  C4H7N30. 

Thus  creatine  represents  an  intermediate  stage  of  the  products  of  meta- 
morphosis, which  finally  appear  in  the  urine  under  the  form  of  creatinine. 
According  to  the  observations  of  Neubauer,  the  quantity  of  creatinine 
discharged  by  a  healthy  man,  under  ordinary  diet,  is  about  1  gramme 
per  day. 

Urea,  CH4N20. 

This  is  one  of  the  most  important  and  well  known  substances  of  its 
class,  as  it  is  the  principal  solid  ingredient  of  the  urine,  and  the  main 
product  of  the  decomposition  of  nitrogenous  matters  in  the  body.  It  is 
most  abundantly  found  in  the  urine,  where  it  is  present  on  the  average, 
in  man,  in  the  proportion  of  26  parts  per  thousand ;  while  in  the  blood 
it  is  only  in  the  proportion  of  0.16  part  per  thousand.  As  it  makes  its 
appearance  in  the  blood,  it  is  constantly  drained  away  by  the  kidneys, 
and  thus  accumulates  in  larger  proportion  in  the  urine.  This  is  further 
shown  by  the  comparative  analyses  of  Picard,  who  found,  in  the  dog, 
the  proportion  of  urea  in  the  blood  of  the  renal  arteries  to  be  0.36  per 
thousand,  in  the  renal  veins  0.18  per  thousand.  Urea  has  also  been 
found  in  minute  quantity  in  the  lymph,  the  aqueous  and  vitreous  humors 
of  the  eye,  the  crystalline  lens,  and  the  perspiration. 

Urea  is  a  colorless,  neutral  substance,  abundantly  soluble  in  water 
and  in  boiling  alcohol,  less  so  in  cold  alcohol,  nearly  insoluble  in  ether. 
It  crystallizes  in  four-sided  prisms,  often  with  blunt  pyramidal  ends, 
which  are  decomposed  on  being  heated  above  120°  (248°  F.).  Its  pure 
watery  solution  may  be  kept  without  change  at  ordinary  temperatures  ; 
but  by  long  continued  boiling,  or  by  a  short  boiling  in  the  presence  of 
alkalies,  it  is  decomposed  with  the  production  of  ammonium  carbonate. 
If  heated  with  water  in  an  hermetically  sealed  tube  to  180°  (356°  F.), 
it  undergoes  the  same  alteration.  This  change  takes  place  with  the 
assumption  of  the  elements  of  water,  as  follows : 

Urea.  Ammonium  carbonate. 

CH4N20  +  HA  «  (NH4)2C03. 

Urea  has  been  produced  artificially  from  albuminous  matter,  by 
placing  the  latter  in  contact  with  potassium  permanganate  in  watery 
solution,  and  subjecting  it  to  a  heat  of  60°  to  80°  (14(P  to  176Q  F.). 
This  reaction,  first  established  by  Bdchamp,1  has  been  confirmed  by 
Hitter,2  in  whose  experiments  30  grammes  of  albumen  furnished  0.09 
gramme  of  urea,  and  the  same  quantity  of  fibrine,  0.0 T  gramme; 

1  Coraptes  Kendus  de  I'AcadSmie  des  Sciences,  Paris,  1870,  tome  Ixx.  p.  866. 

2  Comptes  Rendus,  1871,  Ixxiii.  p.  1219. 


CRYSTALLIZABLE    NITROGENOUS    MATTERS, 


109 


while  from  30  grammes  of  gluten,  in  an  average  of  three  experiments, 
there  was  obtained  0.21  gramme  of  urea.  According  to  Bechamp, 
this 


Fig.  25. 


UREA,  prepared  from  urine,  and  crystallized 
by  slow  evaporation.    (Lehmann.) 


is  not  a  process  of  simple 
oxidation,  but  an  oxidation  with 
decomposition,  in  which  various 
other  substances  are  produced  from 
the  albuminous  matter  at  the  same 
time  with  urea.  The  quantity  of 
urea  excreted  by  a  healthy  man  is 
about  35  grammes  per  day.  This 
amount  varies,  of  course,  with  the 
size  of  the  body,  the  average  daily 
proportion  of  urea  to  the  weight 
of  the  whole  body  being  0.5  per 
thousand  parts.  Lehmann,  in  ex- 
periments on  his  own  person,  found 
the  average  daily  quantity  to  be 
32.5  grammes.  Bischoff,  by  simi- 
lar experiments,  found  it  to  be  35 
grammes.  Prof.  William  A.  Ham- 
mond, whose  weight  was  90  kilogrammes,  found  it  to  be  43  grammes. 
Prof.  John  C.  Draper,  whose  weight  was  66  kilogrammes,  found  it 
26.5  grammes. 

It  has  been  shown  by  Prof.  John  C.  Draper,1  and  confirmed  by  other 
observers,  that  there  is  a  diurnal  variation  in  the  normal  quantity  of 
urea.  A  smaller  quantity  is  produced  during  the  night  than  during 
the  day ;  and  this  difference  exists  even  in  patients  who  are  confined  to 
the  bed  during  the  whole  twenty-four  hours,  as  in  the  case  of  a  man 
under  treatment  for  fracture  of  the  leg.  This  is  probably  owing  to  the 
greater  activity,  during  the  waking  hours,  of  both  the  mental  and  di- 
gestive functions.  More  urea  is  produced  in  the  latter  half  than  in  the 
earlier  half  of  the  day ;  and  the  greatest  quantity  is  discharged  during 
the  four  hours  from  6j  to  10^  P.  M. 

The  quantity  of  excreted  urea  represents  almost  completely  the 
amount  of  decomposition  in  the  nitrogenous  organic  ingredients  of  the 
body ;  since  it  is  the  only  nitrogenous  substance  discharged  in  consider- 
able quantity  by  the  excretions.  A  comparison  of  the  entire  amount 
of  nitrogen  contained  in  the  daily  food  with  that  discharged  from  the 
body  in  various  forms  shows  that  fully  85  per  cent,  of  that  introduced 
reappears  as  an  ingredient  of  the  urea ;  the  remaining  15  per  cent,  being 
contained  in  the  uric  and  hippuric  acids  and  creatinine  of  the  urine,  and 
in  the  nitrogenous  matters  of  the  feces. 

All  observers  are  agreed  that  the  quantity  of  urea  excreted  varies  in 
proportion  to  the  amount  of  nitrogenous  matters  contained  in  the  food. 


1  New  York  Journal  of  Medicine,  March,  1856. 


110  CRYSTALLIZABLE    NITROGENOUS    MATTERS. 

Lehmann  found,1  in  experiments  on  his  own  person,  that  the  daily 
amount  of  urea  was  increased  by  a  diet  of  animal  food,  diminished  by 
one  of  vegetable  food,  and  reduced  to  its  minimum  by  a  diet  consisting 
exclusively  of  non-nitrogenous  matters,  such  as  starch,  sugar,  and  fat. 
The  comparative  results  were  as  follows  : 

Kind  of  diet.  Daily  quantity  of  urea. 

Mixed 32.5  grammes. 

Animal 53.2         " 

Vegetable 22.5         " 

Non-nitrogenous      .......     15.4         " 

It  also  appears  from  the  observations  of  Mahomed2  that  the  influence 
of  a  change  of  diet  in  this  respect  is  manifested  very  rapidly ;  twenty- 
four  hours  of  a  non-nitrogenous  diet  being  sufficient  to  reduce  the  excre- 
tion of  urea  50  per  cent.,  while  it  is  again  restored  to  its  ordinary 
standard  within  three  or  four  hours  after  the  use  of  animal  food. 

Urea,  however,  does  not  depend  exclusively  upon  the  direct  trans- 
formation of  the  nitrogenous  matters  of  the  daily  food,  but  is  also,  in 
part  at  least,  derived  from  the  metamorphosis  of  the  more  permanent 
constituents  of  the  body ;  since  it  continues  to  be  discharged,  though 
in  diminished  quantity,  when  no  food  is  taken.  Lehmann  found  as 
much  urea  in  the  urine  after  twenty -four  hours  of  abstinence  from  all 
food,  as  after  a  diet  of  non-nitrogenous  matters.  In  the  dog,  when 
subjected  to  entire  abstinence,  the  urea  is  reduced  in  three  or  four  days 
to  nearly  one-third  its  former  quantity,  but  is  still  present  in  about  the 
same  proportion  at  the  end  of  seven  days.  In  the  experiments  of  Dr. 
Parkes  on  a  man  subjected  to  a  purely  non-nitrogenous  diet,  the  daily 
excretion  of  urea  fell  on  the  second  day  to  12  grammes,  but  afterward 
remained  nearly  uniform,  at  rather  more  .than  half  that  quantity,  and  on 
the  fifth  day  still  amounted  to  7  grammes.  Urea  has  also  been  found 
by  Lassaigne  in  the  urine  of  man  after  continued  abstinence  from  food 
for  fourteen  days. 

The  quantity  of  urea  has  been  found  by  Lehmann,3  Prof.  A.  Flint,  Jr.,4 
Parkes,5  and  Yogel6  to  be  increased  during  or  after  unusual  muscular 
exertion.  Other  observers  (Fick  and  Wislicenus,  Yoit,  Ranke)  have 
found  no  perceptible  variation  owing  to  this  cause.  The  same  discrep- 
ancy exists  between  different  writers  in  regard  to  creatinine.  It  is 
possible  that  the  details  of  the  process  by  which  the  albuminous  matters 
during  decomposition  give  rise  to  the  formation  of  urea  are  not  }^et 
fully  known  to  us.  But  it  is  a  matter  of  common  experience,  both  for 
man  and  animals,  that  continued  and  laborious  muscular  activity 

1  Physiological  Chemistry.     Sydenham  edition.     London,  1853,  vol.  ii.  p.  450. 

2  Pavy  on  Food  and  Dietetics.     Philadelphia  edition,  1874,  pp.  79-81. 

3  Physiological  Chemistry.     Sydenham  edition,  vol.  ii.  p.  452. 

4  New  York  Medical  Journal,  June,  1871. 

5  Proceedings  of  the  Royal  Society,  March  2d,  1871,  p.  357. 

6  Neubauer  und  Yogel,  Analyse  des  "Earns,,  1872,  p.  338. 


CRYSTALLIZABLE    NITROGENOUS    MATTERS.  Ill 

requires  a  corresponding  supply  of  nitrogenous  food  ;  and  the  final 
result  of  the  internal  metamorphosis  of  such  substances  is  mainly  repre- 
sented by  the  excretion  of  urea. 

Sodium  Urate,  C5H3N403Na. 

As  its  name  indicates,  this  is  a  saline  body,  consisting  of  a  nitro- 
genous organic  acid,  namety,  uric  acid  (C5H4N403),  in  union  with  so- 
dium. A  portion  of  it  is  also  in  combination  with  potassium,  but  the 
sodium  salt  is  in  much  the  greater  quantity  of  the  two.  The  urates 
are  found  normally  only  in  the  urine,  where  they  exist  in  the  proportion 
of  about  1.45  parts  per  thousand.  The  entire  quantity  of  uric  acid 
excreted  by  a  healthy,  full-grown  man,  is  about  0.1  gramme  per  day. 
It  is,  therefore,  very  much  less  abundant  than  urea;  and,  according 
to  the  researches  of  J.  Ranke,  the  proportion  between  them  is  very  con- 
stant, the  relative  daily  quantity  of  the  two  substances  in  the  same 
individual  being  nearly  always — 

Uric  acid       .        .        .        .        .      1  part. 
Urea 45  parts. 

Uric  acid  is  a  colorless,  crystallizable  substance,  only  very  slightly 
soluble  in  either  cold  or  hot  water,  quite  insoluble  in  alcohol  and  in 
ether.  It  is  much  less  easily  decomposed  than  urea,  remaining  for  a 
long  time  unchanged  under  all  ordinary  conditions.  If  treated  with 
concentrated  sulphuric  acid  it  is  decomposed,  with  the  production  of 
ammonia  and  carbonic  acid.  If  boiled  with  dilute  nitric  acid,  it  dis- 
solves with  a  yellow  color  and  abundant  liberation  of  gas-bubbles; 
and,  on  evaporation,  the  solution  leaves  a  brilliant  red  stain,  which  is 
changed  to  purple  by  the  addition  of  a  drop  of  ammonia  water.  This 
is  known  as  the  "  murexide  test"  for  uric  acid  or  the  urates. 

Uric  acid,  like  urea,  is  formed  within  the  body  by  the  metamorphosis 
of  nitrogenous  organic  substances.  It  is  most  abundant  under  the  use 
of  animal  food,  and  diminished  by  a  vegetable  diet,  and  is  reduced  to  a 
minimum,  though  it  does  not  entirely  disappear,  during  complete  absti- 
nence. It  is  this  substance  which  indirectly,  in  great  measure,  causes 
the  acid  reaction  of  the  urine.  It  is  nowhere  present  normally  in  a  free 
form,  being  by  itself  exceedingly  insoluble ;  but  simultaneously  with 
its  production  it  unites  with  part  of  the  alkaline  bases  of  the  phosphates, 
thus  becoming  mainly  sodium  urate,  which  is  soluble  and  neutral  in 
reaction,  and  giving  rise  to  sodium  biphosphate,  which  communicates 
to  the  urine  its  acid  reaction. 

Sodium  Hippurate,  C9H8N03Na. 

This  is  also  a  saline  body,  formed  by  the  union  of  sodium  with  a 
nitrogenous  organic  acid,  namely,  hippuric  acid,  C9H9N03,  so  called 
because  it  was  first  discovered  in  the  urine  of  the  horse.  It  is  com- 
paratively abundant  in  the  urine  of  most  herbivorous  animals,  especially 
the  horse,  ox,  sheep,  goat,  elephant,  camel,  and  rabbit;  while  it  is 


112  CRYSTALLIZABLE    NITROGENOUS    MATTERS. 

absent,  or  nearly  so,  in  that  of  the  carnivorous  animals.  In  human 
urine,  under  an  ordinary  mixed  diet,  it  is  constantly  present,  amount- 
ing to  about  0.35  gramme  per  day,  or  about  one-half  the  quantity  of 
uric  acid.  It  increases,  however,  perceptibly  under  a  vegetable  diet, 
and  diminishes  or  disappears  altogether  under  the  exclusive  use  of  ani- 
mal food.  It  thus  alternates  in  quantity,  under  these  circumstances, 
with  uric  acid.  In  the  urine  of  the  horse,  which  normally  contains 
hippuric  acid,  after  continued  abstinence  from  food,  this  substance 
ceases  to  appear,  and  uric  acid  takes  its  place.  Herbivorous  animals, 
when  deprived  of  food,  are  placed  in  the  condition  of  carnivora,  since 
the  ingredients  of  the  urine  must  then  be  derived  from  the  metamor- 
phosis of  their  own  substance.  In  the  calf,  while  living  upon  the  milk 
of  its  dam,  the  urine  contains  uric  acid ;  after  the  animal  is  weaned  and 
begins  to  live  upon  vegetable  food,  the  uric  acid  disappears,  and  the 
urine  contains  salts  of  hippuric  acid. 


CHAPTEE    VII. 

FOOD. 

UNDER  the  term  "  food"  are  included  all  substances,  both  solid  and 
liquid,  necessary  to  sustain  the  process  of  nutrition.  The  first  act  of 
this  process  is  the  appropriation  from  without  of  the  materials  which 
enter  into  the  composition  of  the  living  frame,  or  of  others  which  may 
be  converted  into  them  in  the  interior  of  the  body.  Like  the  tissues 
and  the  fluids,  therefore,  the  food  contains  various  ingredients,  both 
organic  and  inorganic  ;  and  the  first  important  fact  to  be  noted  with 
regard  to  them  is  that  no  single  class  of  substances,  by  itself,  is  suffi- 
cient to  sustain  life,  but  that  several  must  be  supplied,  in  due  propor- 
tion, in  order  to  maintain  the  body  in  a  healthy  condition. 

Inorganic  Ingredients  of  the  Food. 

It  is  well  known  that  inorganic  substances,  although  they  afford  the 
necessary  materials  for  vegetation,  are  not  sufficient  for  the  nourish- 
ment of  animals,  which  depend  for  their  support  upon  elements  already 
combined  in  the  organic  form.  Nevertheless,  it  is  equally  true  that  the 
inorganic  matters  are  also  essential  to  animal  life,  and  require  to  be  sup- 
plied in  sufficient  quantity  to  keep  up  the  natural  proportion  in  which 
they  exist  in  the  various  solids  and  fluids.  As  we  have  found  it  to 
be  a  general  characteristic  of  these  substances,  that  they  are  exempt 
from  alteration  in  the  interior  of  the  body,  but  are  absorbed,  deposited, 
and  expelled  unchanged,  each  one,  as  a  rule,  requires  to  be  present 
under  its  own  form,  and  in  sufficient  quantity  in  the  food.  This  is 
especially  true  of  water  and  sodium  chloride,  both  of  which  enter  and 
leave  the  system  in  abundant  daily  quantity;  and  of  the  calcareous 
salts,  which  during  the  growth  and  ossification  of  the  skeleton  are 
deposited  in  large  proportion  in  the  osseous  tissue.  The  alkaline  car- 
bonates, phosphates,  and  sulphates  are  partly  formed  within  the  system 
during  the  metamorphosis  or  decomposition  of  organic  substances  ;  but 
the  elements  of  which  they  are  composed  must  of  course  enter  the 
body  in  some  form,  in  order  to  enable  these  changes  to  be  accomplished. 

Since  water  enters  into  the  composition  of  every  part  of  the  body, 
it  is  important  as  an  ingredient  of  the  food.  In  man,  it  is  probably  the 
most  important  substance  to  be  supplied  with  constancy  and  regularity, 
and  the  system  suffers  more  rapidly  when  entirely  deprived  of  fluids, 
than  when  the  supply  of  solid  food  only  is  withdrawn.  A  man  may 
pass  eight  or  ten  hours  without  solid  food,  and  suffer  little  or  no 
inconvenience ;  but  if  deprived  of  water  for  the  same  length  of  time, 

(113) 


114  FOOD. 

he  becomes  exhausted,  and  feels  the  deficiency  in  a  marked  degree. 
Magendie  found,  in  his  experiments  on  dogs  subjected  to  inanition,1  that 
if  the  animals  were  supplied  with  water  alone  they  lived  six,  eight,  and 
even  ten  days  longer  than  if  deprived  at  the  same  time  of  both 
solid  and  liquid  food.  Sodium  chloride,  also,  is  usually  added  to  the 
food  in  considerable  quantity,  and  requires  to  be  supplied  as  a  condi- 
ment with  tolerable  regularity ;  while  the  remaining  inorganic  materials, 
such  as  the  calcareous  salts,  and  the  alkaline  phosphates  and  sulphates, 
occur  naturally  in  sufficient  quantity  in  most  of  the  articles  used  as 
food. 

The  entire  quantity  of  mineral  substances  discharged  daily  by  a 
healthy  adult,  by  both  the  urine  and  perspiration,  averages  as  follows  : 

QUANTITY  OF  MINERAL  MATTERS  DISCHARGED  PER  DAY. 

Sodium  and  potassium  chlorides 15.0  grammes. 

Calcareous  and  magnesian  phosphates    ....       1.0        " 
Sodium  and  potassium  phosphates           .        ,        .  4.5        " 

Sodium  and  potassium  sulphates 4.0        " 

24.5        " 

According  to  the  average  dietaries  for  adults  in  full  health  collected 
by  Dr.  Playfair2  about  20  grammes  of  mineral  matter  are  daily  intro- 
duced with  the  food.  The  remainder  is  to  be  accounted  for  by  the 
phosphates  and  sulphates  formed  within  the  system  as  above  described. 

Non-Nitrogenous  Organic  Ingredients  of  the  Pood. 

These  substances,  so  far  as  they  enter  into  the  composition  of  the 
food,  are  divided  into  the  two  natural  groups  already  mentioned — 
namely,  the  carbohydrates,  including  starch  and  sugar,  and  the  fats, 
including  all  the  varieties  of  oleaginous  matter.  Since  starch  is  always 
converted  into  glucose  in  the  digestive  process,  these  two  substances 
have  the  same  value  and  significance  as  nutritive  materials.  As  the 
carbohydrates  are  to  be  found  as  a  general  rule  only  in  vegetable  pro- 
ducts, they  do  not  constitute  a  part  of  the  food  of  carnivorous  animals. 
It  is  true  that  glucose  exists  in  the  milk  even  of  the  carnivora  during 
lactation,  and  is  consequently  supplied  as  a  nutritive  material  to  the 
young  animal  during  the  early  portion  of  its  growth.  But  this  supply 
ceases  as  soon  as  the  period  of  lactation  is  finished ;  and  the  fact  of  the 
secretion  of  sugar  by  the  mammary  gland,  as  well  as  that  of  its  produc- 
tion in  the  liver,  shows  that  in  the  carnivorous  animal  the  carbohydrates 
requisite  for  the  process  of  nutrition  may  originate  within  the  body  from 
other  organic  substances.  This  does  not  apply,  however,  to  the  vege- 
table feeders  or  to  man.  The  carnivora  have  no  desire  for  vegetable 
food,  while  the  herbivora  live  upon  it  exclusively,  and  in  man  there  is 
a  natural  craving  for  it,  which  is  almost  universal.  It  may  be  dis- 

1  Comptes  Rendus  de  l'Acad£mie  des  Sciences.     Paris,  tome  xiii.  p.  256. 

2  London  Chemical  News,  May  12,  1865. 


FOOD.  115 

pensed  with  for  a  few  days,  but  not  indefinitely.  The  experiment  has 
often  been  tried,  in  the  treatment  of  diabetes,  of  confining  the  patient 
to  a  strictly  animal  diet.  It  has  been  invariably  found  that,  if  this  regi- 
men be  continued  for  some  weeks,  the  desire  for  vegetable  food  becomes 
so  imperative  that  the  plan  of  treatment  is  unavoidably  abandoned. 

A  similar  question  has  arisen  with  regard  to  the  oleaginous  matters. 
Are  these  substances  indispensable  as  ingredients  of  the  food,  or  may 
they  be  replaced  by  other  proximate  principles,  such  as  starch  or  sugar  ? 
It  has  already  been  seen,  from  the  experiments  of  Boussingault  and 
others,  that  a  certain  amount  of  fat  is  produced  in  the  body  over  and 
above  that  which  is  taken  with  the  food ;  and  it  appears  also  that  a 
regimen  abounding  in  saccharine  substances  is  favorable  to  the  produc- 
tion of  fat.  It  is  altogether  probable,  therefore,  that  the  materials  for 
the  production  of  fat  may  be  derived,  under  these  circumstances,  either 
directly  or  indirectly  from  saccharine  matters.  But  saccharine  matters 
alone  are  not  sufficient.  Dumas  and  Milne-Edwards1  found  that  bees, 
fed  on  pure  sugar,  soon  cease  to  work,  and  sometimes  perish  in  con- 
siderable numbers ;  but  if  fed  with  honey,  which  contains  some  waxy 
and  other  matters  beside  the  sugar,  the}r  thrive  upon  it ;  and  produce, 
in  a  given  time,  a  much  larger  quantity  of  fat  than  was  contained  in 
the  whole  supply  of  food. 

The  same  thing  was  established  by  Boussingault  with  regard  to 
starchy  matters.  He  found  that  in  fattening  pigs,  though  the  quantity 
of  fat  accumulated  by  the  animal  considerably  exceeded  that  contained 
in  the  food,  yet  fat  must  enter  to  some  extent  into  the  composition  of 
the  food  in  order  to  maintain  the  animal  in  good  condition ;  for  pigs, 
fed  on  boiled  potatoes  alone  (an  article  abounding  in  starch  but  nearly 
destitute  of  oily  matter),  fattened  slowly  and  with  difficulty ;  while 
those  fed  on  potatoes  mixed  with  a  greasy  fluid  fattened  readily,  and 
accumulated  much  more  fat  than  was  contained  in  the  food. 

The  apparent  discrepancy  between  these  facts  may  be  easily  explained, 
when  we  recollect  that,  in  order  that  an  animal  become  fattened,  it  must 
be  supplied  not  only  with  the  materials  of  the  fat  itself,  but  also  with 
everything  else  necessary  to  maintain  the  body  in  a  healthy  condition. 
Oleaginous  matter  is  one  of  these  necessary  substances.  The  fats  taken 
in  with  the  food  are  not  simply  introduced  into  the  body  and  deposited 
unchanged.  On  the  contrary,  they  are  altered  and  used  up  in  the  pro- 
cess of  digestion  and  nutrition ;  while  the  fats  which  appear  as  con- 
stituents of  the  tissues  are,  in  great  part,  of  new  formation,  and  are 
produced  from  materials  derived,  perhaps,  from  a  variety  of  sources. 

It  is  certain,  then,  that  either  one  or  the  other  of  these  two  groups  of 
substances,  saccharine  or  oleaginous,  must  enter  into  the  composition 
of  the  food ;  and  furthermore,  that,  though  oily  matter  may  sometimes 
be  produced  in  the  body  from  the  sugars,  it  is  also  necessary  for  perfect 
nutrition  that  fat  be  supplied,  under  its  own  form,  with  the  food.  For 

1  Annales  de  Chimie  et  de  Physique,  3d  series,  tome  xiv.  p.  400. 


116  FOOD. 

man  it  is  natural  to  have  them  both  associated  in  the  alimentary  ma- 
terials. They  occur  together  in  most  vegetable  substances,  and  there  is 
a  natural  desire  for  them  both,  as  elements  of  the  food. 

They  are  not,  however,  when  alone,  or  even  associated  with  each 
other,  sufficient  for  the  nutrition  of  the  animal  body.  Magendie  found 
that  dogs,  fed  exclusively  on  starch  or  sugar,  perished  after  a  short 
time  with  symptoms  of  profound  disturbance  of  the  nutritive  functions. 
An  exclusive  diet  of  butter  or  lard  had  a  similar  effect.  The  animal 
became  exceedingly  debilitated,  though  without  much  emaciation;  and 
after  death,  all  the  internal  organs  and  tissues  were  found  infiltrated 
with  oil.  Boussingault1  performed  a  similar  experiment,  with  a  like 
result,  upon  a  duck,  which  was  kept  upon  an  exclusive  regimen  of  butter. 
"The  duck  received  90  to  100  grammes  of  butter  every  day.  At  the 
end  of  three  weeks  it  died  of  inanition.  The  butter  oozed  from  every 
part  of  its  body.  The  feathers  looked  as  though  they  had  been  steeped 
in  melted  butter,  and  the  body  exhaled  an  unwholesome  odor  like  that 
of  butyric  acid." 

Lehinann  was  led  to  the  same  result  by  experiments  performed  upon 
himself  for  the  purpose  of  ascertaining  the  effect  produced  on  the  urine 
by  different  kinds  of  food.2  This  observer  confined  himself  first  to  a 
purely  animal  diet  for  three  weeks,  afterward  to  a  purely  vegetable  one 
for  sixteen  days,  without  any  marked  inconvenience.  He  then  put  him- 
self upon  a  regimen  consisting  entirely  of  non-nitrogenous  substances, 
starch,  sugar,  gum,  and  oil,  but  was  only  able  to  continue  this  diet  for 
two,  or  at  most  for  three  days,  owing  to  the  disturbance  of  the  general 
health  which  supervened.  The  unpleasant  symptoms,  however,  imme- 
diately disappeared  on  his  return  to  an  ordinary  mixed  diet.  In  some 
instances  a  restricted  diet  of  this  kind  can  be  borne  for  a  longer  time. 
Dr.  Parkes3  kept  two  soldiers  upon  non-nitrogenous  food  alone  for  five 
consecutive  days  without  their  exhibiting  serious  signs  of  physical  ex- 
haustion. Prof.  Wm.  A.  Hammond,4  in  experiments  performed  upon 
himself,  was  enabled  to  live  for  ten  days  on  a  diet  of  boiled  starch  and 
water.  After  the  third  day,  however,  the  general  health  began  to 
deteriorate,  and  became  much  disturbed  before  the  termination  of  the 
experiment.  The  prominent  symptoms  were  debility,  headache,  pyrosis, 
and  palpitation.  After  the  starchy  diet  was  abandoned,  it  required 
some  days  to  restore  the  health  to  its  usual  condition. 

Nitrogenous  Ingredients  of  the  Food. 

The  nitrogenous  or  albuminous  nutritive  principles  enter  so  largely 
into  the  constitution  of  the  animal  tissues  and  fluids,  that  their  import- 
ance, as  elements  of  the  food,  is  easily  understood.  No  food  can  be 

1  Chimie  Agricole.     Paris,  1854,  p.  166. 

2  Journal  fur  praktische  Chemie,  Band  xxvii.  p.  257. 

3  Proceedings  of  the  Koyal  Society  of  London,  March  2d,  1871. 

4  Experimental  Eesearches,  being  the  Prize  Essay  of  the  American  Medical 
Association  for  1857. 


FOOD.  117 

long  nutritious,  unless  a  certain  proportion  of  these  substances  be 
present  in  it.  Since  they  are  so  abundant  as  ingredients  of  the  body, 
their  absence  from  the  food  is  felt  more  speedily  than  that  of  any  other 
substance  except  water.  They  have,  therefore,  sometimes  received  the 
name  of  "  nutritious  substances,"  in  contradistinction  to  those  of  the 
second  class,  which  contain  no  nitrogen,  and  which  are  found  to  be 
insufficient  for  the  support  of  life.  The  albuminous  substances,  however, 
when  taken  alone,  are  no  more  capable  of  supporting  life  indefinitely 
than  the  others.  It  was  found  in  the  experiments  of  the  French 
"  Gelatine  Commission"1  that  animals  fed  on  pure  fibrine  and  albumen, 
as  well  as  those  fed  on  gelatine,  become,  after  a  short  time,  much 
enfeebled,  refuse  the  food  offered  to  them,  or  take  it  with  reluctance, 
and  finally  die  of  inanition.  This  result  has  been  explained  by  sup- 
posing that  these  substances,  when  taken  alone,  excite  after  a  time 
such  disgust  that  they  are  either  no  longer  taken,  or  if  taken  are  not 
digested.  But  this  disgust  is  simply  an  indication  that  the  substances 
used  are  insufficient  and  finally  useless  as  articles  of  food,  and  that  the 
system  demands  other  materials  for  its  nourishment.  It  is  well  de- 
scribed by  Magendie,  in  the  report  of  the  commission  above  alluded 
to,  while  detailing  his  investigations  on  the  nutritive  qualities  of  gela- 
tine. "  The  result,"  he  says,  "  of  these  first  trials  was  that  pure  gelatine 
was  not  to  the  taste  of  the  dogs  experimented  on.  Some  of  them  suf- 
fered the  pangs  of  hunger  with  the  gelatine  within  their  reach,  and  would 
not  touch  it ;  others  tasted  of  it,  but  would  not  eat ;  others  still  de- 
voured a  certain  quantity  once  or  twice,  and  then  obstinately  refused  to 
make  any  further  use  of  it." 

In  one  instance,  Magendie  succeeded  in  inducing  a  dog  to  take  a 
considerable  quantity  of  pure  fibrine  daily  throughout  the  whole  course 
of  the  experiment ;  but  notwithstanding  this,  the  animal  became  ema- 
ciated, and  died  at  last  with  the  symptoms  of  inanition. 

It  is  evident,  therefore,  that  no  single  proximate  principle,  nor  even 
any  one  class  alone,  can  be  sufficient  for  nutrition.  The  albuminous 
substances  are  first  in  importance  because  they  constitute  the  largest 
part  of  the  mass  of  the  body ;  and  exhaustion  follows  more  rapidly 
when  they  are  withheld  than  when  the  animal  is  deprived  of  other  kinds 
of  alimentary  matter.  But  starchy  and  oleaginous  substances  are  also 
requisite ;  and  the  body  feels  the  want  of  them  sooner  or  later,  though 
it  may  be  plentifully  supplied  with  albuminous  food.  Finally,  the  inor- 
ganic saline  matters,  though  in  smaller  quantity,  are  also  necessary  to 
the  continued  maintenance  of  life.  In  order  that  the  animal  tissues  and 
fluids  remain  healthy,  and  take  their  proper  part  in  the  functions  of 
life,  they  must  be  supplied  with  all  the  ingredients  necessary  to  their 
constitution  ;  and  a  man  may  be  starved  to  death  at  last  by  depriving 
him  of  sodium  chloride  or  lime  phosphate  as  surely,  though  not  so 
rapidly,  as  if  he  were  deprived  of  albumen  or  oil. 

1  Comptes  Rendus  de  l'Acad6mie  des  Sciences.     Paris,  1841,  torn.  xiii.  p.  267. 


118  FOOD. 

Composition  of  Different  Articles  of  Food. 

In  the  most  valuable  and  nutritious  kinds  of  food,  which  have  been 
adopted  by  the  universal  and  instinctive  choice  of  man,  the  first  three 
classes  of  proximate  principles  are  all  more  or  less  abundantly  repre- 
sented. In  all  there  exists  naturally  a  certain  proportion  of  saline 
matter;  and  water  and  sodium  chloride  are  generally  taken  in  addition. 

Milk. — In  milk,  the  first  food  supplied  to  the  infant,  and  largely 
employed  in  various  culinary  preparations,  all  the  important  groups  of 
nutritive  substances  are  present.  It  is  a  white,  opaque  fluid,  consisting, 
1st,  of  a  serous  portion,  which  contains  albuminous  matters,  sugar,  and 
mineral  salts  in  solution,  and,  2d,  of  fatty  globules  suspended  in  the 
watery  liquid.  It  is  this  mixture  of  oleaginous  particles  with  a  serous 
fluid  which  gives  to  the  milk  its  opacity  and  its  white  color.  Its  rich- 
ness in  fatty  matter  may  therefore  be  estimated  from  these  physical 
qualities.  The  ingredients  in  cow's  milk  are  present  in  the  following 
proportions,  according  to  Payen  : 

COMPOSITION  OF  Cow's  MILK  IN  1000  PARTS. 

Water 864 

Nitrogenous  matter  (caseine  and  albumen)       ....  43 

Sugar  of  milk           . 52 

Fat 37 

Mineral  salts 4 

1000 

Cow's  milk  resembles  human  milk  in  its  general  characters,  but  con- 
tains a  larger  proportion  of  solid  ingredients,  especially  of  the  nitro- 
genous and  saccharine  matters,  fat  being  present  in  nearly  the  same 
amount  in  each.  Sheep  and  goat's  milk  is  richer  in  both  nitrogenous 
and  fatty  matters  ;  while  the  milk  of  the  ass  and  the  mare  contains  a 
greater  abundance  of  sugar,  but  is  comparatively  poor  in  nitrogenous 
matter  and  fat.  The  nitrogenous  matter  of  milk  consists  almost  entirely 
of  caseine,  associated  with  a  very  small  proportion  of  albumen.  Owing 
to  the  relative  quantity  of  these  two  substances,  milk  does  not  solidify 
on  boiling,  but  merely  covers  itself  with  a  thin  pellicle  of  coagulated 
albumen,  the  caseine  remaining  liquid.  The  addition  of  any  acid,  how- 
ever, such  as  acetic  or  tartaric  acid,  will  precipitate  the  caseine  and 
curdle  the  milk.  If  milk  be  allowed  to  remain  exposed  to  the  air  at  a 
moderately  warm  temperature,  it  curdles  spontaneously,  owing  to  the 
development  of  lactic  acid,  due  to  a  transformation  of  its  sugar ;  and 
the  same  change  will  sometimes  occur  instantaneously  from  electric 
disturbance,  during  a  thunder  storm. 

The  caseine  of  milk,  artificially  coagulated  by  the  action  of  rennet, 
constitutes  cheese.  Rennet  is  the  dried  contents  and  mucous  membrane 
of  the  stomach  of  the  calf,  the  animal  being  killed  and  the  stomach 
taken  out  while  digestion  is  in  full  activity  and  the  gastric  fluids  abun- 
dantly secreted.  A  faintly  acidulated  infusion  of  this  substance  even  in 
small  quantity,  added  to  fresh  milk  at  the  temperature  of  30°  (86°  F.) 


FOOD. 


119 


produces  complete  coagulation  in  fifteen  or  twenty  minutes.  The  coagu- 
lum  is  drained  from  the  watery  serum  or  "  whey,"  and  afterward  pressed 
into  the  form  of  cheese.  The  variety  in  consistency  and  flavor  of  differ- 
ent cheeses  depends  mainly  on  the  proportion  of  fatty  matter  retained  in 
the  coagulum,  and  upon  certain  slow  changes,  in  the  nature  of  fermen- 
tations, which  go  on  in  it  subsequently. 

The  fatty  matter  of  milk  is  suspended  in  the  serous  portion  under  the 
form  of  minute  spheroidal  masses.  These  little  masses  or  "  milk-glob- 
ules" are  not  quite  fluid  at  ordinary  temperatures,  but  have  a  semi-solid 
consistency  owing  to  their  containing  a  considerable  proportion  of  pal- 
mitine.  The  fat  globules,  separated  by  churning  from  the  other  ingre- 
dients of  the  milk,  and  made  to  unite  into  a  coherent  mass,  constitute 
butter.  This  substance,  accordingly,  represents  simply  the  oleaginous 
ingredients  of  the  milk ;  and  when  purified  from  the  watery  portions 
entangled  with  it,  consists  mainly  of  palmitine  and  oleine,  together 
with  a  small  proportion  of  peculiar  odoriferous  and  flavoring  ingredi- 
ents, the  principal  of  which  has  received  the  name  of  "  butyrine."  These 
substances  are  usually  mingled  in  the  following  proportions : 

Palmitine 68  parts. 

Oleine 30      " 

Butyrine  and  other  flavoring  matters       .        .        .  2      " 

100 

When  well  prepared  and  in  good  condition,  butter  constitutes  one  of 
the  most  valuable  and  easily  assimilated  forms  of  oleaginous  food.  If 
contaminated  with  the  remains  of  the  nitrogenous  matter  of  the  milk, 
its  fatty  ingredients  after  a  time  become  decomposed  with  the  develop- 
ment of  volatile  fatty  acids  ;  in  which  condition  the  butter  is  said  to  be 
"  rancid,"  and  is  no  longer  fit  for  food. 

Bread. — The  cereal  grains  resemble  each  other  more  or  less  in  their 
constitution,  all  of  them  containing  starch,  nitrogenous  matter,  dextrine 
or  sugar,  fat,  and  mineral  salts  in  various  proportions.  Wheat  is  dis- 
tinguished from  the  remainder  in  containing  a  considerably  larger  quan- 
tity of  nitrogenous  matter  as  compared  with  the  other  ingredients,  and 
in  the  peculiarly  adhesive  or  fibrinous  quality  of  this  substance,  which 
has  received  accordingly  the  name  of  "  gluten."  The  different  grains 
in  common  use  for  food  have  when  dry  the  following  average  compo- 
sition, according  to  Payen. 

COMPOSITION  OF  THE  CEREAL  GRAINS. 


Nitrogenous 
matter. 

Starch. 

Dextrine, 
etc. 

Fat. 

Cellulose. 

Mineral 
salts. 

Wheat  .... 

18.00 

66.80 

7.50 

2.10 

3.10 

2.50 

Eye  

12  50 

64  65 

Udfl 

O  OK 

310 

o  £n 

Barley  .... 

12.96 

66.43 

10.00 

2.76 

4.75 

3.10 

Oats      .... 

14.39 

60.59 

9.25 

5.50 

7.06 

3.25 

Indian  corn    .     . 

12.50 

67.55 

4.00 

8.80 

5.90 

1.25 

Rice       .... 

7.55 

88.65 

1.00 

0.80 

1.10 

0.90 

120  FOOD. 

Thus,  of  the  different  grains,  that  of  oats  contains,  next  to  wheat,  the 
largest  proportion  of  nitrogenous  matters ;  but  it  also  contains  a  con- 
siderable abundance  of  cellulose,  or  indigestible  vegetable  tissue,  which 
interferes  with  its  nutritive  quality  as  human  food.  Indian  corn  is 
especially  rich  in  fatty  ingredients,  while  rice  consists  mainly  of  starch, 
and  is  the  poorest  of  all  in  both  nitrogenous  and  fatty  ingredients. 

Wheat  is  more  valuable  than  the  other  cereal  grains  for  the  purpose 
of  making  bread,  not  only  on  account  of  its  larger  proportion  of  albu- 
minous matter,  but  also  on  account  of  the  peculiar  glutinous  quality  of 
this  ingredient,  already  mentioned. 

In  preparing  the  wheat,  the  grains  are  first  cleansed  from  husks  and 
adherent  foreign  material,  ground  into  meal,  and  the  finer  and  whiter 
portions  derived  from  the  interior  of  the  grain  separated  by  sifting 
and  bolting  from  the  coarser  external  parts,  or  bran.  Thus  purified,  the 
flour  consists  of  starch,  gluten,  diastase,  dextrine,  a  little  fat,  sometimes 
a  trace  of  sugar,  mineral  salts,  and  about  15  per  cent,  of  water,  which  is 
never  fully  expelled  by  ordinary  drying.  For  making  into  bread,  the 
flour  is  mixed  with  about  one-half  its  weight  of  water,  and  kneaded  into 
a  flexible  dough  of  uniform  consistency.  The  next  process  is  the  fer- 
mentation of  the  dough.  For  this  purpose  a  little  yeast  is  incorporated 
with  it,  and  the  mixture  allowed  to  remain  for  a  few  hours  at  a  tem- 
perature of  about  25°  (77° F.).  During  this  time  the  sugar  originally 
present  in  the  flour,  and  that  produced  from  the  starch  and  dextrine  by 
the  action  of  the  diastase,  passes  into  fermentation  under  the  influence 
of  the  yeast,  and  is  transformed  into  alcohol  and  carbonic  acid.  The 
alcohol  is  dissipated  by  evaporation ;  but  the  carbonic  acid,  which  is 
generated  in  small  gas-bubbles,  is  entangled  by  the  tenacious  gluten  of 
the  flour,  and  the  dough  is  thus  puffed  up  into  a  spongy,  reticulated 
mass.  When  the  fermentation  of  the  dough  is  completed,  it  is  placed  in 
ovens,  and  baked  at  a  temperature  of  210°  (about  40(PF.).  The  effect 
of  this  heat  is  to  cook  the  glutinous  part  of  the  dough,  communicating 
to  it  an  agreeable  flavor,  and  at  the  same  time  solidifying  it ;  so  that 
the  substance  of  the  baked  loaf,  when  cut  open,  retains  its  spongy  and 
reticulated  texture.  It  is  thus  made  easy  of  mastication,  and  readily 
permeable  by  the  saliva  and  other  digestive  fluids.  The  spongy  texture 
acquired  by  bread  is  the  main  object  of  its  fermentation,  although  an 
agreeable  flavor  is  also  developed  by  the  process,  which  does  not  exist 
in  unfermented  bread.  The  interior  of  the  loaf,  in  baking,  does  not  rise 
above  100°  (212° F.);  the  exterior,  which  is  subjected  to  a  higher  tem- 
perature, becomes  covered  with  a  crust  formed  of  partially  torrefied 
starch  or  dextrine,  and  caramelized  sugar.  The  interior  of  the  loaf  also 
usually  retains  a  little  glucose,  which  is  not  all  destroyed  in  the  process 
of  fermentation.  A  considerable  portion  of  the  water  which  was  mixed 
with  the  flour  remains  permanently  united  with  its  organic  ingredients ; 
so  that  100  parts  of  flour  will  usually  yield,  after  baking,  130  parts,  by 
weight,  of  bread. 


FOOD.  121 

Wheaten  bread,  prepared  in  this  way,  has  the  following  average  com- 
position : 

COMPOSITION  OF  WHEATEN  BREAD. 

Starchy  matters  (starch,  dextrine,  glucose)     .                 ...  56.7 

Albuminous  matter  (gluten,  etc.) 7.0 

Fatty  matter .        .  1.3 

Mineral  matter  (calcareous,  magnesian,  and  alkaline  salts)     .        .  1.0 

Water 340 

100.0 

Thus,  while  bread  contains  an  abundance  of  albuminous  and  starchy 
matter,  it  is  deficient  in  fat ;  and  instinct  accordingy  leads  us  to  take 
with  it  butter,  fat  bacon,  or  some  other  form  of  oleaginous  food. 

The  good  quality  of  bread,  aside  from  that  of  the  flour  of  which  it  is 
made,  depends  mainly  on  the  success  of  the  process  of  fermentation.  If 
this  be  incomplete,  the  bread  is  heavy,  and  not  sufficiently  reticulated 
in  texture.  If  it  be  allowed  to  go  on  beyond  the  proper  time,  it  passes 
into  an  acid  fermentation,  and  develops  a  sour  taste.  If  properly 
conducted,  the  bread  is  uniformly  light  and  spongy,  and  has  no  -acid 
reaction. 

Meat. — The  muscular  flesh  of  various  animals  affords  an  exceedingly 
valuable  and  nutritious  food,  of  which  beef,  mutton,  and  venison  hold 
the  highest  place.  The  muscular  fibre  itself  consists  almost  exclusively^ 
of  nitrogenous  matters,  but  in  point  of  fact  the  flesh  used  for  food  is 
always  accompanied  with  more  or  less  adipose  tissue,  and  even  when 
freed  from  visible  fat,  there  is  always,  according  to  Payen  and  Pavy, 
more  or  less  oleaginous  matter  entangled  with  the  muscular  fibres.  In 
various  kinds  of  meat,  and  even  in  meat  from  different  parts  of  the 
same  animal,  the  proportion  of  fat  will  vary  considerably ;  but  it  was 
found  by  Pavy,  in  one  of  the  best  and  most  commonly  used  portions  of 
beef,  to  amount  to  about  5  per  cent,  of  the  whole. 

COMPOSITION  OF  BEEF  FLESH. 

Water 77.5 

Albuminous  matter 16.0 

Fat 5.0 

Mineral  salts  ..........  1.5 

100.0 

The  mineral  matters  consist  of  alkaline  chlorides  and  phosphates,  with 
phosphates  of  lime  and  magnesia. 

In  the  cooking  of  meat  by  roasting  or  broiling,  the  external  parts  are 
exposed  to  a  rapid  heat  of  120°  or  130°  (260°  F.)  by  which  their  albu- 
minous parts  are  coagulated,  their  coloring  matter  turned  brown,  and  a 
characteristic  flavor  developed.  The  interior,  which  does  not  rise  above 
65°  (1500  F.)  remains  red  and  juicy,  its  fluids  being  protected  from, 
evaporation  by  the  coagulation  of  the  outer  portions.  In  boiling,  where 
the  meat  is  cooked  by  contact  with  the  boiling  water,  none  of  it  rises. 
9 


122  FOOD 

above  the  temperature  of  100°  (212°  F.)  ;  but  this  may  penetrate 
throughout  the  whole  substance  of  the  meat,  producing  a  uniform 
decolorization.  Notwithstanding  the  coagulation  of  the  albuminous 
liquids  by  boiling,  the  fibrous  connective  tissues  are  gelatinized,  and 
the  muscular  flesh  thus  partially  softened  and  disintegrated.  On  the 
whole,  the  effect  of  cooking  upon  meat  is  to  increase  the  consistency 
of  its  albuminous  ingredients,  its  principal  benefit  being  the  attractive 
flavor  which  is  developed  by  the  aid  of  heat,  and  no  doubt  an  increased 
digestibility  from  the  same  cause.  By  either  method,  meat  loses  in 
cooking  from  25  to  30  per  cent,  of  its  weight,  principally  by  the  escape 
of  water  and  liquefied  fat. 

Eggs. — The  eggs  of  various  animals  are  used  for  food,  as  those  of  the 
common  fowl,  the  duck,  goose,  turkey,  seafowl,  turtles,  and  the  roe  of 
many  kinds  of  fish.  Those  of  the  common  fowl,  which  are  the  most 
abundantly  used,  may  be  considered  as  representing  the  general  quali- 
ties of  this  article  of  nourishment.  They  consist  of  the  globular  "•  yolk," 
surrounded  by  a  layer  of  albumen  or  "  white."  The  composition  of 
these  two  portions  is  nearly  the  same,  excepting  that  the  yolk  contains 
a  larger  proportion  of  solids  and  particularly  of  fatty  matter  which  gives 
to  it  its  yellow  color  and  rich  flavor.  A  comparative  analysis  of  the 
yolk  and  white  is  as  follows : 

COMPOSITION  OF  THE  FOWL'S  EGG. 

Yolk.  White. 

Albuminous  matter 16.0  20.4 

Fat 30.7 

Mineral  salts 1.3  1.6 

Water 52.0  78.0 

100.0  100.0 

The  mineral  matters  consist  mainly  of  the  sodium  and  potassium 
chlorides,  potassium  sulphate,  and  lime  and  magnesium  phosphates. 
Of  the  entire  contents  of  the  egg,  exclusive  of  the  shell,  the  yolk  consti- 
tutes one-third,  and  the  white  two-thirds.  Cooking  produces  but  little 
effect  upon  eggs  except  to  coagulate  their  albuminous  matters,  since 
these  are  comparatively  but  little  susceptible  of  developing  any  marked 
flavor  by  the  action  of  heat. 

Vegetables. — Of  the  different  vegetables  used  as  food,  some  are  valu- 
able for  their  solid  starchy  and  albuminous  ingredients,  others  mainly 
for  their  saccharine  and  watery  juices.  The  former  are  nutritious  in 
the  ordinary  sense  of  the  word,  though  much  less  so  than  bread  or  ani- 
mal food ;  the  latter  are  useful  for  supplying  certain  materials  contained 
in  the  fresh  vegetable  juices  which  are  essential  to  the  continued  main- 
tenance of  health.  The  most  important  of  the  first  group  are  repre- 
sented by  the  potato  and  the  leguminous  seeds.  The  tuber  of  the  potato 
abounds  in  starch,  but  is  poor  in  other  nutritive  ingredients. 


FOOD.  123 

COMPOSITION  OF  THE  POTATO. 
Starch        .........     20.0 

Albuminous  matter   .......      2.5 

Sugar  and  gum          .        .         .        •         •        •         .1.1 
Fatty  matter     .....        .        -        .0.1 

Cellulose  .........      1-0 

Mineral  and  vegetable  salts      .....       1-3 

Water       ......... 


100.0 

The  leguminous  seeds,  on  the  other  hand,  contain  an  abundance  of 
albuminous  matter,  similar  in  character  to  the  caseine  of  milk,  and 
called  u  legumine." 

COMPOSITION  OF  WHITE  BEANS. 
Starch       .........    55.7 

Albuminous  matter  .......     25.5 

Fatty  matter     .        .        .        .  .        .        .2.8 

Cellulose    ......        ...      2.9 

Mineral  salts     ......        .        .3.2 

Water       .........      9-9 

100.0 

The  composition  of  dried  peas  is  very  similar  to  the  above,  the 
starchy  matters  only  being  present  in  rather  larger,  the  albuminous 
ingredients  in  rather  smaller  proportion.  Notwithstanding  the  abund- 
ance of  nitrogenous  matter  in  leguminous  seeds,  its  quality  is  inferior 
to  that  contained  in  the  cereal  grains.  Peas  and  beans  also  have  a 
texture  which  renders  them  comparatively  difficult  of  digestion,  and 
requires  long  boiling  to  fit  them  for  use  as  food.  The  same  is  true  of 
many  juicy  and  saccharine  roots,  such  as  beets  and  parsnips,  which 
appear  to  have  a  comparatively  soft  consistency,  but  which  nevertheless 
need  prolonged  boiling.  The  object  and  effect  of  the  cooking  process 
in  vegetables  generally  is  to  disintegrate  and  soften  their  texture,  and 
particularly,  by  the  aid  of  heat  and  moisture,  to  bring  their  starchy 
ingredients  into  the  hydrated  condition.  Raw  starch  is  nearly  or  quite 
indigestible  by  man,  and  if  taken  into  the  stomach  under  that  form  will 
often  pass  unchanged  from  the  bowels  ;  but  when  thoroughly  hydrated 
it  is  easily  acted  on  and  transformed  into  glucose  by  the  digestive  fluids. 
It  is  for  this  reason  that  starchy  vegetables  require  more  thorough  cook- 
ing to  render  them  digestible  than  most  kinds  of  animal  food. 

Beside  the  more  solid  kinds  of  vegetable  food,  many  of  the  pulpy  and 
succulent  fruits  and  herbaceous  substances  are  valuable  as  an  addition 
to  the  nutritive  regimen  —  celery,  lettuce,  parsley,  spinach,  with  all  the 
sweet  fruits  and  melons,  are  used  with  advantage  either  in  the  raw  or 
cooked  form.  They  introduce  into  the  system  a  large  number  of  salts 
of  the  vegetable  acids,  such  as  malates,  tartrates,  and  citrates,  the 
privation  of  which  for  a  long  time  is  one  of  the  inducing  causes  of 


124  FOOD. 

scurvy.  The  green  parts  of  vegetables  are  no  doubt  also  useful  by 
furnishing  to  the  system  a  supply  of  iron  contained  in  their  chlorophylle. 
From  what  has  been  said  above,  it  will  be  seen  that  the  nutritious 
character  of  any  substance,  or  its  value  as  an  article  of  food,  does  not 
depend  simply  upon  its  containing  either  one  of  the  alimentary  substances 
in  large  quantity;  but  upon  its  containing  them  mingled  together  in 
such  proportion  as  is  requisite  for  the  healthy  nutrition  of  the  body. 
What  these  proportions  are  cannot  be  determined  from  simple  chemical 
analysis,  nor  from  any  other  data  than  those  derived  from  observation 
and  experiment. 

Requisite  Quantity  of  Food  and  of  its  Different  Ingredients, 
The  entire  quantity  of  food  required  per  day  varies  with  the  circum- 
stances of  the  individual,  such  as  the  size  and  weight  of  the  body,  the 
comparative  development  of  the  muscular  and  other  systems,  the  tem- 
perature, and  especially  the  amount  of  physical  activity.  More  food  is 
required,  on  the  average,  in  cold  than  in  warm  weather,  more  by  persons 
of  a  muscular  than  by  those  of  an  adipose  or  phlegmatic  constitution, 
more  in  a  condition  of  active  exertion  than  in  one  of  comparative  repose. 
Even  the  proportion  of  different  classes  of  proximate  principles  required 
for  nutrition  varies  to  a  considerable  extent  according  to  special  condi- 
tions. When  the  individual  is  in  a  perfectly  healthy  condition,  and  so 
situated  that  he  can  supply  himself  at  will  with  any  kind  of  nourishment 
desired,  the  natural  demands  of  the  appetite  afford  the  surest  criterion 
for  both  the  quantity  and  quality  of  the  food  to  be  used.  But  not 
infrequently  provision  must  be  made  in  advance  for  supplies  destined 
to  last  over  a  considerable  period,  as  in  the  case  of  military  or  exploring 
expeditions,  or  for  the  inmates  of  hospitals  or  asylums  where  the  diet 
must  be  regulated  to  a  great  extent  upon  a  uniform  plan.  It  therefore 
becomes  important  to  know  both  the  quantity  and  kind  of  food  necessary 
for  the  support  of  life. 

The  standard  adopted  for  this  estimate  is  that  of  a  healthy  adult 
man,  employed  in  active  but  not  exhausting  occupation.  The  amount 
requisite  will  be  found  to  vary  in  either  direction  from  this  standard, 
according  to  the  circumstances  above  mentioned.  The  average  require- 
ments as  given  by  different  authors  do  not  vary  materially  from  each 
other  in  any  essential  particular.  According  to  our  own  observations, 
a  man  in  full  health,  taking  active  exercise  in  the  open  air,  and  restricted 
to  a  diet  of  bread,  fresh  meat,  and  butter,  with  water  and  coffee  for  drink, 
consumes  the  following  quantities  per  day : 

QUANTITY  OF  FOOD  REQUIRED  PER  DAT. 

Meat 453  grammes. 

Bread 540 

Butter  or  fat 100        " 

Water      .  1530 

This  represents  the  requisite  daily  quantity  of  food  and  the  propor- 
tions of  its  different  kinds,  when  composed  of  such  articles  as  are  most 


FOOD.  125 

completely  nutritious,  and  of  the  most  uniform  composition.  For  the 
continued  maintenance  of  health  and  strength  in  a  working  condition, 
other  articles,  such  as  fresh  vegetables,  sugar,  milk,  fruit,  etc.,  should 
be  mingled  with  the  above,  in  a  variety  of  proportions  ;  but  there  is  no 
doubt  that  bread  and  fresh  meat,  with  a  certain  quantity  of  fat,  will 
prove  sufficient  for  the  wants  of  the  system,  for  a  longer  time  than  any 
other  single  articles  of  food. 

Such  a  diet  also  affords  the  best  means  of  ascertaining  the  absolute 
and  relative  quantities  of  the  different  proximate  principles  required  for 
food.  If  we  take  the  average  composition  of  meat  and  bread,  and  esti- 
mate the  quantities  of  their  solid  albuminous,  starchy,  and  saline  ingre- 
dients, together  with  the  water  contained  in  both  solid  and  liquid  food, 
we  find  that  the  daily  ration  is  composed  nearly  as  follows : 

Albuminous  matter 130  grammes. 

Starch  and  sugar 300        " 

Fat 100        " 

Mineral  salts 20        " 

Water      .        .' 2000        " 

Of  the  mineral  salts,  nearly  eight  grammes  are  naturally  contained  in 
the  substances  used  for  food  and  drink ;  the  remainder  consists  of  sodium 
chloride,  artificially  added  to  the  food,  or  used  in  its  preparation. 

The  proportion  in  which  the  albuminous  and  the  non-nitrogenous 
principles  should  be  mingled  in  the  food  is  of  considerable  importance, 
and  this  proportion  has  been  determined  within  very  accurate  limits. 
In  making  such  an  estimate  it  is  necessary  to  include  the  carbohydrates 
(starch  and  sugar)  and  the  fats  under  the  same  head ;  but  the  fats  are 
properly  regarded  by  all  writers  as  having  a  different  alimentary  value 
from  the  carbohydrates.  This  depends  upon  the  well-known  fact  that 
the  final  result  of  the  transformation  in  the  living  body  of  all  the  non- 
nitrogenous  substances  is  carbonic  acid  and  water,  thus  representing  a 
process  of  oxidation,  the  necessary  oxygen  being  introduced  with  the 
inspired  air.  But  the  capacity  for  oxidation  of  the  fats  is  greater  than 
that  of  the  carbohydrates,  as  shown  by  the  relative  proportion  by  weight 
of  their  constituent  elements. 

.  . .    f  C  72  C  44.47 

The  composition,  by  weight,   1  „  , .  »    « **  TT    / 

of  starch  (C6H1005)  is         }  *  80      "' "         P       '      04936 

162  100.00 

Here  the  oxygen  is  already  present  in  sufficient  proportion  to  saturate 
all  the  hydrogen  by  the  formation  of  water;  while  the  44.47  parts  of 
carbon  will  unite  with  118.58  parts  of  oxygen  to  form  carbonic  acid. 

On  the  other  hand,  if  we  take  palmitine  as  representing  the  average 
constitution  of  the  fats,  we  have — 

The  composition,  by  weight,  (  °  612  C  75'93 

offat(C51H9806)is  {*    99*     -,  in  100  parts,     H  12.15 


806  100.00 


126  FOOD. 

Here  the  oxygen  is  present  in  much  diminished  proportion ;  and,  for 
complete  oxidation  of  the  fat,  to  form  carbonic  acid  and  water,  the  75.93 
parts  of  carbon  will  require  202.48  parts  of  oxygen,  and  the  12.15  parts 
of  hydrogen  will  need  85.28  additional,  over  and  above  the  11.92  parts 
of  oxygen  already  present.  Thus  the  quantities  of  oxygen  appropriated 
during  complete  oxidation,  by  starch  and  fat  respectively,  are  as 
follows : 

QUANTITY  OP  OXYGEN  REQUIRED  FOR  THE  COMPLETE  OXIDATION  OF 

100  parts  of  starch 118.58 

"       "      "   fat 287.76 

A  fatty  substance,  therefore,  has  a  capacity  for  the  production  of  car- 
bonic acid  and  water,  by  oxidation,  about  2.4  times  greater  than  that  of 
starch.  In  estimating,  accordingly,  the  requisite  quantity  of  all  the  non- 
nitrogenous  matters  taken  together,  the  fat  is  calculated  as  starch  upon 
this  basis ;  one  part  of  fat,  by  weight,  being  reckoned  as  equal  to  2.4 
parts  of  starch.  This  quantity,  added  to  that  of  the  carbohydrates  in 
the  food,  is  sometimes  called  the  "  starch-equivalent"  of  the  non-nitro- 
genous matters. 

If  we  ascertain  the  amount  of  solid  albuminous  and  non-nitrogenous 
matter  contained  in  the  daily  food  of  an  ordinary  nutritious  diet  of 
mixed  quality,  we  find  that  the  non-nitrogenous  matters,  reckoned  as 
starch,  amount  to  four  or  five  times  as  much  as  the  albuminous  ingredi- 
ents. A  comparison  of  our  own  observations  with  the  estimates  and 
diet  tables  of  Moleschott,  Payen,  and  Playfair,  all  of  which  correspond  in 
the  main  with  each  other,  gives  the  following  as  the  average  daily 
quantity  of  these  two  classes  of  proximate  principles  in  the  food. 

Albuminous  matter  ......     130  grammes. 

Non-nitrogenous  matter,  as  starch    ....     600        " 

Thus  albuminous  matter  constitutes  rather  less  than  one-fifth  of  the 
entire  food,  for  a  healthy  adult  in  active  occupation ;  and  its  quantity 
is  to  that  of  the  non-nitrogenous  matters  as  1  to  4.62. 

This  proportion  varies  to  some  extent  with  the  age  and  condition  of 
the  individual.  In  human  milk,  which  at  first  forms  the  exclusive  food 
of  the  young  infant,  according  to  the  average  analyses  of  Simon,  Yernois, 
and  Becquerel,  as  given  by  Milne  Edwards,  the  albuminous  ingredients 
are  to  the  non-nitrogenous  matters  reckoned  as  carbohydrates  in  the 
proportion  of  1  to  2.95.  In  cow's  milk,  upon  which  the  young  calf  is 
sustained,  the  proportion  is  as  1  to  3.27  ;  while  in  green  grass  and  hay, 
upon  which  the  adult  animal  feeds,  it  is  as  1  to  11.70  and  1  to  9.28  re- 
spectively. The  larger  proportion  of  albuminous  matter  in  the  food  at 
this  early  age  is  evidently  connected  with  the  growth  which  is  then 
taking  place.  As  the  nitrogenous  principles  constitute  much  the  larger 
part  of  the  solid  organic  matters  contained  in  the  body,  the  steady  in- 
crease in  weight  during  the  growing  period  demands  a  corresponding 
supply  of  these  substances  in  the  food. 

There  is  also  evidence  that  the  requisite  proportion  of  nitrogenous 


FOOD.  127 

principles  varies  in  the  adult  with  the  amount  of  physical  activity.  A 
condition  of  bare  subsistence  may  be  maintained  upon  a  diet  in  which 
the  albuminous  substances  are  in  smaller,  and  the  non-nitrogenous 
matters  in  larger  proportion ;  but  when  the  system  is  habitually  called 
upon  for  a  greater  amount  of  muscular  exertion,  the  proportion  of 
albuminous  matters  in  the  food  must  be  increased.  This  is  a  well-known 
fact  in  regard  to  horses  and  working  cattle  generally.  In  a  state  of 
comparative  inactivity  they  may  be  supported  mainly  upon  grass  or 
hay,  in  which  the  proportion  of  nitrogenous  to  non-nitrogenous  matter 
is  not  more  than  1  to  9.28 ;  but  when  employed  in  active  labor  they 
require  a  liberal  supply  of  oats,  in  which  the  proportion  is  as  1  to  1.13. 
In  Dr.  Play  fair's  diet  tables,  which  were  collected  with  great  care  from 
a  variety  of  sources,  including  those  of  prisons  and  infirmaries,  those  of 
the  American  and  European  armies  during  peace  and  in  active  service, 
and  of  certain  hard-working  laborers,  the  increase  of  albuminous  matter 
with  increased  labor  is  a  marked  feature.  While  in  a  bare  subsistence 
diet  the  proportion  of  albuminous  to  non-nitrogenous  matter  is  as  1  to 
5.87,  in  that  of  active  laborers  it  is  as  1  to  4.34.  The  following  table 
will  show  the  relative  increase  of  the  two  kinds  of  food  under  different 
conditions  of  exercise,  as  calculated  from  Dr.  Play  fair's  data. 

KELATIVE  INCREASE,  UNDER  DIFFERENT  CONDITIONS,  OF  ALBUMINOUS  AND  NON- 
NITROGENOUS  MATTERS  IN  THE  FOOD. 

Albuminous       Non-nitrogenous 
matter.  matter. 

Bare  subsistence  diet         .        .        .        .100  100 

Full  diet  with  moderate  exercise        .         .     180  161 

Diet  of  active  laborer        ....     232  171 

Diet  of  hard-worked  laborer      .         .        .242  189 

As  these  diet  tables  were  adopted  by  the  various  civil  and  military 
authorities  as  the  result  of  long  experience  in  the  practical  adaptation 
of  food  to  the  amount  of  work  performed,  they  may  be  regarded  as 
expressing  with  great  approximation  to  certainty  the  physiological  re- 
quirements under  different  conditions.  They  are  corroborated  by  the 
variation  in  diet  adopted  in  the  convict  establishments  of  Great  Britain, 
as  given  by  Pavy.1  In  the  change  from  "  Light-labor  Diet"  to  "  Hard- 
labor  Diet,"  while  the  non-nitrogenous  food  is  increased  only  13.37  per 
cent.,  the  albuminous  food  is  increased  16.15  per  cent. 

It  is  evident,  therefore,  that  increased  physical  exertion  requires  a 
greater  proportional  increase  in  the  albuminous  than  in  the  non-nitro- 
genous ingredients  of  the  food. 

It  is  also  a  matter  of  interest  to  determine  the  quantity,  source,  and 
destination  of  the  different  chemical  elements  entering  into  the  composi- 
tion of  the  food.  Taking  the  average  chemical  composition  of  albumin- 
ous matters  and  fat,  and  that  of  the  carbohydrates,  we  find  that  a  man 
under  ordinary  full  diet  takes  into  his  system  daily  the  constituents  of 
the  food,  in  round  numbers,  as  follows : 

1  On  Food  and  Dietetics.     Philadelphia  edition,  1874,  p.  433. 


128  FOOD. 

DAILY  CONSUMPTION  IN  THE  FOOD. 

O  H  O  N  S 

Albuminous  matter,  130  grammes,  containing     70        10        29        20        1 
Starch       .        .         300        "  134        18       144 

Fat  .        .        .        100        "  "  76        12        12 

280        40       185 

Of  these  elementary  bodies,  carbon  and  nitrogen  are  considered 
especially  important  as  constituents  of  the  food,  carbon  as  forming 
the  most  abundant  and  characteristic  ingredient  of  all  organic  combi- 
nations, and  nitrogen,  as  the  distinguishing  element  of  albuminous 
substances.  Of  these  two,  accordingly,  the  system  requires  daily,  to 
be  supported  in  an  active  condition,  about  20  grammes  of  nitrogen  and 
about  280  grammes  of  carbon.  This  fact  alone  makes  it  evident  that  a 
mixed  diet  of  animal  and  vegetable  food  is  the  most  available  for  man. 
Meat  contains,  according  to  the  analyses  of  Pay  en,  3  per  cent,  of  nitrogen 
and  11  per  cent,  of  carbon.  Consequently,  if  the  diet  were  composed 
exclusively  of  this  food,  the  necessary  quantity  of  nitrogen  would  be 
supplied  by  666  grammes  of  meat ;  but  in  order  to  obtain  the  required 
carbon,  2545  grammes  would  need  to  be  consumed,  thus  involving  a 
great  waste  of  its  nitrogenous  matter.  On  the  other  hand,  bread,  the 
most  nutritious  of  all  vegetable  substances,  contains  only  1  per  cent,  of 
nitrogen  and  30  per  cent,  of  carbon.  Therefore,  if  this  were  the  only 
food  used,  933  grammes  would  be  sufficient  to  supply  all  the  carbon ; 
but,  in  order  to  obtain  the  due  amount  of  nitrogen,  it  would  be  neces- 
sary to  consume  2000  grammes.  A  mixture,  accordingly,  of  the  two 
kinds  of  food,  in  which  nitrogenous  and  hydrocarbonaceous  matters 
respectively  preponderate,  is  best  adapted  to  supply  the  wants  of  the 
system  without  unnecessary  expenditure  of  material. 

The  changes  undergone  in  the  body,  and  the  final  destination  of  the 
ingredients  of  the  food,  vary  for  different  kinds.  The  carbohydrates  no 
doubt,  after  serving  the  purposes  for  which  they  are  intended  in  the 
animal  economy,  are  finally  expelled  under  the  form  of  carbonic  acid 
and  water.  The  action  of  the  oxygen,  introduced  with  the  inspired  air, 
produces  this  result  by  uniting  with  the  carbon  of  the  organic  body, 
while  its  own  hydrogen  and  oxygen,  already  present  in  the  relative 
quantities  to  produce  water,  are  liberated  under  that  form.  This  result 
is  expressed  by  the  following  formula : 

Starch.  Carbonic  acid.  Water. 

C6H1005    +    012    =     C6012      +      H1005. 

Thus  the  change  undergone  by  starch  and  allied  substances  in  the 
animal  body,  where  they  are  consumed,  is  precisely  the  reverse  of  that 
taking  place  in  plants  during  the  act  of  vegetation,  by  which  they  are 
produced. 

For  the  fats  the  change  is  a  similar  one,  their  only  final  products,  so 
far  as  we  know,  being  carbonic  acid  and  water.  In  this  process,  how- 
ever, the  fats  require,  as  already  mentioned,  a  greater  supply  of  extra- 


FOOD.  129 

neous  oxygen,  since,  beside  their  larger  proportion  of  carbon,  they  also 
contain  hydrogen  which  requires  further  oxidation,  in  order  to  form 
water.  The  change  thus  undergone  by  fatty  substances  may  be  ex- 
pressed as  follows  : 

Fat.  Carbonic  acid.    "Water. 

C5iH9806  +  0145  =  C510102  +  H980,9. 

In  the  case  of  the  albuminous  matters  the  process  is  a  different  one. 
These  substances  contain  an  element,  namely,  nitrogen,  which  does  not 
appear  in  the  carbonic  acid  and  watery  vapor  of  the  expired  breath, 
but  forms  a  distinguishing  constituent  of  the  crystallizable  matters  of 
the  urine.  Of  these  matters,  urea  is  by  far  the  most  abundant,  and,  as 
already  mentioned,  fully  five-sixths  of  the  nitrogen  taken  in  with  the 
food  reappears  as  an  ingredient  of  urea,  while  the  remainder  is  included 
in  the  creatinine  and  uric  and  hippuric  acids  of  the  urine,  and  in  the 
excrementitious  substance  of  the  feces. 

There  is  evidence,  however,  that  the  nitrogenous  matters  also  take 
part  in  the  formation  of  carbonic  acid  ;  that  is,  although  all  their  nitro- 
gen is  discharged  under  the  form  of  urea  and  other  similar  combina- 
tions in  the  urine  and  feces,  all  their  carbon  does  not  appear  in  these 
excretions,  and  must  pass  out  by  some  other  channel.  While,  as  we 
have  seen,  130  grammes  of  albuminous  matter  are  taken  daily  with  the 
food,  containing  70  grammes  of  carbon,  only  35  grammes  of  urea  are 
discharged  during  the  same  time,  containing  7  grammes  of  carbon  ;  and, 
according  to  the  most  accurate  analyses,1  not  more  than  23  grammes 
are  discharged  daily  by  both  the  urine  and  feces  together.  This  leaves 
unaccounted  for  about  47  grammes  of  carbon,  or  two-thirds  of  the 
original  quantity,  which  must  pass  out  from  the  body  under  some  other 
form  of  combination.  The  same  thing  is  true,  to  a  considerable  extent, 
of  the  hydrogen  of  these  substances,  of  which  10  grammes  are  intro- 
duced daily  as  an  ingredient  of  the  albuminous  matters  of  the  food, 
while  not  more  than  5  or  6  grammes  are  discharged  in  organic  combi- 
nations with  the  urine  and  feces.  The  albuminous  matters,  therefore, 
not  only  give  rise  to  the  elimination  of  urea,  but  also  contribute  to  the 
production  of  carbonic  acid  and  water. 

The  manner  in  which  this  takes  place  is  probably  by  the  separation 
of  some  of  the  elements  of  albumen  combined  as  urea,  after  which  the 
remainder  are  left  behind  as  a  non-nitrogenous  substance.  If  we  adopt, 
for  the  constitution  of  an  albuminous  body,  exclusive  of  its  sulphur, 
the  formula  C72H112N18O23,  and  take  away  from  it  all  the  nitrogen  in  the 
form  of  urea,  a  substance  will  remain  analogous  in  composition  to  a 
fat,  th  us- 

Albumen        .....     C-2          H112          N18         023 
9  Urea  (CH4N20)      .        .        .        .     C  H36  N18         09 


1  Kanke,  Grundziige  der  Physiologic  des  Menschen.     Leipzig,  1872,  p.  298. 


130  FOOD. 

The  remaining  substance  nuiy  then  undergo  complete  oxidation 
without  the  further  production  of  any  nitrogenous  compound.  This 
double  result  of  the  decomposition  of  the  albuminous  substances,  to- 
gether with  the  fact  that  we  take  habitually  between  four  and  five 
times  as  much  non-nitrogenous  as  nitrogenous  matter  in  the  food,  will 
explain  the  great  preponderance  in  quantity  of  carbonic  acid  as  an 
excretion  over  urea.  For  while  the  average  daily  quantity  of  urea 
discharged  is  only  35  grammes,  the  carbonic  acid  exhaled  with  the 
breath  amounts  to  from  700  to  800  grammes  per  day ;  the  entire  quan- 
tity of  the  carbonic  acid  produced  being,  by  weight,  fully  twenty  times 
as  great  as  that  of  the  urea.  Urea  is  a  nitrogenous  substance  sepa- 
rated by  decomposition  from  the  albuminous  ingredients  of  the  system  ; 
while  carbonic  acid  represents  the  combination  of  its  remaining  elements 
with  the  abundant  oxygen  introduced  by  the  breath. 

The  quantities  of  the  various  substances  taken  in  with  the  food  and 
discharged  with  the  excretions  are  liable  to  many  variations  from  the 
changing  condition  of  the  individual.  If  the  body  be  increasing  in 
weight,  the  substances  introduced  will  be  greater  in  quantity  than  those 
discharged ;  if  it  be  diminishing,  the  material  discharged  will  be  more 
than  that  introduced.  Even  in  the  healthy  adult,  where  the  body  does 
not  sensibly  gain  or  lose  weight  for  long  intervals,  observation  has 
shown  that  there  are  frequent  fluctuations  of  small  extent,  and  that  the 
income  for  any  single  day  rarely  counterbalances  exactly  the  outgo  for 
the  same  period.  Consequently  the  quantities  given  in  the  preceding 
tables  cannot  be  taken  as  furnishing,  in  any  case,  a  uniform  and 
invariable  standard,  but  only  as  showing  what,  upon  the  whole,  are  the 
relative  proportions  of  the  different  ingredients  entering  into  the  com- 
position of  the  food  and  of  the  bodily  frame.  And  although  for  many 
of  them  we  are  not  yet  able  to  ascertain  their  quantities  with  sufficient 
accuracy  for  determining  all  the  changes  which  they  undergo  in  the 
system,  yet  there  is  no  doubt  of  the  main  result  produced  by  the  internal 
transformation  of  the  ingredients  of  the  food.  We  have  certain  nutri- 
tious substances  introduced  on  the  one  hand,  and  certain  excrementitious 
products  discharged  on  the  other,  which  may  be  expressed  as  follows : 

INTRODUCED  WITH  THE  FOOD.  DISCHARGED  WITH  THE  EXCRETIONS. 

Albuminous  matter.  Urea. 

Fat.  Carbonic  acid. 

Carbohydrates.  Water. 

This  represents  the  decomposition  and  metamorphosis  of  the  organic 
substances  proper ;  while  the  mineral  ingredients  of  the  food,  as  a  rule, 
pass  through  the  system  unchanged. 


CHAPTEE   VIII. 

DIGESTION. 

DIGESTION  is  the  process  by  which  the  food  is  reduced  to  a  form  in 
which  it  can  be  absorbed  from  the  intestinal  canal,  and  taken  up  by  the 
bloodvessels.  This  process  does  not  occur  in  vegetables,  which  are 
dependent  for  their  nutrition  upon  materials  which  are  supplied  to  them 
in  a  form  already  fitted  for  absorption. 

Carbonic  acid,  ammonium  carbonate,  and  ammonium  nitrate  exist  in 
a  gaseous  form  in  the  atmosphere,  or  are  brought  down  in  solution  by 
the  rain,  and  penetrate  the  soil  to  the  roots  of  the  growing  plants  ;  while 
many  of  the  mineral  salts,  as  sulphates,  nitrates,  and  carbonates,  are 
also  present  in  the  soil  in  a  soluble  condition.  Thus  they  require  no 
alteration  before  being  taken  up  by  the  tissues  of  the  plant.  The  only 
known  exception  to  this  is  in  the  case  of  materials  composed  of  the 
earthy  carbonates  and  phosphates,  which  are  insoluble  or  nearly  so  in 
water,  but  which  are  known  to  be  corroded  and  rendered  soluble  by  the 
acid  juices  of  the  plant-roots  in  contact  with  them.  As  a  general  rule, 
the  substances  requisite  for  vegetation  are  directly  absorbed  from  the 
exterior  in  their  original  condition.  But  with  animals  and  man  the 
case  is  different.  They  cannot  subsist  upon  inorganic  substances  only, 
but  require  for  their  support  materials  which  have  already  been  organ- 
ized, and  which  have  previously  constituted  a  part  of  animal  or  vegetable 
bodies.  Their  food  is  almost  invariably  solid  or  semi-solid  when  taken, 
and  insoluble  in  water.  Meat,  bread,  fruits,  vegetables,  and  the  like,  are 
all  taken  into  the  stomach  in  a  solid  and  insoluble  condition  ;  and  even 
substances  naturally  fluid,  such  as  milk,  albumen,  white  of  egg,  are  nearly 
always,  in  the  human  species,  more  or  less  solidified  by  the  process  of 
cooking,  before  being  taken  into  the  stomach. 

In  animals,  accordingly,  the  food  requires  to  undergo  a  process  of 
digestion  or  liquefaction,  before  it  can  be  absorbed.  In  all  cases,  the 
general  characters  of  this  process  are  the  same.  It  consists  essentially 
in  the  food  being  received  into  a  canal,  running  through  the  body  from 
mouth  to  anus,  called  the  "  alimentary  canal,"  in  which  it  comes  in  con- 
tact with  certain  digestive  fluids,  which  act  upon  it  in  such  a  way  as  to 
liquefy  and  dissolve  it.  These  fluids  are  secreted  by  the  mucous  mem- 
brane of  the  alimentary  canal,  and  by  certain  glandular  organs  situated 
in  its  neighborhood.  The  food  consists,  as  we  have  seen,  of  a  mixture 
of  various  substances,  having  different  physical  and  chemical  properties ; 
and  the  several  digestive  fluids  are  also  different  from  each  other,  each 

(131  ) 


132 


DIGESTION. 


Fig.  26. 


one  of  them  exerting  a  peculiar  action,  which  is  more  or  less  confined 
to  particular  species  of  food.  As  the  food  passes  through  the  alimentary 
canal  from  above  downward,  those  parts  of  it  which  become  liquefied 
are  successively  removed  by  absorption,  and  taken  up  by  the  vessels ; 
while  the  remaining  portions,  consisting  of  the  indigestible  matter,  to- 
gether with  the  refuse  of  the  intestinal  secretions,  gradually  acquire  a 
firmer  consistency  owing  to  the  absorption  of 
the  fluids,  and  are  finally  discharged  from  the 
intestine  under  the  form  of  feces. 

In  different  species  of  animals,  the  differ- 
ence in  their  habits,  in  the  constitution  of  their 
tissues,  and  in  the  character  of  their  food,  is 
accompanied  with  a  corresponding  variation 
in  the  anatomy  of  the  digestive  apparatus,  and 
the  character  of  the  secreted  fluids.  As  a 
general  rule,  the  digestive  apparatus  of  herb- 
ivorous animals  is  more  complex  than  that  of 
the  carnivora ;  since,  in  vegetable  substances, 
the  nutritious  matters  are  often  present  in  a 
comparatively  solid  and  unmanageable  form,  as, 
for  example,  in  raw  starch  and  the  cereal  grains, 
and  are  nearly  always  entangled  among  vege- 
table cells  and  fibres  of  an  indigestible  character. 
In  those  instances 'where  the  nutriment  consists 
mostly  of  grass,  leaves,  twigs,  and  roots,  the 
digestible  matters  bear  only  a  small  proportion 
to  the  entire  quantity ;  and  a  large  mass  of  food 
must  therefore  be  taken,  in  order  that  the  re- 
quisite amount  of  nutritious  material  may  be 
extracted  from  it.  In  such  cases,  accordingly, 
the  alimentary  canal  is  large  and  long ;  and  is 
divided  into  many  compartments,  in  which  dif- 
ferent processes  of  disintegration,  transforma- 
tion, and  solution  are  carried  on. 

In  the  common  fowl,  for  instance  (Fig.  26), 
the  food,  consisting  mostly  of  grains,  or  of  in- 
sects with  hard,  coriaceous  integument,  first 
passes  down  the  oesophagus  (a)  into  a  diverti- 
culum  or  pouch  (6)  termed  the  crop.  Here  it 
remains  for  a  time  mingled  with  a  watery  secre- 
tion in  which  the  grains  are  macerated  and 
softened.  The  food  is  then  carried  farther  down 
until  it  reaches  a  second  dilatation  (c)^  the  pro- 
ventriculus,  or  secreting  stomach.  The  mucous  membrane  here  is  thick 
and  glandular,  and  is  provided  with  numerous  secreting  follicles.  From 
them  an  acid  fluid  is  poured  out,  by  which  the  food  is  subjected  to 
further  changes.  It  next  passes  into  the  gizzard  (d),  or  triturating 


ALIMENTARY  CANAL 
OF  FOWL.  — a.  (Esophagus. 
b.  Crop.  c.  Proventriculus, 
or  secreting  stomach,  d.  Giz- 
zard, or  triturating  stomach. 
e.  Intestine.  /.  Two  long 
caecal  tubes  which  open  into 
the  intestine  a  short  distance 
ahove  its  termination. 


DIGESTION. 


133 


stomach,  a  cavity  inclosed  by  thick  muscular  walls,  and  lined  with  a 
tough  and  horny  epithelium.  Here  it  is  subjected  to  the  crushing  and 
grinding  action  of  the  muscular  parietes,  assisted  by  grains  of  sand  and 
gravel,  which  the  fowl  instinctively  swallows  with  the  food,  by  which  it 
is  so  triturated  and  disintegrated,  that  it  is  reduced  to  a  uniform  pulp, 
upon  which  the  digestive  fluids  can  effectually  operate.  The  mass  then 
passes  into  the  intestine  (<?),  where  it  meets  with  the  intestinal  juices, 
which  complete  the  process  of  solution ;  and  from  the  intestinal  cavity 
it  is  finally  absorbed  in  a  liquid  form,  by  the  vessels  of  the  mucous 
membrane. 

In  the  ox,  the  sheep,  the  camel,  the  deer,  and  all  ruminating  animals, 
there  are  four  distinct  stomachs,  each  lined  with  mucous  membrane  of 
a  different  structure,  and  adapted 

to  perform  a  different  part  in  the  Fig-.  27. 

digestive  process.  (Fig.  27.)  The 
first  two,  situated  side  by  side  at 
the  lower  extremity  of  the  oesoph- 
agus (a),  consist  of  the  rumen  or 
paunch  (6),  a  large  sac,  itself  par- 
tially divided  by  incomplete  par- 
titions, and  lined  by  a  mucous 
membrane  thickly  set  with  long 
prominences  or  villi ;  and  the 
reticulum  (c)  or  second  stomach, 
so  called  from  the  intersecting 
folds  or  ridges  of  its  mucous 
membrane,  which  give  it  a  reticu- 
lated or  honey-combed  appear- 
ance. Into  these  two  stomachs 
the  food  is  received  when  first 
swallowed  by  the  animal  in  feed- 
ing or  browsing,  and  remains 
there  for  some  time,  especially  in  the  capacious  rumen,  slowly  macerated 
and  softened  by  the  action  of  the  warmth  and  watery  fluids,  but  not 
undergoing  any  marked  chemical  action.  When  the  animal  has  finished 
browsing,  and  the  process  of  rumination  commences,  the  food  is  regur- 
gitated into  the  mouth  by  an  inverted  action  of  the  muscular  walls  of 
the  paunch  and  oesophagus,  and  slowly  masticated.  It  then  descends 
again  along  the  oesophagus  ;  but  the  lateral  opening  which  communicates 
with  the  first  two  stomachs  is  now  closed  by  muscular  action,  and'  the 
oesophagus,  thus  converted  into  a  tubular  canal,  conducts  the  masticated 
food  into  a  third  stomach,  the  omasus  or  "psalterium"  (d),  in  which  the 
mucous  membrane  is  arranged  in  thin  longitudinal  folds,  lying  parallel 
with  each  other,  like  the  leaves  of  a  book,  thus  increasing  considerably 
its  extent  of  surface.  The  exit  from  this  cavity  leads  directly  into  the 
abomasus  or  "rennet"  (e),  the  true  digestive  stomach,  in  which  the 
mucous  membrane  is  soft,  thick,  and  glandular,  and  in  which  an  acid 


COMPOUND  STOMACH  OP  Ox.— a.  CEsopha- 
gua.  6.  Rumen,  or  first  stomach,  c.  Reticulum, 
or  second,  d.  Omasus,  or  third,  e.  Abomasus, 
or  fourth.  /.  Duodenum.  (Rymer  Jones.) 


134 


DIGESTION. 


Fig.  28. 


solvent  fluid  is  secreted.      Then  follows   the  intestinal  canal  with  its 
various  divisions  and  variations. 

In  the  carnivora  the  alimentary  canal  is  shorter  and  narrower  than  in 
the  preceding,  and  presents  fewer  complexities.     The  food  upon  which 

these  animals  subsist  is  softer 
than  that  of  the  herbivora,  and 
less  encumbered  with  indigest- 
ible matter;  so  that  the  process 
of  its  solution  requires  a  less 
extensive  apparatus. 

In  the  human  species,  the 
food  is  naturally  of  a  mixed 
character,  containing  both  ani- 
mal and  vegetable  substances. 
But,  notwithstanding  this  dif- 
ference in  the  kind  of  nourish- 
ment, the  digestive  apparatus 
in  man  resembles  closely  that 
of  the  carnivora.  For  the 
vegetable  matters  which  we 
take  as  food  are,  in  the  first 
place,  artificially  separated,  to 
a  great  extent,  from  indigesti- 
ble impurities ;  and  secondly, 
they  are  so  softened  by  the 
process  of  cooking  as  to  be- 
come nearly  or  quite  as  di- 
gestible as  animal  substances. 
In  the  human  species  the 
process  of  digestion,  though 
simpler  than  in  the  herbivora, 
is  still  somewhat  complex. 
The  alimentary  canal  is  di- 
vided into  different  compart- 
ments or  cavities,  which  com- 
municate with  each  other  by 
narrow  orifices.  At  its  com- 
mencement (Fig.  28)  we  find 
the  cavity  of  the  mouth,  which 
is  guarded  at  its  posterior  ex- 
tremity by  the  muscular  valve 
of  the  isthmus  of  the  fauces. 
Through  the  pharynx  and 
oesophagus  (a),  it  communi- 
cates with  the  second  compart- 
ment, or  the  stomach  (6),  a  flask-shaped  dilatation,  guarded  at  its  cardiac 
and  pyloric  orifices  by  circular  bands  of  muscular  fibres.  Then  follows 


HUMAN  ALIMENTARY  CANAL.  — a.  (Esoph- 
agus, b.  Stomach,  c.  Cardiac  orifice,  d.  Pylorus. 
e.  Small  intestine.  /.  Biliary  duct.  0.  Pancreatic 
duct.  h.  Ascending  colon,  i.  Transverse  colon. 
;.  Descending  colon,  k.  Rectum. 


DIGESTION.  135 

the  small  intestine  (e),  different  parts  of  which,  owing  to  the  vary- 
ing structure  of  their  mucous  membrane,  have  received  the  different 
names  of  duodenum,  jejunum,  and  ileum.  In  the  duodenum  are  situated 
the  orifices  of  the  biliary  and  pancreatic  ducts  (f,  g).  Finally  comes 
the  large  intestine  (h,  i,j,  &),  separated  from  the  smaller  by  the  ileo-caecal 
valve,  and  terminating,  at  its  lower  extremity,  by  the  anus,  at  which  is 
situated  a  double  sphincter,  for  the  purpose  of  guarding  its  orifice. 
Everywhere  the  alimentary  canal  is  composed  of  a  mucous  membrane 
and  a  muscular  coat,  with  a  layer  of  submucous  connective  tissue  between 
the  two.  The  muscular  coat  is  composed  of  a  double  layer  of  longitudinal 
and  transverse  fibres,  by  the  alternate  contraction  and  relaxation  of  which 
the  food  is  carried  through  the  canal  from  above  downward,  and  the 
arrangement  of  which  varies  indifferent  portions  of  the  alimentary  tract. 
The  mucous  membrane  presents,  also,  a  different  structure,  and  has  dif- 
ferent properties  in  different  parts.  That  of  the  mouth  and  oesophagus 
is  smooth,  with  a  hard,  white,  tessellated  epithelium,  which,  however, 
terminates  abruptly  at  the  cardiac  orifice  of  the  stomach.  The  mucous 
membrane  of  the  gastric  cavity  is  soft  and  glandular,  covered  with  a 
transparent,  columnar  epithelium,  and  thrown  into  minute  folds  or  pro- 
jections on  its  free  surface,  which  are  sometimes  reticulated  with  each 
other.  In  the  small  intestine  it  presents  larger  transverse  folds  known 
as  the  "  valvulse  conniventes,"  is  covered  upon  its  free  surface  with 
thickly  set  villosities  of  various  forms,  and  contains  throughout  an 
abundance  of  tubular  follicles.  Finally,  in  the  large  intestine  the  mu- 
cous membrane  is  smooth  and  shining,  free  from  villosities,  and  pro- 
vided with  a  glandular  apparatus  different  in  structure  and  function 
from  that  of  the  preceding  parts. 

The  digestive  secretions,  also,  vary  in  these  different  regions.  In  its 
passage  from  above  downward,  the  food  meets  with  at  least  five  dif- 
ferent secreted  fluids,  namely,  the  saliva,  in  the  cavity  of  the  mouth: 
the  gastric  juice  in  the  stomach;  and  the  intestinal  juice,  with  the  pan- 
creatic juice  and  the  bile,  discharged  into  the  cavity  of  the  small  intes- 
tine. These  fluids  are  themselves,  in  some  instances,  of  complex  nature, 
resulting  from  the  mingled  secretions  of  several  different  associated 
glands,  or  of  the  various  parts  of  a  single  mucous  membrane.  To  a 
certain  extent,  the  special  action  of  each  digestive  fluid  upon  the  food 
has  been  investigated ;  and  it  is  found  that  certain  of  the  secretions 
have  a  distinct  and  peculiar  influence  upon  special  ingredients  of  the 
food.  As  the  result  of  the  successive  action  of  the  digestive  fluids, 
modified,  perhaps,  by  the  effect  of  their  combined  operation,  the  sub- 
stances composing  the  alimentary  mass  are  gradually  reduced  to  a  fluid 
condition,  in  which  they  are  fit  for  absorption  by  the  vessels  of  the 
intestinal  mucous  membrane. 

The  action  which  is  exerted  upon  the  food  by  the  digestive  fluids  is 
not  that  of  a  simple  chemical  solution.  It  is  a  transformation,  by 
which  the  ingredients  of  the  food  are  altered  in  character  at  the  same 


136  DIGESTION. 

time  that  they  undergo  the  process  of  liquefaction.  The  active  agent 
in  producing  this  change  is  in  every  instance  an  albuminoid  or  nitro- 
genous matter,  which  forms  the  most  important  ingredient  in  the 
digestive  fluid;  and  which,  by  coming  in  contact  with  the  food,  exerts 
upon  it  a  peculiar  action,  transforming  its  ingredients  into  new  sub- 
stances. It  is  these  newly-formed  materials  which  are  finally  absorbed 
by  the  vessels  and  mingled  with  the  general  current  of  the  circulation. 
In  the  human  species  the  first  process  to  which  the  food  is  subjected  is 
that  of  mastication,  while  it  is  at  the  same  time  mingled  with  the  saliva 
in  the  cavity  of  the  mouth. 

Mastication. 

Mastication  consists  in  the  cutting  and  trituration  of  the  food  by  the 
teeth,  by  which  it  is  reduced  to  a  state  of  minute  subdivision.  The 
process  is  entirely  a  mechanical  one,  and  is  necessary  in  order  to  pre- 
pare the  food  for  the  subsequent  action  of  the  digestive  fluids.  As 
this  action  is  chemical  in  its  nature,  it  will  be  exerted  more  promptly 
and  efficiently  if  the  food  be  finely  divided  than  if  brought  in  con- 
tact with  the  digestive  fluids  in  a  solid  mass.  This  is  necessarily 
the  case  when  a  solid  body  is  subjected  to  the  action  of  a  solvent 
fluid ;  since,  by  being  broken  up  into  minute  particles,  it  offers  a  larger 
surface  to  the  contact  of  the  fluid,  and  is  more  readily  attacked  and 
dissolved  by  it. 

In  the  structure  of  the  teeth,  and  their  physiological  action,  there  are 
certain  marked  differences,  corresponding  with  the  habits  of  the  animal 

and  the  kind  of  food  upon  which  it  subsists. 
In  fish  and  serpents,  in  which  the  food  is  swal- 
lowed entire,  and  in  which  the  process  of 
digestion,  accordingly,  is  comparatively  slow, 
the  teeth  are  simply  organs  of  prehension. 
They  have  generally  the  form  of  sharp,  curved 
spines,  with  their  points  set  backward,  and 

SKITLL  OF   RATTLESNAKE.  ,    .  ,    .    , 

(Achiiie  Richard.)  arranged  in   a  double   or   triple   row   about 

the  edges  of  the  jaws,  and  sometimes  cover- 
ing the  mucous  surfaces  of  the  mouth,  tongue,  and  palate.  They  serve 
merely  to  retain  the  prey,  and  prevent  its  escape,  after  it  has  been 
seized  by  the  animal.  In  the  carnivorous  quadrupeds,  there  are  three 
different  kinds  of  teeth,  adapted  to  different  purposes.  (Fig.  30.) 
First,  the  incisors,  twelve  in  number,  situated  at  the  anterior  part  of 
the  jaw,  six  in  the  superior,  and  six  in  the  inferior  maxilla,  of  flat- 
tened form,  and  placed  with  their  thin  edges  running  from  side  to  side. 
The  incisors,  as  their  name  indicates,  are  adapted  for  dividing  the  food 
by  a  cutting  motion,  like  that  of  a  pair  of  shears.  Behind  them  come 
the  canine  teeth,  or  tusks,  one  on  each  side  of  the  upper  and  under  jaw. 
These  are  long,  curved,  conical,  and  pointed ;  and  are  used  as  weapons 
of  offence,  and  for  laying  hold  of  and  retaining  the  prey.  Lastly,  the 


MASTICATION. 


137 


Fig.  30. 


molars,  eight  or  more  in  number  on 
each  side,  are  larger  and  broader  than 
the  incisors,  and  provided  with  serrated 
edges,  each  presenting  several  sharp 
points,  arranged  generally  in  a  direc- 
tion parallel  with  the  line  of  the  jaw. 
In  these  animals,  mastication  is  very 
imperfect,  since  the  food  is  not  ground 
up,  but  only  pierced  and  mangled  by 
the  action  of  the  teeth  before  being 
swallowed  into  the  stomach.  In  the 
herbivora,  on  the  other  hand,  whose 
food  is  more  easily  obtained,  but  is 
generally  more  hard  and  resisting  in 

texture,  the  teeth  are  adapted  especially  for  mastication.  In  the  rumi- 
nating animals  generally,  the  canine  teeth  are  wanting,  and  the  incisors 
are  present  only  in  the  lower  jaw.  In  the  horse  and  allied  species, 
the  incisors  are  present  in  both  upper  and  lower  jaws  (Fig.  31),  and 
are  used  simply  for  cutting  off  the  herbage  upon  which  the  animal  feeds. 

Fig.  31. 


OF  POLAR  BKAR.    Anterior 
view  ;  showing  incisors  and  canines. 


SKULL  OF  THE  HORSE. 

The  canine  teeth  are  absent  in  the  female,  and  only  slightly  developed 
in  the  male,  and  the  real  process  of  mastication  is  performed  altogether 
by  the  molars.  These  are  large  and  thick  (Fig.  32),  and  present  a  broad, 
flat  surface,  diversified  by  variously  folded  and  projecting  ridges  of 
enamel,  with  shallow  grooves  between  them.  By 
the  lateral  rubbing  motion  of  the  roughened  sur- 
faces against  each  other,  the  food  is  effectually  com- 
minuted and  reduced  to  a  pulpy  mass. 

In  the  gnawing  animals,  rats,  mice,  squirrels,  rab- 
bits, and  hares,  the  incisor  teeth  are  developed  to  a 
remarkable  extent,  presenting  two  chisel-like  edges 
opposed  to  each  other  in  the  upper  and  lower  jaws, 
and  growing  from  permanently  vascular  roots ;  so 
that  their  waste  from  mechanical  attrition  is  con- 
10 


Fig.  32. 


MOLARTOOTH   OF 

THK  HORSE.     Grind- 
ing  surface. 


138 


DIGESTION. 


stantly  repaired,  and  the  animal  is  able  to  penetrate  the  hardest  sub- 
stances. 

In  the  human  subject,  the  teeth  combine  the  characters  of  those  of  the 
carnivora  and  the  herbivora.  (Fig.  33.)  The  incisors  (a),  four  in  num- 
ber in  each  jaw,  have,  as  in  other  instances,  a  cutting  edge  running  from 
side  to  side.  The  canines  (6),  which  are  situated  immediately  behind 
the  former,  are  much  less  prominent  and  pointed  than  in  the  carnivora, 
and  differ  less  in  form  from  the  incisors  on  the  one  hand,  and  the 

first  molars  on  the  other. 
The    molars     (c,    d)    are 
thick  and  strong,  and  have 
comparatively  flat  surfaces, 
like  those  of  the  herbivora ; 
but  instead  of  presenting 
curvilinear      ridges,      are 
covered  with  more  or  less 
conical     eminences,     like 
those  of  the  carnivora.     In 
the  human  subject,  there- 
fore, the  teeth  are  evidently 
adapted  for  a  mixed  diet, 
consisting  of  both  animal 
and  vegetable  food.     Mas- 
tication is  here  as  perfect 
as  in  the  herbivora,  though 
less   prolonged  and   labo- 
rious ;  for  the  vegetable  substances  used  by  man,  as  already  remarked, 
are  previously  separated  to  a  great  extent  from  their  impurities,  and 
softened   by  cooking;    so  that   they  do  not  require,  for  their  masti- 
cation, so   extensive   and   powerful  a  triturating  apparatus.     Finally, 
animal  substances  are  more  completely  masticated  in  the  human  subject 
than  in  the  carnivora,  and  their  digestion  is  accordingly  completed  with 
greater  rapidity. 

We  can  easily  estimate,  from  the  facts  above  stated,  the  importance, 
to  the  digestive  process,  of  a  thorough  preliminary  mastication.  If  the 
food  be  hastily  swallowed  in  undivided  masses,  it  must  remain  a  long 
time  undissolved  in  the  stomach,  where  it  will  become  a  source  of  irri- 
tation and  disturbance ;  but  if  reduced  beforehand,  by  mastication,  to  a 
state  of  minute  subdivision,  it  is  readily  attacked  by  the  digestive  fluids, 
and  becomes  speedily  and  completely  liquefied. 


HUMAN  TERTH— UPPER  JAW.— a.  Incisors,   b.  Ca- 
nines,   c.  Anterior  molars,     d.  Posterior  molars. 


The  Saliva  and  its  Action  upon  the  Food. 

The  saliva  is  a  compound  fluid,  derived  from  the  secretion  of  four 
different  glandular  organs — namely,  the  parotid,  submaxillary,  and  sub- 
lingual  glands,  and  the  muciparous  glandules  of  the  cavity  of  the  mouth. 
All  these  glands  resemble  each  other  in  the  essential  points  of  their 


THE    SALIVA. 


189 


structure,  their  substance  being  composed  of  dis- 
tinct irregularly  spherical  or  ovoidal  masses, 
more  or  less  flattened  into  a  polygonal  form  by 
mutual  compression.  The  separate  divisions  or 
lobules  are  connected  with  corresponding  ter- 
minal branches  of  the  salivary  duct,  which  pene- 
trate into  their  interior,  and  there  divide  into 
smaller  tubes  each  one  of  which  finally  termi- 
nates in  a  rounded  sac  called  the  glandular 
follicle  or  alveolus.  The  appearance  presented 
upon  an  injection  of  such  a  lobule  is  as  if  the 
follicles  were  arranged  in  clusters,  like  grapes, 
around  the  ends  of  the  smaller  salivary  tubes. 
(Fig.  34.)  A  more  complete  examination  has 
shown,  however,  that  the  follicles  are  simply 

the  rounded  extremities  of  tubular  or  sac-like  offshoots  from  the 
salivary  tube ;  and  that  it  is  the  windings  and  prolongations  of  the 
tube  itself  which  constitutes  the  secreting  follicles  of  the  gland.  The 
follicles  themselves  are  in  general  about  50  mmm.  in  diameter,  and 
are  lined  with  the  glandular  epithelium  cells,  which  cover  their  in- 
ternal surface  and  nearly  fill  their  cavity ;  so  that  there  is  frequently 
to  be  seen  only  a  comparatively  small  space  toward  the  central  part 
of  the  follicle,  containing  a  transparent  fluid,  produced  by  the  secreting 

Fig.  35. 


LOBUI.B  OF  PAROTID 
GLAND  of  newly-born  in- 
fant,  injected  with  mercury. 
(Wagner.) 


Two  SALIVARY  TUBES  FROM  THE  LOBULE  OF  A  MTTCIPAROUS  GLAND,  entering 
the  main  duct. — a.  Duct  of  the  lobule,  b.  Salivary  tube,  c.  Follicles,  on  one  Bide,  as  they 
appear  in  situ.  d.  Follicles  separated  from  each  other,  showing  the  windings  and  offshoots 
of  the  salivary  tube.  (Kulliker.) 

action  of  the  cells.  The  glandular  cells,  which  are  arranged  in  a 
single  layer,  are  finely  granular  bodies,  about  15  mmm.  in  diameter., 
each  one  provided  with  an  oval  nucleus,  situated  toward  the  external 
part  of  the  follicle.  The  cells  are  closely  packed  together,  and  are  of 
various  polygonal  forms. 

The  salivary  tubes  or  ducts,  outside  the  follicles,  unite  into  larger  and 
larger  branches,  until  they  reach  the  principal  excretory  duct  of  the  gland. 
They  are  lined  with  a  layer  of  cells  which  vary  in  form  from  those  of 
the  follicles,  being  elongated  and  cylindrical,  and  provided  with  a  nucleus 
which  is  situated  about  their  middle  portion.  It  is  very  probable  that 
the  epithelium  of  the  salivary  ducts,  as  well  as  that  of  the  follicles,  takes 


140 


DIGESTION. 


part  in  the  process  of  secretion ;  since  Pfliiger  has  found  that  in  sec- 
tions of  the  gland,  examined  immediately  after  being  taken  out  of  the 

Fig.  36. 


GLANDULAR  FOLLICLES  AND  CELLS;  from  the  subm axillary  gland  of  the  dog. 

(Heidenhain.) 

body,  transparent  drops  of  fluid  may  be  seen  exuding  from  the  ends  of 
the  cylindrical  epithelium  cells  into  the  cavity  of  the  duct.     The  follicles 

Fig.  37. 


SECTION  OF  THE  SUBMAXILLARY  GLAND  FROM  THE  DOG.— a.  Salivary  duct, 
with  cylindrical  epithelium  and  central  cavity.  6.  Follicle,  with  glandular  epithelium  and 
central  cavity.  (Kolliker.) 

and  lobules  are  surrounded  with  a  delicate  layer  of  connective  tissue,  in 
which  are  distributed  the  capillary  bloodvessels,  which  supply  to  the 
gland  the  materials  for  its  secretion. 


THE    SALIVA. 


141 


Physical  and  Chemical  Properties  of  the  Saliva — Human  saliva, 
obtained  directly  from  the  cavity  of  the  mouth,  is  a  colorless,  slightly 
viscid,  and  alkaline  fluid,  with  a  specific  gravity  of  1.005.  When  first 
discharged,  it  is  frothy  and  opaline,  holding  in  suspension  minute  whitish 
flocculi.  On  being  allowed  to  stand  for  some  hours  in  a  cylindrical  glass 
vessel,  an  opaque,  whitish  de- 
posit collects  at  the  bottom, 
while  the  supernatant  fluid  be- 
comes clear.  The  deposit,  when 
examined  by  the  microscope 
(Fig.  38),  is  seen  to  consist  of 
abundant  epithelium  scales 
from  the  internal  surface  of 
the  mouth,  detached  by  me- 
chanical attrition,  minute, 
roundish,  granular,  nucleated 
cells,  apparently  epithelium 
from  the  mucous  follicles,  a 
certain  amount  of  granular 
matter,  and  a  few  oil-globules. 
The  supernatant  fluid  has  a 
faint  bluish  tinge,  and  becomes 
slightly  opalescent  by  boiling, 
or  by  the  addition  of  nitric 
acid.  Alcohol  in  excess  causes  the  precipitation  of  abundant  whitish 
flocculi. 

According  to  the  analyses  of  Bidder  and  Schmidt,  the  composition 
of  the  saliva  is  as  follows  : 


BTTCCAL  AND  GLANDULAR  EPITHELIUM, 
with  Granular  Matter  and  Oil-globules;  deposited 
as  sediment  from  human  saliva. 


COMPOSITION  OF  THE  SALIVA. 

995.16 

Albuminous  matter 1.34 

Potassium  sulphocyanide 0.06 

Calcareous,  magnesian,  and  alkaline  phosphates  .        .  0.98 

Sodium  and  potassium  chlorides 0.84 

Mixture  of  epithelium 1.62 

1000.00 

It  will  be  seen  that  the  saliva  is  one  of  the  least  concentrated  of  the 
digestive  secretions,  containing  but  a  very  small  quantity  of  organic 
matter,  and  by  no  means  a  large  proportion  of  mineral  salts  ;  its  watery 
ingredient  being  by  far  the  most  abundant,  as  compared  with  the  other 
animal  fluids.  The  albuminous  matter  of  the  saliva  consists  of  a  small 
quantity  of  albumen,  coagulable  by  the  ordinary  means ;  more  or  less 
mucosine,  which  gives  to  the  fluid  its  slightly  viscid  character;  and 
ptyaline,  a  substance  peculiar  to  the  saliva,  which  is  not  coagulated, 
like  albumen,  by  nitric  acid  or  potassium  ferrocyanide,  but  is  precipi- 


142  DIGESTION. 

tated  both  by  a  boiling  temperature  and  by  alcohol  in  excess.  Some 
of  these  reagents,  accordingly,  precipitate  all  the  albuminous  matters 
of  the  saliva,  while  others  produce  coagulation  of  only  a  part  of  them. 
The  sodium  sulphocyanide  of  the  saliva  may  be  detected  by  adding  to 
the  secretion  a  small  quantity  of  a  solution  of  iron  chloride,  when  the 
characteristic  red  color  of  iron  sulphocyanide  is  produced.  A  similar 
red  .color  is  also  produced  by  the  action  of  the  ferric  salts  upon 
me  conic  acid,  or  the  meconates ;  but  the  two  substances  may  be  dis- 
tinguished from  each  other  by  the  fact  that  the  red  color  caused  by  the 
presence  of  a  sulphocyanide  is  destroyed  by  the  addition  of  either  gold 
chloride  or  mercurial  bichloride,  neither  of  which  affects  the  tint  pro- 
duced by  meconic  acid.  The  presence  of  a  combination  of  sulphocy- 
anogen  in  human  saliva  is  almost  constant,  and  we  have  never  failed  to 
find  it  in  the  freshly  collected  secretion  by  the  iron-chloride  test. 
Yierordt1  has  calculated  the  amount  of  potassium  sulphocyanide  in 
saliva  by  measuring  the  absorption  of  light  in  the  green  and  blue  por- 
tions of  the  spectrum  of  the  red  fluid  produced  on  the  addition  of  iron 
chloride;  and  has  found  it,  in  an  average  of  six  observations,  to  be  0.16 
parts  per  thousand. 

The  saliva,  like  various  other  animal  fluids,  has  the  property  of  con- 
verting hydrated  starch  into  glucose  if  mingled  with  it  at  or  about  a 
temperature  of  38°  (100°  F.).  The  change  is  not  confined  to  precisely 
this  temperature,  but  will  go  on,  with  diminished  rapidity,  both  above 
and  below  it,  if  the  degree  of  cold  or  warmth  be  not  too  great.  It  is 
entirely  suspended,  however,  at  or  near  the  freezing  point,  and  is  per- 
manently arrested  by  the  temperature  of  boiling  water.  It  depends,  in 
the  saliva,  upon  the  presence  of  pty aline,  which  acts  in  this  respect  like 
the  "diastase"  of  certain  vegetable  substances.  Like  other  similar 
matters  which  exert  a  so-called  "  catalytic"  action,  it  will  produce  its 
effect  only  within  certain  limits  of  temperature,  and  is  most  efficient  at 
about  the  warmth  of  the  living  body.  It  is  affected  differently,  how- 
ever, by  the  action  of  cold  and  that  of  heat ;  for  while  a  freezing  tem- 
perature only  suspends  it  for  the  time  being,  and  allows  it  to  recommence 
when  moderate  warmth  is  again  applied,  a  boiling  temperature  at  once 
•coagulates  the  pty aline  and  destroys  its  catalytic  property.  Saliva, 
therefore,  which  has  been  boiled  for  a  few  instants  and  allowed  to  cool, 
is  found  to  have  permanently  lost  its  power  of  transforming  starch 
into  sugar. 

This  action  of  human  saliva  on  hj^d  rated  starch  takes  place  sometimes 
with  great  rapidity.  Traces  of  glucose  may  often  be  detected  in  the 
mixture  in  one  minute  after  the  two  substances  have  been  brought  in 
contact ;  and  we  have  even  found  that  starch  paste,  introduced  into  the 
cavity  of  the  mouth,  if  already  at  the  temperature  of  38°,  will  yield 
traces  of  sugar  at  the  end  of  half  a  minute.  The  rapidity,  however,  with 

1  Anwendung  des  Spectralapparates  zur  Photometric  der  Absorptionsspectren. 
Tubingen,  1873,  p.  147. 


THE    SALIVA.  143 

which  this  action  is  manifested,  varies  very  much,  as  formerly  noticed 
by  Lehmann,  at  different  times ;  and  it  is  frequently  impossible,  even 
with  the  mixture  kept  steadily  at  the  temperature  of  38°,  to  find  any 
evidence  of  sugar  under  five,  ten,  or  fifteen  minutes.  This  difference 
depends  probably  upon  the  varying  constitution  of  the  saliva  itself. 

Notwithstanding  the  rapidity  with  which  glucose  begins  to  show  itself 
in  a  mixture  of  saliva  with  boiled  starch,  this  action  is  not  a  very  ener- 
getic one ;  that  is,  only  a  very  small  quantity  of  the  starch  is  converted 
into  glucose  within  a  given  time,  the  greater  portion  remaining  un- 
changed. This  is  proved  by  the  fact  that  such  a  mixture  will  show 
the  characteristic  reaction  of  starch  with  iodine  long  after  Fehlmg'a 
test  has  shown  the  existence  of  traces  of  glucose.  If  a  weak  solu- 
tion of  boiled  starch,  made  in  the  proportion  of  3  parts  of  starch  to 
100  parts  of  water,  be  mixed  with  one-third  of  its  volume  of  fresh  human 
saliva  and  placed  in  the  water-bath  at  the  temperature  of  38°,  it  will 
often  give,  in  one  minute,  a  prompt  sugar -reaction  with  Fehling's  test ; 
but  it  also  contains,  at  the  same  time,  an  abundance  of  unaltered  starch. 
Even  at  the  end  of  an  hour,  according  to  our  own  observations,  the  starch 
is  far  from  being  entirely  converted,  as  the  mixture  will  still  give  a  strong 
purple-blue  color  on  the  addition  of  iodine.  The  same  persistence  of 
starch  in  considerable  proportion  may  be  seen  when  the  mixture  is 
retained  in  the  mouth  itself.  If  a  thin  paste  of  hydrated  starch,  con- 
taining no  traces  of  sugar,  be  taken  into  the  mouth  and  thoroughly 
mixed  with  the  buccal  secretions,  it  will  often,  as  above  mentioned, 
begin  to  show  the  reaction  of  glucose  in  half  a  minute ;  but  some  of  the 
starchy  matter  still  remains,  and  will  continue  to  manifest  its  character- 
istic reaction  with  iodine  for  fifteen  or  twenty  minutes,  or  even  for  half 
an  hour. 

The  secretions  produced  by  the  different  salivary  glands  vary  some- 
what in  their  physical  properties,  especially  in  the  degree  of  their  vis- 
cidity, depending  mainly  upon  the  quantity  of  mucosine  present.  The 
parotid  saliva  is  obtained  in  a  state  of  purity  from  the  dog  by  exposing 
the  duct  of  Steno  where  it  crosses  the  masseter  muscle,  and  introducing 
into  it,  through  an  artificial  opening,  a  silver  canula.  The  secretion 
then  runs  directly  from  its  external  orifice,  without  being  mixed  with 
that  of  the  other  salivary  glands.  It  is  clear,  limpid,  and  watery,  and 
without  the  slightest  viscidity.  The  submaxillary  saliva  is  obtained  in 
a  similar  manner,  by  inserting  a  canula  into  Wharton's  duct.  It  dif- 
fers from  the  parotid  secretion,  so  far  as  its  physical  properties  are 
concerned,  chiefly  in  possessing  a  well  marked  viscidity.  The  sublingual 
saliva  is  also  colorless  and  transparent,  and  possesses  a  greater  degree  of 
viscidity  than  that  from  the  submaxillary.  The  secretion  of  the  muci- 
parous  glandules,  which  forms  properly  a  part  of  the  saliva,  is  obtained 
b}^  placing  a  ligature  simultaneously  on  Wharton's  and  Steno's  ducts, 
and  on  that  of  the  sublingual  gland,  so  as  to  shut  out  from  the  mouth 
all  the  glandular  salivary  secretions,  and  then  collecting  the  fluid  se- 
creted by  the  buccal  mucous  membrane.  This  fluid  is  very  scanty,  and 


144  DIGESTION. 

much  more  viscid  than  either  of  the  other  secretions  ;  so  much  so,  that 
it  cannot  be  poured  out  in  drops  when  received  in  a  glass  vessel,  but 
adheres  strongly  to  the  surface  of  the  glass.  All  the  salivary  secretions 
are  alkaline  in  reaction. 

We  have  obtained  the  parotid  saliva  of  the  human  subject  in  a  state 
of  purity  by  introducing  directly  into  the  orifice  of  Steno's  duct  a 
silver  canula  a  little  over  one  millimetre  in  diameter.  The  other  ex- 
tremity of  the  canula  projects  from  the  mouth  between  the  lips,  and 
the  saliva  is  collected  as  it  runs  from  the  open  orifice.  This  method 
gives  results  much  more  valuable  than  observations  made  on  salivary 
fistulae  and  the  like,  since  the  secretion  is  obtained  under  perfectly 
healthy  conditions,  and  unmixed  with  other  animal  fluids. 

The  result  of  many  different  observations,  conducted  in  the  manner 
above  described,  is  that  the  human  parotid  saliva,  like  that  of  the  dog, 
is  colorless,  watery,  and  distinctly  alkaline  in  reaction.  It  differs  from 
the  mixed  saliva  of  the  mouth,  in  being  perfectly  clear,  without  tur- 
bidity or  opalescence.  Its  flow  is  scanty  while  the  cheeks  and  jaws 
remain  at  rest ;  but  as  soon  as  the  movements  of  mastication  are  excited 
by  the  introduction  of  food,  it  runs  in  much  greater  abundance.  We 
have  collected,  in  this  way,  from  the  parotid  duct  of  one  side  only,  in  a 
healthy  man,  31.1  grammes  of  saliva  in  the  course  of  twenty  minutes  ; 
and  in  seven  successive  observations,  made  on  different  days,  comprising 
in  all  three  hours  and  nine  minutes,  we  have  collected  a  little  over  194 
grammes. 

The  parotid  saliva  obtained  in  this  way  has  been  analyzed  by  Prof. 
Maurice  Perkins,  with  the  following  result : 

COMPOSITION  OF  HUMAN  PAROTID  SALIVA. 

Water 983.308 

Organic  matter  precipitable  by  alcohol      ....  7.352 
Substance  destructible  by  heat,  but  not  precipitated  by  alcohol  4.810 

Sodium  sulphocyanide 0.330 

Lime  phosphate 0.240 

Potassium  chloride 0.900 

Sodium  chloride  and  carbonate  .  3.060 


1000.000 

Prof.  Perkins  found,  in  accordance  with  our  own  observations,  that 
the  fresh  parotid  saliva,  when  treated  with  iron  chloride,  showed  no 
evidences  of  sulphocyanogen ;  but  after  the  organic  matters  had  been 
precipitated  by  alcohol,  the  filtered  fluid  was  found  to  contain  an  appre- 
ciable quantity  of  sulphocyanide. 

The  parotid  saliva,  accordingly,  differs  from  the  mixed  saliva  of  the 
mouth  in  containing  some  substance  which  masks  the  reaction  of  sul- 
phocyanogen. If  the  parotid  saliva  and  that  from  the  mouth  be  drawn 
from  the  same  person  within  the  same  hour,  the  addition  of  iron  chloride 
will  produce  a  distinct  red  color  in  the  latter,  while  no  such  change 
takes  place  in  the  former.  And  yet  the  parotid  saliva  itself  contains  a 


THE    SALIVA.  145 

sulphocyanide  which  may  be  detected,  as  we  have  seen,  after  the  organic 
matters  have  been  precipitated  by  alcohol. 

Both  the  parotid  saliva  and  that  from  the  submaxillary  gland  in  the 
human  subject  contain  ptyaline,  but  they  differ  considerably,  as  in  the 
case  of  the  lower  animals,  in  their  degree  of  viscidity. 

Mode  of  Secretion  of  the  Saliva.— The  different  salivary  glands  vary 
in  the  quantity  of  fluid  secreted  by  them  and  in  the  different  influences 
which  excite  them  to  activity.  As  shown  by  Bernard,  the  parotid 
saliva  is  most  abundantly  poured  out  under  the  stimulus  of  anything 
which  excites  the  movement  of  the  jaws,  as  in  the  mastication  of  dry 
substances,  or  continuous  speaking ;  while  that  of  the  submaxillary  is 
especially  increased  by  the  introduction  of  substances  which  excite  the  I 
sense  of  taste.  According  to  the  same  experiments,  the  secretion  of  the 
sublingual  glands  in  the  dog  is  particularly  excited  at  the  moment  of 
deglutition,  and  aids,  together  with  that  of  the  muciparous  glandules,  in 
lubricating  the  surface  of  the  mouth  and  fauces,  and  in  facilitating  the 
passage  of  the  masticated  food  through  the  oesophagus.  Colin,  in  expe- 
rimenting upon  the  horse  and  the  ox,1  found  also  that  the  parotid  saliva 
in  these  animals  is  abundantly  excited  by  the  movements  of  mastication, 
but  not  by  the  simple  contact  of  sapid  substances  with  the  mucous  mem- 
brane of  the  mouth ;  while,  on  the  other  hand,  the  secretion  of  the  sub- 
maxillary saliva  is  considerably  increased  by  introduction  into  the  mouth 
of  substances  having  a  marked  taste.  Both  the  parotid  and  submaxillary 
secretions  are  abundant  while  the  animal  is  feeding,  their  quantity  being 
proportional  to  the  rapidity  of  mastication  and  the  sapid  quality  of  the 
alimentary  substances.  They  are  both  either  suspended  or  very  much 
diminished  during  abstinence.  In  the  ruminants,  however,  the  sublingual 
saliva,  like  the  submaxillary,  is  excited  by  sapid  substances ;  it  is  also 
secreted  continuously  while  the  animal  is  feeding,  and  not  simply  at  the 
moment  of  deglutition.  It  continues  to  be  secreted  during  abstinence, 
and  contributes  to  the  supply  of  fluid  by  which  the  surfaces  are  kept  in 
a  moist  condition. 

Another  fact  observed  by  Colin  which  indicates  the  different  nervous 
influences  by  which  the  salivary  glands  are  controlled,  is  that  in  the 
ruminant  animals  while  feeding  both  the  parotid  and  submaxillary 
glands  furnish  an  abundant  supply  of  saliva ;  but  during  the  process  of 
rumination,  although  the  parotid  glands  are  in  full  secretion,  discharging 
frequently  as  much  as  900  grammes  of  saliva  in  a  quarter  of  an  hour, 
the  submaxillary  glands  are  entirely  inactive  or  produce  only  an  insig- 
nificant quantity  of  fluid.  Colin  has  also  found  that  in  the  horse  and  ass, 
as  well  as  in  the  ox  and  other  ruminating  animals,  the  parotid  glands  of 
the  two  opposite  sides,  during  mastication,  are  never  in  active  secretion 
at  the  same  time;  but  that  they  alternate  with  each  other,  one  remain- 
ing quiescent  while  the  other  is  active,  and  vice  versa.  In  these  animals 
mastication  is  said  to  be  unilateral,  that  is,  when  the  animal  commences 

Physiologie  compare  des  Animaux  Domestiques.     Paris,  1854,  tome  i.  p.  468. 


146  DIGESTION. 

feeding  or  ruminating,  the  food  is  triturated  for  fifteen  minutes  or  more 
by  the  molars  of  one  side  only.  It  is  then  changed  to  the  opposite  side ; 
and  for  the  next  fifteen  minutes  mastication  is  performed  by  the  molars 
of  that  side  only.  It  is  then  changed  back  again,  and  so  on  alternately, 
so  that  the  direction  of  the  lateral  movements  of  the  jaw  may  be  reversed 
many  times  during  the  course  of  a  meal.  By  establishing  a  salivary 
fistula  simultaneously  on  each  side,  it  is  found  that  the  flow  of  saliva 
corresponds  with  the  direction  of  the  masticatory  movement.  When 
the  animal  masticates  on  the  right  side,  it  is  the  right  parotid  which 
secretes  actively,  while  but  little  saliva  is  supplied  by  the  left ;  when 
mastication  is  on  the  left  side,  the  left  parotid  pours  out  an  abundance 
of  fluid,  while  the  right  is  nearly  inactive. 

We  have  observed  a  similar  alternation  in  the  flow  of  parotid  saliva 
in  the  human  subject,  when  mastication  is  changed  from  side  to  side. 
In  an  experiment  of  this  kind,  the  tube  being  inserted  into  the  parotid 
duct  of  the  left  side,  the  quantity  of  saliva  discharged  during  twenty 
minutes,  while  mastication  was  performed  mainly  on  the  opposite  side 
of  the  mouth,  was  8.26  grammes ;  while  the  quantity  during  the  same 
period,  mastication  being  on  the  same  side  of  the  mouth,  was  24.25 
grammes — being  nearly  three  times  as  much  in  the  latter  case  as  in  the 
former. 

Daily  Quantity  of  the  Saliva. — Owing  to  the  physiological  variations 
in  the  rapidity  of  secretion  of  the  saliva,  and  also  to  the  fact  that  it  is 
not  excited  in  the  same  way  by  artificial  stimulus  as  by  the  presence  of 
food,  it  is  somewhat  difficult  to  ascertain  with  exactness  its  total  daily 
quantity.  The  first  attempts  to  do  so  were  made  upon  patients  affected 
with  fistula  of  the  parotid  duct,  and  the  amounts  collected  were  so  small 
as  to  lead  to  the  conclusion  that  the  entire  quantity  secreted  by  all  the 
glands  was  not  more  than  ten  or  twelve  ounces,  or  about  350  grammes 
per  day.  As  in  these  cases,  however,  the  subjects  of  experiment  were 
not  in  a  healthy  condition,  and  as  the  proportion  in  quantity  between  the 
parotid  saliva  and  that  secreted  by  the  remaining  glands  must  necessarily 
be  a  matter  of  conjecture,  the  above  calculation  could  hardly  be  regarded 
as  correct.  Bidder  and  Schmidt,1  from  the  results  of  direct  observation, 
were  led  to  make  a  higher  estimate.  One  of  these  observers,  in  experi- 
menting upon  himself,  collected  from  the  mouth  in  one  hour,  without 
using  any  artificial  stimulus,  97  grammes  of  saliva;  and  calculates, 
therefore,  the  amount  secreted  daily,  making  an  allowance  of  seven 
hours  for  sleep,  as  not  far  from  1620  grammes. 

On  repeating  this  experiment  we  have  not  been  able  to  collect  from 
the  mouth,  without  artificial  stimulus,  more  than  36  grammes  of  saliva 
per  hour.  This  quantity,  however,  may  be  greatly  increased  by  the 
introduction  into  the  mouth  of  any  smooth  unirritating  substance, 
as  glass  beads  or  the  like ;  and  during  the  mastication  of  food,  the 
saliva  is  poured  out  in  very  much  greater  abundance.  The  sight  and 

1  Yerdauungssaefte  und  Stoffwechsel.     Leipzig,  1852,  p.  1 


THE    SALIVA.  147 

odor  of  nutritious  food,  when  the  appetite  is  excited,  will  stimulate 
to  a  remarkable  degree  the  flow  of  saliva;  and,  as  it  is  often  expressed, 
"  bring  the  water  into  the  mouth."  Any  estimate,  therefore,  of  the  total 
quantity  of  saliva,  based  on  the  amount  secreted  in  the  intervals  of  mas- 
tication, would  be  imperfect.  We  may  make  a  tolerably  accurate  calcu- 
lation, by  ascertaining  how  much  is  really  secreted  during  a  meal,  over 
and  above  that  which  is  produced  at  other  times.  We  have  found,  by 
experiments  performed  for  this  purpose,  that  wheaten  bread  gains  during 
complete  mastication  55  per  cent,  of  its  weight  of  saliva ;  and  that  fresh 
cooked  meat  gains,  under  the  same  circumstances,  48  per  cent,  of  its 
weight.  We  have  already  seen  that  the  daily  allowance  of  these  two 
substances,  for  a  man  in  full  health  and  activity,  is  about  540  grammes 
of  bread  and  450  grammes  of  meat.  The  quantity  of  saliva,  accordingly, 
employed  in  the  mastication  of  these  two  substances  is,  for  the  bread 
29 1  grammes,  and  for  the  meat  216  grammes.  If  we  now  calculate  the 
quantity  secreted  between  meals  as  continuing  for  twenty-two  hours  at 
the  rate  of  36  grammes  per  hour,  we  have : 

Saliva  required  for  the  mastication  of  bread  =  297  grammes. 

'•     "  "  "    meat  =  216         " 

"     secreted  in  intervals  of  meals  =  792         " 

Total  quantity  per  day,  a  little  over          1300        " 

Physiological  Action  of  the  Saliva. — The  principal  function  of  the 
saliva  is  undoubtedly  to  moisten  the  food  and  provide  in  this  way  for  its 
further  solution,  and  especially  to  assist  in  mastication,  by  which  the 
food  is  converted  into  a  pultaceous  mass.  This  is  mainly  accomplished 
by  the  watery  ingredients  of  the  secretion,  while  the  albuminous  matters 
contained  in  it  not  only  aid  in  giving  to  the  masticated  food  the  requi- 
site consistency,  but  also  act  by  lubricating  its  surface,  and  facilitating 
its  deglutition.  This  is  evident  from  the  fact  that  the  principal  trouble 
which  results  from  absence  or  deficiency  of  the  saliva  is  a  difficulty  in 
the  mechanical  processes  of  mastication  and  swallowing.  Food  which 
is  hard  and  dry,  like  crusts  or  crackers,  cannot  be  masticated  and 
swallowed  with  readiness,  unless  moistened  by  some  fluid.  If  the 
saliva  be  prevented  from  entering  the  cavity  of  the  mouth,  its  loss 
does  not  interfere  directly  with  the  chemical  changes  of  the  food  in 
digestion,  but  only  with  its  physical  preparation.  This  is  the  result 
of  direct  experiments  performed  by  various  observers.  Bidder  and 
Schmidt,1  after  tying  Steno's  duct,  together  with  the  common  duct  of 
the  submaxillary  and  sublingual  glands  on  both  sides  in  the  dog, 
found  that  the  immediate  effect  of  such  an  operation  was  "  a  remark- 
able diminution  of  the  fluids  which  exude  upon  the  surfaces  of  the 
mouth ;  so  that  these  surfaces  retained  their  natural  moisture  only  so 
long  as  the  mouth  was  closed,  and  readily  became  dry  on  exposure  to 
the  air.  Accordingly,  deglutition  became  evidently  difficult  and  labo- 

1  Verdauungssaefte  und  Stoffwechsel,  p.  3. 


148  DIGESTION. 

rious,  not  only  for  dry  food,  like  bread,  but  even  for  that  of  a  tolerably 
moist  consistency,  like  fresh  meat.  The  animals  also  became  very 
thirsty,  and  were  constantly  ready  to  drink." 

Bernard1  also  found  that  the  only  marked  effect  of  cutting  off  the  flow 
of  saliva  from  the  mouth  was  a  difficulty  in  the  mechanical  processes  of 
mastication  and  deglutition.  He  first  administered  to  a  horse  500 
grammes  of  oats,  in  order  to  ascertain  the  rapidity  with  which  mastica- 
tion would  naturally  be  accomplished.  The  above  quantity  of  grain  was 
thoroughly  masticated  and  swallowed  at  the  end  of  nine  minutes.  An 
opening  had  been  previously  made  in  the  esophagus  at  the  lower  part 
of  the  neck,  so  that  none  of  the  food  reached  the  stomach ;  but  each 
mouthful,  as  it  passed  down  the  oesophagus,  was  received  at  the  cesopha- 
geal  opening  and  examined  by  the  experimenter.  The  parotid  duct  on 
each  side  of  the  face  was  then  divided,  and  another  similar  quantity  of 
oats  given  to  the  animal.  Mastication  and  deglutition  were  both  found 
to  be  immediately  retarded.  The  alimentary  masses  passed  down  the 
03sophagus  at  longer  intervals,  and  their  interior  was  no  longer  moist 
and  pasty,  as  before,  but  dry  and  brittle.  Finally,  at  the  end  of  twenty- 
five  minutes,  the  animal  had  succeeded  in  masticating  and  swallowing 
only  about  three-quarters  of  the  quantity  which  he  had  previously  dis- 
posed of  in  nine  minutes. 

It  appears  from  the  experiments  of  Magendie,  Bernard,  and  Las- 
saigne,  on  horses  and  cows,  that  the  quantity  of  saliva  absorbed  by 
the  food  during  mastication  is  in  direct  proportion  to  its  hardness  and 
dryness,  but  has  no  particular  relation  to  its  chemical  qualities.  These 
experiments  were  performed  as  follows :  The  oesophagus  was  opened  at 
the  lower  part  of  the  neck,  and  a  ligature  placed  upon  it,  between  the 
wound  and  the  stomach.  The  animal  was  then  supplied  with  a  pre- 
viously weighed  quantity  of  food,  and  this,  as  it  passed  out  by  the  oeso- 
phageal  opening,  was  received  into  appropriate  vessels  and  again 
weighed.  The  difference  in  weight,  before  and  after  swallowing,  indi- 
cated the  quantity  of  saliva  absorbed  by  the  food.  The  following  table 
gives  the  results  of  some  of  Lassaigne's  experiments,  performed  upon  a 
horse. 

Kind  of  Food  employed.  Quantity  of  Saliva  absorbed. 

For  100  parts  of  hay 400  parts. 

barley  meal 186      " 

oats 113      " 

green  stalks  and  leaves         .         .  49      " 

It  is  evident  from  the  above  facts,  that  the  quantity  of  saliva  pro- 
duced has  not  so  much  to  do  with  the  chemical  character  of  the  food 
as  with  its  physical  condition.  When  the  food  is  dry  and  hard,  and 
requires  much  mastication,  the  saliva  is  secreted  in  abundance;  when  it 
is  soft  and  moist,  a  smaller  quantity  of  the  secretion  is  poured  out ;  and 
finally,  when  the  food  is  taken  in  a  fluid  form,  as  soup  or  milk,  or 
reduced  to  powder  and  moistened  artificially  with  a  large  quantity  of 

1  Leqons  de  Physiologic  Experimental.     Paris,  1856,  p.  146. 


THE    SALIVA.  149 

water,  it  is  not  mixed  at  all  with  saliva,  but  passes  at  once  into  the 
cavity  of  the  stomach. 

A  difference  of  opinion  exists  among  various  authors  as  to  whether 
the  transforming  power  of  the  saliva  upon  starch  be  also  an  essential 
part  of  its  physiological  action.  If  the  digestion  of  the  food  took  place 
in  the  cavity  of  the  mouth,  or  if  it  were  retained  there  for  any  consider- 
able time,  there  would  be  no  doubt  in  this  respect.  But  in  reality  the 
food  is  in  only  momentary  passage  though  the  mouth,  remaining  there 
merely  long  enough  to  allow  for  mastication.  We  have  already  seen 
that  this  time  is  too  short  to  complete  the  conversion  into  glucose 
of  even  the  small  quantity  of  starch  contained  in  a  dilute  solution, 
much  more  so  the  abundant  semi-solid  starchy  matters  of  bread  or 
vegetables.  There  can  be  no  question  whatever  that  in  point  of  fact, 
the  starchy  elements  of  the  food  are  not  digested  or  transformed  to  any 
considerable  extent  while  in  the  cavity  of  the  mouth.  They  are  swal- 
lowed into  the  stomach  with  by  far  their  greater  portion  still  unchanged. 
Some  observers  (Schiff,  F.  G.  Smith,  Flint,  Kanke,  Brunton)  believe 
that  the  transforming  action  of  the  saliva,  which  is  commenced  in  the 
mouth,  may  continue  subsequently  in  the  stomach  in  presence  of  the 
gastric  juice.  Others  (Bernard,  Robin,  Colin)  assert  that  the  action 
of  the  saliva  on  starch  is  arrested  by  the  gastric  juice,  and,  as  a  matter 
of  fact,  does  not  go  on  in  the  stomach.  This  discrepancy  no  doubt 
depends  partly  upon  differences  in  the  mode  of  experimentation ;  some 
writers  contenting  themselves  with  testing  the  effect  of  dilute  acids  only 
on  the  saliva,  others  using  the  gastric  juice  itself.  The  proportion  in 
which  the  two  secretions  are  mingled  also  makes  a  difference  in  the 
result,  and  the  properties  of  either  one  may  vary  somewhat  according 
to  the  time  at  which  it  is  collected.  Our  own  observations  lead  to 
the  conclusion  that  gastric  juice  certainly  interferes  with  the  chemical 
action  of  saliva,  usually  to  a  very  marked  degree,  when  mingled  with  it 
in  equal  volumes.  If  we  take  fresh  unfiltered  human  saliva,  which  is 
shown  by  a  preliminary  experiment  to  be  capable  of  producing  a  prompt 
sugar-reaction  in  a  solution  of  boiled  starch  at  the  end  of  one  minute, 
mix  it  with  an  equal  volume  of  freshly  collected  gastric  juice  from  the 
dog,  then  add  the  starch-solution,  and  place  the  mixture  in  the  .water- 
bath  at  the  temperature  of  38°  (100°F.)5  there  is  no  sugar-reaction 
whatever  at  the  end  of  five  minutes,  and  only  an  imperfect  one  in 
half  an  hour;  while  at  the  end  of  an  hour  there  may  be  distinct 
reduction  by  Fehling's  test.1  But  if  three  volumes  of  gastric  juice 
be  added  for  one  volume  of  saliva,  the  mixture  gives  no  indication  of 
sugar  even  at  the  end  of  an  hour.  As  all  observations  tend  to  show 
that  the  gastric  juice  is  naturally  secreted  in  much  larger  quantity  than 
the  saliva,  these  proportions  undoubtedly  indicate,  more  nearly  than 

1  In  these  examinations  the  fluid  mixture  is  always  treated  with  animal  char- 
coal previously  to  applying  Fehling's  test;  otherwise  the  albuminous  matter  of  the 
secretions  would  interfere  with  its  certainty. 


150  DIGESTION. 

the  former,  the  relative  quantities  in  which  the  two  secretions  are 
present  in  the  stomach  during  ordinary  digestion. 

Experiments  upon  the  lower  animals,  provided  with  gastric  fistulse, 
show  furthermore  that  in  them  starch  is  not,  in  point  of  fact,  converted 
into  sugar  in  the  stomach.  In  the  dog,  the  horse,  the  sheep,  and  the 
ox,  according  to  Bernard,  Schiff,  and  Colin,  the  action  of  saliva  upon 
hydrated  starch  is  distinct,  though  less  rapid  than  that  of  the  human 
subject.  In  the  gnawing  animals  generally  it  is  present,  and  in  the 
guinea  pig,  according  to  Schiff,  is  more  decided  than  in  man.  But 
if  a  dog,  with  a  gastric  fistula,  be  fed  with  a  mixture  of  meat  and 
boiled  starch,  and  portions  of  the  fluid  contents  of  the  stomach  with- 
drawn afterward  through  the  fistula,  the  starch  is  easily  recognizable 
by  its  reaction  with  iodine  for  ten,  fifteen,  and  twenty  minutes  after- 
ward. In  forty-five  minutes  it  is  diminished  in  quantity,  and  in  one 
hour  has  usually  disappeared ;  but  no  sugar  is  to  be  detected  at  any 
time.  Sometimes  the  starch  disappears  more  rapidly  than  this ;  but  at 
no  time,  according  to  our  observations,  is  there  any  indication  of  the 
presence  of  sugar  in  the  gastric  fluids.  Bernard1  has  shown  the  same 
want  of  transformation  in  the  dog's  stomach  after  swallowing  a  mix- 
ture of  hydrated  starch  with  ordinary  food.  Briicke,2  in  dogs  fed  with 
starch  paste,  found  in  the  stomach  more  or  less  unchanged  starch,  and 
either  no  sugar  or  only  traces  of  it,  after  the  lapse  of  from  one  to  five 
hours.  This  does  not  depend  upon  any  want  of  power  in  dogs  to  digest 
hydrated  starch,  since  this  substance  is  converted  into  glucose  in  these 
animals  with  great  promptitude  on  arriving  in  the  duodenum,  by  the 
influence  of  the  pancreatic  and  intestinal  juices. 

It  is  also  an  important  consideration,  in  this  respect,  that  the  saliva 
exerts  its  transforming  power  only  upon  starch  which  has  been  cooked 
or  hydrated.  All  observers  agree  that  it  is  nearly  or  quite  without 
action  upon  raw  starch,  which  remains  unchanged  in  contact  with  it  at 
all  temperatures.  But  in  the  herbivorous  animals,  where  the  salivary 
glands  are  at  least  as  fully  developed  and  the  saliva  as  abundant  as 
in  man,  the  starchy  elements  of  the  food  are  habitually  taken  in 
the  raw  state.  Even  in  the  ruminating  animals,  where  the  food  is 
retained,  for  some  time  after  the  first  mastication,  in  the  paunch, 
unmixed  with  gastric  juice,  it  does  not  undergo  there  the  sugar- 
conversion.  Prof.  Francis  G.  Smith,  in  a  series  of  experiments  upon 
Alexis  St.  Martin,  affected  with  a  gastric  fistula,  in  1856,3  withdrew 
the  contents  of  the  stomach  two  and  a  half  hours  after  bread  had  been 
masticated  and  swallowed;  and  in  the  mixed  fluids  so  obtained,  he 
detected  at  the  end  of  that  time  unchanged  starch,  both  by  the  micro- 
scope and  by  the  iodine  test.  Glucose  was  also  found  in  the  fluid,  but, 
as  bread  nearly  always  contains  glucose,  it  is  uncertain  how  much, 

1  SScre'tions  Digestives.     Paris,  1856,  p.  159. 

2  Jahresberichte  der  Anatomie  und  Physiologie.     Leipzig,  1873,  p.  467. 

3  Philadelphia  Medical  Examiner,  July  and  September,  1856. 


THE    SALIVA.  151 

if  any,  had  been  produced  by  transformation  of  the  starch.  Colin1 
has  found  the  farinaceous  matter  of  oats  and  of  starchy  roots  recogniz- 
able by  its  iodine  reaction,  after  these  substances  had  remained  in  the 
first  stomach  of  the  ox,  mixed  with  saliva,  for  twenty-four  hours.  The 
same  observer  introduced  into  the  interior  of  the  paunch,  through  a 
fistula,  small  muslin  bags  containing  uncooked  potato  starch,  which 
were  found  in  the  same  cavity,  still  full  of  unaltered  starch,  at  the  end 
of  twenty  and  twenty-two  hours.  It  is  worth  remembering  furthermore 
that  the  salivary  glands  and  their  secretion  are  also  abundantly  devel- 
oped in  the  carnivora,  whose  food  never  in  the  natural  condition  con- 
tains starch  as  an  ingredient. 

It  appears  evident,  therefore,  that  the  chemical  action  of  the  saliva  in 
the  lower  animals  forms  no  part  of  the  natural  process  of  digestion ; 
and  that  in  man  it  is  insignificant  in  amount,  and  quite  subordinate  to 
that  of  other  digestive  fluids.  In  both  animals  and  man,  however,  and 
in  the  carnivora  as  well  as  in  the  herbivora,  its  physical  properties  are 
important  in  accomplishing  the  processes  of  mastication  and  degluti- 
tion. 

Mastication  is  aided  and  controlled  in  great  measure  by  the  sen- 
sibilities of  touch  and  taste,  residing  in  the  surface  of  the  tongue  and 
other  parts  of  the  mucous  membrane.  The  sense  of  taste  notifies  us 
of  the  alimentary  qualities  of  the  food  taken  into  the  mouth,  and 
its  sapid  qualities  must  be  fully  brought  out  by  the  comminution  and 
moistening  of  the  food  before  mastication  is  complete.  The  taste  itself 
depends,  for  one  of  its  essential  conditions,  upon  a  sufficient  supply  of 
saliva,  and  this  is  by  no  means  an  unimportant  function  of  the  secretion. 
No  substance  can  produce  an  impression  upon  the  nerves  of  taste  unless 
it  be  in  a  fluid  form  and  capable  of  absorption  by  the  mucous  membrane. 
The  saliva  produces  this  effect  upon  the  soluble  ingredients  of  the  food, 
and  brings  them  in  contact  with  the  papillae  of  the  tongue  in  sufficient 
quantity  to  produce  a  gustatory  sensation. 

The  general  sensibility  of  the  tongue,  which  is  highly  developed, 
also  enables  this  organ  to  appreciate  the  physical  condition  of  the  food 
and  how  far  it  is  prepared  for  deglutition.  At  the  same  time  its  mus- 
cular apparatus  provides  for  its  movement  in  every  direction.  When 
the  alimentary  material  is  finally  reduced,  by  mastication  and  mixture 
with  the  saliva,  to  a  sufficiently  pasty  and  homogeneous  condition,  the 
softened  mass  is  collected  from  every  part  of  the  mouth  by  the  move- 
ments of  the  tongue  and  brought  together  upon  its  upper  surface.  It 
is  then  pressed  backward  by  the  muscular  force  of  the  organ,  and  car- 
ried through  the  fauces  into  the  pharynx  and  upper  part  of  the  oesopha- 
gus. Here  it  passes  beyond  the  control  of  the  will.  It  is  then  grasped 
by  the  muscular  fibres  of  the  oesophagus,  and  by  the  continuous  and  rapid 
peristaltic  action  of  this  canal  is  carried  downward  into  the  stomach. 

1  Physiologic  compare  des  Animaux  Domestiques.     Paris,  1854,  tome  i.  p.  603. 


152 


DIGESTION. 


The  Gastric  Juice  and  Stomach  Digestion, 

The  stomach  has  long  been  recognized  as  the  organ  in  which  the 
most  important  part  of  the  digestive  process  is  inaugurated,  and  in 
which  the  essential  chemical  modifications  of  the  alimentary  matters  first 
take  place.  Its  action  consists  in  the  production  of  a  special  digestive 
fluid,  the  gastric  juice,  furnished  by  the  glandular  apparatus  of  its 
mucous  membrane. 

The  gastric  mucous  membrane  presents  certain  variations,  both  in  its 
general  appearance  and  its  intimate  structure,  in  different  portions  of 
the  stomach.  It  is  red  in  the  cardiac  and  middle  portion,  paler  in  the 
cardiac  portion.  It  increases  also  in  thickness  from  the  cardia  toward 
the  pylorus ;  being,  according  to  the  measurements  of  Kolliker,  about 
half  a  millimetre  thick  in  the  cardiac  portion,  one  millimetre  in  the 
middle,  and  one  and  a  half  to  two  millimetres  near  the  pylorus.  Its 
free  surface  is  everywhere  more  or  less  uneven  and  marked  with  minute 
ridges  or  eminences.  In  the  cardiac  portion  (Fig.  39)  these  ridges  are 
reticulated  with  each  other,  so  as  to  include  between  them  polygonal 
interspaces,  each  of  which  is  encircled  by  a  network  of  capillary  blood- 
vessels. In  the  pyloric  portion  Fig.  40)  the  eminences  are  more  distinct 


Fig.  39. 


Fig.  40. 


Free  surface  of  GASTRIC  Mucous  MEM-  Free  surface  of  GASTRIC  Mucous  MEM- 
BRANE, viewed  from  above;  from  Pig's  BRANE,  viewed  in  vertical  section;  from 
Stomach,  Cardiac  portion.  Moderately  mag-  Pig's  Stomach,  Pyloric  portion.  More  highly 
nified.  magnified. 

from  each  other,  pointed  in  form,  about  one-tenth  of  a  millimetre  in 
height,  and  generally  flattened  from  side  to  side.  In  the  human  subject 
these  villus-like  projections  have  even  been  found  extending  over  the 
whole  surface  of  the  gastric  mucous  membrane.  Each  one  contains  a 
capillary  bloodvessel,  which  returns  upon  itself  in  a  loop  at  the  extremity 
of  the  projection,  and  communicates  freely  with  adjacent  vessels. 

The  entire  thickness  of  the  mucous  membrane  of  the  stomach  consists 
of  glandular  follicles  or  tubules,  some  of  which  are  simple  in  structure, 


THE    GASTRIC    JUICE    AND    STOMACH    DIGESTION.      153 


while  others  are  compound  or  branched.  Another  distinction  between 
the  follicles  is  that  some  of  them  are  lined  throughout  with  cylindrical 
epithelium  cells,  not  very  different  from  those  on  the  free  surface  of  the 
mucous  membrane,  while  others  contain  also  larger  cells  of  a  rounded 
form,  which  give  to  the  follicles  a  peculiar  aspect.  Both  simple  and 
branched  follicles  may  be  found,  presenting  both  these  two  kinds  of  epi- 
thelium ;  but  as  a  general  rule,  the  simple  tubular  follicles  are  distin- 
guished by  their  lining  of  cylindrical  epithelium,  while  the  compound  or 
branched  follicles  more  especially  contain  the  larger  cells  of  glandular 
epithelium. 

In  the  pyloric  portion  of  the  stomach,  the  follicles  with  cylindrical 
epithelium  preponderate,  or  in  some  instances  are  present  exclusively. 
In  the  dog,  according  to  the  observations  of  Ebstein,  and  in  man,  ac- 
cording to  Kb'lliker,  the  mucous  membrane  in  the  immediate  proximity 
of  the  pylorus,  for  a  zone  of  considerable  width,  contains  follicles  of  this 
kind  only.  They  present  the  same  essential  characters  in  man  and  in 
different  species  of  animals.  They  are  nearly  straight  or  slightly  tor- 
tuous tubules,  y1^  of  a  millimetre  in  diameter,  lined  with  cylindrical 
epithelium  cells,  and  terminating  in  blind  extremities  at  the  under  sur- 
face of  the  mucous  membrane  (Fig.  41).  In  their  lower  half  they  are 


Fig.  41. 


Fig.  42. 


Mucous  MEMBRANE  OF  PIG'S  STO- 
MACH, from  Pyloric  portion;  vertical  sec- 
tion; showing  tubular  follicles,  and,  at  o,  a 
closed  follicle.  Moderately  magnified. 


TUBULAR  FOLLICLES,  from  Pyloric 
portion  of  Pig's  Stomach,  showing  their 
coecal  extremities  and  epithelial  lining.  At 
a,  the  torn  end  of  a  follicle,  showing  its 
cavity.  More  highly  magnified. 


often  slightly  branched,  one  or  more  lateral  diverticula  passing  off  from 
the  principal  tubule,  and  forming  a  little  mass  or  lobule  of  glandular 
tubes.  At  their  upper  extremities  they  open  on  the  free  surface  of  the 
mucous  membrane,  in  the  interspaces  between  the  projecting  folds  or 
villi.  The  cylindrical  epithelium  cells,  which  cover  the  general  surface 
of  the  gastric  mucous  membrane,  extend  downward  into  the  cavity  of 
11 


154 


DIGESTION. 


the  follicles  and  reach  even  to  their  blind  extremities  (Fig.  42) ;  only  in 
the  interior  of  the  follicles  they  are  shorter,  less  transparent,  and  more 
glandular  in  appearance  than  on  the  free  surface  of  the  mucous  mem- 
brane. 

In  the  cardiac  portion  of  the  stomach  the  superficial  part  of  the 
mucous  membrane  contains  wide  depressions  or  tubes,  lined  with  large 
cylindrical  epithelium  cells.  These  tubes,  at  a  short  distance  below 
the  surface,  are  joined  each  by  two  or  more  tubular  follicles,  lined  with 
small  glandular  epithelium  cells,  and  terminating  below,  like  the  pre- 
ceding, in  rounded  extremities  (Fig.  43). 


Fig.  43. 


Fig.  44. 


GASTRIC  FOLLICLES,  from  Pig's  Sto- 
mach, Cardiac  portion.  At  a,  two  follicles 
joining  a  larger  tube ;  6,  portion  of  a  tube 
seen  endwise  ;  c,  its  centra/I  cavity. 


G-ASTRIO  FOLLICLES,  with  large  gland- 
ular cells ;  from  middle  portion  of  Pig's 
Stomach. 


In  the  mucous  membrane  of  both  the  fundus  and  middle  portion  of 
the  stomach,  but  especially  in  the  middle  portion,  there  are  follicles 
which  are  distinguished  by  containing,  in  addition  to  the  cylindrical  or 
small  glandular  epithelium  cells,  larger  spheroidal  cells  of  peculiar 
aspect.  As  already  mentioned,  these  follicles  are  usually  compound, 
but  they  are  also  met  with  of  a  simple  tubular  form.  The  spherical 
cells  which  they  contain  are  usually  most  abundant  in  their  lower 
portions,  but  are  often  more  distinctly  defined  in  the  middle  part  of  the 
follicle.  These  cells  are  rounded  in  form,  about  20  mmm.  in  diameter, 
finely  granular,  and  provided  with  well-marked  oval  nuclei.  They  nearly 
fill  the  cavity  of  the  follicle,  and  also  project  laterally  from  its  external 
surface,  giving  to  it  from  this  cause  an  extremely  characteristic  varicose 
or  irregularly  tumefied  appearance  (Fig.  44).  In  the  compound  follicles 
of  the  cardiac  portion  of  the  human  stomach  (Fig.  45),  the  spherical  cells 
are  found  more  or  less  abundantly  throughout  their  deeper  and  middle 


THE    GASTRIC    JUICE    AND    STOMACH    DIGESTION.      155 


Fig.  45. 


parts,  up  to  the  point  where  they  join  the  wider  tube  leading  to  the 
surface. 

These  spheroidal  cells  have  been  designated  by  the  name  of  "  pepsine 
cells,"  and  the  glandular  follicles  con- 
taining them  as  "  peptic  glands,"  from 
a  supposition  that  they  are  exclusively 
concerned  in  the  production  of  the 
essential  organic  ingredient  of  the  gas- 
tric juice.  Opinions,  however,  are 
divided  upon  this  point.  The  follicles 
in  question  contain  both  the  so-called 
"pepsine  cells"  and  the  smaller  cells 
of  glandular  epithelium ;  the  two  kinds 
of  cells  being  found  associated  in  the 
same  follicles  over  a  large  portion  of 
the  stomach.  It  is  only  in  the  pyloric 
region  that  the  follicles  contain  cells 
of  the  smaller  variety  alone.  It  is 
acknowledged  by  all  that  by  the  action 
of  glycerine  a  substance  having  the 
properties  of  pepsine  may  be  extracted 
from  the  middle  or  cardiac  portions  of 
the  gastric  mucous  membrane,  and  not 
from  the  pyloric  portion.  But  Ebstein 
has  shown1,  that,  if  two  digestive  fluids 
be  prepared  by  macerating  the  gastric 
mucous  membrane  in  water  acidulated 
with  hydrochloric  acid,  using  for  one 
the  pyloric  portion  and  for  the  other  the 
middle  portion,  both  of  these  fluids  pos- 
sess under  similar  conditions,  digestive  properties  which  are  the  same  in 
kind,  and  differ  only  in  degree.  The  principal  distinction  between  the 
two  kinds  of  cells,  according  to  the  same  observer,  is  that  the  substance 
of  the  cylindrical  cells  becomes  cloudy  and  shrivelled  by  the  action  of 
acids  generally  ;  while  that  of  the  spheroidal  cells  is  thus  affected  only 
by  mineral  acids,  acetic  acid,  on  the  contrary,  causing  them  to  become 
swollen  and  transparent.  From  this  it  is  concluded  that  the  smaller 
cells  contain  a  substance  like  mucosine,  while  the  larger  consist  of 
materials  more  closely  resembling  albumen. 

It  cannot  therefore  be  said  with  certainty,  that  either  the  larger  cells 
or  the  follicles  containing  them  produce  exclusively  either  the  pepsine 
or  the  acid  of  the  gastric  juice.  No  doubt  the  follicles  in  different  por- 
tions of  the  stomach  differ  from  each  other  more  or  less,  in  function  as 
well  as  in  appearance ;  but  it  is  not  yet  possible  to  determine  the  exact 
nature  of  the  differences  between  them.  By  the  combined  action  of  all 


COMPOUND  GASTRIC  FOLLICLE, 
from  the  Cardiac  portion  of  human 
stomach.  1.  Excretory  tube,  leading 
to  the  surface.  2.  Tubular  follicles, 
containing  spheroidal  cells.  (Kolliker.) 


1  Archiv  fur  Mikroskopische  Anatomie,  1870,  vi.  p.  515. 


156  DIGESTION. 

parts  of  the  glandular  apparatus  is  produced  the  characteristic  secretion 
of  the  gastric  juice. 

Physical  Qualities  and  Composition  of  the  Gastric  Juice. — The  earliest 
decisive  investigations  in  regard  to  the  existence  and  properties  of  the 
gastric  juice  were  those  made  by  Dr.  Beaumont,  of  the  United  States 
Army,  in  the  case  of  Alexis  St.  Martin,  a  Canadian  boatman,  who  was 
affected  with  a  permanent  gastric  fistula,  the  result  of  an  accidental  gun- 
shot wound.  The  musket,  which  was  loaded  with  buckshot  at  the  time 
of  the  accident,  was  discharged,  at  the  distance  of  a  few  feet  from  St. 
Martin's  body,  in  such  a  manner  as  to  tear  away  the  integument  at  the 
lower  part  of  the  left  chest,  open  the  pleural  cavity,  and  penetrate, 
through  the  lateral  portion  of  the  diaphragm,  into  the  great  pouch  of  the 
stomach.  After  the  integument  and  the  pleural  and  peritoneal  surfaces 
had  united  and  cicatrized,  there  remained  a  permanent  opening  about  two 
centimetres  in  diameter  leading  into  the  left  extremity  of  the  stomach, 
which  was  usually  closed  by  a  circular  valve  of  protruding  mucous 
membrane.  This  valve  could  be  readily  depressed  at  any  time,  so  as  to 
open  the  fistula  and  allow  the  contents  of  the  stomach  to  be  extracted 
for  examination. 

Dr.  Beaumont  experimented  upon  this  person  at  various  intervals 
from  the  year  1825  to  1832.1  He  established  during  the  course  of  his 
examinations  the  following  important  facts  :  First,  that  the  active  agent 
in  digestion  is  an  .acid  fluid,  secreted  by  the  walls  of  the  stomach; 
secondly,  that  this  fluid  is  poured  out  by  the  glandular  walls  of  the 
organ  only  during  digestion,  and  under  the  stimulus  of  the  food ;  and 
finally,  that  it  will  exert  its  solvent  action  upon  the  food  outside  the 
body  as  well  as  in  the  stomach,  if  kept  in  glass  phials  upon  a  sand-bath 
at  the  temperature  of  38°  (100°  F.).  He  made  also  a  variety  of  other 
interesting  investigations  as  to  the  effect  of  various  kinds  of  stimulus  on 
the  secretion  of  the  stomach,  the  rapidity  with  which  the  process  of 
digestion  takes  place,  and  the  comparative  digestibility  of  various  kinds 
of  food. 

The  same  person,  with  his  gastric  fistula  unchanged,  after  an  interval 
of  twenty-four  years,  came  under  the  observation  of  Prof.  Francis  G. 
Smith,  of  the  University  of  Pennsylvania,  who  again  made  a  series  of 
important  experiments  of  a  similar  nature,  confirming  and  extending 
those  of  Dr.  Beaumont ;  and  another  case,  in  a  young  and  otherwise 
healthy  woman,  the  result  of  a  local  inflammation  and  abscess,  happened 
in  Germany  in  1854,  and  was  investigated  by  Prof.  C.  Schmidt. 

Since  Dr.  Beaumont's  time  similar  experiments  have  been  frequently 
performed  by  means  of  gastric  fistulae  artificially  established  upon  the 
lower  animals,  especially  upon  the  dog,  which  has  been  found  most 
convenient  for  this  purpose ;  the  result  of  examinations  conducted  by 
this  and  other  methods  being  that  the  gastric  juice  presents  the  same 
essential  characters  in  man  and  in  the  carnivorous  and  herbivorous 

1  Experiments  and  Observations  upon  the  Gastric  Juice.     Boston,  1834. 


THE    GASTKIC    JUICE    AND    STOMACH    DIGESTION.      157 

animals.  The  simplest  and  most  effectual  mode  of  establishing  a  gas- 
tric fistula  in  the  dog  is  the  following :  A  longitudinal  incision,  about 
six  centimetres  in  length,  is  made  through  the  abdominal  parietes  in  the 
median  line,  over  the  great  curvature  of  the  stomach.  The  anterior  wall 
of  the  organ  is  then  to  be  seized  with  a  pair  of  hooked  forceps,  drawn 
out  at  the  external  wound,  and  opened  with  the  point  of  a  bistoury.  A 
short  silver  canula  from  one  to  two  centimetres  in  diameter,  armed  at 
each  extremity  with  a  narrow  projecting  rim  or  flange,  is  inserted  into 
the  wound  in  the  stomach,  the  edges  of  which  are  fastened  round  the 
tube  with  a  ligature  in  order  to  prevent  the  escape  of  the  gastric  fluids 
into  the  peritoneal  cavity.  The  stomach  is  then  returned  to  its  place  in 
the  abdomen,  and  the  canula  allowed  to  remain  with  its  external  flange 
resting  upon  the  edges  of  the  wound  in  the  abdominal  integuments, 
which  are  to  be  drawn  together  by  sutures.  The  animal  may  be  kept 
perfectly  quiet,  during  the  operation,  by  the  administration  of  ether 
or  chloroform.  In  a  few  days  the  ligatures  come  away,  the  wounded 
peritoneal  surfaces  unite  with  each  other,  and  the  canula  is  retained  in 
a  permanent  gastric  fistula ;  being  prevented  by  its  flaring  extremities 
both  from  falling  out  of  the  abdomen  and  from  being  accidentally 
pushed  into  the  stomach.  It  is  closed  externally  by  a  cork,  which  may 
be  withdrawn  at  pleasure,  and  the  contents  of  the  stomach  thus  obtained 
for  examination. 

Experiments  conducted  in  this  manner  confirm,  in  the  main,  the  results 
obtained  by  Dr.  Beaumont.  Their  results  are  even,  in  some  respects, 
more  satisfactory  than  those  obtained  from  the  human  subject ;  since 
animals  are  more  completely  under  the  control  of  the  experimenter,  and 
all  sources  of  deception  or  mistake  are  thereby  avoided,  while  the  inves- 
tigation is,  at  the  same  time,  facilitated  by  the  simple  character  of  the 
food  administered. 

The  gastric  juice  obtained  by  this  method  is  a  clear,  colorless,  or 
faintly  amber-colored  fluid,  of  a  perfectly  watery  consistency  and  a  dis- 
tinctly acid  reaction.  Its  specific  gravity  does  not  vary  much  from 
1010.  It  becomes  slightly  opalescent  on  boiling. 

The  following  is  the  composition  of  the  gastric  juice  of  the  dog, 
based  upon  a  comparison  of  various  analyses  by  Lehmann,  Blondlot, 
Otto,  Bidder  and  Schmidt. 

COMPOSITION  OF  GASTRIC  JUICE. 

Water  ..........  975.00 

Free  acid 4.78 

Pepsine 15.00 

Sodium  chloride 1.70 

Potassium     " 1.08 

Calcium        " 0.20 

Ammonium  "........  0.65 

Lime  phosphate 1.48 

Magnesium  "........  0.06 

Iron              "  0.05 


1000  00 


158  DIGESTION. 

Prof.  C.  Schmidt1  found  the  gastric  juice  of  the  human  subject  similar 
in  constitution  to  the  above,  except  that  it  contained  a  larger  propor- 
tion of  water  and  a  considerably  smaller  proportion  botli  of  free  acid 
and  pepsine,  as  well  as  of  solid  ingredients  generally.  From  our  own 
repeated  observations  upon  the  dog,  there  is  no  doubt  that  both  the 
quantity  and  density  of  the  gastric  juice  vary,  within  certain  limits,  in 
different  individuals  even  of  the  same  species — the  proportion  of  solid 
ingredients  being  less  when  the  secretion  is  more  abundant,  and  greater 
when  the  secretion  is  in  small  quantity. 

The  most  striking  physical  property  of  the  gastric  juice  is  its  acid 
reaction,  which  is  always  strongly  marked,  and  by  which  it  is  distin- 
guished from  all  the  other  digestive  secretions  and  internal  fluids  of  the 
body.  This  property,  as  indicated  in  the  foregoing  table,  depends  upon 
the  presence  in  the  secretion  of  a  free  acid.  Notwithstanding  the 
numerous  investigations  which  have  been  directed  to  this  point,  it  is 
still  uncertain  whether  the  reaction  of  the  gastric  juice  be  due  to  free 
hydrochloric  or  free  lactic  acid ;  each  of  these  two  substances  having 
been  found  by  different  observers.  Those  who  attribute  the  reaction  of 
the  gastric  juice  to  hydrochloric  acid  (Prout,  Dunglison,  Enderlin, 
Bidder  and  Schmidt)  depend  upon  its  being  obtainable  by  distillation, 
and  more  especially  upon  a  quantitative  determination  of  all  the  alka- 
line and  earthy  bases  contained  in  the  secretion,  and  an  estimate  of 
the  amount  of  hydrochloric  acid  necessary  to  saturate  these  bases ;  the 
hydrochloric  acid,  actually  obtainable,  being  found  to  be  more  than 
sufficient  to  unite  with  the  above  bases  in  neutral  combination.  On  the 
other  hand,  various  experimenters  (Lehmann,  Leuret,  Lassaigne,  Francis 
G.  Smith,  Bernard  and  Barreswil)  have  not  only  found  evidences  of 
the  presence  of  free  lactic  acid  in  the  gastric  juice,  but  some  of  them 
have  also  shown3  that  during  distillation  the  concentrated  lactic  acid 
would  set  free  hydrochloric  acid  by  decomposition  of  the  alkaline  chlo- 
rides, although  none  were  originally  present  in  the  fluid.  They  also 
point  out  that  the  addition  of  a  small  quantity  of  oxalic  acid  to  the 
gastric  juice  produces  a  precipitate  of  lime  oxalate,  while  no  such  pre- 
cipitation will  take  place  in  a  fluid  containing  two  parts  per  thousand 
of  free  hydrochloric  acid.  It  is  certain,  however,  that  either  of  these 
acids  may  replace  that  which  naturally  exists  in  the  gastric  juice  with- 
out essentially  impairing  its  digestive  properties. 

The  remaining  important  ingredient  of  the  gastric  juice  is  its  albu- 
minoid matter,  known  under  the  name  of  pepsine.  This  substance  is 
not  precipitated  by  either  the  organic  or  the  mineral  acids,  but  is  thrown 
down  by  the  action  of  heat  and  by  alcohol  in  excess.  It  may  also  be 
precipitated,  like  ptyaline,  from  its  watery  solution  acidulated  with 
dilute  phosphoric  acid,  by  the  addition  of  lime  water ;  the  precipitated 
lime  phosphate  bringing  down  the  pepsine  entangled  with  it.  Pepsine 

1  Annalen  der  Chemie  und  Pharmacie,  1854,  p.  42. 

2  Bernard.     Le<;ons  de  Physiologic  Exp6rimentale.     Paris,  1856,  p.  396. 


THE    GASTRIC    JUICE    AND    STOMACH    DIGESTION.      159 

is  not  affected  in  the  same  way,  however,  by  all  the  agents  which  cause 
its  coagulation.  After  precipitation  by  alcohol  or  by  lime  phosphate,  it 
is  unchanged  in  its  chemical  qualities,  and  may  be  again  dissolved  in 
water  without  losing  any  of  its  original  digestive  properties ;  but  when 
coagulated  by  boiling,  it  is  permanently  altered  and  cannot  again  be 
brought  into  an  active  condition. 

Pepsine  may  also  bek  precipitated  from  the  gastric  juice  by  contact 
with  the  bile.  If  ten  to  fifteen  drops  of  dog's  bile  be  added  to  10  cubic 
centimetres  of  fresh  gastric  juice  from  the  same  animal,  a  complete  pre- 
cipitation takes  place ;  so  that  the  whole  of  the  biliary  coloring  matter 
is  thrown  down  as  a  deposit  and  the  filtered  fluid  is  found  to  have  lost 
its  digestive  power  although  it  still  retains  an  acid  reaction.  This  ex- 
plains the  disturbing  effect  upon  digestion  produced  by  a  regurgitation 
of  bile  through  the  pylorus  into  the  stomach. 

Pepsine  may  be  extracted  from  the  fresh  mucous  membrane  of  the 
stomach  by  cutting  it  into  small  pieces  and  macerating  it  for  some  hours 
with  distilled  water.  The  filtered  fluid,  acidulated  with  dilute  hydro- 
chloric acid  until  it  presents  a  similar  grade  of  acid  reaction  to  that  of 
the  fresh  gastric  juice,  is  found  to  possess  the  peculiar  digestive  proper- 
ties of  the  natural  secretion. 

These  digestive  properties  depend  accordingly  upon  the  presence  of 
both  the  pepsine  and  the  free  acid.  They  are  not  exhibited  by  a  dilute 
acid  alone,  nor  by  a  solution  of  pepsine  which  is  neutral  or  alkaline  in 
reaction.  The  pepsine,  which  acts  in  some  unexplained  manner,  like 
other  so  called  "  catalytic"  bodies,  requires,  as  a  special  condition  of  its 
activity,  the  presence  of  a  free  acid.  Accordingly,  the  fluids  of  the  sto- 
mach, even  though  they  contain  pepsine,  will  not  act  upon  the  food  unless 
they  have  also  an  acid  reaction.  If  the  fresh  gastric  juice  be  neutralized 
by  the  addition  of  an  alkali,  it  loses  its  digestive  properties  as  soon  as 
the  point  of  neutralization  is  reached;  but  these  properties  may  be 
restored  by  again  acidulating  the  fluid.  For  this  purpose,  either  lactic 
or  hydrochloric  acids  may  be  used,  both  of  which  yield  very  active 
digestive  fluids  with  pepsine.  Dilute  sulphuric,  nitric,  and  acetic  acids, 
on  the  other  hand,  according  to  Lehmann,1  produce  a  mixture  of  only 
slight  digestive  power ;  while  phosphoric,  oxalic,  and  tartaric  acids  are 
nearly  inert  in  this  respect.  If  the  gastric  juice,  again,  be  subjected  to 
a  boiling  temperature,  it  is  found  to  have  lost  its  digestive  properties 
owing  to  the  chemical  alteration  of  its  pepsine,  notwithstanding  its  acid 
reaction  may  remain  the  same  as  before. 

The  characteristic  property  of  the  fresh  gastric  juice,  as  well  as  of 
acidulated  solutions  of  pepsine,  is  that  it  has  the  power  of  digesting  and 
dissolving  substances  of  an  albuminous  nature.  This  is  best  shown  by 
suspending  in  gastric  juice  pieces  of  coagulated  fibrine  and  keeping 
the  fluid  at  the  temperature  of  38°  (100°  F.).  The  fibrine  rapidly  swells 

1  Physiological  Chemistry.  Cavendish  Society  edition.  London,  1853,  vol.  ii. 
p.  58. 


160  DIGESTION. 

up,  becomes  transparent  and  gelatinous,  and  after  a  time  dissolves. 
The  same  effect  is  produced,  though  more  slowly,  upon  hard-boiled  white 
of  egg.  The  solid  caseine  of  cheese  is  liquefied  and  the  oleaginous 
particles  set  free.  This  action  is  in  every  case  more  or  less  dependent 
upon  the  temperature.  It  is  entirely  suspended  at  or  near  the  freezing 
point,  but  becomes  more  and  more  active  with  the  increase  of  warmth, 
and  is  most  energetic  from  35°  to  40°  (about  100°  P.).  Above  that 
point  its  activity  again  diminishes,  and  at  a  boiling  temperature  it  is 
entirely  destroyed.  It  is  owing  to  the  influence  of  temperature  that 
digestion  is  more  slowly  performed  in  the  cold-blooded  reptiles  than  in 
the  warm-blooded  birds  and  quadrupeds.  This  difference  has  been 
shown  by  Schiff,1  who  made  acidulated  infusions  of  the  stomachs  of  two 
serpents,  and  placed  in  each  the  same  measured  quantity  of  coagulated 
albumen  ;  one  of  the  infusions  being  allowed  to  remain  at  a  temperature 
varying  from  10°  to  11°  (50°  to  62°  F.),  the  other  being  introduced,  in  a 
closed  glass  tube,  into  the  stomach  of  a  living  dog.  The  second  was 
found  to  have  digested  in  six  hours  as  much  albumen  as  the  first  at  the 
end  of  three  weeks. 

The  changes  produced  in  solid  albuminous  matters  during  digestion 
by  gastric  juice  are  as  follows:  The  first  effect  is  a  swelling  and  gela- 
tinization  of  the  substance  under  the  influence  of  the  free  acid.  This 
will  take  place  by  the  action  of  a  dilute  acid  alone,  and  with  the  aid  of 
continuous  warmth  a  part  of  the  substance  will  after  a  time  even  be 
dissolved.  This  solution,  however,  is  not  a  true  digestion  of  the  albu- 
minous body.  It  has  merely  been  modified  in  such  a  way  as  to  be 
soluble  in  an  acidulated  liquid,  and  it  may  be  again  precipitated  by 
neutralizing  the  solution  by  means  of  an  alkali  or  an  alkaline  carbonate. 
This  modification  of  the  albuminous  matter,  however,  by  the  action  of 
the  free  acid,  seems  to  be  an  essential  preliminary  in  the  digestive  act. 
If  it  be  allowed  to  go  on  farther,  the  influence  of  the  pepsine  produces 
a  more  important  change,  by  which  the  original  substance  is  converted 
into  albuminose.  In  this  form  it  is  no  longer  precipitable  by  neutral- 
ization of  the  fluid,  and  has  consequently  become  soluble  in  water.  It 
is  not  coagulable  by  boiling,  either  in  a  neutral,  acid,  or  alkaline  liquid ; 
and  it  is  not  precipitable  by  nitric  acid  or  by  potassium  ferrocyanide, 
although  it  may  still  be  thrown  down  by  alcohol  in  excess.  It  has  thus 
become  essentially  altered  in  its  chemical  relations. 

An  equally  or  even  more  important  change  has  also  taken  place  in 
its  physical  characters ;  that  is,  it  has  acquired  the  property  of  diffusi- 
bility.  The  other  liquid  albuminous  matters,  as  albumen,  caseine, 
mucosine,  and  the  like,  do  not  pass  through  parchment  paper  or  the  sub- 
stance of  an  animal  membrane ;  or  they  pass,  if  at  all,  very  slowly  and 
in  small  quantity.  Even  pepsine  is  retained  in  this  way  almost  com- 
pletely by  such  a  membrane.  Albuminose,  on  the  contrary,  diffuses 
itself  with  great  readiness  through  membranous  partitions,  and  can  be 

1  Lecons  sur  la  Physiologic  de  la  Digestion.     Paris,  1867,  tome  ii.  p.  19. 


THE    GASTRIC    JUICE    AND    STOMACH    DIGESTION.      161 

detected  by  its  ordinary  reactions  in  the  external  liquids.  It  is  thus 
suited  for  absorption  by  the  mucous  membrane  of  the  alimentary  canal. 

All  the  albuminous  matters,  without  exception,  which  are  susceptible 
of  digestion,  whether  of  animal  or  vegetable  origin,  are  finally  converted 
by  the  action  of  the  gastric  juice  into  albuminose.  They  therefore  lose 
their  original  distinctive  properties,  and,  when  fully  prepared  for  absorp- 
tion into  the  bloodvessels,  are  all  reduced  to  the  condition  of  a  single 
substance. 

A  further  very  remarkable  peculiarity  of  the  gastric  juice  is  its  apti- 
tude for  resisting  putrefaction.  While  other  animal  fluids,  as  the  saliva, 
the  bile,  the  pancreatic  juice,  mucus  and  blood,  enter  into  putrefaction 
with  great  readiness,  the  gastric  juice  remains  when  exposed  to  the  air 
at  ordinary  temperatures  for  many  months  without  developing  any 
putrescent  odor  or  losing  its  characteristic  properties.  It  becomes 
somewhat  darker  in  color,  and  after  a  time  deposits  a  brownish  sediment 
upon  the  bottom  of  the  vessel,  but  it  still  retains  its  acid  reaction  and 
its  power  of  digesting  albuminous  matters.  Gastric  juice  will  even 
arrest  putrefactive  changes  when  they  have  already  begun  in  organic 
substances ;  and  consequently  putrefaction  does  not  go  on  in  the  living 
stomach.  Dr.  Beaumont  preserved  some  fragments  of  meat  unaltered  for 
a  month  in  gastric  juice,  while  other  portions  of  the  same  substances, 
kept  in  saliva,  were  putrefied  in  ten  days.  Spallanzain  found  in  the 
stomach  of  a  viper  the  body  of  a  lizard  which  had  remained  there  for 
sixteen  days  without  undergoing  any  putrefactive  alteration ;  and  similar 
observations  have  been  made  by  other  physiologists. 

Mode  of  Secretion  of  the  Gastric  Juice. — As  a  rule,  the  gastric  juice 
is  not  a  constant  but  an  occasional  secretion,  being  poured  out  only  when 
food  is  taken  into  the  stomach.  Dr.  Beaumont  found  it  to  be  entirely 
absent  during  the  intervals  of  digestion,  the  stomach  containing  at  that 
time  no  acid  watery  fluid,  but  only  a  little  neutral  or  alkaline  mucus. 
He  was  able  to  obtain  a  sufficient  quantity  of  gastric  juice  for  examina- 
tion, by  gently  irritating  the  mucous  membrane  with  a  gum-elastic 
catheter,  or  the  end  of  a  glass  rod,  and  by  collecting  the  secretion  as  it 
ran  in  drops  from  the  fistula;  and  on  the  introduction  of  food  he  found 
'that  the  mucous  membrane  became  turgid  and  reddened,  a  clear  acid  fluid 
collected  everywhere  in  drops  underneath  the  layer  of  mucus  lining  the 
walls  of  the  stomach,  and  was  soon  poured  out  abundantly  into  its 
cavity.  Prof.  F.  G.  Smith,  in  his  subsequent  observations  upon  Alexis 
St.  Martin,  also  found  the  fluids  obtained  from  the  empty  stomach 
invariably  neutral  in  reaction  ;  while  during  digestion,  whatever  might 
be  the  nature  of  the  food,  they  were  always  acid.  Other  observers,  in 
experimenting  upon  the  dog,  have  found  more  or  less  acid  reaction 
always  present  at  the  surface  of  the  mucous  membrane.  According  to 
our  own  observations,  the  irritability  of  the  gastric  mucous  membrane, 
and  the  readiness  with  which  the  flow  of  gastric  juice  may  be  excited, 
varies  considerably  in  different  animals,  even  in  those  belonging  to  the 
same  species.  In  experimenting  with  gastric  fistulas  on  different  dogs, 


162  DIGESTION. 

for  example,  we  have  found  in  one  instance,  like  Dr.  Beaumont,  that  the 
gastric  j  uice  was  always  entirely  absent  in  the  intervals  of  digestion ; 
the  mucous  membrane  then  presenting  invariably  either  a  neutral  or 
slightly  alkaline  reaction.  In  this  animal,  which  was  a  perfectly  healthy 
one,  the  secretion  could  not  be  excited  by  any  artificial  means,  such  as 
glass  rods,  metallic  catheters,  and  the  like ;  but  only  by  the  natural 
stimulus  of  ingested  food.  Tough  and  indigestible  pieces  of  tendon, 
introduced  through  the  fistula,  were  expelled  again  in  a  few  minutes,  one 
after  the  other,  without  exciting  the  flow  of  a  single  drop  of  acid  fluid ; 
while  pieces  of  fresh  meat,  introduced  in  the  same  way,  produced  at 
once  an  abundant  supply.  Jn  other  instances,  on  the  contrary,  the 
introduction  of  metallic  catheters  or  glass  rods  into  the  empty  stomach 
has  produced  a  scanty  flow  of  gastric  juice  ;  and  in  experimenting  upon 
dogs  that  have  been  kept  without  food  during  various  periods  of  time 
and  then  killed  by  section  of  the  medulla  oblongata,  we  have  usually, 
though  not  always,  found  the  gastric  mucous  membrane  to  present  a 
distinctly  acid  reaction,  even  after  an  abstinence  of  six,  seven,  or  eight 
days.  There  is  at  no  time,  however,  under  these  circumstances,  any 
considerable  amount  of  fluid  present  in  the  stomach  ;  but  only  sufficient 
to  moisten  the  gastric  mucous  membrane,  and  give  it  an  acid  reaction. 

The  gastric  juice  which  is  obtained  by  irritating  the  stomach  with  a 
metallic  catheter  is  clear,  perfectly  colorless,  and  acid  in  reaction.  A 
sufficient  quantity  of  it  cannot  be  obtained  by  this  method  for  any 
extended  experiments;  and  for  that  purpose,  the  animal  should  be  fed, 
after  a  fast  of  twenty-four  hours,  with  fresh  lean  meat,  a  little  hardened 
by  short  boiling,  in  order  to  coagulate  the  fluids  of  the  muscular  tissue, 
and  prevent  their  mixing  with  the  gastric  secretion.  No  effect  is  usually 
apparent  within  the  first  five  minutes  after  the  introduction  of  the  food. 
At  the  end  of  that  time  the  gastric  juice  begins  to  flow  ;  at  first  slowly, 
and  in  drops.  It  is  at  first  perfectly  colorless,  but  soon  acquires  a 
slight  amber  tinge.  It  then  begins  to  flow  more  freely,  usually  in  drops, 
but  often  running  for  a  few  seconds  in  a  continuous  stream.  In  this 
way,  from  60  to  75  cubic  centimetres  may  be  collected  in  the  course  of 
fifteen  minutes.  Afterward  it  becomes  somewhat  turbid  with  the  debris 
of  the  food,  which  has  begun  to  be  disintegrated ;  but  from  this  it  may 
be  readity  separated  by  filtration.  After  three  hours,  it  continues  to 
run  freely,  but  has  become  very  much  thickened,  and  even  grumous  in 
consistency,  from  the  abundant  admixture  of  alimentary  debris.  In  six 
hours  after  the  commencement  of  digestion  it  runs  less  freely,  and  in 
eight  hours  has  become  very  scanty,  though  it  continues  to  preserve  the 
same  physical  appearances  as  before.  It  ceases  to  flow  altogether  in 
from  nine  to  twelve  hours,  according  to  the  quantity  of  food  taken. 
For  purposes  of  examination,  the  fluid  drawn  during  the  first  fifteen 
minutes  after  feeding  should  be  collected,  and  at  once  separated  by 
filtration  from  accidental  impurities.  Obtained  in  this  way  it  repre- 
sents, as  closely  as  possible,  the  normal  constitution  of  the  gastric  juice 
as  secreted  by  the  stomach  during  the  digestive  process. 


THE    GASTRIC    JUICE    AND    STOMACH    DIGESTION.      163 

Both  the  essential  constituents  of  the  gastric  juice,  namely,  the  pep- 
sine  and  the  free  acid,  are  produced  by  the  glandular  mucous  membrane 
of  the  stomach.  It  would  appear,  however,  that  the  mode  of  their 
production  is  somewhat  different.  Pepsine  is  an  albuminoid  substance 
formed  by  the  nutritive  process  in  the  glands  themselves.  It  probably 
accumulates  in  the  intervals  of  digestion,  and  may  therefore  be  extracted 
from  the  substance  of  the  mucous  membrane  in  the  manner  already  de- 
scribed. On  the  other  hand,  the  free  acid  appears  in  quantity  only  at 
the  time  of  digestion,  and  is  poured  out  with  the  watery  constituents 
of  the  secretion.  There  is  evidence,  however,  that  the  acid  is  not  imme- 
diately formed  by  the  glandular  cells,  but  is  produced  by  a  subsequent, 
though  very  rapid,  change  after  the  fluid  has  been  secreted.  The  acid 
reaction  of  the  gastric  fluids  is  never  strongly  pronounced  in  the  deeper 
and  middle  parts  of  the  mucous  membrane,  but  only  upon  its  free  sur- 
face. This  was  shown  by  Bernard,1  who  injected  into  the  jugular  vein 
of  a  rabbit  two  successive  solutions,  one  of  iron  lactate,  the  other  of 
potassium  ferrocyanide.  These  two  salts  would  remain  unaltered  in 
neutral  or  alkaline  fluids,  but  in  the  presence  of  a  free  acid  would  unite 
to  form  Prussian  blue  (iron  ferrocyanide).  On  killing  the  animal  three- 
quarters  of  an  hour  afterward,  no  blue  coloration  was  found  anywhere 
excepting  in  the  stomach ;  and  in  this  organ  it  was  confined  to  the  free 
surface  of  the  mucous  membrane,  not  being  perceptible  in  the  substance 
of  the  glands.  As  the  two  salts  must  have  both  exuded  from  the  blood- 
vessels of  the  mucous  membrane,  it  is  evident  that  it  was  only  at  or 
near  its  upper  surface  that  they  met  with  a  sufficient  quantity  of  free 
acid  to  cause  their  combination.  According  to  Dr.  Lauder  Brunton,2 
moreover,  a  horizontal  section  through  the  lower  part  of  the  gastric 
glands  of  the  pigeon,  if  tested  by  litmus  paper,  will  be  found  to  have  a 
neutral  or  extremely  weak  acid  reaction,  while  the  inner  surface  of  the 
stomach  presents  a  strongly  marked  acidity.  At  the  same  time,  the 
deeper  parts  of  the  mucous  membrane  contain  pepsine  in  sufficient 
quantity  to  form  a  digestive  fluid,  if  extracted  and  acidulated  in  the 
usual  way.  Finally,  the  free  acid  continues  to  be  formed  during  a  certain 
time  after  death;  for  it  has  been  found  that  if  the  fresh  gastric  mucous 
membrane  of  a  rabbit  or  a  pig  be  cut  in  small  pieces  and  washed  with 
distilled  water  until  all  trace  of  acidity  is  removed,  it  will  again  acquire 
an  acid  reaction  after  being  left  to  itself  for  some  hours.  The  materials 
of  the  free  acid  of  the  gastric  juice  are  therefore  furnished  during  life 
by  the  alkaline  fluids  of  the  circulating  blood ;  but  the  acid  itself  origi- 
nates subsequently  by  some  change  taking  place  in  the  products  of 
exudation. 

Self-digestion  of  the  Stomach  after  Death. — Notwithstanding  that  the 
gastric  juice  has  the  power,  at  the  temperature  of  the  living  body,  of 
digesting  all  soft  tissues  composed  of  albuminous  matter,  yet  owing  to 

1  Liquides  de  TOrganisme.     Paris,  1859,  torn.  ii.  p.  375. 

2  Handbook  for  the  Physiological  Laboratory.     Philadelphia,  1873,  p.  491. 


164  DIGESTION. 

the  mode  of  its  production  it  does  not  attack  the  walls  of  the  stomach 
itself.  As  the  pepsine  alone  accumulates  in  any  considerable  quantity 
in  the  gastric  follicles,  while  the  acid  ingredient  appears  abundantly  only 
at  the  time  of  digestion,  no  dissolving  action  can  be  manifested  while 
the  organ  is  empty  of  food.  It  has  already  been  seen,  furthermore,  that 
during  the  active  secretion  of  the  gastric  juice,  its  free  acid  is  formed  by 
some  modification  in  the  exuded  fluids,  so  that  it  is  distinctly  perceptible 
only  in  the  fluids  on  the  free  surface  and  in  the  cavity  of  the  stomach. 
In  the  substance  of  the  mucous  membrane,  the  acid  fluid,  even  if  ab- 
sorbed, could  not  exert  its  solvent  action,  since  it  must  be  at  once  neu- 
tralized by  the  alkaline  plasma  of  the  circulating  blood. 

Even  after  death  the  gastric  mucous  membrane  usually  remains  nearly 
intact,  because,  as  a  general  rule,  digestion  has  been  at  least  partially 
suspended  during  the  last  hours  of  life,  and  the  stomach  accordingly 
contains  little  or  no  gastric  juice.  Still  it  is  rare,  in  the  human  subject, 
to  make  an  examination  of  the  body  twenty-four  or  thirty-six  hours 
after  death,  without  finding  the  mucous  membrane  in  the  great  pouch 
of  the  stomach  more  or  less  softened  and  altered  in  its  appearance  from 
this  cause.  Sometimes,  when  death  takes  place  suddenly,  by  violence 
or  accident,  in  a  healthy  person,  soon  after  the  ingestion  of  food, 
and  when  the  body  has  been  protected  against  rapid  cooling,  the  accu- 
mulated gastric  juice  acts  powerfully  upon  the  walls  of  the  stomach  as 
well  as  upon  the  food  which  it  contains.  Owing  to  the  stoppage  of 
the  circulation,  the  local  alkalescence  of  the  fluids  is  no  longer  main- 
tained, and  the  increasing  quantity  of  free  acid  at  last  preponderates 
over  the  blood  remaining  in  the  capillary  vessels.  The  mucous  mem- 
brane becomes  imbibed  with  an  active  digestive  fluid,  and  in  the  course 
of  ten  or  twelve  hours  may  be  thoroughly  softened  and  disintegrated, 
exposing  the  submucous  layer  of  connective  tissue;  and  occasionally  all 
the  coats  of  the  organ  have  been  found  destroyed,  with  a  perforation 
leading  into  the  peritoneal  cavity.  These  changes  show  that,  after  death, 
the  gastric  juice,  if  present  in  sufficient  quantity,  may  dissolve  the  coats 
of  the  stomach  without  difficulty ;  while  during  life,  the  changes  of  nutri- 
tion going  on  in  the  tissues  protect  them  from  its  influence,  and  effectu- 
ally preserve  their  integrity. 

Daily  Quantity  of  the  Gastric  Juice. — The  quantity  of  gastric  juice, 
secreted  during  a  given  time,  like  that  of  the  saliva,  varies  very  much 
according  to  the  condition  of  the  secreting  organ.  In  many  instances, 
as  we  have  already  seen,  it  is  entirely  absent  during  the  intervals  of 
digestion,  and  is  poured  out  in  abundance  under  the  stimulus  of  recently 
introduced  food.  An  exact  estimate  of  the  normal  daily  quantity  is 
difficult  for  several  reasons.  First,  it  is  evident  that  if  the  secretion  be 
excited  by  artificial  irritation  of  the  gastric  mucous  membrane  with  in- 
soluble glass  or  metallic  substances,  its  quantity  is  not  so  abundant  as 
when  produced  by  the  stimulus  of  natural  food.  Secondly,  if  excited 
by  the  introduction  of  food,  a  part  of  it  is  almost  necessarily  absorbed 
by  the  alimentary  material,  and  consequently  cannot  be  collected  for 


THE    GASTRIC    JUICE    AND    STOMACH    DIGESTION.      165 

measurement ;  and  thirdly,  if  we  measure  the  quantity  obtainable  by 
either  of  these  means  during  a  short  period,  it  does  not  follow  that  it 
would  continue  to  be  secreted  at  the  same  rate  during  the  remainder  of 
the  twenty-four  hours,  because  the  rapidity  of  its  production  is  so  much 
influenced  by  the  condition  of  the  digestive  process.  Neither  can  we 
draw  from  an  animal  with  a  stomach  fistula  all  the  gastric  juice  which 
will  flow  during  twenty-four  hours,  and  consider  that  as  representing 
the  normal  daily  quantity ;  because  we  should  then  be  drawing  away  a 
quantity  of  secreted  fluid  which  in  the  natural  condition  is  retained  in 
the  alimentary  canal  and  reabsorbed  by  the  bloodvessels.  Its  supply 
would  therefore  be  necessarily  diminished  by  the  continuous  loss  of 
fluids  from  the  system.  Notwithstanding  these  difficulties,  however,  a 
sufficient  number  of  facts  have  been  observed  to  show  that  the  usual 
daily  secretion  of  the  gastric  juice  is  undoubtedly  far  more  abundant 
than  that  of  the  other  digestive  fluids.  Dr.  Beaumont  was  able  to  ob- 
tain from  the  stomach  of  St.  Martin,  simply  by  the  introduction  of  a 
gum-elastic  catheter,  44  grammes  of  gastric  juice  in  the  course  of  fifteen 
minutes.  We  have  often  collected  from  a  medium-sized  dog,  under  the 
stimulus  of  commencing  digestion,  from  60  to  75  grammes  in  the  same 
time.  Bidder  and  Schmidt  found  that,  in  a  dog  weighing  about  15.5 
kilogrammes,  they  were  able  to  obtain,  by  separate  experiments,  con- 
suming in  all  twelve  hours,  793  grammes  of  gastric  juice.  If  these 
separate  experiments,  therefore,  as  is  probable,  indicate  the  average 
rate  of  its  production  at  diflerents  parts  of  the  day,  the  entire  quantity 
for  twenty-four  hours,  in  an  animal  of  that  size,  would  be  1586  grammes ; 
or  about  100  grammes  for  every  kilogramme  in  weight  of  the  body 
of  the  animal.  By  applying  this  calculation  to  a  man  of  ordinary  size 
the  authors  estimate  the  average  daily  quantity  of  gastric  juice  in 
the  human  subject  as  about  6500  grammes.  It  is,  however,  quite 
unsafe  to  estimate  the  quantity  of  this  secretion  as  necessarily  in  pro- 
portion to  the  weight  of  the  body.  It  is  probably  more  strictly  in 
proportion  to  the  quantity  of  food  which  it  is  its  function  to  digest ;  and 
the  dog  habitually  consumes  a  much  larger  quantity  of  animal  food,  in 
proportion  to  his  size,  than  a  man.  Schmidt,  in  the  series  of  observa- 
tions already  quoted,1  performed  upon  a  woman  with  accidental  gastric 
fistula,  whose  weight  was  only  53  kilogrammes,  obtained,  as  the  mean 
result  of  several  observations,  580  grammes  of  gastric  juice  from  the 
fistula  in  the  course  of  an  hour.  In  this  case,  however,  the  secretion 
was  much  poorer  in  its  characteristic  ingredients  than  that  usually 
obtained  from  the  dog,  and  was  also  much  inferior  in  digestive  power. 

Another  method  which  has  been  adopted  for  estimating  the  quantity 
of  the  gastric  juice  is  to  ascertain  the  amount  capable  of  digesting  the 
quantity  of  albuminous  food  required  per  day.  According  to  the  experi- 
ments of  Lehmann,2  one  gramme  of  coagulated  albumen,  calculated  as 

1  Annalen  der  Chemie  und  Pharmacie,  1854,  Band  xcii.  p.  42. 

2  Physiological  Chemistry.     London,  1853,  vol.  ii.  p.  53. 


166  DIGESTION. 

dry,  requires  for  its  solution  20  grammes  of  gastric  juice.  As  the  aver- 
age daily  consumption  of  albuminous  matter  in  man  is  130  grammes, 
this  would  accordingly  require  in  him  the  secretion  of  2600  grammes 
of  gastric  juice  per  day.  Our  own  observations  on  the  digestibility  of 
fresh  meat  make  the  daily  requirement  still  higher.  A  weighed  quantity 
of  fresh  lean  meat,  containing  18  per  cent,  of  water  and  22  per  cent,  of 
solid  ingredients,  was  cut  into  small  pieces,  and  digested  for  ten  hours, 
with  frequent  agitation,  in  a  measured  quantity  of  fresh  gastric  juice  at 
the  temperature  of  38°  (100°  F.).  At  the  end  of  that  time,  the  liquefied 
portions  were  filtered  away,  the  residue  evaporated  to  dryness,  and  the 
quantity  of  fresh  meat  remaining  undissolved  thus  calculated  from  the 
percentage  of  its  solid  ingredients.  In  this  way  it  was  found  that  one 
gramme  of  meat  had  been  liquefied  by  13.5  grammes  of  the  digestive 
fluid;  and  accordingly  the  453  grammes  of  meat  consumed  by  a  man 
in  twenty-four  hours  would  require  for  complete  solution  a  little  over 
6000  grammes  of  gastric  juice.  This  agrees  very  nearly  with  the  esti- 
mate of  Bidder  and  Schmidt  given  above.  If  the  gastric  juice  were  the 
only  digestive  fluid  which  acts  on  the  food,  we  could  rely  fully  011  the 
foregoing  estimate.  But  below  the  stomach  other  secretions  also  take 
part  in  the  digestive  process ;  and  it  is  possible  that  some  of  them, 
especially  the  pancreatic  juice,  have  also  a  certain  amount  of  action 
upon  albuminous  matters,  and  may  facilitate  considerably  their  solu- 
tion in  the  intestine.  For  the  partial  solution  of  meat,  the  disintegra- 
tion of  its  fibres,  and  its  reduction  to  a  soft,  grumous,  liquid  or  semi- 
liquid  consistency,  Dr.  Beaumont  found  a  much  smaller  quantity  of 
gastric  juice  to  be  sufficient.  In  one  experiment  1  gramme  of  cooked 
meat  was  completely  disintegrated  in  this  way  by  2.5  grammes,  and  in 
another  by  1.83  grammes  of  gastric  juice.  Its  entire  solution  would  of 
course  have  required  a  larger  quantity. 

These  data  are  accordingly  insufficient  for  determining  the  precise 
quantity  of  the  secretion  required  for  the  digestive  process.  But  if  we 
allow  sufficient  weight  to  all  the  observations  on  this  subject,  it  is  evi- 
dent that  the  gastric  juice  is  very  abundant ;  and  it  would  not  be  an 
extravagant  calculation  to  estimate  its  quantity  as  at  least  3000  grammes 
per  clay. 

Physiological  Action  of  the  Gastric  Juice. — From  the  properties  of 
the  gastric  juice  already  ascertained,  it  is  seen  to  have  an  energetic 
action  upon  the  albuminous  ingredients  of  the  food.  As  but  few  of  the 
alimentary  substances,  however,  habitually  taken  by  either  man  or 
animals,  consist  solely  of  albuminous  matter,  the  changes  which  they 
actully  undergo  in  the  stomach  become  a  subject  for  further  investi- 
gation. 

The  first  effect  of  the  introduction  of  food  into  the  stomach,  according 
to  all  observers,  is  an  increased  vascularity  of  its  mucous  membrane,  a 
slight  elevation  of  its  temperature,  and  the  immediate  exudation,  in 
more  or  less  abundant  quantity,  of  its  acid  secretion.  At  the  same 
time  the  stimulus  of  the  ingested  food  excites  the  peristaltic  movement 


THE    GASTRIC    JUICE    AND    STOMACH    DIGESTION.      167 

of  the  stomach,  which  is  accomplished  by  the  alternate  contraction  and 
relaxation  of  the  longitudinal  and  circular  fibres  of  its  muscular  coat. 
The  motion  is  minutely  described  by  Dr.  Beaumont,  who  examined  it, 
both  by  watching  the  movements  of  the  food  through  the  gastric  fistula, 
and  also  by  introducing  into  the  stomach  the  bulb  and  stem  of  a  ther- 
mometer. According  to  his  observations,  when  the  food  first  passes 
into  the  stomach,  and  the  secretion  of  the  gastric  juice  commences,  the 
muscular  coat,  which  was  before  quiescent,  is  excited  and  begins  to 
contract  actively.  The  contraction  takes  place  in  such  a  manner  that 
the  food,  after  entering  the  cardiac  orifice  of  the  stomach,  is  first  car- 
ried to  the  left  into  the  great  pouch  of  the  organ,  thence  downward  and 
along  the  great  curvature  to  the  pyloric  portion.  At  a  short  distance 
from  the  pylorus,  Dr.  B.  often  found  a  circular  constriction  of  the  gastric 
parietes,  by  which  the  bulb  of  the  thermometer  was  gently  grasped  and 
drawn  toward  the  pylorus,  at  the  same  time  giving  a  twisting  motion 
to  the  stem  of  the  instrument,  by  which  it  was  rotated  in  his  fingers. 
In  a  moment  or  two,  this  constriction  was  relaxed,  and  the  bulb  of 
the  thermometer  again  released  and  carried,  together  with  the  food, 
along  the  small  curvature  of  the  organ  to  its  cardiac  extremity.  This 
circuit  was  repeated  so  long  as  any  food  remained  in  the  stomach ; 
but,  as  the  liquefied  portions  were  successively  removed  toward  the  end 
of  digestion,  it  became  less  active,  and  at  last  ceased  altogether  when 
the  stomach  had  become  completely  empty,  and  the  organ  returned  to 
its  ordinary  quiescent  condition. 

It  is  easy  to  observe  the  muscular  action  of  the  stomach  during  diges- 
tion in  the  dog,  by  the  assistance  of  a  gastric  fistula,  artificially  estab- 
lished. If  a  metallic  catheter  be  introduced  through  the  fistula  when 
the  stomach  is  empty,  it  must  usually  be  held  carefully  in  place,  or  it 
will  fall  out  by  its  own  weight.  But  immediately  upon  the  introduction 
of  food,  it  can  be  felt  that  the  catheter  is  grasped  and  retained  with 
some  force,  by  the  contraction  of  the  muscular  coat.  A  twisting  or 
rotatory  motion  of  its  extremity  may  also  be  frequently  observed,  similar 
to  that  described  by  Dr.  Beaumont.  This  peristaltic  action  of  the 
stomach,  however,  is  a  gentle  one,  and  not  at  all  active  or  violent  in 
character.  We  have  never  seen,  in  opening  the  abdomen,  any  such 
energetic  or  extensive  contractions  of  the  stomach,  even  when  full  of 
food,  as  may  be  easily  excited  in  the  small  intestine  by  the  mere  con- 
tact of  the  atmosphere,  or  by  pinching  with  the  blades  of  a  forceps. 
This  difference  in  activity  between  the  peristaltic  movement  of  the 
stomach  and  that  of  the  intestine  corresponds  to  the  difference  in  its 
object  and  result.  In  the  intestine  the  peristaltic  action  carries  the 
semifluid  contents  of  the  alimentary  canal  continuously  from  above 
downward ;  in  the  stomach  it  produces  a  kneading  effect  upon  the  mas- 
ticated food,  and  mixes  it  intimately  with  the  gastric  juice.  This  action 
of  the  stomach,  accordingly,  though  quite  gentle,  is  sufficient  to  pro- 
duce a  constant  churning  movement  of  the  food,  by  which  it  is  carried 
back  and  forward  to  every  part  of  the  stomach,  and  incorporated  with 


168  DIGESTION. 

the  gastric  juice,  which  is  at  the  same  time  poured  out  by  the  mucous 
membrane ;  so  that  the  digestive  fluid  is  made  to  penetrate  equally 
every  part  of  the  alimentary  mass,  and  the  digestion  of  all  its  albu- 
minous ingredients  goes  on  simultaneously.  This  movement  of  the 
stomach  is  one  which  cannot  be  completely  imitated  in  experiments  on 
artificial  digestion  with  gastric  juice  in  test-tubes  ;  and  consequently  the 
process,  under  these  circumstances,  is  never  so  rapid  as  when  it  takes 
place  in  the  interior  of  the  stomach. 

The  result  of  the  action  of  the  gastric  juice,  thus  incorporated  in  the 
stomach  with  the  alimentary  matters,  is  that  they  are  disintegrated  by 
the  softening  and  liquefaction  of  their  albuminous  ingredients.  Bread 
consists  mainly  of  hydrated  starch,  entangled  and  incorporated  with 
the  semi-solid  gluten.  By  digestion  in  the  stomach,  the  gluten  is  di- 
gested and  liquefied  by  its  conversion  into  albuminose,  the  starch  being 
thus  set  free,  and  the  whole  reduced  to  a  diffluent  condition.  The  same 
effect  can  be  seen  when  bread  is  subjected  to  the  action  of  gastric  juice 
in  a  test-tube,  the  gluten  passing  into  the  condition  of  liquid  albuminose, 
while  a  deposit  of  unaltered  starch  settles  at  the  bottom.  Cheese,  con- 
sisting of  coagulated  caseine  and  milk  globules,  undergoes  an  analogous 
change.  Its  caseine  is  liquefied  by  digestion,  while  its  liberated  fat 
globules  rise  to  the  upper  part  of  the  fluid,  forming  a  creamy-looking 
layer  upon  its  surface. 

Adipose  tissue  is  very  readily  disintegrated  by  the  liquefaction  of  its 
connective  tissue,  which  is  formed  of  albuminous  matter,  while  the  fatty 
matter  escapes  in  the  form  of  oil  drops,  floating  upon  the  surface  of 
the  other  contents  of  the  stomach.  Dr.  Beaumont  always  found  free 
fat,  in  the  form  of  oil  globules,  thus  extricated  from  the  fatty  tissues 
soon  after  they  had  been  introduced  into  the  stomach  with  the  food ; 
and  it  is  easy  to  verify  this  observation,  either  by  artificial  digestion  of 
adipose  tissue  in  gastric  juice,  or  by  opening  the  stomach  of  an  animal 
soon  after  the  administration  of  food  containing  fat. 

The  digestion  of  muscular  flesh  is  also  at  first  a  process  of  disintegra- 
tion. The  connective  tissue  intervening  between  the  fibrous  bundles 
yields  to  the  action  of  the  gastric  juice,  and  the  fibres  themselves  thus 
become  separated  from  each  other,  and  form  a  gruelly  mixture  of  minute 
and  almost  microscopic  threads  and  fragments.  The  substance  of  the 
muscular  fibres  then  also  begins  to  become  altered — they  break  up  into 
shorter  fragments,  and,  when  examined  by  the  microscope,  are  found  to 
have  lost  the  distinctness  of  their  transverse  striations.  If  the  food 
have  been  thoroughly  masticated  before  being  taken  into  the  stomach, 
this  change  goes  on  rapidly  and  uniformly  throughout  the  mass.  If, 
as  in  the  dog,  the  meat  be  swallowed  without  much  mastication,  or  if 
portions  be  suspended  in  a  test  tube  containing  gastric  juice,  the  action 
progresses  regularly  from  without  inward.  The  external  parts  of  the 
muscular  tissue  are  first  softened  and  decolorized,  and  become  covered 
with  a  grayish  layer,  of  grumous  consistency,  containing  the  isolated 
and  partially  destroj^ed  fragments  of  muscular  fibre.  As  these  por- 


THE    GASTKIC    JUICE    AND    STOMACH    DIGESTION.      169 

tions  are  removed  by  the  peristaltic  movements  of  the  stomach,  the 
digestive  action  extends  to  the  parts  underneath,  and  so  on  until  the 
whole  has  been  reduced  to  a  uniform  mixture,  of  a  thickish  gruelly  con- 
sistency, in  which  the  distinctive  elements  of  the  tissue  are  no  longer 
recognizable  by  the  eye,  and  in  which  the  remnants  of  the  muscular 
fibres  can  only  be  detected  by  the  microscope.  It,  is  this  apparently 
homogeneous,  pultaceousor  gruelly  semi-fluid  material  that  was  formerly 
designated  by  the  name  of  "Chyme."  It  is  evidently  nothing  more 
than  a  mixture  of  the  disintegrated  remnants  of  the  digested  tissues, 
portions  of  which  have  been  completely  liquefied  while  others  are  not 
yet  reduced  to  a  state  of  solution. 

When  milk  is  taken  into  the  stomach  in  a  fresh  condition,  its  caseine 
is  at  first  coagulated,  afterward  dissolved.  The  preliminary  coagula- 
tion, which  is  due  to  the  action  of  the  pepsine  and  dilute  acid,  takes 
place  very  rapidly.  Dr.  Beaumont  found  that  milk  could  be  withdrawn 
in  a  coagulated  condition  in  fifteen  minutes  after  its  introduction  into 
the  stomach ;  and  that  if  the  mixture  were  kept  at  the  temperature  of 
38°  (100°  F.),  the  coagula  were  again  liquefied  in  the  course  of  eight 
hours.  The  coagulation  of  milk,  thus  produced  by  its  first  contact 
with  the  gastric  juice  is,  however,  no  obstacle  to  its  subsequent  diges- 
tion. The  caseine  does  not  form  a  solid  uniform  clot,  but  is  thrown 
down  in  the  form  of  minute  flocculi,  of  soft  consistency,  which  are 
constantly  bathed  by  the  digestive  fluids,  and  at  the  temperature  of  the 
living  body  undergo  readily  the  conversion  into  albuminose.  As  it  is 
this  chemical  change  which  constitutes  the  real  process  of  digestion, 
the  preliminary  coagulation  of  the  caseine  does  not  interfere  with  its 
accomplishment.  Milk,  furthermore,  as  used  by  adults,  is  to  a  large 
extent  incorporated,  in  the  coagulated  form,  with  other  solid  or  semi- 
solid  articles  of  food. 

The  substance  of  vegetable  tissues,  as  a  rule,  is  digested  in  a  similar 
manner  to  that  described  above.  The  albuminous  matters  are  dissolved 
out,  leaving  the  starchy  or  oleaginous  ingredients  in  a  free  condition, 
but  chemically  unchanged.  As  these  tissues  generally  contain  a  much 
smaller  proportion  of  albuminous  matter  than  most  kinds  of  animal 
food,  their  disintegration  is  the  main  result  of  the  changes  which  they 
undergo  in  the  stomach. 

The  gastric  juice,  together  with  the  disintegrated  debris  of  the  food, 
after  commencing  its  action  in  the  stomach,  passes  into  the  upper  part 
of  the  intestine.  This  can  be  seen  readily  in  the  dog  by  killing  the 
animal  after  feeding,  and  examining  the  contents  of  the  intestine.  We 
have  observed  the  same  thing  by  establishing,  in  the  dog,  an  artificial 
duodenal  fistula,  by  means  of  an  operation  similar  to  that  for  producing 
a  permanent  fistula  of  the  stomach.  A  silver  tube,  armed  at  each 
end  with  narrow  projecting  flanges,  is  introduced  into  the  lower  part 
of  the  duodenum,  and  the  wound  allowed  to  heal,  after  which  the 
contents  of  the  intestine  may  be  withdrawn  at  will,  and  subjected  to 
examination  at  different  periods  during  digestion. 
12 


170  DIGESTION. 

By  examining  in  this  wa}T,  from  time  to  time,  the  intestinal  fluids,  it 
becomes  manifest  that  the  action  of  the  gastric  juice,  in  the  digestion 
of  albuminous  substances,  is  not  confined  to  the  stomach,  but  con- 
tinues after  the  food  has  passed  into  the  intestine.  About  half  an 
hour  after  the  ingestion  of  a  meal,  the  gastric  juice  begins  to  pass  into 
the  duodenum,  where  it  may  be  recognized  by  its  strongly-marked 
acidity,  and  by  its  peculiar  action,  already  described,  in  interfering  with 
Trommer's  test  for  glucose.  It  has  accordingly  already  dissolved  some 
of  the  ingredients  of  the  food,  and  contains  a  certain  quantity  of 
albuminose  in  solution.  It  soon  afterward,  as  it  continues  to  pass 
into  the  duodenum,  becomes  mingled  with  the  debris  of  muscular 
fibres,  fat  vesicles,  and  oil  drops  ;  substances  which  are  easily  recog- 
nizable under  the  microscope,  and  which  produce  a  grayish  turbidity 
in  the  fluid  withdrawn  from  the  fistula.  By  the  continuous  passage, 
in  this  way,  of  the  alimentary  material,  mixed  with  gastric  juice, 
through  the  pylorus  into  the  intestine,  the  stomach  becomes  gradually 
cleared  of  its  contents.  According  to  Dr.  Beaumont  the  time  required 
for  the  entire  disappearance  of  food  from  the  stomach  varies  from  one 
hour  to  five  hours  and  a  half,  according  to  the  quality  and  quantity  of 
the  material  used.  In  the  experiments  of  Prof.  Francis  G.  Smith  upon 
the  same  subject,  food  seldom  remained  in  the  stomach  more  than  two 
hours  after  its  introduction.  Three  hours  is  probably  sufficient,  as  a 
rule,  for  the  completion  of  stomach  digestion,  in  the  human  subject, 
when  the  food  is  in  moderate  quantity  and  has  been  properly  prepared 
by  cooking  and  mastication.  In  the  carnivorous  animals  generally, 
where  the  food  is  swallowed  in  fragments  of  some  size,  the  process  is 
longer;  and  in  the  dog  a  moderate  meal  of  fresh  uncooked  meat 
requires  from  nine  to  twelve  hours  for  its  complete  liquefaction  and 
disappearance  from  the  stomach. 

The  gastric  juice,  after  having  accomplished  its  work  in  the  digestion 
of  the  food,  is  reabsorbed  from  the  alimentary  canal  and  taken  up  by 
the  bloodvessels.  It  thus  forms  a  vehicle  for  the  dissolved  nutritious 
materials,  and  again  enters  the  circulation  with  the  alimentary  substances 
which  it  holds  in  solution.  It  is  in  this  way  that  the  system  is  enabled 
to  furnish  so  abundant  a  secretion  without  being  exhausted  by  drainage. 
The  reabsorption  of  the  gastric  juice  goes  on  simultaneously  with  its 
secretion  during  the  continuance  of  the  digestive  act;  and  the  fluids 
which  the  blood  loses  by  one  process  are  incessantly  restored  to  it  by 
the  other.  An  abundant  supply,  therefore,  of  the  secretion  may  be 
poured  out  during  the  digestion  of  a  meal,  at  an  expense  to  the 
blood,  at  any  one  time,  of  only  a  small  quantity  of  fluid.  The  simplest 
investigation  shows  that  the  gastric  juice  does  not  accumulate  in  the 
stomach  to  any  considerable  amount  during  digestion ;  but  that  it  is 
gradually  secreted  so  long  as  any  food  remains  undissolved ;  each  por- 
tion, as  it  is  digested,  being  disposed  of  by  reabsorption,  together 
with  its  solvent  fluid.  There  is  accordingly,  during  digestion,  a  con- 
tinuous circulation  of  the  digestive  fluids  from  the  bloodvessels  to 


PANCREATIC    JUICE    AND    ITS    ACTION    UPON    FOOD.      171 

the  alimentary  canal,  and  from  the  alimentary  canal  back  again  to  the 
bloodvessels. 

That  this  circulation  really  takes  place  is  shown  by  the  following 
facts :  First,  if  a  dog  be  killed  some  hours  after  feeding,  there  is  never 
more  than  a  very  small  quantity  of  fluid  found  in  the  stomach,  just  suf- 
ficient to  smear  over  and  penetrate  the  half  digested  pieces  of  meat ;  and 
secondly,  in  the  living  animal,  gastric  juice,  drawn  from  the  fistula  five 
or  six  hours  after  digestion  has  been  going  on,  contains  little  or  no  more 
albuminous  matter  in  solution  than  that  extracted  fifteen  to  thiity 
minutes  after  the  introduction  of  food.  It  has  evidently  been  freshly 
secreted  ;  and,  in  order  to  obtain  gastric  juice  saturated  with  alimentary 
matter,  it  must  be  artificially  digested  with  food  in  test-tubes,  where 
this  constant  absorption  and  renovation  cannot  take  place. 

The  secretion  of  the  gastric  juice  is  much  influenced  by  nervous  condi- 
tions. It  was  noticed  by  Dr.  Beaumont,  in  his  experiments  upon  St. 
Martin,  that  irritation  of  the  temper,  and  other  moral  causes,  would  fre- 
quently diminish  or  altogether  suspend  the  supply  of  the  gastric  fluids. 
Any  febrile  action  in  the  system,  or  any  unusual  fatigue,  was  liable  to 
exert  a  similar  effect.  Every  one  is  aware  how  readily  any  mental  dis- 
turbance, such  as  anxiety,  anger,  or  vexation,  will  take  away  the  appe- 
tite and  interfere  with  digestion. '  Any  nervous  impression  of  this  kind, 
occurring  at  the  commencement  of  digestion,  seems  moreover  to  pro- 
duce some  change  which  has  a  lasting  effect  upon  the  process ;  for  it  is 
often  noticed  that  when  any  anno3rance,  hurry,  or  anxiety  occurs  soon 
after  the  food  has  been  taken,  though  it  may  last  only  for  a  few  moments, 
the  digestive  process  is  not  only  liable  to  be  suspended  for  the  time, 
but  to  be  permanently  disturbed  during  the  entire  day.  In  order  that 
digestion,  therefore,  may  go  on  properly  in  the  stomach,  food  must  be 
taken  only  when  the  appetite  demands  it ;  it  should  be  thoroughly 
masticated  at  the  outset ;  and,  finally,  both  mind  and  body,  particularly 
during  the  commencement  of  the  process,  should  be  free  from  any- 
unusual  or  disagreeable  excitement. 

The  Pancreatic  Juice  and  its  Action  upon  the  Food. 

The  pancreas,  which  is  a  lobulated  gland,  similar  in  its  general  struc- 
ture to  the  salivary  glands,  lies  across  the  upper  part  of  the  abdo- 
men in  such  a  manner  that  its  larger  or  right-hand  extremity  is  in 
contact  with  the  duodenum.  It  is  traversed  in  its  longitudinal  direction 
by  its  main  excretory  duct,  which  receives,  as  it  passes  from  left  to  right, 
the  lateral  branches  coming  from  the  glandular  lobules,  and  finally,  in 
the  human  subject,  opens  into  the  cavity  of  the  duodenum,  closely 
adjacent  to  the  situation  of  the  common  biliary  duct,  at  about  ten  centi- 
metres below  the  pyloric  orifice  of  the  stomach.  Its  secretion  thus 
enters  the  intestine,  and  mingles  with  the  substances  undergoing  diges- 
tion, almost  immediately  after  they  have  passed  from  the  stomach  into 
the  duodenum. 

The  arrangement  of  the  gland  and  its  duct  is  similar  to  the  above,  in 


172  DIGESTION. 

its  essential  particulars,  in  most  of  the  lower  animals.  In  the  dog  and 
cat,  there  are  two  ducts  opening  into  the  intestine,  one  of  them  in  juxta- 
position with  the  orifice  of  the  biliaiy  duct,  the  other  from  one  to  three 
centimetres  farther  down.  The  lower  of  these  ducts  is  usually,  though 

Fig.  46. 


PORTION  OF  HUMAN  PANCREAS  AND  DUODENUM.— a.  Cavity  of  duodenum,  b.  Orifice 
of  the  pancreatic  duct.   c.  Orifice  of  lower  pancreatic  duct.    (Bernard.) 

not  always,  the  larger  of  the  two,  and  they  generally  communicate 
with  each  other  by  a  transverse  branch,  in  the  substance  of  the  gland, 
before  opening  into  the  intestine.  Even  in  the  human  subject,  as  shown 
by  Bernard,  Kolliker,  and  Sappey,  there  is  often  a  smaller  accessory  duct 
opening  into  the  intestine,  sometimes  above  and  sometimes  below  the 
situation  of  the  principal  one.  The  most  marked  peculiarity  in  the 
arrangement  of  the  parts  is  seen  in  the  rabbit,  where  the  pancreatic  duct 
is  single,  but  opens  into  the  intestine  at  a  distance  of  from  30  to  40 
centimetres  below  the  orifice  of  the  biliary  duct. 

The  pancreatic  juice  has  been  obtained  in  many  instances  from  the 
living  animal  by  opening  the  abdomen  during  the  act  of  digestion,  and 
inserting  a  silver  canula  into  the  principal  pancreatic  duct,  immediately 
before  its  entrance  into  the  intestine.  The  canula  being  secured  in  its 
position  by  a  ligature  placed  round  the  duct,  the  parts  are  returned 
into  the  abdominal  cavity,  and  the  external  wound  closed  with  sutures, 
leaving  the  open  extremity  of  the  canula  projecting  between  its  edges. 
The  secretion  is  thus  diverted  from  the  intestine,  and  may  be  collected 
for  examination  as  it  flows  from  the  canula.  This  operation  has  been 
done  most  frequently  upon  the  dog,  but  also  upon  the  rabbit,  the  ox, 


PANCREATIC    JUICE    AND    ITS    ACTION    UPON    FOOD.      173 

the  sheep,  the  goat,  the  pig,  and  the  goose.  The  secretion  has  also  been 
obtained  from  the  horse,  by  opening  the  duodenum  and  inserting  the 
canula  into  the  natural  orifice  of  the  pancreatic  duct. 

Under  these  circumstances,  the  fistula  produced  is  only  a  temporary 
one;  since  the  ligature  soon  cuts  its  way  through  the  duct  by  ulcera- 
tion,  when  the  canula  falls  out  and  the  wound  closes  spontaneously, 
the  natural  communication  of  the  duct  with  the  intestine  being  at  the 
same  time  re-established.  Even  in  the  ox,  Colin  found  that  the  canula 
became  displaced  within  six  or  eight  days  after  the  operation ;  and  in 
the  dog,  according  to  Bernard,  the  same  thing  happens  at  the  end  of 
two  or  three  days.  Furthermore,  the  pancreas  being  very  sensitive  to 
external  irritation,  its  secretion  is  liable  to  become  altered  in  character 
during  the  inflammatory  process,  and  it  is  therefore  to  be  collected  for 
examination  only  within  the  first  twenty-four  hours  after  the  insertion 
of  the  canula. 

A  permanent  pancreatic  fistula  has  been  successfully  established  by 
Ludwig  and  Bernstein,  by  making  an  incision  in  the  side  of  the  pan- 
creatic duct  near  the  intestine,  introducing  into  the  orifice  thus  made  a 
leaden  wire  extending  a  short  distance  each  way,  toward  the  gland  and 
toward  the  duodenum,  and  provided  with  an  arm  projecting  at  right 
angles  from  its  middle,  which  is  allowed  to  protrude  from  the  external 
wound.  After  the  healing  of  the  parts,  the  fistula  is  thus  kept  perma- 
nently open  by  the  wire,  which  lies  somewhat  loosely  in  the  cavity  of  the 
duct  and  allows  the  secretion  to  escape  by  its  side.  The  objection  to 
the  plan  is  that,  as  the  secretion  passes  by  a  narrow  fistulous  passage, 
it  may  be  mingled  with  unnatural  secretions. 

Physical  Character  and  Composition  of  the  Pancreatic  Juice. The 

pancreatic  juice  obtained  from  the  dog  within  the  first  day  after  the 
introduction  of  the  canula,  and  while  digestion  is  going  on,  is  a  clear 
colorless  fluid,  with  a  distinctly  alkaline  reaction.  It  has  a  well  marked 
viscidity,  somewhat  like  that  of  the  serum  of  blood,  or  uncoagulated 
white  of  egg,  and  differs  strongly  in  this  respect  from  the  watery  con- 
sistency of  the  gastric  juice.  It  coagulates  completely  by  the  applica- 
tion of  a  boiling  temperature,  often  solidifying  into  a  uniform  jelly-like 
mass.  It  also  gelatinizes  partially  on  being  cooled  down  to  the  zero 
point  (320  F.).  According  to  the  analyses  of  Schmidt,1  it  has  the  fol- 
lowing composition : 

COMPOSITION  OF  PANCREATIC  JUICE. 

Water 900.76 

Pancreatine 90.44 

Sodium  chloride .        .         .  7.35 

Potassium  chloride 0.02 

Lime  phosphate 0.41 

Magnesium  phosphate 0.12 

Soda,  lime,  and  magnesia,  in  combination  with  the  pancreatine     .  0.90 


100000 
1  Annaleu  der  Chemie  und  Pharmacie,  1854,  xcii.  p.  33. 


174  DIGESTION". 

The  most  important  ingredient  of  the  pancreatic  juice  is  its  animal 
matter,  known  as  pancreatine.  It  is  this  substance  which  gives  to  the 
fluid  its  tenacious  or  viscid  character,  and,  in  the  secretion  obtained  by 
the  above  method,  it  amounts  to  over  ten  per  cent,  of  the  whole, 
being  more  abundant  than  all  the  other  solids  taken  together.  It  is 
also  considerably  more  abundant,  in  proportion,  than  the  albuminous 
ingredient  of  any  other  of  the  digestive  fluids.  It  is  coagulable  by 
heat,  by  nitric  acid,  by  alcohol,  and  also  by  magnesium  sulphate  added 
in  excess.  In  this  last  particular  it  differs  from  albumen,  which  is  not 
affected  by  magnesium  sulphate.  Another  peculiarity,  in  which  it 
resembles  pepsine,  is  that  after  being  precipitated  by  alcohol,  it  may 
be  again  dissolved  in  water,  retaining  all  •  its  original  properties.  By 
some  observers  it  is  considered  as  a  mixture  of  several  substances 
which  differ  from  each  other  in  their  chemical  relations ;  but,  taken  as 
a  whole,  it  forms  a  strongly  marked  distinguishing  ingredient  of  the 
pancreatic  juice. 

When  drawn  from  the  canula  several  days  after  its  introduction,  or 
obtained  by  means  of  a  permanent  fistula,  the  secretion  is  usually  more 
abundant,  but  poorer  in  its  organic  constituents.  Schmidt  found  that 
in  the  dog,  immediately  after  the  operation,  the  pancreatic  juice  was 
of  a  thick,  tenacious  consistency,  containing  an  abundance  of  solid 
ingredients,  consisting  principally  of  organic  matter ;  while  that  ob- 
tained from  a  permanent  fistula  was  comparatively  thin  and  watery, 
containing  only  from  1.5  to  3.6  per  cent,  of  solids,  of  which  not  more 
than  two-thirds  consisted  of  organic  matter.  Other  observers  have 
met  with  the  same  difference.  The  fluid  obtained  soon  after  the  intro- 
duction of  the  canula,  during  the  period  of  digestion,  probably  repre- 
sents most  fully  the  normal  secretion. 

The  organic  matter  of  pancreatic  juice,  like  that  of  the  other 
digestive  secretions,  may  be  extracted  from  the  substance  of  the  gland- 
ular tissue.  For  this  purpose  the  pancreas  is  taken  out  from  the  dog 
or  pig,  killed  while  digestion  is  going  on,  a  few  hours  after  the  inges- 
tion  of  food,  cut  into  small  pieces,  or  ground  to  a  pulp  with  sand, 
and  allowed  to  macerate  for  two  hours  in  water  at  25°  (77°  F.).  The 
filtered  fluid  contains  a  substance  nearly  or  quite  identical  in  its  pro- 
perties with  that  contained  in  the  pancreatic  juice  itself.  It  may  also 
be  obtained,  in  a  form  better  adapted  for  permanent  use,  by  placing  the 
freshly  divided  pancreas  for  twenty-four  hours  in  absolute  alcohol,  then 
separating  it  from  the  alcohol,  and  macerating  it  for  several  days  in 
glycerine,  which  is  afterward  filtered.  The  glycerine  extracts  the  or- 
ganic matter  of  the  glandular  tissue,  and  preserves  it  without  alteration. 
It  may  be  precipitated  at  any  time  from  the  glycerine  solution  by  the 
addition  of  strong  alcohol,  and  afterward  dissolved  in  water.  It  thus 
forms  a  watery  extract  of  the  pancreas. 

Physiological  Properties  of  the  Pancreatic  Juice — This  secretion 
has  certain  well  marked  characters  which  indicate  that  its  action  is  of 


PANCREATIC    JUICE    AND    ITS    ACTION    UPON    FOOD.      175 

great  importance  in  the  digestive  process,  although  the  precise  limits 
of  its  operation  are  not  yet  fully  determined. 

In  the  first  place,  the  pancreatic  juice  has  the  power  of  transforming 
starch  into  sugar.  This  action  takes  place  with  great  rapidity  at  the 
temperature  of  the  living  body.  According  to  Hardy,1  it  is  much  more 
prompt  as  well  as  more  complete  than  the  corresponding  change 
produced  by  saliva,  being  at  the  temperature  of  40°  (104°  F.)  almost 
instantaneous;  and,  while  the  transforming  action  of  saliva  is  very 
partial,  much  of  the  starch  remaining  unchanged,  that  of  the  pancreatic 
juice  appears  to  convert  the  whole  of  it  into  glucose.  Kroeger  found2 
that  one  gramme  of  fresh  pancreatic  juice,  at  the  temperature  of  35° 
(95°  F.),  transformed  into  sugar,  within  thirty  minutes,  4.67  grammes 
of  starch  ;  while,  according  to  our  own  observations,  if  one  gramme  of 
fresh  human  saliva  be  mixed  at  38°  (lOQOF.),  with  a  watery  solution 
containing  less  than  0.1  gramme  of  boiled  starch,  though  the  sugar  re- 
action becomes  manifest  in  one  minute,  a  large  portion  of  the  starch 
is  still  unchanged  at  the  end  of  an  hour.  It  is  certain  that  hydrated 
starch,  although  it  may  be  recognized  for  a  long  time  in  the  stomach 
by  its  iodine  reaction,  disappears  completely  as  soon  as  it  enters  the 
upper  part  of  the  duodenum.  According  to  Ranke,3  pancreatic  juice 
causes  the  transformation  not  only  of  hydrated,  but  also  of  raw  starch; 
a  property  which  was  found  by  Bouchardat  and  Sandras  to  be  very 
energetic  in  the  secretion  of  the  common  fowl,  if  aided  by  a  slight  ele- 
vation of  temperature. 

The  organic  matter  of  the  pancreatic  juice,  which  produces  this 
change,  is  coagulable  by  a  boiling  temperature,  and  after  its  solution 
has  once  been  boiled,  it  is  inactive  in  regard  to  starchy  matters.  It  is 
produced  in  the  substance  of  the  gland,  probably  by  the  transformation 
of  some  previousl}7"  formed  material,  since  it  has  been  found  by  Liver- 
sidge,4  that  after  it  lias  been  completely  extracted  from  the  chopped 
glandular  tissue  by  treatment  with  glycerine,  if  the  inactive  residue  be 
transferred  to  a  filter,  and  allowed  to  remain  exposed  to  the  air  for  five 
or  six  hours,  it  is  regenerated,  and  may  be  again  extracted  by  the  addi- 
tion of  water  or  glycerine.  This  is  undoubtedly  due  to  a  real  reproduc- 
tion of  the  active  organic  substance,  and  is  not  the  result  of  a  putrefac- 
tive change,  since  the  same  observer  found  that  a  watery  extract  of  the 
pancreas,  which  had  once  been  deprived  of  its  action  on  starch  by  boil- 
ing, never  regained  this  property  at  any  stage  of  subsequent  decompo- 
sition. 

Secondly,  the  pancreatic  juice  has  the  power  of  emulsifying  the  fats. 
This  is  perhaps  its  most  marked  and  peculiar  property,  by  which  it  is 

1  Chimie  Biologique.     Paris,  1871,  p.  152. 

2  Cited  in  Milne  Edwards,  LeQons  sur  la  Physiologic.     Paris,  1862,  tome  vii. 
p.  68. 

3  Physiologic  des  Menschens.     Leipzig,  1872,  p.  271. 

4  Studies  from  the  Physiological  Laboratory  of  the  University  of  Cambridge, 
Part  I.     Cambridge,  1873,  p.  49. 


176  DIGESTION. 

especially  distinguished  from  the  other  digestive  secretions.  If  a  fluid 
fatty  substance,  such  as  olive  oil  or  melted  butter,  be  shaken  up  in  a 
test-tube  with  the  saliva,  the  gastric  juice,  the  bile,  or  any  of  the 
excreted  fluids,  it  suffers  no  change  in  its  physical  characters.  It  is 
partially  broken  up  by  the  mechanical  agitation,  but,  on  being  allowed 
to  remain  at  rest,  the  oil  globules  run  together  and  soon  collect  in  a 
distinct  layer  upon  the  surface  of  the  liquid.  If,  on  the  contrary,  the' 
same  experiment  be  tried  with  fresh  pancreatic  juice,  the  oil  is  instantly 
broken  up  into  a  state  of  fine  subdivision,  producing  a  uniformly  white, 
opaque,  milky  looking  fluid.  The  emulsion  thus  formed  is  permanent, 
the  microscopic  fat  granules  being  held  in  suspension  by  the  organic 
matter  of  the  secretion,  and  thus  prevented  from  uniting  into  visible  oil 
drops.  If  the  proportion  of  oily  matter  be  considerable,  a  part  of  it  may 
rise  to  the  surface  as  a  creamy  layer,  and  if  it  be  in  excess,  the  super- 
fluous portion  will  also  rise  to  the  upper  part  of  the  liquid ;  but  the 
remainder  will  continue  indefinitely  in  the  emulsioned  condition,  dis- 
seminated uniformly  through  the  fluid  mixture. 

The  emulsifying  property  of  the  pancreatic  juice  is  very  active,  when 
the  secretion  exhibits  its  normal  characters.  Bernard  found  that  the 
freshly  extracted  j uice  formed  a  complete  emulsion  at  38°  (100°  F.)  with 
olive  oil,  butter,  suet,  or  lard,  when  mixed  with  either  of  these  substances 
in  the  proportion  of  one  gramme  of  oleaginous  matter  to  two  grammes 
of  pancreatic  juice.  The  emulsion  thus  produced  retained  its  physical 
appearance  unchanged,  although  allowed  to  remain  at  the  above  tempe- 
rature for  fifteen  or  eighteen  hours. 

The  power  of  the  pancreatic  juice  to  emulsify  oils,  though  facilitated 
by  its  alkaline  reaction,  does  not  depend  upon  the  free  alkali,  but  is 
mainly  due  to  the  action  of  its  organic  matter.  This  is  indicated  by  the 
fact  that  other  animal  fluids  which  are  also  alkaline  do  not  have  the 
same  power  in  a  corresponding  degree  ;  and  Bernard  has  shown  that  the 
pancreatic  juice,  after  being  neutralized  by  a  dilute  acid,  still  retains  its 
property  of  acting  upon  the  fats. 

The  property  of  emulsifying  oily  matters,  first  shown  to  exist  in  the 
pancreatic  juice  of  the  dog,  has  been  found  by  Colin  in  that  of  the 
horse,  the  ass,  the  ox,  the  sheep,  and  the  pig;  and  by  Bernard  has  been 
found  fully  developed  in  that  of  the  goose.  According  to  Colin,  its 
intensity,  in  these  different  animals,  is  proportional  to  the  quantity  of 
albuminous  matter  contained  in  the  secretion  ;  one  part  of  oil  requiring, 
for  complete  emulsion,  from  two  to  three  parts  of  pancreatic  juice 
when  its  albuminous  ingredient  is  abundant,  and  four,  five,  or  six  parts 
when  the  proportion  of  this  substance  is  diminished. 

There  is  every  evidence  that  the  emulsifying  action  of  the  pancreatic 
juice  is  of  the  first  importance  in  the  digestion  of  fatty  substances. 
These  substances  are  not  affected  by  contact  with  gastric  juice  outside 
the  body  ;  and  examination  shows  that  they  are  not  digested  .in  the 
stomach,  but  are  unchanged  in  their  essential  character  so  long  as  they 
remain  in  the  gastric  cavity.  They  are  merely  melted  by  the  warmth 


PANCKEATIC    JUICE    AND    ITS    ACTION    UPON    FOOD.      177 

of  the  organ,  and  set  free  by  the  solution  of  the  vesicles,  fibres,  or  capil- 
lary tubes  in  which  they  are  contained,  or  among  which  they  are 
entangled ;  and  they  are  still  readily  discernible,  floating  in  larger  or 
smaller  drops  on  the  surface  of  the  semi-fluid  alimentary  mass.  Very 
soon,  however,  after  its  entrance  into  the  intestine,  the  oily  portion  of 
the  food  loses  its  characteristic  appearance,  and  is  converted  into  a 
white,  opaque  emulsion,  which  is  gradually  absorbed.  This  emulsion 
is  termed  the  chyle,  and  is  always  found  in  the  small  intestine  during 
the  digestion  of  fat,  entangled  among  the  valvulse  conniventes,  and 
adhering  to  the  surface  of  the  villi.  The  digestion  of  fatty  substances 
accordingly  consists  mainly  in  their  emulsion,  by  which  they  are  con- 
verted into  chyle  and  made  ready  for  absorption.  This  change  begins 
to  take  place  in  the  duodenum,  immediately  below  the  orifice  of  the 
pancreatic  duct.  But  as  the  pancreatic  and  biliary  ducts  in  most  ani- 
mals open  into  the  intestine  in  company  or  in  close  juxtaposition  with 
each  other,  it  might,  from  this  circumstance  alone,  be  doubtful  whether 
the  two  secretions  have  not  an  equal  share  in  producing  the  effect.  Ber- 
nard first  removed  the  doubt  by  examining  the  products  of  digestion  in 
the  rabbit.  In  this  animal,  the  biliary  duct  opens,  in  the  usual  manner, 
just  below  the  pylorus,  while  the  pancreatic  duct,  as  stated  above,  com- 
municates separately  with  the  intestine  30  or  40  centimetres  farther 
down ;  so  that  there  is  here  a  considerable  extent  of  the  small  intestine 
already  containing  bile,  but  into  which  the  pancreatic  juice  has  not 
yet  been  discharged.  Bernard  fed  these  animals  with  substances  con- 
taining oil,  or  injected  melted  butter  into  the  stomach  ;  and,  on  killing 
them  afterward,  found  that  there  was  no  chyle  in  the  intestine  between 
the  openings  of  the  biliary  and  pancreatic  ducts,  but  that  it  was  abun- 
dant immediately  below  the  orifice  of  the  latter.  Above  this  point,  also, 
he  found  the  lacteals  empty  or  transparent,  while  below  it  they  were 
full  of  white,  opaque  chyle.  These  experiments,  which  were  confirmed 
by  Prof.  Samuel  Jackson,1  fully  demonstrate  that  the  emulsifying  action 
of  the  pancreatic  juice  upon  oily  matters  is  exerted  within  the  body 
during  digestion,  and  is  the  direct  agent  in  the  production  of  chyle  in 
the  intestine. 

Thirdly,  the  pancreatic  juice  at  the  temperature  of  the  living  body 
gradually  dissolves  coagulated  albuminous  matters.  This  property  of 
the  secretion,  first  recognized  by  Bernard  and  Corvisart,  has  been  alter- 
nately confirmed  and  denied  by  various  subsequent  observers.  Among 
those  who  found  in  the  pancreatic  juice  more  or  less  power  of  this  kind, 
some  stated  it  to  be  only  present  when  the  fluid  was  acidulated  (Meissner), 
while  others  maintained  that  it  could  only  be  exerted  in  presence  of  an 
alkaline  reaction  (Wundt) ;  and  the  information  obtained  in  regard  to 
the  process  has  been  generally  much  less  distinct  and  satisfactory  than 
that  relating  to  the  other  properties  of  the  secretion.  The  most  definite 

1  American  Journal  of  the  Medical  Sciences.     Philadelphia,  October,  1854. 


178  DIGESTION. 

and  valuable  observations  on  this  subject  are  those  of  Kiihne,1  who  ex- 
perimented both  with  the  pancreatic  juice  of  the  dog,  and  also  with  infu- 
sions of  the  glandular  tissue.  He  found  that  the  fresh  viscid  secretion 
could,  in  from  half  an  hour  to  three  hours,  effect  the  solution  of  coagulated 
fibrine  and  albumen,  without  any  modification  of  its  alkaline  reaction, 
and  without  giving  rise  to  signs  of  putrefaction ;  the  albuminous  mat- 
ters, thus  dissolved,  being  changed  into  a  substance  not  coagulable  by 
boiling  and  readily  diffusible  through  parchment  paper.  The  product  of 
this  action  accordingly  resembles  that  obtained  from  a  similar  digestion 
with  the  pepsine  of  gastric  j  nice. 

In  his  experiments  with  the  glandular  tissue,  Kiiline  placed  the  finely 
divided  gland  in  warm  water  together  with  a  weighed  quantity  of  the 
substance  to  be  experimented  on  ;  allowing  the  infusion  of  the  pancreas 
and  the  digestion  of  the  albuminous  matter  to  proceed  simultaneously. 
He  found  that  when  employing  for  this  purpose  a  dog's  pancreas  of  from 
50  to  60  grammes  weight,  400  grammes  of  boiled  and  pressed  fibrine, 
after  remaining  in  the  infusion  at  40°  to  45°  (104°  to  113°  F.)  for  from 
three  to  six  hours,  were  reduced  to  an  insignificant  residue,  the  reaction 
of  the  mass  continuing  throughout  faintly  alkaline. 

The  details  of  this  process,  however,  are  different  in  some  respects 
from  those  of  digestion  in  gastric  juice.  If  bits  of  coagulated  fibrine 
be  placed  in  gastric  juice,  or  an  acidulated  solution  of  pepsine,  they  first 
swell  up  and  become  transparent  under  the  influence  of  the  free  acid; 
and  this  action  is  preliminary  to  their  subsequent  solution  and  transfor- 
mation into  albuminose.  But  in  an  infusion  of  the  pancreas,  according 
to  Kiihne,  the  pieces  of  fibrine  do  not  become  at  all  swollen  or  altered 
in  transparency,  even  when  considerably  softened  and  near  the  point 
of  solution.  They  are,  however,  essentially  modified  in  their  physical 
and  chemical  properties.  Boiled  fibrine,  by  itself,  is  but  slowly  affected 
by  dilute  acids  or  alkalies,  and  is  nearly  or  quite  insoluble  in  a  ten  per 
cent,  solution  of  hydrochloric  acid;  but  after  remaining  for  a  time  in 
an  infusion  of  the  pancreas,  a  part  of  it  is  found  to  be  almost  instantly 
soluble  in  a  solution  of  hydrochloric  acid  of  one  part  per  thousand. 

It  is  evident,  accordingly,  that  the  organic  matter  of  the  pancreatic 
juice  may  exert  a  transforming  action  on  the  albuminous  matters,  some- 
what analogous  to  that  of  the  pepsine  of  gastric  juice.  How  far  this 
action  takes  place  in  the  natural  process  of  digestion  has  not  been 
demonstrated  by  direct  observation,  but  it  is  possible  that  the  two 
secretions  may  be  in  some  degree  complementary  to  each  other.  In  the 
gastric  juice,  we  have  an  abundant  fluid  with  an  acid  reaction,  and  with 
a  small  proportion  of  organic  substance ;  in  the  pancreatic  juice  a  com- 
paratively scanty  secretion,  but  with  a  much  larger  proportion  of  organic 
matter,  capable  of  exerting  a  transforming  power  on  the  albuminous 
ingredients  of  the  food.  While  the  gastric  juice  acts  alone  in  the 
stomach,  softening  and  disintegrating  the  food,  and  actually  dissolving 

1  Archiv  fur  Pathologische  Anatomie  und  Physiologie,  1867,  xxxix.  p.  130. 


PANCREATIC    JUICE    AND    ITS    ACTION    UPON    FOOD.      179 

a  part  of  it ;  in  the  intestine  the  two  secretions  may  act  together,  to 
complete  the  liquefaction  of  the  alimentary  materials. 

Mode  of  Secretion  and  Daily  Quantity  of  the  Pancreatic  Juice. — 
If  examined  in  the  living  animal  by  means  of  a  canula  introduced  into 
its  excretory  duct,  it  is  found  that  the  action  of  the  pancreas  is  by  no 
means  the  same  at  different  times.  If  there  be  no  food  in  the  stomach  or 
intestine,  or  if  the  process  of  digestion  be  arrested  from  any  cause,  no 
fluid  whatever  is  discharged  from  the  canula.  If  digestion  be  going  on, 
the  pancreatic  juice  soon  begins  to  run  from  the  orifice  of  the  tube,  at 
first  slowly  and  in  successive  drops.  Sometimes  the  drops  follow  each 
other  with  rapidity  for  a  few  moments,  and  then  an  interval  occurs 
during  which  the  secretion  seems  entirely  suspended.  After  a  time  it 
recommences,  and  continues  to  exhibit  similar  fluctuations  during  the 
whole  course  of  the  experiment.  Its  flow,  however,  is  at  all  times 
scanty,  as  compared  with  that  of  the  gastric  juice.  We  have  never 
been  able  to  collect,  in  a  good  sized  dog,  more  than  75  grammes  in  the 
course  of  three  hours,  and  usually  the  quantity  was  much  less  than  this. 
Colin  found  a  great  variation  in  the  animals  upon  which  he  experimented, 
the  quantity  being  from  two  and  a  half  to  thirty  times  as  abundant  at 
one  period  as  at  another.  In  the  bullock,  the  largest  quantity  obtained 
was  342  grammes  per  hour  while  the  animal  was  engaged  in  rumination. 

The  entire  quantity  of  pancreatic  juice  secreted  per  day  cannot  be 
determined  with  precision,  but  it  is  evidently  moderate  in  amount,  as 
compared  with  the  other  digestive  fluids.  In  the  ox,  cow,  and  horse, 
Colin  found  the  average  quantity  nearly  the  same,  corresponding  to 
about  0.58  gramme  per  hour  for  every  kilogramme  of  the  animal's 
weight.  Schmidt,  in  his  experiments  upon  the  dog,  found  it,  in  recently 
established  fistulae,  not  more  than  0.2  gramme  per  kilogramme  per  hour. 
In  the  most  successful  instances,  we  have  found  it  in  the  dog,  as  much 
as  1.25  grammes  per  kilogramme  per  hour  during  active  digestion,  but 
much  less  than  this  in  the  intervals.  If  we  take,  as  the  average  of  these 
estimates,  0.5  gramme  per  hour  for  every  kilogramme  of  bodily  weight, 
it  would  give  for  a  man  of  medium  size  about  800  grammes  as  the  entire 
quantity  of  pancreatic  juice  secreted  per  day. 

The  condition  of  the  pancreas  varies  at  different  periods  corresponding 
with  the  activity  of  its  secretion.  In  the  intervals  of  digestion  it  is 
comparatively  pallid  and  dense ;  during  digestion  it  becomes  turgid  and 
vascular,  its  ruddy  color  showing  the  increased  quantity  of  blood  circu- 
lating in  its  vessels.  According  to  most  observers,  the  substance  which 
is  efficient  in  the  solution  of  albuminous  matters  can  only  be  extracted 
from  the  pancreas  at  this  time,  during  the  height  of  its  vascularity  and 
digestive  action,  which,  in  the  dog,  is  from  five  to  seven  hours  after  the 
ingestion  of  food.  When  the  process  of  digestion  is  terminated,  its 
vascularity  again  diminishes,  and  the  organ  returns  to  its  quiescent 
condition.  This  periodical  excitement  during  the  period  of  functional 
activity,  though  well  marked  in  the  pancreas,  is  not  peculiar  to  it,  but 
may  also  be  seen  in  the  mucous  membrane  of  the  stomach  and  the  small 


180 


DIGESTION. 


intestine.     It  probably  exists,  more  or  less  fully  developed,  in  all  the 
organs  taking  part  in  the  digestive  process. 

The  Intestinal  Juice  and  Digestion  in  the  Intestine. 
The  secretory  apparatus  of  the  small  intestine  consists  of  two  sets  of 
glandular  organs,  namely,  first,  Brunner's  glands,  which  are  compound 
or  lobulated,  and  confined  to  the  upper  part  of  the  duodenum,  forming 
a  sort  of  collar  round  the  intestine  for  a  distance  of  several  centimetres 
from  the  pylorus  ;  and,  secondly,  the  follicles  of  Lieberkuhn,  which  are 
simple  tubular  glandules,  occupying  the  substance  of  the  mucous  mem- 
brane for  the  whole  length  of  the  small  intestine.  ^ 

Fig.  47. 


LONOITTJDINALSKCTION  OF  WALL  OF  DUODENUM  IN  THE  DOG;  showing  the  sub- 
mucous  layer  of  Brunner's  Glands,  a.  Mucous  membrane,  b.  Layer  of  submucous  connective 
tissue,  in  which  the  glands  are  situated,  c.  Muscular  coat.  d.  Peritoneal  coat.  e.  Brunner's 
glands,  with  their  ducts  opening  upon  the  free  surface  of  the  mucous  membrane.  (Bernard.) 

Brunner's  glands,  or  the  duodenal  glandules  as  they  are  sometimes 
called,  are  situated  in  the  submucous  layer  of  connective  tissue  in  this 
part  of  the  intestine.  They  are  spherical,  or,  when  thickly  set,  irregu- 
larly flattened  or  polygonal  in  shape  from  mutual  pressure,  and  from  ^ 
to  1  millimetre  in  diameter. 


Fig.  48. 


Fig.  49. 


Entire  BRUNNER'S  GLAND,  from  human  intestine. 
(Frey.) 


Portion    of    one  of   BRUNNER'S 
GLANDS,  from  human  intestine. 


In  their  structure,  the  glands  are  similar  to  the  lobulated  glandules 
of  the  mouth,  being  composed  of  rounded  follicles  clustered  about  a 
central  branching  excretory  duct.  Each  follicle  is  about  TV  of  a  milli- 
metre in  diameter,  and  consists  of  a  delicate  membranous  wall,  lined 


INTESTINAL    JUICE    AND    DIGESTION    IN    INTESTINE.      181 


with  cells  of  glandular  epithelium,  showing  small  but  distinctly  marked 
nuclei.  The  follicles  collected  round  each  terminal  branch  of  the  main 
duct  are  bound  together  by  a  thin  layer  of  connective  tissue,  and  covered 
with  a  plexus  of  capillary  bloodvessels. 

The  follicles  of  Lieberkiihn,  which  are  much  more  numerous  than  the 
preceding,  are  not  situated  in  the  submucous  connective  tissue,  but 
occupy  the  entire  thickness  of  the  mucous  membrane,  forming,  like  the 
gastric  follicles  in  the  mucous  membrane  of  the  stomach,  the  greater  part 
of  its  substance.  They  are 

simple,  nearly  straight  tubules,  Fl£-  50- 

from  y1^  to  TV  of  a  millimetre 
in  diameter,  lined  throughout 
with  cylindrical  epithelium, 
opening  by  their  orifices  upon 
the  free  surface  of  the  intes- 
tinal mucous  membrane  and 
terminating  below  by  rounded 
extremities.  They  are  so 
thickly  set  that  in  many  places 
there  appears  to  be  no  space 
left  between  them,  except  that 
occupied  by  the  capillary 
bloodvessels  which  encircle 
them  in  every  direction. 

The  fluid  produced  by  the 

mucous  membrane  of  the  small  testine  of  Dog. 

intestine  consists  of  a  mixture 

of  the  secretions  of  these  two  sets  of  glands.  But  as,  owing  to  the  situa- 
tion of  Brunner's  glands,  it  has  been  found  impossible  to  obtain  their 
secretion  unmixed  with  other  fluids,  and  as  it  is  evidently  much  less 
abundant  than  that  produced  in  the  remainder  of  the  intestine,  the 
secretion  of  the  follicles  of  Lieberkiihn  is  regarded  as  the  main  con- 
stituent of  the  intestinal  juice.  It  is  by  no  means  easy  to  obtain  this 
fluid  in  a  pure  form  and  in  normal  condition.  There  is  no  single  excre- 
tory duct,  like  that  of  the  pancreas,  into  which  a  canula  might  be 
inserted  ;  and  a  fistulous  opening  made  in  the  intestine  itself  would  of 
course  yield  a  mixture  of  all  the  secretions  discharged  into  its  cavity. 
If  these  should  be  shut  off  by  a  ligature  permanently  applied  above 
the  fistula,  the  disturbance  of  the  digestive  process  would  be  so  great, 
that  the  experiment  could  hardly  be  expected  to  give  a  valuable  result. 

Nevertheless,  attempts  have  been  made,  ~by  various  methods, '  to 
obtain  the  intestinal  juice  in  condition  sufficiently  pure  for  examination. 
Bidder  and  Schmidt  first  tied  the  biliary  and  pancreatic  ducts,  and  then 
established  an  intestinal  fistula  below,  from  which  they  extracted  the 
fluids  accumulated  in  the  cavity  of  the  gut.  Frerichs  operated  by 
opening  the  abdomen,  taking  out  a  loop  of  intestine,  emptying  it  so 
far  as  possible  by  gentle  pressure,  isolating  its  cavity  by  the  application 


FOLLICLES  OF 


from  Small  In- 


182 


DIGESTION. 


of  two  ligatures  15  or  20  centimetres  apart,  and  returning  the  whole 
into  the  abdominal  cavity.  After  a  few  hours  the  animal  was  killed, 
and  the  fluid,  which  had  collected  in  the  isolated  portion  of  intestine, 
taken  out  and  examined.  Colin  adopted  a  similar  method,  but  with 
greater  precautions,  in  the  horse.  In  one  of  these  animals,  while  diges- 

Fig.  51. 


LOOP  OF  SMALL   INTESTINE,  from  the  horse,  isolated  by  compressors,  for  obtaining 
intestinal  juice.    (Colin.) 

tion  was  in  full  activity,  he  took  out,  through  an  opening  in  the  left 
flank,  a  loop  of  small  intestine,  which  he  isolated  by  two  compressors, 
made  of  flat  wooden  or  metallic  strips,  enveloped  by  a  ribbon  of  velvet, 
and  fastened  by  screws  in  such  a  way  that  the  inner  surfaces  of  the 
intestine  might  be  retained  in  close  contact,  without  bruising  or  lacerat- 
ing their  tissues.  The  compressors  being  applied  at  a  distance  of  from 
one  to  twro  metres  apart  after  the  included  portion  of  intestine  had 
been  emptied  by  gentle  pressure,  the  whole  was  returned  into  the  abdo- 
men, the  external  wound  closed  by  sutures  and  the  animal  killed  at  the 
end  of  half  an  hour. 

On  the  average,  100  grammes  of  fluid  had  accumulated  within  this 
time.  It  was  clear,  with  a  slightly  yellowish  or  amber  tint,  alkaline  in 
reaction,  and  with  a  specific  gravity  of  1010.  According  to  the  analysis 
of  Lassaigne,  it  was  composed  as  follows : 


INTESTINAL    JUICE    AND    DIGESTION    IN    INTESTINE.      183 

COMPOSITION  OF  INTESTINAL  JUICE  FROM  THE  HORSE. 

Water 981.0 

Albuminous  matter 4.5 

Sodium  chloride 
Potassium  chloride     i 


Sodium  phosphate 
Sodium  carbonate 


1000.0 


Thiry  separated  a  portion  of  the  small  intestine  from  the  remainder 
by  two  transverse  sections,  leaving  the  mesentery  and  vessels  of  the 
isolated  portion  uninjured,  and  then  united  by  sutures  the  divided  ends 
of  the  remaining  portions,  so  as  to  re-establish  the  continuity  of  the  intes- 
tine, but  with  a  portion  of  it,  10  or  15  centimetres  long,  left  out.  Of 
this  isolated  portion,  still  nourished  by  its  vessels,  he  closed  one  end 
by  sutures,  so  as  to  make  of  it  a  blind  extremity,  while  the  other  he 
fastened  to  the  edges  of  the  external  wound  in  such  a  way  as  to  make 
of  it  a  permanent  fistula.  When  all  the  parts  had  healed,  and  natural 
digestion  was  re-established,  he  collected  the  fluid  discharged  from  the 
open  end  of  the  isolated  portion  of  intestine.  This  operation  has  been 
repeated  by  other  observers.  The  objection  to  it  is  that  the  isolated  por- 
tion of  intestine,  after  being  for  some  weeks  precluded  from  taking  part 
in  the  process  of  digestion,  becomes  partially  atrophied,  and  cannot 
be  relied  on  as  furnishing  a  secretion  similar  to  the  normal  intestinal 
juice.  The  results  obtained  vary,  some  of  them  indicating  that  the 
secretion  converts  starch  into  sugar  and  has  a  dissolving  action  on 
coagulated  albuminous  matters,  others  that  these  properties  are  some- 
times absent  or  but  slightly  developed. 

On  the  whole,  the  method  adopted  by  Frerichs  and  Colin,  with  its 
various  modifications,  seems  to  be  the  best  and  has  furnished  the  most 
uniform  results.  Colin  found  that  the  fluid  obtained  in  this  way  has  the 
power  of  slowly  transforming  hydrated  starch  into  sugar,  and  of  emul- 
sioning  fatty  matters  with  considerable  energy.  One  part  of  olive  oil, 
treated  with  five  or  six  parts  of  intestinal  juice,  was  transformed  into  a 
homogeneous  mixture  of  a  white  color;  and  oil  injected  into  the  isolated 
portion  of  intestine,  in  the  living  animal,  was  found,  after  an  hour,  re- 
duced to  the  condition  of  whitish  homogeneous  flakes. 

Bernard  obtained  from  a  healthy  dog  which  had  been  without  food 
for  twelve  days,  by  an  opening  in  the  intestine  60  centimetres  below  the 
pylorus,  a  transparent,  amber  colored,  alkaline  fluid,  which  coagulated 
by  heat,  emulsioned  oily  matters  distinctly  though  not  strongly,  and 
effected  the  transformation  of  hydrated  starch.  A  small  quantity  of 
melted  lard  having  been  injected  into  the  lower  part  of  the  intestine 
and  a  ligature  placed  above,  at  the  end  of  an  hour  and  a  half  the  lower 
part  of  the  intestine  was  found  turgid,  with  emulsioned  fat  in  its  cavity, 
and  its  chyliferous  vessels  filled  with  opaque  chyle. 

It  appears  accordingly  that  the  intestinal  juice,  so  far  as  ascertained 


184  DIGESTION. 

by  direct  observation,  is  a  comparatively  scanty,  alkaline  fluid,  contain- 
ing an  albuminous  ingredient  capable  of  coagulation  by  heat.  It  exerts 
an  action  upon  starchy  and  fatty  matters  similar  to  that  of  the  pancreatic 
juice,  but  less  energetic  in  operation.  Its  action  upon  albuminous 
matters  is  less  distinct,  and  has  sometimes  been  found  to  be  absent  or 
feebly  developed.  It  is  undoubtedly  of  importance  as  accessory  to  the 
other  digestive  secretions,  but  the  precise  mode  and  extent  of  its  opera- 
tion have  not  yet  been  determined. 

In  the  process  of  intestinal  digestion  a  number  of  different  actions 
are  going  on  at  the  same  time.  The  materials  of  the  food,  disinte- 
grated and  partly  dissolved  in  the  stomach,  pass  through  the  pylorus 
into  the  intestine  still  mingled  with  a  notable  quantity  of  gastric  juice, 
and  are  there  subjected  to  the  action  of  the  remaining  digestive  secre- 
tions. Hydrated  starch,  set  free  by  the  solution  of  the  albuminous 
matters  with  which  it  was  associated,  rapidly  undergoes  the  conver- 
sion into  glucose,  and  the  saccharine  fluid  so  produced  is  promptly  ab- 
sorbed. If  a  dog  be  fed  with  a  mixture  of  meat  and  boiled  starch, 
although  this  conversion  does  not  begin  until  the  fluids  enter  the  duo- 
denum, we  have  found,  in  some  instances,  that  at  the  end  of  three- 
quarters  of  an  hour  all  traces  of  both  starch  and  sugar  had  disappeared 
from  both  stomach  and  intestine.  Raw  starch  in  the  lower  animals  is 
digested  more  slowly  but  in  a  similar  manner.  Bouchardat  and  Sandras, 
in  examining  the  alimentary  canal  of  the  rabbit  when  fed  with  potato, 
found  the  grains  of  starch  only  slightly  changed  in  the  stomach,  but  in 
the  small  intestine  they  were  altered,  corroded,  and  more  or  less  dis- 
solved in  proportion  as  they  had  descended  the  intestinal  canal,  while  in 
the  rectum  only  feeble  traces  of  them  remained. 

All  observers  agree  that  cane  sugar  undergoes  the  transformation 
into  glucose  by  contact  with  the  intestinal  juices.  This  conversion 
may  be  slowly  effected  by  the  action  of  gastric  juice  alone.  If  one 
part  of  cane  sugar  be  dissolved  in  20  parts  of  dog's  gastric  juice,  and 
kept  at  38°  (lOtPF.)  the  mixture  will  give  traces  of  glucose  at  the  end 
of  two  hours,  and  in  three  hours  its  quantity  is  considerable.  It  cannot 
be  shown,  however,  that  the  gastric  juice  exerts  this  effect  on  sugar  dur- 
ing ordinary  digestion.  If  pure  cane  sugar  be  given  to  a  dog  with  a 
gastric  fistula  while  digestion  of  meat  is  going  on,  it  disappears  in  from 
two  to  three  hours,  without  any  glucose  being  detected  in  the  fluids 
withdrawn  from  the  stomach.  It  is,  therefore,  either  directly  absorbed 
under  the  form  of  cane  sugar,  or  passes,  little  by  little,  into  the  duode- 
num, where  the  intestinal  fluids  convert  it  into  glucose. 

Fatty  matters,  which  are  simply  melted  in  the  stomach,  or  set  free  by 
the  liquefaction  of  the  tissues  which  contain  them,  on  entering  the  intes- 
tine begin  to  be  emulsified  by  the  pancreatic  and  intestinal  juices.  This 
process  continues  throughout  the  small  intestine,  together  with  the  com- 
plete solution  of  muscular  flesh  which  has  been  disintegrated  by  stomach 
digestion.  If  a  dog,  with  a  permanent  duodenal  fistula,  be  examined 
during  the  digestion  of  animal  food,  the  fluid  drawn  from  the  fistula 


INTESTINAL    JUICE    AND    DIGESTION    IN    INTESTINE.      185 


Fig.  52. 


within  the  first  hour  contains  gastric  juice,  and  is  turbid  with  the  rem- 
nants of  disintegrated  muscular  tissue,  mixed  with  fat  vesicles  and  oil 
drops.  This  turbid  mixture  grows  constantly  thicker  and  more  gruelly 
in  consistency  from  the  second  to  the  tenth  or  the  twelfth  hour  ;  after 
which  the  discharge  of  fluid  from  this  part  of  the  intestine  becomes  less 
abundant,  and  finally  ceases  almost  completely,  as  digestion  comes  to 
an  end. 

The  gradual  alteration  in  the  ingredients  of  the  food  may  also  be 
seen  by  killing  the  animal  while  digestion  is  going  on,  and  examining 
the  contents  of  the  alimentary 
canal.  If  the  food  consisted  of 
muscular  flesh  and  adipose  tis- 
sue, the  stomach  contains  (Fig. 
52)  masses  of  softened  meat, 
smeared  over  with  gastric  juice, 
and  also  a  moderate  quantity 
of  a  grayish  grumous  fluid  with 
an  acid  reaction.  This  fluid 
contains  muscular  fibres,  iso- 
lated from  each  other  and  more 
or  less  reduced  to  imperfect 
fragments.  The  fat  vesicles  of 
the  solid  adipose  tissue  of  beef 
are  but  little  altered,  and  there 
are  only  a  few  free  oil  globules 
to  be  seen  floating  in  the  mixed 
fluids  in  the  cavity  of  the 
stomach.  In  the  duodenum 
the  muscular  fibres  are  further 
disintegrated  (Fig.  53).  They 

become  much  broken  up,  pale,  and  transparent,  but  can  still  be  recog- 
nized, under  the  microscope,  by  their  characteristic  granular  markings 
and  striations.  The  fat  vesicles  also  begin  to  become  altered  in  the 
duodenum.  The  solid  granular  fat  of  beef  and  similar  kinds  of  meat 
becomes  liquefied  and  emulsioned  ;  and  appears  under  the  form  of  free 
oil  drops  and  fatty  molecules ;  while  the  fat  vesicle  itself  is  partially 
emptied,  and  becomes  more  or  less  collapsed  and  shrivelled.  In  the 
middle  and  lower  parts  of  the  intestine  (Figs.  54  and  55)  these  changes 
continue.  The  muscular  fibres  become  constantly  more  and  more  dis- 
integrated, and  a  large  quantity  of  granular  debris  is  produced,  which 
is  at  last  also  dissolved.  The  fat  also  progressively  disappears,  and  the 
vesicles  may  be  seen  in  the  lower  part  of  the  intestine,  collapsed  and 
empty. 

In  this  way  the  digestion  of  the  different  ingredients  of  the  food  goes 
on  in  a  continuous  manner,  from  the  stomach  throughout  the  entire 
length  of  the  small  intestine.     At  the  same  time,  it  results  in  the  pro- 
duction of  three  different  substances,  namely :  1st.  Albuminose,  produced 
13 


CONTENTS  OF  STOMACH  DURING  DIGES- 
TION OF  MEAT,  from  the  Dog. — a.  Fat  Vesicle, 
filled  with  opaque,  solid,  granular  fat.  b,  b.  Bits 
of  partially  disintegrated  muscular  fibre,  c.  Oil 
globules. 


186 


DIGESTION. 


by  the  digestion  of  albuminous  matters ;  2d.  A  chylous  fluid,  from  the 
emulsion  of  the  fats ;  and  3d.  Glucose,  produced  by  the  transformation 


Fig.  53. 


Fig.  54. 


FROM  DUODENUM  OF  DOG,  DURING 
DIGESTION  OP  MEAT.—  a.  Fat  vesicle, 
with  its  contents  diminishing.  The  vesicle 
is  beginning  to  shrivel  and  the  fat  breaking 
up.  6,  6.  Disintegrated  muscular  fibre,  c,  c. 
Oil  globules. 


FROM  MIDDLE  OF  SMALL  INTESTINE. 
— a,  a.  Fat  vesicles,  nearly  emptied  of  their 
contents. 


of  starch.  These  substances  are  then  ready  to  be  taken  up  into  the  cir- 
culation :  and  as  the  mingled  ingredients  of  the  intestinal  contents  pass 

successively  downward  through 

Fig.  55.  the  intestine,  the  products  of  di- 

gestion, together  with  the  diges- 
tive secretions  themselves,  are 
gradually  absorbed  by  the  vessels 
of  the  mucous  membrane,  and 
carried  away  by  the  current  of  the 
circulation. 

The  Large  Intestine  and  its 
Contents. 

The  mucous  membrane  of  the 
large  intestine  is  abundantly  pro- 
vided with  tubular  glandules 
which  are  not  essentially  differ- 
ent, in  their  anatomical  charac- 
ters, from  the  follicles  of  Lieber- 
ktihn.  Their  secretion,  however, 
appears  to  be  comparatively 

scanty,  at  least  in  the  watery  and  albuminous  ingredients  which  are 
present  in  the  other  intestinal  juices.  According  to  Ranke,  fistulous 
openings  in  the  large  intestine  do  not  yield  any  notable  quantity  of 


FROM  LAST  QUARTER  OF  SMALL  IN- 
TESTINE.—  a,  a.  Fat  vesicles,  quite  empty  and 
shrivelled. 


THE    LARGE    INTESTINE    AND    ITS    CONTENTS.          187 

fluid  ;  and  if  a  loop  of  the  gut  itself  be  isolated  by  ligatures,  an  accumu- 
lation of  mucus-like  matter  is  the  only  result.  In  the  rabbit,  however, 
after  ligature  of  the  vermiform  appendix,  Funke  obtained,  at  the  end  of 
from  two  to  four  hours,  a  quantity  of  a  turbid  alkaline  secretion,  with 
which  the  appendix  had  become  filled.  This  fluid  was  without  action 
upon  coagulated  albumen ;  but  it  transformed  starch  into  sugar,  and 
also  decomposed  the  sugar,  with  production  of  lactic  and  butyric  acids. 
The  same  change  was  produced  upon  starch  introduced  into  the  cavity 
of  the  appendix.1  This  accounts  for  the  acid  reaction  sometimes  found 
in  the  caecum  of  herbivorous  animals,  from  the  decomposition  of  undi- 
gested starch,  although  the  mucous  surface  of  the  large  intestine  is 
constantly  alkaline. 

As  the  remnants  of  the  alimentary  mass  pass  the  situation  of  the 
ileo-csecal  valve  and  enter  the  large  intestine,  they  begin  to  acquire  a 
more  pasty  consistency  and  a  peculiar  repulsive  odor.  Both  these 
changes  become  more  marked  in  the  middle  and  lower  part  of  the  gut, 
until  all  the  superfluous  fluids  have  disappeared,  and  the  consistency 
and  odor  of  the  feces  are  fully  developed.  This  odor  is  not  a  putrefac- 
tive one,  but  is  characteristic  of  the  contents  of  the  large  intestine.  Its 
source  may  be  either  a  peculiar  transformation  of  some  of  the  ingre- 
dients of  the  food,  or  an  excretory  action  of  the  mucous  membrane  of 
the  intestine.  It  is  probably  in  great  part  the  result  of  an  excretion, 
since  in  different  kinds  of  animals,  whatever  be  the  nature  of  their  food, 
the  feces  have  usually  a  distinct  odor  characteristic  of  the  species. 

The  average  daily  quantity  of  the  feces  in  the  human  subject  is  150 
grammes,  of  which  about  75  per  cent,  is  water,  and  25  per  cent,  solid 
residue.  They  consist,  first,  of  the  undigested  remnants  of  the  food ; 
and,  secondly,  of  the  excreted  materials  from  the  alimentary  canal. 
The  undigested  substances  derived  from  the  food  are  mainly  animal  or 
vegetable  tissues,  which,  from  their  constitution,  are  incapable  of  diges- 
tion. These  are  elastic  fibres,  or  bits  of  elastic  tissue,  which  nearly 
always  pass  the  intestine  unchanged ;  shreds  of  tendon  or  fascia,  not 
sufficiently  softened  by  cooking ;  horny  epidermic  tissues,  both  animal 
and  vegetable ;  and  the  spiral  tubes  and  ducts  of  vegetable  substances. 
The  excreted  materials  of  internal  origin  are  the  mucus  of  the  large 
intestine,  and  probably  also  the  volatile  substances  which  produce  the 
fecal  odor.  The  coloring  matters  of  the  bile  are  present  in  a  more  or 
less  altered  form. 

The  mineral  salts  contained  in  the  feces  amount  to  a  little  over  one- 
tenth  of  the  solid  ingredients.  They  are,  for  the  most  part,  the  same 
with  those  common  to  the  animal  fluids  in  general,  but  are  mingled  in 
different  proportions ;  only  about  4  per  cent,  consisting  of  the  soluble 
chlorides  and  sulphates,  while  fully  80  per  cent,  are  composed  of  lime 
and  magnesium  phosphates.  They  are  regarded  as  mainly  derived  from 

1  Kanke,  Physiologic  des  Menschen.     Leipzig,  1872,  p.  297. 


188  DIGESTION. 

the  unabsorbed  mineral  ingredients  of  the  food,  and  partly  from  the 
saline  matters  of  the  intestinal  secretions. 

Beside  the  above,  the  feces  contain  two  crystallizable  matters  of 
organic  origin,  which,  though  not  present  in  large  quantity,  are  of 
importance  from  their  chemical  characters  and  the  mode  of  their  pro- 
duction ;  namely,  excretine  and  stercorine. 

Excretine.  —  This  was  discovered  and  described  by  Dr.  W.  Marcet,1 
as  an  ingredient  of  human  feces,  though  it  does  not  occur  in  those  of 
the  lower  animals,  either  carnivorous  or  herbivorous.  It  is  a  neutral  or 
faintly  alkaline  crystallizable  substance,  insoluble  in  water,  but  soluble 
in  ether  and  hot  alcohol.  It  crystallizes  in  radiated  groups  of  four- 
sided  prismatic  needles.  It  fuses  at  96°  (204°  F.)?  and  burns  at  a  higher 
temperature.  It  is  non-nitrogenous,  and  consists  of  carbon,  hydrogen, 
oxygen,  and  sulphur,  in  the  following  proportions:  — 


It  is  thought  to  be  present  mostly  in  a  free  state,  but  partly  in  union 
with  certain  organic  acids,  as  a  saline  compound. 

Stercorine.  —  This  substance  was  discovered  by  Prof.  A.  Flint,  Jr., 
both  in  human  feces  and  in  those  of  the  dog,  and  was  obtained  by  him 
in  proportions  varying  from  O.Ot  to  0.3  per  cent,  of  the  entire  fecal 
mass.  It  is  most  abundant  in  the  feces  of  the  human  subject,  where  its 
average  quantity  is  estimated  by  its  discoverer  as  about  0.65  gramme 
per  day.  It  is  insoluble  in  water,  soluble  in  ether  and  in  boiling  alco- 
hol, neutral  in  reaction,  and,  like  excretine,  crystallizes  in  the  form  of 
radiating  needles.  It  differs  from  excretine,  however,  in  having  a  much 
lower  fusion  point,  becoming  liquefied  at  36°  (96°.  8  F.).  It  is  regarded 
as  produced  by  transformation  in  the  intestine  from  the  cholesterine  of 
the  bile.2 

1  Philosophical  Transactions.     London,  1857,  p.  410. 

2  American  Journal  of  the  Medical  Sciences.     Philadelphia,  October,  1862. 


CHAPTEE    IX. 


Fig.  56. 


ABSORPTION. 

THE  mucous  membrane  of  the  small  intestine,  beside  containing  the 
glandular  follicles  already  described,  is  provided  with  a  special  appa- 
ratus for  the  process  of  absorption.  This  apparatus  consists  of  innu- 
merable minute  eminences  or  prolongations  of  its  substance,  so  closely 
set  over  its  free  surface  that  they  give  to  it  a  characteristic  velvety  appear- 
ance. These  are  the  so-called  villosities  or  villi  of  the  small  intestine. 
They  are  found  throughout  this  part  of  the  alimentary  canal,  from  the 
pylorus  to  the  free  border  of  the  ileo-csecal  valve,  most  abundant  in  the 
duodenum  and  jejunum,  rather  less  so  in  theileum,  but  in  general  in  the 
proportion  of  from  20  to  40  to  the  square  millimetre.  In  the  upper 
part  of  the  intestine  they  are  flattened,  laminated,  or  leaf-like  in  form, 
becoming  cylindrical  and  filamentous  in  the  middle  and  lower  portions. 
In  the  human  subject  they  are  about  one-half  a  millimetre  in  length. 

Each  villus  consists  of  a  mass  of  tissue  continuous  with  that  of  the 
mucous  membrane  beneath.  It  is  covered 
with  a  uniform  layer  of  nucleated,  finely 
granular  cylindrical  epithelium  cells,  closely 
united  with  each  other  by  their  lateral  sur- 
faces, and  presenting  at  their  outermost  por- 
tion a  thin  layer  which  is  more  transparent 
than  the  rest  of  their  substance,  and  is 
marked,  according  to  Kolliker,  Frey,  and 
other  observers,  by  fine  vertical  striations. 
The  villus  is  penetrated  from  below  by  blood- 
vessels supplied  from  a  terminal  twig  of  the 
mesenteric  artery,  which  form  by  their  fre- 
quent division  and  inosculation  an  exceed- 
ingly abundant  capillary  network,  almost 
immediately  beneath  the  epithelial  layer. 
At  its  base  they  reunite  to  form  a  venous 
branch,  which  is  one  of  the  commencing 
rootlets  of  the  mesenteric  vein. 

In  the  deeper  part  of  the  villus,  and  lying 
nearly  in  its  longitudinal  axis,  there  is  also 
the  commencement  of  a  lymphatic  vessej, 
which,  after  its  emergence  from  the  base  of 
the  organ,  joins  the  general  system  of  the 
abdominal  lymphatic  or  lacteal  vessels.  The 
lymphatic  vessel  is  usually  single  in  the  fili- 


AN  IHTESTTTTAL    YlLLUS. 

— a.  Layer  of  cylindrical  epithe- 
lium, with  its  external  trans- 
parent  striated  portion,  b  b. 
Bloodvessels  entering  and  leav- 
ing the  villus.  c.  Lymphatic 
vessel  occupying  its  central 
axis.  (Leydig.) 

(189) 


190 


ABSORPTION. 


Fig.  57. 


form  or  cylindrical  villi,  sometimes  double  or  even  triple  in  those  of  a 
more  flattened  form.  It  has  exceedingly  thin  walls,  consisting  only  of 
a  single  layer  of  flattened  epithelium  cells. 

Closed  Follicles  of  the  Small  Intestine — In  addition  to  the  secreting 
glandules  and  villi,  the  intestine  presents,  throughout  its  extent,  two 

sets  of  glandular  looking  organs,  known 
as  the  glandules  solitariae  and  the 
glandular  agminatae.  The  first  of  these, 
or  the  solitary  glandules,  are  found  in 
the  upper  part  of  the  intestine,  scattered 
at  intervals  over  its  surface,  as  minute 
whitish  points.  Farther  down  they 
begin  to  occur  in  clusters  of  several  to- 
gether, and  in  the  lower  part  of  the 
jejunum  and  in  the  ileum  they  consti- 
tute rounded  or  elongated  oval  patches, 
from  1J  to  5  centimetres  in  length, 
known  by  the  name  of  "Peyer's  patches." 
These  patches  are  always  situated  op- 
posite the  attachment  of  the  mesentery, 
and  with  their  long  diameter  parallel  to 
the  axis  of  the  intestine. 

The  structure  of  the  solitary  gland- 
ules and  of  those  forming  Peyer's 
patches  is  the  same.  The  only  differ- 
ference  between  them  is  that  in  one  case 
the  follicles  are  distributed  separately  over  the  surface  of  the  intestine, 
while  in  the  other  they  are  collected  into  distinct  groups. 

Each  follicle  is  a  rounded  or 

Fig.  58.  ovoid  body,  from  one-half  to  two 

millimetres  in  diameter,  situated 
partly  in  the  thickness  of  the 
mucous  membrane,  and  partly 
below.  It  consists  of  an  ex- 
ternal investing  capsule,  closed 
on  all  sides,  from  the  inner  sur- 
face of  which  slender  anastomos- 
ing filaments  pass  through  the 
substance  of  the  organ,  forming 
a  delicate  scaffolding  or  frame- 
work of  minute  fibres.  In  the 
interstices  between  these  fibres 
there  is  a  small  quantity  of  fluid, 
together  with  an  abundance  of 

O 

OF  THE  CLOSED  FOLLICLES  OP  PET-     lymph    corpuscles,   or    faintly 

ER'S  PATCHES,  from  Small  Intestine  of  Pig,  ffranular  cells  about  13  mmm. 
showing  the  bloodvessels  in  its  interior.  Magni-  . 

fled  60  diameters.  in  diameter.    The  follicle  is  also 


FK  visit's     PATCH     of 
glandules  from  the  ileum. 


nominated 
(Boehm.) 


ABSORPTION.  191 

penetrated  by  capillary  bloodvessels,  which  pass  through  its  investing 
capsule  from  without,  inosculate  freely  with  each  other  in  its  interior, 
and  return  upon  themselves  in  loops  near  its  centre. 

The  follicles  have  a  close  relation  with  the  lymphatics  of  the  intestine. 
The  lymphatic  vessels  coming  from  the  villosities  form  a  plexus  in  the 
substance  of  the  mucous  membrane  from  which  branches  pass  to  the 
follicles  and  ramify  upon  their  surface,  forming  another  close  plexus  upon 
their  investing  capsule.  The  lymphatic  vessels,  however,  do  not  pene- 
trate into  the  interior  of  the  follicles,  which  are  occupied  by  blood- 
vessels alone  Owing  to  the  analogy  in  structure  between  these 
bodies  and  portions  of  the  lymphatic  glands,  as  well  as  to  the  fact  that 
the  lacteals  coming  from  the  neighborhood  of  Peyer's  patches  are 
more  numerous  than  from  other  points  of  the  intestine,  the  closed  folli-  , 
cles  are  generally  regarded  as  belonging  to  the  system  of  the  lym-  i-- 
phatic  glands.  They  constitute  the  simplest  form  of  these  glands, 
situated  in  or  immediately  beneath  the  intestinal  mucous  membrane. 
They  furnish  no  fluid  secretion  to  the  intestinal  cavity,  but  are  con- 
nected in  some  way  with  the  preparation  or  elaboration  of  the  absorbed 
materials. 

Mechanism  of  Absorption  by  the  Villi. — The  villi  are  the  active 
agents  in  the  process  of  absorption.  The  entire  extent  of  the  mucous 
membrane  of  the  small  intestine,  including  the  valvulse  conniventes,  is 
estimated  at  about  6000  square  centimetres  of  surface ;  and  as  the 
number  of  the  villi  is,  on  the  average,  not  less  than  30  to  the  square 
millimetre,  there  must  be  at  least  from  fifteen  to  twenty  millions  of  them 
in  the  whole  length  of  the  small  intestine.  By  their  great  abundance, 
accordingly,  as  well  as  by  their  projecting  form,  they  multiply  the  ex- 
tent of  surface  over  which  the  digested  fluids  come  in  contact  with  the 
intestinal  mucous  membrane,  and  increase,  to  a  corresponding  degree, 
the  energy  with  which  absorption  takes  place*  They  hang  out  into  the 
nutritious,  semi-fluid  mass  contained  in  the  intestinal  cavity,  as  the 
roots  of  a  tree  penetrate  the  soil ;  and  they  imbibe  the  liquefied  portions 
of  the  food  with  a  rapidity  which  is  in  direct  proportion  to  their  extent 
of  surface  and  the  activity  of  the  circulation. 

The  process  of  absorption  is  also  hastened  by  the  peristaltic  move- 
ments of  the  intestine.  The  muscular  layer  here,  as  in  other  parts  of 
the  alimentary  canal,  is  double,  consisting  of  both  circular  and  longitu-  I/ 
dinal  fibres.  The  action  of  these  fibres  maybe  readily  seen  by  pinching 
the  exposed  intestine  with  the  blades  of  a  forceps.  A  contraction  takes 
place  at  the  spot  irritated,  by  which  the  intestine  is  reduced  in  diame- 
ter, its  cavity  partially  obliterated,  and  its  contents  forced  onward  into 
the  succeeding  portion  of  the  alimentary  canal.  The  local  contraction 
then  propagates  itself  to  the  neighboring  parts,  while  the  portion 
originally  contracted  becomes  relaxed ;  so  that  a  slow,  continuous, 
creeping  motion  of  the  intestine  is  produced,  by  successive  waves  of 
contraction  and  relaxation,  which  follow  each  other  from  above  down- 
ward. At  the  same  time,  the  longitudinal  fibres  have  a  similar  alter- 


192 


ABSORPTION. 


Fig.  59. 


nating  action,  drawing  the  narrowed  portions  of  intestine  up  and  down, 
as  they  successively  enter  into  contraction  or  become  relaxed  in  the 
intervals.  The  effect  of  the  whole  is  to  produce  a  peculiar,  writhing, 
worm-like,  or  "  vermicular"  motion,  among  the  different  coils  of  intes- 
tine. During  life,  the  vermicular  or  peristaltic  motion  of  the  intestine 
is  excited  by  the  presence  of  food  undergoing  digestion.  By  its  action, 
the  substances  which  pass  from  the  stomach  into  the  duodenum  are 
steadily  carried  from  above  downward,  so  as  to  traverse  the  entire 
length  of  the  small  intestine,  and  to  come  in  contact  successively  with 
the  whole  extent  of  its  mucous  membrane.  During  this  passage  the 
absorption  of  the  digested  food  is  constantly  going  on.  Its  liquefied 
portions  are  taken  up  by  the  villi  of  the  mucous  membrane,  and  succes- 
sively disappear;  so  that,  at  the  termination  of  the  small  intestine, 
there  remains  only  the  undigested  portion  of  the  food,  together  with 
the  refuse  of  the  intestinal  secretions.  These  pass  through  the  ileo- 
csecal  orifice  into  the  large  intestine,  and  there  become  reduced  to  the 
condition  of  feces. 

The  digested  fluids  taken  up  from  the  intestine  are  first  absorbed  by 
the  epithelial  cells  covering  the  surface  of  the  villi,  and   are  thence 

transmitted  to  the  deeper  por- 
tions of  their  tissue.  This  pas- 
sage of  the  products  of  diges- 
tion through  the  substance  of 
the  epithelial  cells  is  difficult 
of  demonstration  for  perfectly 
homogeneous  liquids,  but  it 
may  be  distinctly  seen  in  the 
case  of  the  fatty  matters  of  the 
chyle.  As  already  described, 
the  oleaginous  matters  of  the 
food  are  emulsified  by  diges- 
tion, forming  in  the  intestine  a 
white  milky  fluid,  termed  the 
"  chyle,"  which  is  entangled  in 
the  folds  of  the  mucous  mem- 
brane, and  adheres  to  the  sur- 
face of  the  villi.  In  chyle 
which  is  drawn  either  from  the 

lacteal  vessels  or  the  thoracic  duct,  the  fatty  matter  still  presents  itself 
in  the  same  condition,  and  retains  all  the  chemical  properties  of  oil. 
Examined  by  the  microscope,  it  is  seen  to  exist  under  the  form  of  fine 
granules  and  molecules,  varying  in  size  from  2.5  mmm.  downward, 
which  present  the  ordinary  appearances  of  oil  in  a  state  of  minute  sub- 
division. The  chyle,  therefore,  does  not  represent  the  entire  product  of 
the  digestive  process,  but  consists  of  the  fatty  substances,  suspended  by 
emulsion  in  a  serous  fluid. 

The  emulsioned  oil  has  accordingly  passed  from  the  cavity  of  the 


CHYLE  PROM  COMMENCEMENT  OF  THORACIC 
DUCT,  from  the  Dog. 


ABSORPTION. 


193 


intestine  into  that  of  the  lacteal  vessels.  Its  transmission  is  facilitated 
by  the  alkaline  condition  of  the  blood  and  of  the  intestinal  juices.  Oil 
by  itself  is  a  non-diffusible  substance;  that  is,  it  is  incapable  of 
passing  through  an  animal  membrane  by  endosmosis.  If  a  fluid  con- 
taining oil  be  placed  on  one  side  of  an  animal  membrane,  and  pure 
water  on  the  other,  the  water  will  readily  penetrate  the  substance  of 
the  membrane,  while  the  oily  particles  cannot  be  made  to  pass  under 
any  ordinary  pressure.  Though  this  be  true,  however,  for  pure  water, 
it  is  not  true  for  slightly  alkaline  fluids  like  the  serum  of  blood  or  the 
lymph.  This  has  been  demonstrated  by  the  experiments  of  Matteucci, 
in  which  he  made  an  emulsion  with  an  alkaline  fluid  containing  4.3 
parts  per  thousand  of  potassium  hydrate.  Such  a  solution  has  no  per- 
ceptible alkaline  taste,  and  its  action  on  reddened  litmus  paper  is  about 
equal  to  that  of  the  lymph  and  chyle.  If  this  emulsion  were  placed  in 
an  endosmometer,  together  with  a  watery  alkaline  solution  of  similar, 
strength,  it  was  found  that  the  oily  particles  penetrated  the  animal 
membrane  without  much  difficulty,  and  mingled  with  the  fluid  on  the 
opposite  side.  Endosmosis  will  thus  take  place  with  a  fatty  emulsion, 
provided  the  fluids  used  in  the  experiment  be  slightly  alkaline  in  re- 
action. 

The  fatty  molecules  of  the  chyle,  accordingly,  are  taken  up  by  the 
layer  of  epithelium  cells  covering  the  surface  of  the  villi,  and  their 
passage  into  and  through  the  epithelial  layer  produces  a  marked  altera- 
tion in  the  physical  appearance  of  the  cells  composing  it.  In  the  inter- 
vals of  digestion  these  cells  are  nearly  transparent  and  homogeneous- 


60. 


Fig.  61. 


INTESTINAL   EPITHELIUM;  from  the 
Dog,  while  fasting. 


INTESTINAL  EPITHELIUM;  from  the  Dog, 
during  the  digestion  of  fat. 


looking,  presenting  under  the  microscope  only  the  appearance  of  a  very 
fine  and  delicate  granulation.  (Fig.  60.)  But  if  examined  during  the 
digestion  and  absorption  of  fatty  matters,  their  substance  is  seen  to  be 


194  ABSORPTION. 

crowded  with  oily  particles,  taken  up  by  absorption  from  the  intestinal 
cavity.  (Fig.  61.)  The  oily  matter  then  passes  onward,  penetrating 
deeper  into  the  substance  of  the  villus,  until  it  is  at  last  received  by  the 
capillary  vessels  in  its  interior. 

Absorption  by  the  Bloodvessels. — The  final  absorption  of  the  digested 
fluids  is  accomplished  mainly  by  the  bloodvessels  of  the  intestinal  villi. 
Their  situation,  their  numbers,  and  the  rapid  movement  of  the  blood 
through  these  channels,  are  all  circumstances  especially  favorable  for 
the  performance  of  this  function.  The  capillary  plexus  of  each  villus 
is  situated  in  the  most  superficial  part  of  its  substance,  almost  immedi- 
ately beneath  the  epithelium  cells  which  cover  its  surface,  so  that  the 
absorbed  fluids,  after  passing  through  the  epithelial  layer,  come  at  once 
in  contact  with  the  capillaries  of  the  vascular  network.  The  exten- 
sion of  absorbing  surface,  from  the  repeated  division  and  inosculation 
of  these  vessels,  and  the  constant  renovation  of  the  fluids  which  they 
contain,  by  the  movement  of  the  circulation,  provide  for  their  constant 
activity,  and  drain  away  the  absorbed  fluids  from  the  substance  of  the 
villus  as  fast  as  they  are  taken  up  by  its  exposed  surface. 

Fig.  62. 


CAPILLARY  BLOODVESSELS  OF  THE  INTESTINAL  VILLI;  from  the  Mouse. 

(KOlliker  ) 

The  activity  of  the  bloodvessels  in  the  process  of  absorption  is  also 
a  matter  of  direct  observation.  Abundant  experiments  have  demon- 
strated, not  only  that  soluble  substances  introduced  into  the  intestine 
may  be  soon  afterward  detected  in  the  blood  of  the  portal  vein,  but 
that  absorption  takes  place  more  rapidly  and  abundantly  by  the  blood- 
vessels than  by  the  lacteals.  This  was  first  shown  by  Magendie,1  who 
found  that  the  absorption  of  poisonous  substances  would  take  place,  in 
the  living  animal,  both  from  the  cavity  of  the  intestine  and  from  the 
tissues  of  the  lower  extremity,  notwithstanding  that  all  communication 
through  the  lacteals  and  lymphatics  was  cut  off,  and  the  passage  by  the 

1  Journal  de  Physiologic.    Paris,  1825,  tome  i.  p.  18. 


ABSORPTION.  195 

bloodvessels  alone  remained.  These  results  were  afterward  corroborated 
by  Panizza,  who  succeeded  in  detecting  the  substance  which  had  been 
absorbed  in  the  venous  blood  returning  from  the  part.  This  observer 
opened  the  abdomen  of  a  horse,  and  drew  out  a  fold  of  the  small  intes- 
tine, about  20  centimetres  in  length  (Fig.  63,  a,  a),  which  he  included 

Fig.  63. 


PANIZZA'S  EXPERIMENT. — aa.  Intestine,  b.  Point  of  ligature  of  mesenteric  vein. 
c.  Opening  in  intestine  for  introduction  of  poison,  d.  Opening  in  mesenteric  vein  behind  the 
ligature. 

between  two  ligatures.  A  ligature  was  then  placed  (at  6)  upon  the 
mesenteric  vein  receiving  the  blood  from  this  portion  of  intestine;  and, 
in  order  that  the  circulation  might  not  be  interrupted,  an  opening  was 
made  (at  d)  in  the  vein  behind  the  ligature,  so  that  the  blood  brought 
by  the  mesenteric  artery,  after  circulating  in  the  intestinal  capillaries, 
passed  out  at  the  opening,  and  was  collected  in  a  vessel  for  examination. 
Hydrocyanic  acid  was  then  introduced  into  the  intestine  by  an  opening 
at  c,  and  almost  immediately  afterward  its  presence  was  detected  in  the 
venous  blood  flowing  from  the  orifice  at  d.  The  animal,  however,  was 
not  poisoned,  since  the  acid  was  prevented  from  gaining  an  entrance 
into  the  general  circulation  by  the  ligature  at  6. 

Panizza  afterward  varied  this  experiment  in  the  following  manner: 
Instead  of  tying  the  mesenteric  vein,  he  simply  compressed  it.  Then, 
hydrocyanic  acid  being  introduced  into  the  intestine,  as  above,  no  effect 
was  produced  on  the  animal,  so  long  as  compression  was  maintained 
upon  the  vein.  But  as  soon  as  the  blood  was  again  allowed  to  pass 
through  the  vessels,  symptoms  of  general  poisoning  became  manifest. 
Lastly,  in  a  third  experiment,  the  same  observer  removed  all  the  nerves 
a'nd  lacteal  vessels  supplying  the  intestinal  fold,  leaving  the  blood- 
vessels alone  untouched.  Hydrocyanic  acid,  now  being  introduced  into 
the  intestine,  found  an  entrance  at  once  into  the  general  circulation,  and 


\ 


196  ABSORPTION. 

the  animal  was  immediately  poisoned.  The  bloodvessels,  therefore,  are 
not  only  capable  of  absorbing  fluids  from  the  intestine,  but  take  them 
up  even  more  rapidly  than  the  lacteals. 

The  entrance  of  digested  materials  into  the  bloodvessels  of  the  intes- 
tine is  readily  demonstrated  in  a  similar  way.  After  the  digestion  of 
food  containing  a  mixture  of  albuminous  and  starchy  ingredients,  both 
sugar  and  albuminose  are  to  be  met  with  in  the  blood  of  the  mesenteric 
and  portal  veins.  Digested  and  emulsioned  fatty  matters  may  also  be 
distinctly  followed,  in  their  passage  through  the  same  channels,  by  the 
turbid  and  chylous  aspect  which  they  communicate  to  the  portal  blood. 
It  is  easy  to  see  that  the  blood  of  the  portal  system,  in  the  carnivorous 
animals  during  digestion,  contains  fatty  matter  in  a  state  of  minute 
subdivision,  similar  in  appearance  to  that  found  in  the  chyle  and  in  the 
substance  of  the  villi,  often  so  abundant  as  to  communicate  a  turbid 
appearance  to  the  serum  after  coagulation;  and  various  observers 
(Lehmann,  Schultz,  Simon),  in  examining  the  blood  from  different  parts 
of  the  body,  have  also  found  the  blood  of  the  portal  system  consider- 
ably richer  in  fat  than  that  of  the  arteries  or  of  other  veins,  particularly 
while  intestinal  digestion  is  going  on  with  activity. 

Absorption  by  the  Lacteals. — The  absorption  of  digested  materials, 
but  more  particularly  of  the  fatty  matters,  is  also  accomplished  by  the 
lymphatics  or  lacteals  of  the  small  intestine.  These,  however,  do  not 
form  a  distinct  class  of  vessels  by  themselves,  but  are  simply  a  part  of 
the  great  system  of  lymphatic  or  absorbent  vessels,  which  are  to  be 
found  everywhere  in  the  integuments  of  the  head,  the  parietes  of  the 
trunk,  the  upper  and  lower  extremities,  and  in  the  glandular  and  mus- 
cular organs  and  mucous  membranes  throughout  the  body.  Originat- 
ing in  the  tissues  of  the  above  mentioned  parts,  they  pass  from  the 
periphery  toward  the  centre,  their  branches  converging  and  uniting  with 
each  other  like  those  of  the  veins,  and  passing,  at  various  points  in 
their  course,  through  certain  glandular-looking  bodies,  known  as  the 
lymphatic  glands. 

The  fluid  generally  contained  in  these  vessels  is  called  the  "  lymph." 
It  is  a  colorless  or  slightly  yellowish  transparent  liquid,  which  is  ab- 
sorbed by  the  lymphatic  vessels  from  the  tissues  in  which  they  originate. 
So  far  as  regards  its  composition,  it  is  known  to  contain,  beside  water 
and  saline  matters,  a  small  quantity  of  fibrine  and  albumen.  Its  ingre- 
dients are  evidently  derived  from,  the  metamorphosis  of  the  tissues,  and 
are  returned  to  the  centre  of  the  circulation  to  be  eliminated  by  excretion, 
or  to  undergo  some  new  transforming  process,  the  details  of  which  are 
not  as  yet  fully  understood. 

The  lymphatic  vessels  of  the  intestine  originate,  as  we  have  seen,  in 
the  substance  of  the  villi,  where  they  commence  by  longitudinal  spaces 
lined  with  flattened  epithelium  cells,  becoming  provided,  at  a  short  dis- 
tance from  their  origin,  with  thin,  transparent,  elastic  coats,  like  those 
of  the  capillary  bloodvessels.  After  leaving  the  base  of  the  villi  they 
become  part  of  the  lymphatic  plexus,  from  which  the  main  branches  pass 


ABSORPTION.  197 

inward,  between  the  layers  of  the  mesentery,  from  the  intestine  toward 
the  posterior  part  of  the  abdomen.  During  their  course  through  the 
mesentery,  they  inosculate  with  each  other  by  transverse  branches,  and 
pass  in  succession  through  several  ranges  of  mesenteric  glands,  which 
have  the  same  structure  with  those  already  mentioned,  and  which  are 
accordingly  the  lymphatic  glands  of  the  abdominal  cavity.  On  arriving 
near  the  attached  portion  of  the  mesentery,  on  the  right  side  of  the 
abdomen,  at  about  the  level  of  the  second  lumbar  vertebra,  they  terminate 
iii  a  saccular  dilatation,  known  as  the  "  receptaculum  chyli."  From 
this  point  the  thoracic  duct  passes  upward  through  the  cavity  of  the 
chest,  crossing  obliquely  from  the  right  to  the  left  of  the  median  line, 
and  finally  discharges  its  contents  into  the  left  subclavian  vein,  at  its 
junction  with  the  jugular  of  the  same  side. 

In  the  intervals  of  digestion  the  fluid  contained  in  the  lymphatic 
vessels  is  the  same  in  appearance  throughout  the  body.  Its  colorless 
and  transparent  character,  together  with  the  small  size  of  the  lymphatics 
themselves,  and  the  thinness  and  delicacy  of  their  coats,  make  these 
vessels  nearly  or  quite  invisible  to  the  unaided  eye.  But  during  the 
digestion  and  absorption  of  food  the  elements  of  the  chyle  are  taken  up 
by  the  lymphatics  of  the  small  intestine,  which  are  distended  with  a 
milky  fluid,  and  thus  become  visible  as  an  abundant  network  of  opaque 
white  filaments,  ramifying  in  the  intestinal  walls,  converging  from  the 
intestine  to  the  receptaculum  chyli,  and  contrasting  strongly  with  the 
ruddy  and  semi-transparent  color  of  the  neighboring  tissues.  If,  when 
in  this  condition,  one  of  them  be  opened  with  the  point  of  a  scalpel,  it 
discharges  a  chylous  liquid,  which  is  easily  seen  to  be  the  same  in 
character  with  that  contained  in  the  cavity  of  the  intestine  itself,  namely, 
an  emulsion  of  fatty  molecules  and  granulations.  Owing  to  the  appear- 
ance thus  given  to  the  vessels  themselves,  and  to  the  milky  fluid  which 
they  contain,  they  have  received  the  name  of  the  lacteals,  or  lactiferous 
vessels  of  the  abdomen. 

The  presence  of  chyle  in  the  lacteals  is,  therefore,  not  a  constant,  but 
only  a  periodical  phenomenon.  The  fatty  substances  constituting  the 
chyle  begin  to  be  absorbed  during  the  process  of  digestion,  as  soon  as 
they  have  been  disintegrated  and  emulsioned  by  the  action  of  the  intes- 
tinal fluids.  As  digestion  proceeds,  they  accumulate  in  larger  quantity, 
and  gradually  fill  the  whole  lacteal  system,  giving  to  its  vessels  the 
characteristic  aspect  above  described.  But  as  digestion  and  absorption 
from  the  intestinal  cavity  come  to  an  end,  the  milky  fluid  disappears 
from  the  lymphatics,  and  they  resume  their  former  transparent  and 
colorless  appearance. 

The  lacteals  accordingly  are  nothing  more  than  the  lymphatics  of  the 
small  intestine,  which,  in  addition  to  the  transparent  and  colorless 
lymph  which  they  usually  contain,  have  absorbed  a  fluid  rich  in  fat 
derived  from  the  process  of  digestion.  While  this  process  is  going  on, 
they  are  distinguished  from  the  lymphatics  elsewhere  by  the  milky 
character  of  their  contents,  which  accumulate  in  the  receptaculum  chyli, 


198 


ABSOKPTION. 


Fiff.  64. 


and  may  be  followed  thence  through  the  thoracic  duct,  to  the  point 
where  it  terminates  in  the  left  subclaviaii  vein. 

It  was  owing  to  the  opacity  and  visibility  of  the  lacteals  during  diges- 
tion that  these  vessels  were  discovered  in  1622  by  Asellius,  who  first 
saw  them  on  opening  the  abdomen  of  a  dog,  a  few  hours  after  the  inges- 
tion  of  food.  The  discovery  of  the  general  system  of  lymphatic  vessels 

was  made  subsequently  by  Hud- 
beck  and  Bartholin,  in  1651  and 
1653,  and  was  consequent  upon 
the  previous  observations  on 
the  lacteals  of  the  abdomen. 

That  the  white  color  of  the 
chyle  during  digestion  is  really 
due  to  the  presence  of  fatty  sub- 
stances absorbed  from  the  intes- 
tine, is  shown  by  the  fact  that 
the  intensity  of  this  color  is  in 
proportion  to  the  quantity  of 
fat  contained  in  the  food.  It 
is  generally  less  marked  in  her- 
bivorous than  in  carnivorous 
animals.  According  to  the- ob- 
servations of  Tiedemann  and 
Gmelin,  in  a  dog  fed  with  fatty 
matters  the  lacteals  are  abund- 
antly filled  with  an  opaque  white 
fluid,  while  in  the  same  animal 
fed  with  starchy  matters  alone, 
the  chyle  is  pale  and  but  slightly 
opaline ;  and  finally  Bernard  has 
shown  that  if,  in  a  dog  after 
several  days  fasting,  a  little 
ether,  containing  fat  in  solution, 
be  injected  into  the  stomach, 
without  the  introduction  of  any 
other  food,  at  the  end  of  a  few 
hours  the  lacteals  are  found 
fully  distended  with  milky  chyle, 
precisely  similar  in  appearance 
to  that  obtained  during  ordinary 
digestion. 

Passage  of  Absorbed  Materials  into  the  Circulation.— The  products 
of  digestion,  which  are  taken  up  by  the  bloodvessels  and  lymphatics  of 
the  intestine,  pass  by  two  different  routes  into  the  general  circulation. 
The  blood  of  the  portal  system,  containing  albuminose,  sugar,  and 
molecular  fat,  is  carried  at  once  to  the  liver,  where  it  traverses  the 
capillary  vessels  of  this  organ  before  reaching  the  vena  cava  and  the 


LACTEALS  AND  LYMPHATICS,  during 
digestion. 


ABSORPTION. 

right  side  of  the  heart.  The  chyle,  on  the  other  hand,  containing  also 
a  large  proportion  of  fatty  ingredients,  passes  by  the  thoracic  duct 
directly  to  the  left  subclavian  vein  and  is  there  mingled  with  the  return- 
ing current  of  the  venous  blood.  But  all  these  substances,  after  entering 
the  circulation  and  coming  in  contact  with  the  organic  ingredients  of 
the  blood,  are  modified  in  such  a  way  as  no  longer  to  be  recognizable 
under  their  original  form.  This  change  takes  place  very  rapidly  with 
the  albuminose  and  the  sugar,  both  of  which  are  taken  up  in  greatest 
proportion  by  the  bloodvessels  and  are  carried  at  once  through  the 
hepatic  capillaries.  The  albuminose  passes,  in  all  probability,  into  the 
condition  of  ordinary  albumen,  while  the  sugar  rapidly  becomes  decom- 
posed, or  transformed,  and  loses  its  characteristic  properties ;  so  that, 
on  arriving  at  the  entrance  of  the  general  circulation,  both  these  newly 
absorbed  ingredients  have  become  already  assimilated  to  those  which 
previously  existed  in  the  blood.  The  fatty  matters  also,  which  reach 
the  blood  on  the  right  side  of  the  heart  both  by  the  portal  and  hepatic 
veins,  and  by  the  thoracic  duct  and  subclavian  vein,  undergo  a  trans- 
formation while  passing  through  the  lungs  by  which  their  distinctive 
characters  are  destroyed,  and  they  are  no  longer  visible  as  oleaginous 
molecules.  This  alteration  is  so  complete,  during  the  early  part  of 
digestion,  or  when  the  proportion  of  fat  in  the  food  is  small,  that  all  the 
oleaginous  matter  disappears  in  the  lungs  and  none  of  it  is  to  be  de- 
tected in  the  blood  of  the  general  circulation. 

But  as  digestion  proceeds,  especially  when  the  food  has  been  abun- 
dant in  oleaginous  substances,  an  increasing  quantity  of  fatty  matter 
finds  its  way,  by  these  two  passages,  into  the  blood ;  and  a  time  at  last 
arrives  when  the  whole  of  the  fat  so  introduced  is  not  destroyed  during 
its  passage  through  the  lungs.  Its  absorption  taking  place  at  this  time 
more  rapidly  than  its  decomposition,  it  begins  to  appear,  in  moderate 
quantity,  in  the  blood  of  the  general  circulation ;  and,  lastly,  when  the 
intestinal  absorption  is  at  its  point  of  greatest  activity,  it  is  found  in 
considerable  abundance  throughout  the  entire  vascular  system.  At  this 
period,  some  hours  after  the  ingestion  of  food  rich  in  oleaginous  matters, 
the  blood,  not  only  of  the  portal  vein,  but  also  of  the  general  circula- 
tion, everywhere  contains  a  superabundance  of  fat,  derived  from  the 
digestive  process.  If  blood  be  then  drawn  from  the  veins  or  the  arteries 
in  any  part  of  the  body,  it  will  present  the  peculiar  appearance  known  as 
that  of  "chylous"  or  "  milky"  blood.  On  the  separation  of  the  clot  the 
serum  is  turbid ;  and  after  a  few  hours  of  repose,  the  fatty  substances 
which  it  contains  rise  to  the  top  and  cover  its  surface  with  a  partially 
opaque  and  creamy-looking  pellicle.  This  appearance  has  been  occa- 
sionally observed  in  the  blood  of  the  human  subject,  particularly  in 
cases  of  apoplexy  occurring  after  a  full  meal.  It  is  a  purely  normal  / 
phenomenon,  and  depends  simply  on  the  rapid  absorption,  at  certain 
periods  during  the  digestive  process,  of  oleaginous  substances  from  the 
intestine.  It  can  be  observed  in  the  dog  at  any  time  by  feeding  him  with 


200  ABSORPTION. 

fat  meat,  and  drawing  blood,  seven  or  eight  hours  afterward,  from  the 
carotid  artery  or  the  jugular  vein. 

This  state  of  things  continues  for  a  varying  length  of  time,  according 
to  the  amount  of  oleaginous  matters  contained  in  the  food.  When 
digestion  is  terminated,  and  the  fat  ceases  to  be  introduced  in  unusual 
quantity  into  the  circulation,  its  transformation  and  decomposition  con- 
tinuing to  take  place  in  the  blood,  it  disappears  gradually  from  the 
veins,  arteries,  and  capillaries  of  the  general  system ;  and,  finally,  when 
the  whole  of  it  has  been  disposed  of  by  the  nutritive  process,  the  serum 
again  becomes  transparent,  and  the  blood  returns  to  its  ordinary  condi- 
tion. 

In  this  manner  the  nutritive  elements  of  the  food,  prepared  for  ab- 
sorption by  the  digestive  process,  are  taken  up  into  the  circulation  under 
the  different  forms  of  albuminose,  sugar,  and  chyle,  and  accumulate  as 
such,  at. certain  times,  in  the  blood.  But  these  conditions  are  tempo- 
rary and  transitional.  The  nutritive  materials  soon  pass  by  transfor- 
mation into  other  forms,  and  become  assimilated  to  the  pre-existing 
elements  of  the  circulating  fluid.  In  this  way  they  accomplish  finally 
the  object  of  digestion,  and  replenish  the  blood  by  a  supply  of  new 
materials  from  without. 


CHAPTEE  X. 

THE   BILE. 

THE  first  peculiarity  of  the  liver,  as  compared  with  other  secreting 
organs,  is  that  it  is  supplied  with  blood  at  the  same  time  from  two  dif-' 
lerent  sources  ;  namely,  from  the  hepatic  artery  and  the  portal  vein. 
The  ramifications  of  the  hepatic  artery  are  especially  distributed  to  the 
walls  of  the  hepatic  ducts,  to  those  of  the  portal  vein,  to  the  capsule  of 
Glisson,  and  to  the  peritoneal  covering  of  the  organ ;  while  those  of  the 
portal  vein  pass  in  a  peculiar  manner  into  the  glandular  parenchyma, 
and  after  traversing  its  substance  as  a  capillary  plexus  become  continu- 
ous with  the  rootlets  of  the  hepatic  vein.  Beside  arterial  blood,  accord- 
ingly, which  it  receives  in  common  with  the  other  abdominal  organs, 
in  moderate  quantity,  it  is  supplied  with  an  abundance  of  venous  blood, 
collected  by  the  portal  system  from  the  stomach,  the  spleenr  the  pancreas 
and  the  intestinal  canal. 

Secondly,  the  liver  is  distinguished  by  its  large  size.  While  the 
weight  of  all  the  salivary  glands  taken  together,  in  the  human  species, 
is  but  little  over  100  grammes,  and  that  of  the  pancreas  about  75 
grammes,  the  liver  forms  a  compact  vascular  and  glandular  organ, 
weighing  nearly  or  quite  1600  grammes,  and  occupying  a  considerable 
portion  of  the  abdominal  cavity. 

Lastly,  the  liver  is  peculiar  in  its  texture,  and  differs  so  much  in  this 
respect  from  the  other  secretory  organs,  as  to  require  a  special  descrip- 
tion. As  in  other  instances,  the  secreting  apparatus  consists  essentially 
of  glandular  cells  and  capillary  bloodvessels,  with  the  ducts  which  col- 
lect and  transport  the  secreted  fluid  ;  but  these  elements,  instead  of 
being  arranged  as  elsewhere  in  distinct  groups  of  tubular  or  rounded 
follicles,  are  closely  united  with  each  other,  forming  on  all  sides  a  con- 
tinuous mass  by  their  mutual  contact  and  adhesion. 

The  substance  of  the  liver,  in  man  and  in  the  quadrupeds  generally, 
is  divided  into  pentagonal  or  hexagonal  masses  or  islets,  about  1.5  milli- 
metre in  diameter,  which  are  known  by  the  name  of  the  hepatic  lobules. 
These  lobules,  however,  are  not  distinctly  separated  from  each  other, 
but  are  simply  made  visible  by  the  relative  arrangement  of  the  afferent 
and  efferent  bloodvessels.  Each  lobule  is  embraced  upon  its  external 
surface  by  the  terminal  branches  of  the  portal  vein,  which  ramify  be- 
tween the  lobules  lying  adjacent  to  each  other.  These  vessels  are 
accordingly  known  as  the  interlobular  veins.  From  the  side  of  the 
interlobular  vein,  minute  vessels  pass  into  the  substance  of  the  lobule, 
and  there  form  by  their  division  and  inosculation  an  abundant  capillary 
14  (  201  ) 


202 


THE    BILE. 


plexus,  the  vessels  of  which  have  a  general  convergent  direction  from 
the  periphery  toward  the  centre.  At  the  middle  part  of  the  lobule  they 
unite  to  form  the  commencement  of  an  efferent  vessel  which,  from  its 

central   or   interior   posi- 

Fig.  65.  tion,  is  termed  the  intra- 

lobular  vein.  This  root- 
let continues  its  course 
until  it  joins  one  of  the 
smaller  branches  of  the 
hepatic  vein.  Each  lobule 
may  therefore  be  con- 
sidered as  a  more  or  less 
ovoid,  cylindrical  or  pris- 
matic mass,  resting  upon 
a  branch  of  the  hepatic 
vein,  and  attached  to  this 
vessel  by  its  own  intra- 
lobular  vein,  which  passes 
through  its  axis  and  re- 
ceives the  blood  collected 
from  its  capillary  vessels  ; 
while  it  is  encircled  by 
terminal  branches  of  the 
portal  vein  supplying  the 
blood  for  its  interior  cir- 
culation. 

Beside  its  capillary  bloodvessels,  the  mass  of  the  lobule  is  made  up 
mostly  of  glandular  cells.     These  cells  are  generally  of  a  five-  or  six- 


HEPATIC  LOBULE,  in  transverse  section,  showing 
the  distribution  of  its  bloodvessels. — a,  a.  Interlobular 
veins,  b.  Intralobular  vein,  c,  c,  c.  Plexus  of  Capillary 
bloodvessels  in  the  substance  of  the  lobule,  d,  d.  Twigs 
of  inteilobular  vein,  passing  to  adjacent  lobules. 


Fig.  66. 


GLANDULAR  HEPATIC  CELLS.    From  the 
human  liver. 


sided  prismatic  form,  often  with 
one  or  two  of  their  borders  ex- 
cavated by  curvilinear  furrows 
at  the  points  where  they  are  in 
contact  with  a  capillary  blood- 
vessel. They  are,  on  the  aver- 
age, 22  mmm.  in  diameter,  of  a 
finely  granular  aspect,  usually, 
in  the  human  subject,  containing 
one  or  more  minute  fat  globules, 
and  provided  with  a  well-marked 
round  or  oval  nucleolated  nu- 
cleus. The  cells  are  every- 
where in  contact  with  each 
other  by  their  plane  surfaces, 
and  each  one  is  also  in  direct 
relation  at  several  points  with 
a  capillary  bloodvessel.  Thus 


THE    BILE. 


203 


the  union  of  these  two  elements  is  intimate  and  complete  throughout 
the  substance  of  the  hepatic  lobule. 

There  is  an  equally  close  connection  between  the  glandular  substance 
of  the  liver  and  the  biliary  ducts.  The  main  hepatic  duct,  which  with 
its  ramifications  accompanies  the  divisions  of  the  portal  vein,  breaks  up 
into  branches  which  finally  reach  the  interlobular  spaces.  The  biliary 
ducts  in  the  human  liver  which  have  a  larger  diameter  than  about  200 
mmm.  are  lined  with  cells  of  cylindrical  epithelium ;  while  in  those 
which  are  below  100  mmm.  in  diameter,  the  form  of  the  cells  changes 
gradually  to  that  of  pavement  epithelium.  The  biliary  ducts  which 
occupy  the  interlobular  spaces  are  of  the  smaller  variety,  being  not 
more  than  50  mmm.  in  diameter,  and  are  lined  accordingly  with  pave- 
ment epithelium.  They  break  up  into  communicating  branches  which 
cover  the  surface  of  the  lobule  with  a  plexus  of  biliary  canaliculi. 

Fig.  67. 


FINER  BILIARY  CANALS  AND  BILIARY  DTTCTS,  from  the  frog's  liver.— a.  Small 
biliary  duct,  with  its  lining  of  epithelium  cells.  6,  c.  Terminal  branches  of  the  minute  bili- 
ary canals,  surrounded  by  glandular  cells,  d.  Transverse  communicating  branch  between 
two  biliary  canals,  e,  e.  Sheath  of  glandular  secreting  cells,  surrounding  the  biliary  canals. 
/.  Section  of  capillary  bloodvessel.  (Eberth.) 

From  this  superficial  plexus  the  finest  biliary  tubes  penetrate  into  the 
substance  of  the  lobule  and  there  inosculate  with  each  other  between 
the  glandular  secreting  cells.  In  the  liver  of  the  amphibia  (frogs  and 
water-lizards),  as  shown  by  the  investigations  of  Hering  and  Eberth,  the 
Itimate  structure  of  the  secreting  apparatus  is  not  essentially  different 
from  that  of  other  lobulated  glands.  The  smaller  biliary  ducts,  lined 
with  pavement  epithelium,  give  off  minute  branches  which  communicate 
with  each  other  more  or  less  abundantly  and  are  themselves  in  contact 
everywhere  with  the  large  glandular  cells ;  each  terminal  branch  being 


204 


THE    BILE. 


Fig.  68. 


surrounded  by  a  single  sheath  of  such  glandular  cells,  which  stand  in 
place  of  the  epithelial  lining  of  a  tube  or  follicle. 

In  the  liver  of  the  warm-blooded  quadrupeds,  the  texture  of  the  organ 
is  more  compact,  the  glandular  cells  and  capillary  bloodvessels  more 
closely  united,  and  especially  the  finest  biliary  passages  in  the  substance 
of  the  lobule  are  more  abundant  and  inosculate  more  frequently  with 
each  other.  From  the  plexus  of  biliary  canaliculi  upon  the  surface  of 
the  lobule,  already  described,  branches  of  much  smaller  size  penetrate 
into  its  interior,  and  these  inosculate  so  abundantly  by  transverse  com- 
munications that  they  encircle  each  glandular  cell  in  the  meshes  formed 
by  their  network.  These  interior  communicating  passages  are  the  capil- 
lary bile-ducts.  They  are  much  smaller  than  the  capillary  bloodvessels, 
being  in  the  rabbit's  liver,  according  to  Kolliker,  not  more  than  2  mmm. 
in  diameter,  regularly  cylindrical  in  form,  and  without  any  perceptible 
dilatations  at  the  points  of  inosculation.  They  embrace  the  glandular 
cells  in  such  a  way  that  they  are  always  situated  at  the  greatest  possible 
distance,  that  is,  half  the  diameter  of  a  cell,  from  the  nearest  capillary 
bloodvessel ;  the  bloodvessels  running  along  the  borders  or  angular 
edges  of  the  prismatic  cells  (Kolliker),  while  the  capillary  bile-ducts 
pass  along  the  middle  of  their  plane  surfaces.  Thus,  the  two  sets  of 

canals,  namely,  capillary  blood- 
vessels and  bile-ducts,  form  a 
double  series  of  inosculating 
passages  embracing  the  gland- 
ular cells,  the  meshes  of  which 
are  always  directed  nearly  or 
quite  at  right  angles  to  each 
other. 

The  intralobular  capillary  bile 
ducts,  above  described,  as  de- 
monstrated by  injections,  have 
been  regarded  by  some  authori- 
ties as  artificially  produced  by 
the  accidental  extravasation  of 
the  injection  fluid  and  its  infiltra- 
tion between  the  glandular  cells. 
But  the  existence  of  these  ducts 
as  a  natural  formation  has  been 
corroborated  by  too  many  ob- 
servers to  leave  it  a  matter  of 
doubt,  especially  considering  the 
regular  and  uniform  arrange- 
ment under  which  they  present  themselves.  Their  situation  is  also 
against  the  hypothesis  of  their  artificial  origin,  since  they  are  not  placed 
at  the  angular  borders  of  the  glandular  cells,  where  an  extravasated 
fluid  would  naturally  find  its  way,  but  run  along  the  middle  of  their 
plane  surfaces  where  they  lie  in  close  contact  with  each  other ;  and. 


SECTION  OP  PART   ov    A 

L.OBULE    PROM     THE     RABBIT'S    LlVER.— 

a, 0,0.  Nucleated  glandular  cells.  b,b,b.  Capil- 
lary bile-ducts  passing  between  the  adjacent 
cells.  c,c,c.  Sections  of  capillary  bloodvessels. 
(Genth.) 


THE    BILE.  205 

finally,  Kolliker  has  found  that  the  capillary  bile  ducts  in  the  liver  of 
the  rabbit  may  become  visible  in  their  usual  positions  in  thin  sections 
hardened  in  alcohol,  where  no  injection  has  been  practised.  They  are, 
therefore,  to  be  regarded  as  the  finest  commencing  ramifications  of  the 
biliary  canals,  which  receive  the  secreted  fluids  directly  from  the  sub- 
stance of  the  glandular  cells. 

Physical  and  Chemical  Characters  of  the  Bile. — The  bile  is  distin- 
guished from  all  the  other  secretions  discharged  into  the  alimentary 
canal  principally  by  the  fact  that  it  does  not  contain  any  albuminous 
ingredient  analogous  to  those  of  the  saliva,  the  gastric,  pancreatic,  or 
intestinal  juices ;  its  most  important  constituents  being  nitrogenous 
crystallizable  substances,  together  with  cholesterine  and  coloring  mat- 
ters. Bile  taken  from  the  gall-bladder  contains,  it  is  true,  a  certain 
amount  of  mucus,  which  gives  it  more  or  less  of  a  ropy  and  viscid  charac- 
ter; but  this  mucus  is  secreted  by  the  gall-bladder  itself,  and  bile  taken 
from  the  gall-ducts  in  the  substance  of  the  organ  is  always  perfectly 
fluid  and  watery  in  consistency.  Furthermore,  the  gall-bladder  is  by 
no  means  constantly  present,  even  in  the  higher  animals,  being  absent, 
according  to  Wagner,  in  the  horse,  the  camel,  most  of  the  pach^dermata 
and  several  of  the  gnawing  animals,  and  at  the  same  time  present  in 
many  closely  allied  species.  The  bile  accordingly,  in  its  essential  in- 
gredients, differs  in  a  marked  degree  from  the  digestive  secretions 
proper. 

The  bile,  as  it  comes  from  the  gall-bladder,  is  a  clear,  more  or  less 
tenacious  and  ropy  fluid,  neutral  in  reaction,  with  a  faint  and  rather 
indefinite  animal  odor.  If  it  be  shaken  up  with  air,  or  if  air  be  blown 
into  it  through  a  narrow  tube,  it  easily  foams  up  into  a  frothy  mixture 
which  remains  for  a  long  time  on  the  surface  of  the  fluid.  This  property 
of  frothing  upon  agitation  with  air  does  not  depend  upon  the  mucus  which 
it  contains,  but  upon  the  biliary  salts  proper,  namely,  the  sodium  glyco- 
cholate  and  taurocholate ;  since  these  salts  iu  a  pure  watery  solution 
exhibit  the  same  property. 

Its  specific  gravity  is  rather  high,  as  compared  with  that  of  the  other 
secretions.  In  ox-bile,  we  have  found  it  to  be  1024,  in  pig's  bile  1030 
to  1036.  The  specific  gravity  of  human  bile,  according  to  Robin,  is 
from  1020  to  1026 ;  according  to  Jacobsen,  in  bile  from  a  biliary  fistula, 
but  little  over  1010.  We  have  found  it,  in  bile  taken  from  the  gall- 
bladder, 1018. 

Its  color  varies,  in  different  species  of  animals,  from  a  reddish-orange 
to  a  nearly  pure  green,  and  in  different  instances  presents  all  the  inter- 
mediate tints  of  golden-yellow,  reddish-brown,  olive-brown,  olive,  yel- 
lowish-green, and  bronze-green.  It  may  be  described  in  general  terms  as 
a  greenish-bronze,  with  sometimes  more  or  less  of  an  orange  tint. 
Human  bile  from  a  biliary  fistula  was  found  by  Jacobsen  to  be  of  a 
clear  yellowish  bronze-green;  that  taken  from  the  gall-bladder  after 
death  is  usually  of  a  dark  golden-brown.  Dog's  bile  is  of  a  brownish- 
olive  or  bronze  color;  pig's  bile  of  a  reddish-orange  or  reddish-brown; 


206  THE    BILE. 

and  sheep  and  ox-bile  of  a  greenish-olive,  or  more  frequently  of  a  pure 
green.  As  a  general  rule,  the  bile  of  the  herbivorous  animals  is  more 
decidedly  green  in  hue,  that  of  the  carnivora  and  omnivora  orange  or 
brown.  All  these  differences  may  be  referred  to  two  main  classes  of 
tints,  corresponding  with  two  different  coloring  matters;  in  one  of  which 
the  predominating  color  is  red  or  reddish-brown,  dependent  on  biliru- 
bine,  while  in  the  other  it  is  green  owing  to  the  presence  of  biliverdinc. 
As  the  proportion  of  these  two  substances  varies  in  any  given  specimen, 
it  will  exhib^  a  corresponding  color  of  the  pure  or  mingled  tints. 

The  color  of  the  bile  is  also  modified  by  oxidizing  agents,  which  pro- 
duce a  green  hue  in  bile  which  was  originally  olive  or  brown,  and 
increase  the  intensity  of  the  green  tint  when  this  color  is  already  pre- 
sent. If  brown  or  olive-colored  bile  be  exposed  to  the  air  for  a  short 
time,  its  surface  becomes  green  by  contact  with  the  atmosphere.  The 
same  change  may  be  instantly  produced  by  adding  to  the  bile  a  few 
drops  of  a  watery  solution  of  iodine ;  and  a  little  nitric  acid  acts  with 
great  energy,  developing  a  bright  grass-green  hue.  These  changes 
depend  upon  the  oxidation  of  the  bilirubine,  and  its  consequent  con- 
version into  biliverdine. 

The  green  color  of  bile  also  disappears  rapidly  when  excluded  from 
all  sources  of  oxidation.  If  ox-bile,  of  a  pure  green  or  olive-green  hue, 
be  inclosed  in  a  perfectly  full  and  securely  stoppered  vessel,  so  as  to  be 
entirely  protected  from  the  air,  it  gradually  loses  its  green  color  and 
becomes  of  a  dull  yellow.  This  change  progresses  from  the  external 
parts  of  the  liquid  toward  its  centre,  until  at  the  end  of  twelve,  twenty- 
four,  or  thirty-six  hours  the  whole  of  it  has  become  of  a  light  yellow  or 
yellowish-brown.  In  this  condition  the  green  hue  may  be  again  restored 
by  the  addition  of  iodine,  or  by  exposing  the  bile  in  thin  layers  to  the 
air.  The  green  color  of  the  bile  accordingly  appears  to  be  dependent 
on  continued  oxidation. 

The  bile  presents,  in  addition,  certain  remarkable  optical  properties 
which  distinguish  it  from  other  animal  fluids. 

In  the  first  place,  it  is  dichroic ;  that  is,  it  has  two  different  colors 
by  transmitted  light,  according  to  the  thickness  of  its  mass.  If  ox-bile, 
which  is  of  a  pure  transparent  green  by  ordinary  daylight  in  layers  of 
two  or  three  centimetres,  be  viewed  by  strong  sunlight  in  a  thickness 
of  five  or  six  centimetres,  it  is  red.  In  this  respect  it  resembles  a  solu- 
tion of  chlorophylle,  which  presents  the  contrast  of  the  same  two  colors 
in  a  very  marked  manner. 

Secondly,  the  bile  is  fluorescent?  that  is,  it  becomes  faintly  luminous 

1  This  property,  so  called  from  fluor  spar,  in  which  it  was  first  observed,  is 
shown  by  various  transparent  substances,  when  illuminated  by  solar  light,  or  by 
that  of  certain  parts  of  the  spectrum.  Thus  a  solution  of  quinine  sulphate,  which 
is  perfectly  colorless  by  ordinary  diffused  daylight,  becomes  blue  at  any  spot  where 
the  sun's  rays  are  concentrated  upon  it  by  a  lens ;  and  it  exhibits  a  distinct  lumi- 
nosity in  both  the  violet  and  ultra-violet  parts  of  the  spectrum. 


THE    BILE.  207 

with  a  color  of  its  own,  when  viewed  by  the  more  refrangible  rays  of 
the  solar  spectrum.  If  a  specimen  of  bile,  of  a  clear  greenish  color,  be 
placed  in  the  track  of  either  the  violet  or  blue  rays  of  the  solar  spec- 
trum, it  becomes  visible  with  a  light  yellowish-green  tint.  In  the  green 
it  is  more  yellowish ;  and  in  the  yellow  it  has  a  distinct  tinge  of  red ; 
while  in  the  red  ray  its  fluorescence  is  hardly  perceptible.  Thus  in  all 
parts  of  the  spectrum  where  it  exhibits  this  property,  it  emits  a  light 
of  less  refrangibility  than  that  of  the  ray  by  which  it  is  illuminated. 
The  property  of  fluorescence  is  also  manifested,  to  a  remarkable  degree, 
by  solutions  of  chlorophylle,  which,  although  of  a  clear  green  color  by 
diffused  daylight,  are  of  a  pure  red,  when  viewed  by  either  the  violet, 
blue,  green,  or  yellow  rays  of  the  spectrum. 

The  fluorescence  of  bile,  however,  does  not  depend  altogether  upon 
its  coloring  matter,  but  is  due  mainly  to  the  presence  of  the  biliary  salts, 
since  it  is  exhibited  in  an  equal  degree  by  watery  or  alcoholic  solutions 
of  sodium  taurocholate  and  glycocholate ;  the  only  difference  being  that 
the  color  of  these  solutions  by  the  violet  and  blue  rays  is  nearly  pure 
yellow  instead  of  yellowish-green. 

Thirdly,  the  spectrum  of  bile  is  distinguished  by  certain  peculiar 
characters  and  absorption  bands,  dependent  upon  its  coloring  matter.1 
All  the  more  refrangible  rays  are  absorbed  with  great  intensity,  so  that 
the  visible  spectrum  is  very  short,  terminating  usually  within  the  limits 
of  the  green,  about  midway  between  the  lines  E  and  F.  A  portion  of 
the  green,  accordingly,  and  the  whole  of  the  blue,  indigo,  and  violet  are 
completely  absorbed,  even  when  the  bile 'is  viewed  in  a  layer  only  one 
centimetre  in  thickness.  In  dog's  and  pig's  bile  the  spectrum  some- 
times terminates  in  the  first  half  of  the  green,  at  or  just  beyond  the 
situation  of  the  line  E  ;  and  in  human  bile  even  within  this  point,  about 
the  commencement  of  the  green  part  of  the  spectrum. 

Another  peculiarity  of  the  spectrum  of  bile  is  that  its  light  does  not 
fade  away  gradually  toward  the  more  refrangible  portions,  as  is  the  ^ 
case  with  most  other  colored  fluids,  but  it  terminates  suddenly,  so  that 
the  light  is  cut  off  abruptly  at  the  situations  above  mentioned,  thus 
making  a  strong  contrast  with  the  complete  darkness  immediately 
beyond  its  limits.  This  peculiarity  is  perceptible  in  bile  of  all  shades 
of  green,  olive,  yellow,  or  reddish-brown. 

1  If  any  colored  fluid  be  placed  before  the  slit  of  a  spectroscope,  so  that  the 
light  which  passes  through  it  is  afterward  dispersed  by  the  prism  of  the  instru- 
ment, to  form  a  spectrum,  it  is  found  that  it  absorbs  the  light  of  the  different 
colors  with  different  degrees  of  intensity.  When  the  absorption  of  light  in  any 
particular  part  of  the  spectrum  is  so  strong  as  to  cause  at  that  spot  a  decided 
dimness  in  comparison  with  the  neighboring  regions,  it  is  called  an  "  absorption 
band,"  and  is  characteristic  of  the  fluid  which  produces  it.  The  situation  of  an 
absorption  band  is  usually  indicated  by  reference  to  Frauenhofer's  lines  of  the 
solar  spectrum,  known  as  A,  B,  C,  D.  E,  F,  G,  and  H. 


208  THE    BILE. 

The  spectrum  of  bile  shows  furthermore  three  absorption  bands,  situ- 

.  /  ated  in  the  red,  the  orange,  and  the  yellow. 

V  The  first  is  a  dark  and  strongly  marked  band  in  the  red,  at  the  situa- 
tion of  the  line  C,  but  extending  usually  a  considerable  distance  to  the 
left  toward  B.  Its  width  varies  with  the  thickness  of  the  layer  of  fluid 
examined,  but  when  this  is  increased  beyond  a  certain  limit  the  whole 
of  the  red  disappears,  so  that  the  absorption  of  light  at  this  spot  is  no 
longer  visible  as  a  distinct  band  with  red  on  each  side  of  it.  The  band 
itself  rarely  reaches  the  situation  of  the  line  B,  and  seldom  or  never 
passes  beyond  it  without  extinguishing  at  the  same  time  all  the  red 
light  of  the  spectrum.  In  layers  of  two  or  three  centimetres'  thickness 
it  is  quite  dark,  often  almost  black,  while  the  red  on  each  side  of  it  is 
still  very  brilliant. 

Asa  rule,  the  intensity  of  the  absorption  band  at  C  is  in  proportion  to 

L  the  preponderance  of  green  in  the  color  of  the  bile.     Though  easily  seen, 

I  in  comparatively  thin  layers,  in  specimens  of  a  pure  green  or  a  decided 
greenish-olive  color,  it  is  less  perceptible  in  specimens  of  a  yellowish, 
yellowish-brown,  or  olive-brown  tint.  But  if  a  specimen  of  reddish  or 
yellowish-brown  bile,  which  does  not  show  the  band  distinctly,  be  turned 
green  by  the  addition  of  a  few  drops  of  an  iodine  solution,  the  band  at 
C  at  once  becomes  visible,  often  to  a  very  marked  degree. 

Fig.  69. 


A    BC        D 


Red     Or.  Yel.  Green     Blue       Inditfo       Violet 


, 


SPECTRUM  OF  G-KEEN  (SHEEP'S)  BILE. 

It  would  appear  from  this  that  the  band  at  C  in  the  spectrum  of  bile 
is  probably  due  to  the  presence  of  its  green  rather  than  its  red  coloring 
matter.  As  the  bilirubine  is  well  known  to  be  converted  by  oxidizing 
agents  into  biliverdine,  and  as  this  change  is  accompanied  by  the 
appearance  of  the  C  band  when  it  was  not  previously  visible,  it  is  evi- 
dent that  the  band  in  question  belongs  to  the  green  coloring  matter. 
At  the  same  time  it  is  occasionally  to  be  seen  in  the  spectrum  of  dog's 
bile  which  is  olive-brown  or  even  brownish-yellow  in  hue  ;  its  intensity 
in  these  cases  being  much  increased  by  turning  the  bile  of  a  decided 
green  with  iodine. 

The  absorption  band  at  C  is  a  normal  characteristic  of  the  bile,  and  is 
not  dependent  on  post-mortem  changes  in  the  secretion.  We  have  seen 
it  distinctly  marked  in  the  spectrum  of  perfectly  fresh  sheep's  bile, 


THE    BILE.  209 

examined  within  fifteen  minutes  after  the  animal  was  killed  and  the  gall- 
bladder taken  out  of  the  abdomen. 

The  two  other  absorption  bands  of  bile  are  exceedingly  faint  in  com- 
parison with  the  first,  and  much  less  constant  in  their  occurrence.  One 
of  them,  very  dim  and  ill-defined,  is  situated  at  the  junction  of  the  orange 
and  yellow,  immediately  to  the  left  of  the  line  D,  occupying  about  the 
last  third  of  the  space  between  C  and  D.  The  remaining  band  is  much 
narrower  than  either  of  the  others,  but  a  little  more  distinctly  defined 
than  the  second.  It  is  situated  at  about  one-third  the  distance  between 
D  and  E.  The  last  two  absorption  bands  are  more  frequently  visible  in 
sheep's  bile  than  in  that  of  other  animals  ;  but  all  three  may  be  some- 
times seen  in  a  watery  solution  of  desiccated  ox-bile  which  has  been 
kept,  in  the  form  of  a  dry  powder,  for  several  years. 

Lastly,  the  spectrum  of  bile  exhibits  a  remarkable  diminution  in 
intensity  of  the  orange  and  yellow  colors.  As  the  second  absorption 
band  is  situated  at  the  junction  of  these  colors,  it  will  account  for  a 
part  of  this  diminution;  but  the  light  of  the  spectrum  is  also  remark- 
ably dim  in  the  space  between  the  second  and  third  absorption  bands,  £^ 
where,  in  the  normal  spectrum,  it  is  at  the  brightest.  This  is  the 
place  naturally  occupied  by  pure  yellow,  but  in  the  great  majority  of 
cases,  in  the  spectrum  of  bile,  there  is  no  pure  yellow  perceptible,  and 
but  little  or  no  orange.  The  situation  of  these  two  colors  is  encroached 
upon  by  the  red  and  green  respectively ;  and  in  not  a  few  instances,  as 
the  spectrum  terminates  before  the  commencement  of  the  blue,  the  only 
colors  really  perceptible  in  it  are  red  and  green^  The  line  C  in  the 
normal  spectrum  is  situated  at  the  junction  of  the  red  and  orange,  and 
yet  the  principal  absorption  band  at  this  point,  when  viewed  in  the 
spectrum  of  bile,  nearly  always  appears  to  be  situated  entirely  in  the 
red,  owing  to  this  color  taking  the  place  of  the  orange  on  the  right  of 
the  line  C.  This  peculiarity  in  the  spectrum  of  bile  shows  itself,  whether 
the  color  of  the  specimen  be  greenish  or  yellowish-brown. 

If  a  tolerably  thick  layer  of  bile  be  placed  before  the  spectroscope, 
and  the  slit  of  the  instrument  gradually  opened,  the  first  light  which 
appears  in  the  spectrum  is  a  green  light,  in  the  latter  half  of  the  space 
between  D  and  E.  On  continuing  to  increase  the  size  of  the  opening, 
if  the  bile  be  deeply  colored,  the  next  to  appear  is  a  red  light,  at  the 
extreme  end  of  the  spectrum  between  A  and  B  ;  in  less  concentrated 
specimens  the  red  light  may  show  itself  simultaneously  on  both  sides  of 
the  absorption  band  at  C.  Afterward  the  green  light  extends  further 
toward  the  left  until  the  spectrum  is  complete. 

The  spectrum  of  bile,  in  its  most  important  feature,  namely,  the  ab- 
sorption  band  at  C,  presents  a  remarkable  similarity  to  that  of  chloro- 
phylle.  The  band  at  C  is  identical  in  the  two  spectra  so  far  as  regards 
its  position  and  general  appearance ;  the  only  perceptible  difference 
being  that  in  an  alcoholic  solution  of  chlorophylle  its  edges  are  more 
sharply  defined  than  is  usually  the  case  in  the  spectrum  of  bile.  In 
other  respects,  however,  the  spectrum  of  chlorophylle  differs  from  that 


210 


THE    BILE. 


of  bile,  since  it  has  three  additional  absorption  bands  less  distinct  than 
at  C,  but  sufficiently  well  marked  and  differently  situated  from  those  of 
bile.  One  of  these  additional  bands  is  placed  at  about  three-quarters 
the  distance  from  C  to  D,  another  a  little  to  the  left  of  E,  and  a  third, 

Fig.  70. 


SPECTRUM  OP  CHLOROPHYLLS  iff  ALCOHOLIC  SOLUTION. 

wider  than  the  others,  but  very  faint  and  ill-defined,  about  midway 
between  E  and  F.  In  the  spectrum  of  chloroplrylle,  also,  notwithstand- 
ing the  strong  absorption  of  light  at  the  situation  of  the  principal 
bands,  the  yellow  of  the  spectrum  appears  in  its  proper  place  and  with 
nearly  its  natural  hue.  An  additional  distinction  of  chlorophylle,  as 
compared  with  that  of  bile,  is  that  its  light  does  not  terminate  abruptly, 
,  but  fades  more  or  less  gradually  toward  the  refrangible  end. 

The  bile  exhibits  a  peculiar  reaction  when  treated  with  nitric  acid, 
owing  to  the  effect  upon  its  coloring  matter.  If  a  moderate  quantity 
of  dilute  nitric  acid  be  added  to  fresh  bile  and  the  mixture  shaken  up, 
the  whole  becomes  of  a  bright  grass-green,  the  first  color  produced  by 
oxidation  of  the  bilirubine  and  biliverdine.  But  if  the  bile  be  brought 
in  contact,  in  a  cylindrical  glass  vessel,  with  a  layer  of  strong  nitric 
acid,  especially  if  it  contain  a  trace  of  nitrous  acid,  and  allowed  to 
remain  without  agitation,  a  series  of  colored  rings  are  produced  at  the 
surface  of  contact  of  the  two  liquids,  following  each  other  in  a  definite 
order,  from  the  bile  to  the  nitric  acid,  as  green,  blue,  violet,  red,  and 
yellow.  These  colors  represent  successive  stages  of  oxidation  and 
,  final  destruction  of  the  biliary  coloring  matter.  The  test  is  known  as 
s  "  Gmelin's  bile  test,"  and  may  be  applied  to  other  animal  fluids  in  which 
bilirubine  or  its  derivatives  are  supposed  to  be  present. 

Composition  of  the  Bile. — In  its  immediate  composition  the  bile  is 
especially  destinguished  by  the  presence  of  the  two  peculiar  biliary  salts, 
namely,  sodium  glycocholate  and  sodium  taurocholate,  which  have  been 
described  in  Chapter  VI.,  under  their  appropriate  heads.  It  is  evidently 
these  substances  which  give  to  the  secretion  its  most  important  charac- 
ters. They  vary  in  relative  quantity  in  the  bile  of  different  animals, 
and  perhaps  also  in  that  of  the  same  species  at  different  times.  They 
are  produced,  like  the  coloring  matters,  in  the  substance  of  the  liver 
itself,  while  other  ingredients  of  the  secretion,  such  as  the  various  inin- 


... 


THE    BILE.  211 

eral  salts,  fatty  matters  and  cholesterine,  occur  in  other  parts  of  the 
system,  and  are  supplied  to  the  liver,  ready  formed,  in  the  blood.  In 
the  inferior  animals,  bile  can  be  obtained,  for  purposes  of  analysis,  in  a 
state  of  freshness  and  purity,  from  the  gall-bladder  of  the  recently 
slaughtered  animal ;  but  in  man  it  is  usually  more  or  less  altered  in 
character  by  remaining  in  the  gall-bladder  for  some  hours  after  death. 
It  was  obtained  in  a  case  of  accidental  biliary  fistula  in  the  human  sub- 
ject by  Jacobsen,  who  found  that  the  entire  solid  ingredients  amounted 
to  about  22.5  parts  per  thousand ;  a  little  over  one-third  consisting  of 
mineral  salts,  the  remaining  two-thirds  of  organic  matters.  Sodium 
glycocholate  was  invariably  present,  the  taurocholate  being  less  con- 
stant; and  the  fluid  always  contained  both  bilirubine  and  biliverdine. 
The  proportions  of  all  the  different  ingredients,  according  to  the  results 
of  his  analyses,  were  as  follows : — 

COMPOSITION  OF  HUMAN  BILE,  ACCORDING  TO  THE  ANALYSES  OF  JACOBSEN. 

Water        .        .         .         ....         .  977.40 

C  Sodium  glycocholate 9.94 

Cholesterine       .         .         .        .                 .  0.54 

Organic  I  Free  fats    .                          ....  0.10 

matters  '  Sodium  palmitate  and  stearate  .         .        .  1.36 

Lecithine 0.04 

Other  organic  matters        ....  2.26 

Sodium  chloride         .....  5.45 

Potassium  chloride     .....  0.28 

Sodium  Phosphate 1.33 

Lime  phosphate          .....  0.37 

Sodium  carbonate      ...  0.93 


1000.00 

In  ox-bile,  as  shown  by  the  previous  analyses  of  Berzelius,  Frerichs, 
and  Lehmann,  the  proportion  of  both  mineral  and  organic  ingredients 
may  be  very  much  greater  than  the  above,  the  biliary  salts  themselves 
amounting  to  90  parts  per  thousand.  According  to  Robin1  they  may 
exist,  even  in  human  bile,  in  the  proportion  of  56  to  106  per  thousand 
parts. 

Tests  for  the  Biliary  Salts. — In  testing  for  the  existence  of  bile  in 
other  animal  fluids,  a  distinction  must  be  made  between  those  reactions 
which  indicate  only  the  presence  of  the  coloring  matters,  and  those 
which  are  appropriate  for  the  detection  of  the  biliary  salts  proper.  The 
optical  properties  of  bilirubine  and  biliverdine,  already  described,  and 
especially  the  colors  produced  by  the  action  of  nitric  acid,  constitute  a 
test  for  these  coloring  matters  alone.  They  do  not  indicate  the  presence 
of  the  most  essential  ingredients  of  the  secretion,  which  may  be  con- 
tained in  an  animal  fluid  unaccompanied  by  the  coloring  matters,  or,  on 
the  other  hand,  may  be  absent  where  the  coloring  matters  are  to  be 

1  Lecjons  sur  les  Humeurs.     Paris,  1874,  p.  656. 


212  THE    BILE. 

found  in  appreciable  quantity.  Other  tests  are  therefore  necessary  in 
investigations  for  the  biliary  salts  proper. 

The  ordinary  characters  of  the  biliary  salts  are  that  they  are  soluble 
in  water  and  in  absolute  alcohol,  and  insoluble  in  ether ;  and  that  they 
will  gradually  crystallize  in  the  form  of  radiating  needles,  if  precipitated 
from  their  alcoholic  solution  by  the  addition  of  ether  in  excess.  Fur- 
thermore, they  are  both  precipitable  from  their  watery  solutions  by  the 
tribasic  lead  acetate,  while  the  sodium  glycocholate  is  also  precipitable 
by  the  neutral  acetate  of  the  same  metal. 

Pettenkofer's  Test. — The  biliary  salts  accordingly,  when  in  consider- 
able quantity,  may  be  recognized  by  the  above-named  properties ;  but 
when  present  in  smaller  proportions  they  are  to  be  detected  by  the 
reaction  known  as  *'  Pettenkofer'ls  test."  This  consists  in  the  production 
of  a  red  color,  changing  to  a  purple  or  violet,  on  the  addition  of  cane 
sugar  and  sulphuric  acid.  The  test  is  applied  in  the  following  way : 
One  part  of^cjine  sugar  is  dissolved  in  four  parts  of  water.  Of  this 
saccharine  liquid,  one  drop  is  added  to  each  cubic  centimetre  of  the  solu- 
tion of  biliary  salts.  The  sugar  should  not  be  used  in  larger  quantity, 
because  it  might  in  that  case  give  a  perceptible  brown  tinge  under  the 
action  of  sulphuric  acid  and  heat.  The  admixture  of  the  sugar  pro- 
duces no  visible  change  in  the  solution  of  biliary  salts.  On  adding  a 
few  drops  of  pure  sulphuric  acid,  the  biliary  acids  are  decomposed,  form- 
ing cholic  acid.  If  the  biliary  salts  were  originally  present  in  the  solu- 
tion in  a  proportion  of  not  more  than  one  part  in  500,  the  fluid  remains 
clear ;  if  in  larger  quantity,  the  cholic  acid  is  precipitated,  forming  a 
whitish  turbidity.  This  turbidity  is  again  cleared  up  on  the  continued 
addition  of  sulphuric  acid  ;  and  in  the  course  of  a  few  minutes,  a  cherry- 
red  color  appears,  which  rapidly  changes  to  a  violet,  and  subsequently, 
if  the  biliary  salts  be  present  in  the  proportion  of  one  part  in  500,  or 
over,  to  a  deep  rich  purple.  In  very  dilute  solutions,  the  violet  or  purple 
color  may  not  be  distinctly  visible  before  the  end  of  an  hour. 

The  precautions  necessary  to  observe  in  using  this  test  are  as  follows : 
First,  the  liquid  to  be  examined  should  be  free  from  other  organic  sub- 
stances, particularly  albuminous  and  coloring  matters,  which  might 
themselves  cause  discoloration  of  the  mixture.  For  this  purpose,  the 
suspected  fluid  should  always  be  first  evaporated  to  dryness,  the  dry 
residue  extracted  with  absolute  alcohol,  the  alcoholic  solution  decolorized, 
if  necessary,  with  animal  charcoal,  then  precipitated  with  ether  in  excess, 
and  the  ether  precipitate  finally  dissolved  in  water.  This  gives  a  clear, 
colorless  solution,  free  from  other  organic  contamination.  Secondly, 
as  the  liquid  becomes  heated  by  the  liberal  admixture  of  sulphuric  acid 
with  the  watery  solution,  its  temperature  should  not  be  allowed  to  rise 
above  70°  (158°F.)  nor  to  fall  much  below  this  point.  The  test-tube 
may  therefore  be  cooled  by  occasionally  moistening  it  in  cold  water. 
Thirdly,  the  addition  of  the  sulphuric  acid  should  be  made  slowly,  and 
should  be  stopped  as  soon  as  a  red  tint  begins  to  show  itself,  the  mix- 


THE    BILE.  213 

ture  being  allowed  to  remain  at  rest  until  the  violet  and  purple  colors 
are  developed. 

There  are  various  other  substances  which  yield  a  red,  violet,  or  purple 
color,  when  treated  with  sugar  and  sulphuric  acid.  Among  these  are 
oleine,  oleic  acid,  ethereal  oil,  amyl-alcohol,  albuminous  matters  and  the 
salts  of  morphine  and  codeine.  Albumen  of  the  blood,  white  of  egg, 
and  the  opium  alkaloids  in  the  proportion  of  ten  parts  per  thousand,  if 
treated  with  Pettenkofer's  test,  all  produce  a  color  un distinguishable 
from  that  obtained  with  the  biliary  salts.  These  substances,  however, 
with  the  exception  of  morphine,  may  all  be  excluded  by  previously 
treating  the  fluid  as  above  described  ;  namely,  evaporating  to  dryness, 
extracting  with  alcohol,  precipitating  with  ether,  and  dissolving  the 
precipitate  in  water.  The  salts  of  morphine  might  still  remain,  as  they 
are  soluble  both  in  water  and  in  alcohol,  and  may  be  precipitated  by 
ether  from  their  alcoholic  solution.  This  substance,  however,  is  very 
unlikely  to  be  present  in  an  extract  of  the  animal  fluids,  especially  in 
the  proportion  of  ten  parts  per  thousand. 

Pettenkofer's  test  is  a  very  delicate  one  for  either  or  both  of  the 
biliary  salts.  A  watery  solution  of  pure  sodium  glycocholate,  made  in 
the  proportion  of  1  part  to  2000,  yields,  at  the  end  of  fifteen  minutes,  a 
clear  violet  pink  color,  if  the  test  be  applied  with  care ;  and  a  solution 
of  sodium  taurocholate,  in  the  proportion  of  1  part  to  3000,  will  give  a 
similar  color  at  the  end  of  an  hour.  The  general  characters  of  the  test 
are  the  same  in  both  cases,  as  the  reaction  is  really  produced  by  cholic 
acid,  derived  from  the  decomposition  of  either  the  glycocholic  or  tauro- 
cholic  acid  of  the  original  biliary  salts. 

Fig.  71. 


SPECTBUM  OF  PETTENKOFER'S  TEST,  with  the  Biliary  Salts  in  watery  solution. 

The  spectrum  of  Pettenkofer's  test  presents  certain  characters  which 
may  be  of  service  in  distinguishing  it  from  the  reactions  produced  by 
other  organic  substances.  Jf  either  or  both  of  the  biliary  salts,  dis- 
solved in  water,  be  treated  with  sugar  and  sulphuric  acid  until  a  violet 
or  purple  color  is  produced,  and  the  colored  fluid  then  placed  before  the 
slit  of  the  spectroscope,  its  spectrum  shows  a  wide  and  dark  absorption 
band  at  E,  extending  usually  from  midway  between  D  and  E  to  a 
quarter  part  the  distance  between  E  and  F,  the  central  parts  of  the 


214 


THE    BILE. 


band  being  darker  than  the  edges.  Beyond  the  absorption  band,  the 
light  of  the  spectrum  is  dim,  fading  gradually  and  terminating  some- 
where about  the  line  G. 

When  the  purple  color  produced  by  Pettenkofer's  test  with  the  biliary 
salts  is  very  pronounced,  it  is  usually  found  that  the  fluid  is  altogether 
too  opaque  for  spectroscopic  examination,  even  in  a  layer  of  only  one 
centimetre.  But  if  it  be  diluted  with  water,  it  becomes  turbid,  owing 
to  a  re-precipitation  of  cholic  acid,  and  the  purple  color  disappears. 
This  difficulty,  however,  may  be  obviated  by  using  a  solution  of  the 
biliary  salts  which  is  sufficiently  dilute  in  the  first  instance.  If  sodium 
glycocholate  be  dissolved  in  water,  in  the  proportion  of  1  part  to  500,  and 
the  solution  treated  with  Pettenkofer's  test,  it  gives  in  a  few  moments 
a  clear  violet-pink  color,  which  afterward  becomes  a  rich  purple.  This 
fluid  is  so  opaque  that,  when  placed  before  the  slit  of  the  spectroscope 
in  a  layer  of  one  centimetre,  it  extinguishes  completely  everything  but 
the  red ;  and  yet  it  may  be  diluted  with  water  without  showing  any  tur- 
bidity or  losing  its  color.  A  watery  solution  of  this  strength  is  amply 
sufficient  to  exhibit  the  reaction  of  Pettenkofer's  test  and  the  spectro- 
scopic appearances  belonging  to  it.  If  any  solution,  therefore,  of  the 
biliary  salts  should  prove,  on  trial,  too  opaque  for  spectroscopic  exam- 
ination when  treated  by  Pettenkofer's  test,  another  portion  of  it  may  be 
diluted,  before  applying  the  test,  until  it  is  reduced  to  about  the 
strength  of  1  part  to  500.  Even  when  a  strongly  colored  purple  fluid 
has  been  rendered  turbid  and  decolorized  by  the  addition  of  water,  its 
transparency  and  color  may  be  again  restored  by  the  addition  of  sul- 
phuric acid ;  but  this  method  is  less  convenient  than  the  former. 

Fig.  72. 


SPECTKUM  OF  PETTENKOFEK'S  TEST,  with  the  Biliary  Salts  in  alcoholic  solution. 

If  Pettenkofer's  test  be  applied  to  the  biliary  salts  in  alcoholic  solu- 
tion, its  spectrum  is  modified.  There  are  now  two  absorption  bands 
instead  of  one.  The  first  is  situated  at  E,  and  is  identical  with  that 
obtained  in  a  watery  solution  of  the  same  salts.  The  second  is  at  F, 
and  usually  rather  narrower  and  fainter  than  the  first,  although  some- 
times the  two  bands  are  of  equal  intensity. 

The  pink  or  purplish -red  fluid,  produced  by  Pettenkofer's  test  with 


THE    BILE. 


215 


both  codeine  and  morphine,  has  a  spectrum  very  similar  to  that  of  the 
biliary  salts.  If  the  ruddy  color  of  the  fluid  be  strongly  pronounced, 
its  spectrum,  even  when  viewed  in  a  layer  of  one  centimetre,  is  very 
short,  terminating  completely  about  midway  between  D  and  E,  or  even 
before  that  point,  showing  the  red  and  yellow  clear  and  bright,  but  very 
little  of  the  green.  If  diluted  with  water,  the  mixture  is  not  rendered 
turbid,  but  its  color  is  very  much  reduced,  being  soon  changed  to  a 
faint  amber  or  often  to  a  light  apple-green,  while  the  former  peculiari- 
ties of  the  spectrum  disappear.  The  best  way  is  to  place  the  fluid 
before  the  slit  of  the  spectroscope  in  a  layer  of  two  centimetres  before 
its  color  is  fully  developed,  and  while  it  is  still  of  a  light  pink.  The 
color  then  gradually  becomes  more  pronounced,  and,  when  it  has  at- 
tained the  proper  degree  of  strength,  the  spectrum  exhibits  a  certain 
though  ill-defined  absorption-band  at  E.  Beyond  the  band,  the  whole 
spectrum  is  very  dim,  and  terminates  gradually  between  F  and  G. 

The  distinction  between  the  spectrum  of  Pettenkofer's  test  with 
biliary  salts  and  that  with  the  opium  alkaloids  is,  that  in  the  former 
case  the  absorption-band  at  E  is  very  marked  and  distinct,  and  often 
quite  black,  when  viewed  in  a  layer  of  two  centimetres'  thickness,  while 
in  the  latter  it  is  always  dim  and  very  ill-defined.  With  the  biliary 
salts,  also,  the  fluid  may  frequently  be  diluted  with  its  own  or  even 
twice  its  volume  of  water,  and  the  absorption-band  still  remain  plainly 
visible;  but  with  morphine  or  codeine  a  very  moderate  dilution  rapidly 
destroys  the  character  of  the  spectrum  and  causes  the  absorption-bar. d 
to  disappear. 

Fig.  73. 


SPECTRUM  OF  PETTENKOFEB'S  TEST,  with  albumen. 

The  violet-colored  fluid  produced  by  Pettenkofer's  test  with  albumen 
has  a  well-marked  and  peculiar  spectrum,  easily  distinguishable  from 
that  belonging  to  the  biliary  salts.  If  tolerably  dense,  it  requires  to  be 
diluted  with  water  for  spectroscopic  examination,  and  afterward  cleared 
up  by  the  further  addition  of  sulphuric  acid.  The  spectrum  then  shows 
a  single  absorption-band,  extending  from  somewhere  about  the  line  E 
to  the  line  F,  and  occupying  the  intermediate  space.  In  concentrated 
specimens  it  may  begin  considerably  to  the  left  of  E,  and  extend  thence 
to  F.  If  the  albuminous  liquid  be  more  dilute,  it  may  reach  only  from 


216  THE    BILE. 

a  short  distance  beyond  E  to  F.  It  is,  therefore,  always  limited  on  the 
right  by  the  line  F,  but  extends  farther  toward  E  and  D,  according  to 
the  degree  of  concentration  of  the  liquid.  Its  edsres  are  not  very  well 
defined,  but  are  more  distinct  when  the  band  is  narrow  than  when  it  is 
wide.  Beyond  the  band,  the  refrangible  portion  of  the  spectrum  is 
quite  dim. 

Mode  of  Secretion  of  the  Bile. — It  is  a  matter  of  importance,  in 
regard  to  the  bile,  as  well  as  the  other  intestinal  fluids,  to  ascertain 
whether  it  be  a  constant  secretion,  like  the  urine  and  perspiration,  or 
whether  it  be  intermittent,  like  the  gastric  juice,  and  discharged  only 
during  the  digestive  process.  Bidder  and  Schmidt  have  investigated 
this  point  in  the  following  manner :  They  operated  by  tying  the  common 
bile-duct,  and  then  opening  the  fundus  of  the  gall-bladder,  so  as  to  pro- 
duce a  biliary  fistula,  by  which  the  whole  of  the  bile  was  drawn  off. 
By  doing  this  operation,  and  collecting  and  weighing  the  fluid  discharged 
at  different  periods,  they  came  to  the  conclusion  that  the  flow  of  bile 
begins  to  increase  within  two  and  a  half  hours  after  the  introduction  of 
food  into  the  stomach,  but  that  it  does  not  reach  its  maximum  of  activity 
till  the  end  of  twelve  or  fifteen  hours.  Other  observers,  however,  have 
obtained  different  results.  Arnold,1  for  example,  found  the  quantity  to 
be  largest  soon  after  meals,  decreasing  again  after  the  fourth  hour. 
Kolliker  and  Miiller,3  again  found  it  largest  between  the  sixth  and 
eighth  hours.  It  appears,  accordingly,  that  the  bile  is  not  an  intermittent 
but  a  constant  secretion ;  and  that  the  quantity  produced  varies  with 
the  condition  of  the  digestive  process,  being,  according  to  the  majority 
of  observers,  most  abundant  some  time  after  the  digestion  and  absorp- 
tion of  food  have  commenced  in  the  intestinal  canal. 

Discharge  of  Bile  into  the  Intestinal  Canal. — As,  in  those  animals 
which  have  been  the  subject  of  experiment,  the  liver  is  provided  with  a 
gall-bladder,  in  which  the  secretion  may  be  partially  accumulated  after 
its  production,  and  from  which  it  may  find  its  way  at  regular  or  irregular 
intervals  into  the  alimentary  canal,  it  becomes  important  to  ascertain 
by  other  means  at  what  time  and  in  what  quantity  it  is  really  discharged 
into  the  intestine.  In  order  to  determine  this  point,  we  have  performed 
the  following  series  of  experiments  on  dogs.  The  animals  were  kept 
confined,  and  killed  at  various  periods  after  feeding,  sometimes  by  the 
inoculation  of  woorara,  sometimes  by  hydroc}ranic  acid,  but  most  fre- 
quently by  section  of  the  medulla  oblongata.  The  contents  of  the 
intestine  were  then  collected  and  examined.  In  all  instances,  the  bile 
was  also  taken  from  the  gall-bladder  and  treated  in  the  same  way,  for 
purposes  of  comparison.  The  intestinal  contents  always  presented  some 
peculiarities  of  appearance  when  treated  with  alcohol  and  ether,  owing 
probably  to  the  presence  of  other  substances  than  the  bile ;  but  they 
always  gave  evidence  of  the  presence  of  biliary  matters  as  well.  The 

1  Cited  in  the  American  Journal  of  the  Medical  Sciences,  April,  1856. 
8  Ibid.,  April,  1857. 


THE    BILE. 


217 


CRYSTALLINE  AND  EKSINOUS  BILIARY 
SUBSTANCES;  from  Small  Intestine  of  Dog, 
after  two  days  fasting. 


biliary  substances  could  almost  Fig.  74. 

always  be  recognized  by  the 
microscope  in  the  ether  preci- 
pitate of  the  alcoholic  solution ; 
both  as  a  resinous  matter, 
under  the  form  of  rounded, 
oily-looking  drops  (Fig.  74), 
and  also  under  the  form  of 
crystalline  groups,  generally 
presenting  the  appearance  of 
double  bundles  of  slender, 
radiating,  slightly  curved  or 
wavy,  needle-shaped  crystals. 
These  substances,  dissolved  in 
water,  gave  a  purple  color  with 
sugar  and  sulphuric  acid. 
These  experiments  were  tried 
after  the  animals  had  been  kept 
for  one,  two,  three,  five,  six, 

seven,  eight,  and  twelve  days  without  food.  The  result  showed  that, 
in  all  these  instances,  bile  was  present  in  the  small  intestine.  The  bile, 
therefore,  is  not  only  constantly  secreted  by  the  liver  in  the  intervals 
of  digestion,  as  well  as  during  that 
process,  but  it  also  continues  to  be 
discharged  into  the  intestine  for 
many  days  after  the  animal  has 
been  deprived  of  food. 

But  the  quantity  of  bile  passing 
into  the  intestine  within  a  given 
time  is  greatest  soon  after  the  com- 
mencement of  digestion.  Our  own 
experiments  bearing  on  this  point 
were  performed  on  dogs,  by  mak- 
ing a  permanent  duodenal  fistula, 
on  the  same  plan  as  that  used  for 
gastric  fistulse  (Fig.  75).  An  inci- 
sion was  made  through  the  abdomi- 
nal walls,  a  short  distance  to  the 
right  of  the  median  line,  the  floating 
portion  of  the  duodenum  drawn  up 
toward  the  external  wound,  opened 
by  a  longitudinal  incision,  and  a 
silver  tube,  armed  at  each  end  with 
a  narrow  projecting  flange,  inserted 
into  it  by  one  extremity,  about 
fourteen  centimetres  below  the 
pylorus,  and  seven  centimetres 
15 


Fig.  75. 


DUODENAL  FISTULA — a.  Stomach.  6. 
Duodenum,  c,  c,  c.  Pancreas ;  its  two  ducts 
are  seen  opening  into  the  duodenum,  one 
near  the  orifice  of  the  biliary  duct,  d,  the 
other  a  short  distance  lower  down.  e.  Silver 
tube  passing  through  the  abdominal  walls 
and  opening  into  the  duodenum. 


218 


THE    BILE. 


below  the  orifice  of  the  lower  pancreatic  duct.  The  other  extremity  of 
the  tube  was  left  projecting  from  the  external  opening  in  the  abdo- 
minal parietes,  the  parts  secured  by  sutures,  and  the  wound  allowed  to 
heal.  After  cicatrization  was  complete,  and  the  animal  had  entirely 
recovered  his  healthy  condition  and  appetite,  the  intestinal  fluids 
were  drawn  off  at  various  intervals  after  feeding,  and  their  contents 
examined.  This  operation,  which  is  rather  more  difficult  than  that  of 
making  a  permanent  gastric  fistula,  is  nevertheless  exceedingly  useful 
when  it  succeeds,  since  it  enables  us  to  study  the  actual  time  and  rate 
of  the  biliary  discharge  into  the  upper  part  of  the  intestinal  canal. 

In  order  to  ascertain  the  absolute  quantity  of  bile  discharged  into  the 
intestine,  and  its  variations  during  digestion,  the  duodenal  fluids  were 
drawn  off,  for  fifteen  minutes  at  a  time,  at  various  periods  after  feeding, 
collected,  weighed,  and  examined  separately,  as  follows :  each  separate 
quantity  was  evaporated  to  dryness,  its  dry  residue  extracted  with 
absolute  alcohol,  the  alcoholic  solution  precipitated  with  ether,  and  the 
ether-precipitate,  regarded  as  representing  the  amount  of  biliary  salts 
present,  dried,  weighed,  and  then  treated  with  Pettenkofer's  test,  in 
order  to  determine,  as  nearly  as  possible,  their  degree  of  purity  or  ad-: 
mixture.  The  result  of  these  experiments  is  given  in  the  following 
table.  At  the  eighteenth  hour  so  small  a  quantity  of  fluid  was  obtained 
that  the  amount  of  its  biliary  ingredients  was  not  ascertained.  It 
reacted  perfectly,  however,  with  Pettenkofer's  test,  showing  that  bile 
was  really  present. 

DISCHARGE  OF  INTESTINAL  AND  BILIARY  FLUIDS  FROM  DUODENAL  FISTULA  IN  A 
DOG  WEIGHING  16.5  KILOGRAMMES. 


Time  after  feed- 
ing. 

Quantity  of  fluid 
in  15  minutes. 

Dry  residue  of  the 
same. 

Quantity  of  bili- 
ary salts. 

Proportion  of  bili- 
ary salts  in  the 
dry  residue. 

Immediately. 
1  hour. 

(Grammes.) 
41.467 
128.936 

(Grammes.) 
2.138 
6.803 

(Grammes.) 
0.648 
0.259 

(Per  cent.) 
30 
3 

3  hours. 

50.537 

3.887 

0.259 

7 

6 

48.594 

4.729 

0.227 

5 

9 

55.721 

5.053 

0.291 

6 

12 

21.057 

1.490 

0.243 

16 

15 

22.482 

1.166 

0.259 

22 

18 





— 

— 

21 

24.880 

0.712 

0.064 

9 

24 

10.561 

0.615 

0.210 

34 

25 

9.783 

0.324 

0.194 

60 

From  this  it  appears  that  the  bile  passes  into  the  duodenum  in  by  far 
the  largest  quantity  immediately  after  feeding.  This  is  undoubtedly 
due  to  a  contraction  of  the  gall-bladder  and  a  discharge  of  the  surplus 
bile  accumulated  in  it  during  the  interval  of  digestion.  It  is  a  matter 
of  common  observation  that  the  gall-bladder,  in  animals  killed  after  a 
day  or  two  of  fasting,  is  distended  with  an  unusual  quantity  of  thick 
and  dark-looking  bile ;  while  in  those  killed  immediately  or  soon  after 


THE    BILE.  219 

feeding,  it  is  comparatively  collapsed  and  empty.  This  evacuation  of 
the  gall-bladder,  excited  by  the  ingestion  of  food,  causes  a  sudden  flow 
of  bile  into  the  duodenum.  After  that  time,  its  discharge  remains  pretty 
constant ;  not  varying  much,  in  a  dog  of  sixteen  and  a  half  kilogrammes' 
weight,  from  256  milligrammes  of  the  biliary  salts  every  fifteen  minutes, 
or  a  little  over  one  gramme  per  hour.  In  a  man  of  ordinary  size  (65 
kilogrammes),  if  the  quantity  of  bile  were  increased  in  proportion,  this 
would  amount  to  8.667  grammes  of  solid  biliary  matter  per  hour  dis- 
charged into  the  intestine  during  the  greater  part  of  the  digestive  process. 

Daily  Quantity  of  the  Bile. — The  first  experiments  of  value  upon  this 
point  were  those  of  Bidder  and  Schmidt,  published  in  1852.1  They  were 
performed  upon  dogs,  cats,  sheep,  and  rabbits,  in  the  following  manner : 
The  abdomen  was  opened,  and  a  ligature  placed  upon  the  common 
biliary  duct,  so  as  to  prevent  the  bile  finding  its  way  into  the  intestine. 
An  opening  was  then  made  in  the  fundus  of  the  gall-bladder,  by  which 
the  bile  was  discharged  externally.  The  bile,  so  discharged,  was  received 
into  previously  weighed  vessels,  and  its  quantity  accurately  determined. 
Each  observation  usually  occupied  about  two  hours,  during  which  period 
the  temporary  fluctuations  occasionally  observable  in  the  quantity  of 
bile  discharged  were  mutually  corrected,  so  far  as  the  entire  result  was 
concerned.  The  animal  was  then  killed,  weighed,  and  carefully  ex- 
amined, in  order  to  make  sure  that  the  biliary  duct  had  been  securely 
tied,  and  that  no  inflammatory  alteration  had  taken  place  in  the  ab- 
dominal organs.  The  observations  were  made  at  different  periods  after 
the  last  meal,  so  as  to  determine  the  influence  exerted  by  the  digestive 
process  upon  the  rapidity  of  the  secretion.  The  average  quantity  of 
bile  for  twenty-four  hours  was  then  calculated  from  a  comparison  of  the 
above  results ;  and  the  quantity  of  its  solid  ingredients  was  also  ascer- 
tained in  each  instance  by  evaporating  a  portion  of  the  bile  in  the  water 
bath,  and  weighing  the  dry  residue. 

Bidder  and  Schmidt  found  in  this  way  that  the  daily  quantity  of  bile 
varied  considerably  in  different  species  of  animals.  It  was  much  greater 
in  the  herbivorous  animals  used  for  experiment  than  in  the  carnivora. 
The  results  obtained  by  these  observers  were  as  follows  : 

For  every  kilogramme  of  the  entire  bodily  weight  of  the  animal,  there 
is  secreted,  in  twenty-four  hours, 

Fresh  bile.  Dry  residue. 

In  the  cat      .        .        .        14.537  grammes.     0.816  grammes. 
"       dog      .        .        .         19.956         "  0.985 

"      sheep  .        .        .        25.372        "  1.340 

"      rabbit  .         .         .       136.556         "  2.464 

According  to  the  later  researches  of  Schiff,2  these  estimates  are  cer- 
tainly not  beyond  the  truth,  since  he  obtained  considerably  larger 
quantities  in  the  dog,  by  simply  establishing  an  open  fistula  of  the  gall- 

Verdauungssaefte  und  Stoffwechsel.     Leipzig,  1852. 

Archiv  fur  die  Gesammte  Physiologie.     Bonn,  1870,  Band  iii.  p.  598. 


220  THE    BILE. 

bladder,  without  tying  the  common  biliary  duct.  While  the  average 
quantity  obtained  in  Bidder  and  Schmidt's  experiments  on  the  dog  was 
0.832  grammes  of  fresh  bile  per  hour  for  every  kilogramme  of  bodily 
weight,  in  those  of  Schiff  it  was  1.3  to  3.2  grammes  per  kilogramme  per 
hour. 

Since  in  the  human  subject  the  processes  of  digestion  and  nutrition 
resemble  those  of  the  carnivora,  rather  than  those  of  the  herbivora,  the 
former  should  be  selected  to  serve  as  a  term  of  comparison  in  estimating 
the  probable  daily  quantity  of  the  bile  in  man.  If  we  apply  accordingly 
to  the  human  subject  the  average  of  the  results  obtained  by  Bidder  and 
Schmidt  from  the  cat  and  dog,  the  entire  quantity  of  bile,  for  a  man 
weighing  65  kilogrammes,  would  be  a  little  over  1 100  grammes  per  day. 
Ranke1  obtained  from  direct  observation  a  result  not  essentially  different 
from  this.  He  collected  at  various  times  the  bile  discharged  in  a  case 
of  biliary  fistula  in  a  man  weighing  only  47  kilogrammes,  and  found  the 
average  quantity  for  twenty-four  hours  to  be  652  grammes;  the  max- 
imum quantity  for  the  same  period  being  .945  grammes.  In  a  man  of 
65  kilogrammes'  weight  this  would  correspond,  for  the  average,  to  902 
grammes,  and  for  the  maximum  to  1307  grammes.  The  entire  quantity 
of  bile,  therefore,  for  a  man  of  medium  size,  is  evidently  not  far  from 
1000  grammes  per  day.  This  contains  about  30  grammes  of  solid  ingre- 
dients. 

Decomposition  of  the  Biliary  Matters  in  the  Intestine. — Observers 
generally  are  agreed  that  the  biliary  salts,  though  constantly  poured 
into  the  upper  part  of  the  intestinal  canal,  are  not  discharged  with  the 
feces.  Although  traces  of  them  are  sometimes  to  be  found  in  the  evacua- 
tions, they  are  always  very  far  from  representing  the  total  quantity  pro- 
duced by  the  liver,  and  as  a  general  rule  they  disappear  altogether  in 
their  passage  through  the  intestine.  This  may  be  readily  demonstrated 
by  experiments  upon  dogs,  which  are  conducted  in  the  following  man- 
ner. The  animals  are  to  be  fed  with  fresh  meat,  and  then  killed  at 
various  intervals  after  the  meals,  the  abdomen  opened,  ligatures  placed 
upon  the  intestine  at  various  points,  and  the  contents  of  its  upper, 
middle,  and  lower  portions  collected  and  examined  separately.  The 
results  thus  obtained  show  that,  under  ordinary  circumstances,  the  bile, 
which  is  quite  abundant  in  the  duodenum  and  upper  part  of  the  small 
intestine,  diminishes  in  quantity  from  above  downward,  and  is  not  to  be 
found  in  the  large  intestine.  The  entire  quantity  of  the  intestinal  con- 
tents also  diminishes  and  their  consistency  increases,  as  we  approach 
the  ileo-csecal  valve ;  and  at  the  same  time  their  color  changes  from  a 
light  yellow  to  a  dark  bronze  or  blackish-green,  which  is  always  strongly 
pronounced  in  the  last  quarter  of  the  small  intestine. 

If  the  contents  of  the  small  and  large  intestine  be  furthermore  evapo- 
rated to  dryness,  extracted  with  absolute  alcohol,  and  the  alcoholic  solu- 
tions precipitated  with  ether,  the  quantity  of  ether-precipitate  being 

1  Grundziige  der  Physiologie  des  Menschen.     Leipzig,  1872,  p.  284. 


THE    BILE.  221 

regarded  as  representing  approximately  that  of  the  biliary  substances 
proper,  the  result  shows  that  the  quantity  of  ether-precipitate  is,  both 
positively  and  relatively,  very  much  less  in  the  large  intestine  than  in 
the  small.  Its  proportion  to  the  entire  solid  contents  is  only  one-fifth 
or  one-sixth  as  great  in  the  large  intestine  as  it  is  in  the  small.  But 
even  this  inconsiderable  quantity,  found  in  the  contents  of  the -large 
intestine,  does  not  consist  of  biliary  matters ;  for,  the  watery  solutions 
being  treated  with  sugar  and  sulphuric  acid,  those  from  both  the  upper 
and  lower  portions  of  the  small  intestine  always  give  Pettenkofer's  reac- 
tion perfectly  in  less  than  a  minute  and  a  half;  while  in  that  from  the 
large  intestine  no  red  or  purple  color  is  usually  produced,  even  at  the 
end  of  three  hours. 

The  small  intestine  consequently  contains,  at  all  times,  substances 
presenting  the  usual  reactions  of  the  biliary  ingredients ;  while  in  the 
contents  of  the  large  intestine  no  such  substances  can  be  recognized  by 
Pettenkofer's  test. 

It  is  not  possible  to  say,  however,  what  is  the  precise  nature  of  the 
changes  undergone  by  the  biliary  salts  in  the  intestinal  canal.  The  sup- 
posed decomposition  of  these  salts  by  contact  with  the  acid  secretions 
of  the  alimentary  canal,  and  the  separation  of  the  glycine,  taurine,  and 
cholic  acid  of  their  organic  ingredients,  with  their  subsequent  transfor- 
mations, are  all  more  or  less  hypothetical,  and  without  sufficient  basis  of 
experimental  evidence.  The  biliary  matters  in  the  intestine  pass,  by 
decomposition  or  metamorphosis,  into  the  condition  of  other  unknown 
substances  which  do  not  respond  to  Pettenkofer's  test. 

Physiological  Function  and  Destination  of  the  Bile. — The  physio- 
logical function  of  the  bile  is  still  very  obscure.  With  regard  to  its 
action  in  the  digestive  process,  we  may  say  that  nothing  whatever  is  yet 
known  which  can  account  for'  the  constant  presence  of  so  important  and 
peculiar  a  secretion.  By  itself,  in  experiments  on  artificial  digestion,  it 
does  not  exhibit  any  direct  action  upon  either  of  the  principal  alimentary 
substances,  of  such  a  definite  character  as  those  which  belong  to  the  gas- 
tric, pancreatic,  and  intestinal  juices ;  its  action  being  limited  to  simple 
solution  of  a  certain  proportion  of  oily  matter,  and  to  a  feeble  and  incon- 
stant transforming  power  upon  hydrated  starch.  Two  other  actions  have 
also  been  attributed  to  it,  from  certain  properties  which  observation 
shows  it  to  possess ;  namely,  first,  that  of  exciting  the  secretions  and 
peristaltic  movement  of  the  intestine  and  thus  serving  as  a  natural 
cathartic,  and  secondly,  that  of  facilitating  the  absorption  of  oily  matters 
by  the  intestinal  mucous  membrane.  But  although  the  bile  is  found,  when 
applied  to  the  muscular  coat  of  the  intestine,  to  excite  its  contraction, 
and  similar  effects  are  thought  to  have  been  seen  even  in  the  villi,  yet 
the  alimentary  canal  is  known  to  be  naturally  excited  to  action  by  the 
ingestion  of  food,  or  its  downward  passage  from  other  parts ;  and  there 
is  nothing  to  show  that  the  intestine,  below  the  orifice  of  the  biliary 
duct,  should  require  any  peculiar  or  exceptional  stimulus  for  the  excite- 
ment of  its  normal  actions.  It  is  true,  in  the  second  place,  that  the  bile 


222  THE    BILE. 

has  been  shown,  by  direct  experiment,  to  facilitate  the  passage  of  oily 
matters  by  osmosis  through  closed  organic  membranes  or  parchment 
paper ;  that  is,  oily  matters  will  pass  through  these  membranes  more 
readily  when  they  are  moistened  with  bile,  than  when  simply  wetted 
with  water ;  and  it  is  upon  these  experiments  that  the  supposed  func- 
tion of  the  bile,  in  effecting  the  absorption  of  oil  in  the  intestine,  has 
been  based.  But  the  villi  of  the  intestine  are  not  simply  membranes 
moistened  with  water.  They  are  penetrated  throughout  by  alkaline  and 
albuminous  fluids,  their  bloodvessels  contain  an  abundance  of  organic 
material  in  the  liquid  form,  and  the  fatty  emulsion  formed  by  the  pan- 
creatic juice  is  itself  fully  adapted  for  absorption  by  the  villi.  There 
seems  to  be  no  good  reason  for  assigning  to  the  physical  properties  of 
the  bile,  in  this  respect,  any  special  importance  for  the  absorption  of 
fatty  substances. 

An  action  of  quite  the  opposite  nature  has  also  been  attributed  to  the 
bile,  namely  that  of  precipitating  the  half-digested  ingredients  of  the 
food  from  their  solution  in  the  gastric  juice.  But  there  is  reason  to 
believe  that  this  also  rests  upon  an  error,  and  that  there  is  no  such 
antagonism  between  the  bile  and  the  gastric  juice  in  the  intestine  as 
when  they  are  mingled  together  in  a  test-tube. 

It  has  already  been  stated  (page  159)  that  the  bile  precipitates  by  con- 
tact with  the  gastric  juice.  If  one  or  two  drops  of  dog's  bile  be  added 
to  as  many  cubic  centimetres  of  fresh  gastric  juice  from  the  same  ani- 
mal, a  copious  yellowish-white  precipitate  falls  down,  containing  the 
whole  of  the  coloring  matter  of  the  bile  which  has  been  added ;  and  if 
the  mixture  be  then  filtered,  the  filtered  fluid  passes  through  quite  color- 
less. The  gastric  juice,  however,  still  retains  its  acid  reaction.  This 
precipitation  depends  upon  the  presence  of  the  biliary  substances  proper, 
namely,  the  sodium  glycocholate  and  taurocholate ;  for  if  the  bile  be 
evaporated  to  dryness  and  the  biliary  substances  extracted  by  alcohol 
and  precipitated  by  ether  in  the  usual  manner,  their  watery  solution  will 
precipitate  with  gastric  juice,  in  the  same  way  as  fresh  bile  would  do. 

Although  the  biliary  matters,  however,  precipitate  by  contact  with 
fresh  gastric  juice,  they  do  not  do  so  with  gastric  juice  which  holds  albu- 
minose  in  solution.  We  have  invariably  found  that  if  the  gastric  juice 
be  digested  for  several  hours  at  the  proper  temperature  with  boiled 
white  of  egg,  the  filtered  fluid,  which  contains  an  abundance  of  albu- 
minose,  will  no  longer  give  the  slightest  precipitate  on  the  addition  of 
bile  or  of  a  watery  solution  of  the  biliary  substances,  even  in  very  large 
amount.  The  gastric  juice  and  the  bile,  therefore,  are  not  finally  incom- 
patible with  each  other  in  the  digestive  process,  notwithstanding  the 
reaction  which  takes  place  between  them  when  artificially  mingled. 

Although,  however,  the  bile  cannot  be  shown  to  exert  any  direct 
action  in  the  digestion  of  the  food,  similar  to  that  of  the  other  intestinal 
fluids,  yet  there  is  evidence  that  it  takes  part,  in  the  intestine,  in  some 
process  which  is  important,  and  even,  in  the  long  run,  essential  to  life. 
This  is  shown  by  the  fact  that  if  the  bile  be  permanently  diverted  from 


THE    BILE.  223 

the  cavity  of  the  intestine  by  closure  of  the  common  bile-duct,  and 
evacuated  by  a  fistula  of  the  gall-bladder,  the  animals  which  are  the 
subjects  of  the  operation  gradually  emaciate,  and  die  with  general 
symptoms  of  disordered  nutrition. 

This  experiment  has  been  successfully  performed  at  least  ten  times  by 
Schwann,  Bidder  and  Schmidt,1  Bernard,2  and  Prof.  A.  Flint,  Jr.,3  the 
animals  surviving  the  immediate  effects  of  the  operation,  the  biliary 
fistula  remaining  open,  and  the  common  bile-duct,  as  shown  by  subse- 
quent post-mortem  examination,  being  permanently  closed  so  that  none 
of  the  bile  could  have  found  its  way  into  the  intestine.  The  general 
results  were  alike  in  these  cases.  The  animals  died  with  the  signs  of 
inanition,  usually  between  30  and  40  days  after  the  operation  ;  although 
in  one  instance  death  occured  at  the  end  of  the  seventh  day,  and  in 
another  not  until  the  eightieth.  The  average  length  of  life,  in  all  the 
cases  taken  together,  was  36  days.  The  symptoms  were  constant  and 
progressive  emaciation,  which  proceeded  to  such  a  degree  that  nearly 
every  trace  of  fat  disappeared  from  the  body.  The  loss  of  flesh  amounted, 
in  one  case,  to  more  than  two-fifths,  and  in  another  to  nearly  one-half 
the  entire  weight  of  the  animal.  There  was  also  sometimes  a  falling  off 
of  the  hair,  and  an  unusually  disagreeable,  putrescent  odor  in  the  feces 
and  in  the  breath.  Notwithstanding  this,  the  appetite  remained  good. 
Digestion  was  not  essentially  interfered  with,  and  none  of  the  food  was 
discharged  with  the  feces ;  but  there  was,  in  the  cases  of  Bidder  and 
Schmidt,  much  rumbling  and  gurgling  in  the  intestines,  and  abundant 
discharge  of  flatus,  more  strongly  marked  in  one  instance  than  in  the 
other.  There  was  no  pain ;  and  death  took  place,  at  last,  without  any 
violent  symptoms,  but  by  a  simple  and  gradual  failure  of  the  vital 
powers. 

It  appears  therefore  that  the  bile  is  not  simply  an  excrementitious  fluid 
destined  to  be  eliminated  from  the  system  ;  but  that,  after  being  secreted 
and  discharged  by  the  liver,  it  must  pass  into  and  through  the  small 
intestine,  in  order  to  maintain  the  continuous  and  healthy  nutrition  of 
the  body.  We  have  already  seen,  furthermore,  that  its  most  essential 
ingredients,  namely,  the  biliary  salts,  disappear  during  their  passage 
through  the  alimentary  canal,  and  are  not  to  be  found  in  the  fecal 
evacuations.  This  may  be  accounted  for  in  two  different  ways.  Either 
the  biliary  salts,  while  in  the  intestine,  may  become  altered  and  insolu- 
ble, so  as  to  lose  their  reaction  with  Pettenkofer's  test,  and  be  finally 
evacuated  with  the  feces  under  this  insoluble  form;  or,  on  the  other 
hand,  they  may  be  reabsorbed  from  the  alimentary  canal  and  thus  re-enter 
the  circulation  as  ingredients  of  the  blood. 

The  conclusion  generally  adopted  by  physiologists  is  that  they  are 
reabsorbed.  The  most  positive  evidence  on  this  point  is  that  derived 

1  Yerdauungssaefte  und  Stoffwechsel.     Leipzig,  1852,  p.  103. 

2  Liquides  de  1'Organisme.     Paris,  1859,  torn.  ii.  p.  199. 

3  Physiology  of  Man.     New  York,  1867,  p.  369. 


224  THE    BILE. 

from  the  experiments  of  Bidder  and  Schmidt  on  the  quantity  of  sulphur 
contained  in  the  feces  of  the  dog,  as  compared  with  that  in  the  tauro- 
cholic  acid  of  his  biliary  salts.  The  significance  of  these  experiments 
depends  upon  the  fact  that  the  biliary  salts  themselves,  being  compound 
bodies,  might  be  so  altered  by  decomposition  in  the  intestine  as  to  lose 
their  characteristic  reactions,  and  yet  their  separated  materials  might 
remain ;  but  as  sulphur,  on  the  other  hand,  is  a  chemical  element,  not 
decomposable  by  any  known  means,  it  must  be  capable  of  detection,  if 
present,  by  ultimate  analysis.  The  dog  was  selected  as  the  subject  of 
experiment,  for  the  reason  that  the  bile  in  this  animal  contains  so  large 
a  proportion  of  the  sodium  taurocholate,  of  which  sulphur  is  a  constituent 
part. 

The  results  obtained  by  Bidder  and  Schmidt1  showed  that  the  quantity 
of  sulphur  evacuated  in  the  feces  was  much  less  than  that  discharged 
into  the  intestine  with  the  bile. 

These  observers  collected  and  analyzed  all  the  feces  passed,  during 
five  days,  by  a  healthy  dog,  weighing  8  kilogrammes.  The  entire  fecal 
mass  during  this  period  weighed  97.716  grammes, 

("Water 56.642  grammes. 

I  Solid  residue       ....    41.074        " 

97.716 
The  solid  residue  was  composed  as  follows  : — 

Neutral  fat,  soluble  in  ether   .         .  2.832  grammes. 

Fat,  with  traces  of  biliary  matter  .  4.991         " 

Alcohol  extract,  with  biliary  matter  3.816  containing  0.070  of  sulphur. 

Substances  not  of  a  biliary  nature 

extracted  by  muriatic  acid  and 

hot  alcohol  ....  9.641  containing  0.085  of  sulphur. 

0.155 

Fatty  acids  with  oxide  of  iron         .       6.377 
Residue  consisting  of  hair,  sand,  etc.     13.417 

41.074 

As  it  has  already  been  shown  (page  219)  that  the  dog  secretes,  during 
24  hours,  0.985  gramme  of  solid  biliary  matter  for  every  kilogramme 
of  bodily  weight,  the  entire  quantity  of  biliary  matter  secreted  in  five 
days  by  the  above  animal,  weighing  8  kilogrammes,  must  have  been 
39.4  grammes,  or  nearly  as  much  as  the  whole  weight  of  the  dried  feces. 
But  furthermore,  the  natural  proportion  of  sulphur  in  dog's  bile,  derived 
from  the  sodium  taurocholate,  is  6  per  cent,  of  the  dry  residue.  The 
39.4  grammes  of  dry  bile,  secreted  during  five  days,  contained,  there- 
fore, 2.364  grammes  of  sulphur.  But  the  entire  quantity  of  sulphur, 
existing  in  any  form  in  the  feces,  was  0.385  gramme  ;  and  of  this  only 
0.155  gramme  could  have  been  the  product  of  biliary  matters — the  re- 

1  Yerdauungssaefte  und  Stoffwechsel.     Leipzig,  1852,  p.  217 


THE    BILE.  225 

mainder  being  derived  from  the  hairs  which  are  always  contained  in 
abundance  in  the  feces  of  the  dog.  That  is,  not  more  than  one-fifteenth 
part  of  the  sulphur  originally  present  in  the  bile  could  be  detected  in 
the  feces.  It  must,  accordingly,  have  been  reabsorbed  from  the  intestine. 

A  still  further  corroboration  of  the  reabsorption  of  the  biliary  materials 
from  the  intestinal  canal  is  furnished  by  the  very  careful  and  ingenious 
experiments  of  Schiff,1  performed  in  a  different  manner.  This  observer 
found  that,  in  animals  provided  with  a  gall-bladder,  less  pressure  is  re- 
quired to  make  a  fluid  pass  from  the  hepatic  duct  into  the  cavity  of  the 
gall-bladder  than  to  force  it  through  the  common  duct  into  the  intes- 
tine. Unless,  therefore,  the  pressure  under  which  the  bile  is  secreted  be 
increased,  either  by  distension  or  by  muscular  contraction,  it  passes  into 
the  gall-bladder  more  readily  than  into  the  intestine  ;  and  a  fistula  of  the 
fundus  of  the  gall-bladder,  if  kept  freely  open,  will  be  of  itself  sufficient 
to  discharge  all,  or  nearly  all,  the  secreted  bile,  without  any  considerable 
portion  of  it  reaching  the  intestine.  He  demonstrated  furthermore  that 
this  was  really  the  fact  by  establishing  at  the  same  time,  in  the  same 
animal,  a  fistula  of  the  gall-bladder  and  one  of  the  duodenum.  So  long 
as  the  cystic  fistula  remained  open,  either  no  biliary  matters,  or  only 
insignificant  traces  of  them,  could  be  detected  in  the  fluids  drawn  from 
the  duodenum. 

The  advantage,  for  certain  purposes,  of  this  method  of  operating, 
over  that  in  which  the  common  duct  is  also  tied  and  obliterated,  is  that 
by  the  last  operation  the  bile  is  permanently  shut  off  from  the  intestine, 
in  consequence  of  which  the  animal  soon  passes  into  an  abnormal  and 
enfeebled  condition.  One  of  the  earliest  results  of  this  unhealthy  state 
is  a  diminution  in  the  daily  quantity  of  bile  secreted.  On  the  other 
hand,  by  Schiff 's  method,  so  long  as  the  cystic  fistula  is  closed,  the  bile 
continues  to  pass  through  the  common  duct  into  the  intestine,  thus 
maintaining  the  animal  in  a  healthy  condition.  At  any  time,  however, 
by  opening  the  cystic  fistula  and  emptying  the  gall-bladder,  the  rate  at 
which  the  bile  is  secreted  may  be  observed  with  facility.  It  has  already 
been  mentioned  that  larger  quantities  of  bile  were  usually  obtained  by 
this  than  by  the  older  method. 

The  observations  of  Schiff  show  that  by  leaving  open  the  cystic  fistula, 
and  thus  practically  diverting  all  the  bile  from  the  intestine,  its  rate  of 
secretion  by  the  liver  is  at  once  diminished,  so  that  even  at  the  end  of 
twenty-four  hours,  if  the  influence  of  digestion  be  eliminated,  it  is  already 
reduced  to  a  minimum,  and  this  minimum  continues  afterward  with  only 
insignificant  fluctuations.  On  the  other  hand,  if,  in  the  same  animal, 
the  fistula  be  kept  closed  for  some  hours,  the  quantity  of  bile  soon  rises 
to  its  normal  standard. 

The  same  observer  experimented  upon  the  dog  with  similar  results 
by  making  a  duodenal  fistula,  through  which  he  introduced  a  canula  into 
the  orifice  of  the  common  bile-duct.  This  canula  had  a  lateral  opening 

1  Archiv  fiir  die  Gesammte  Physiologic.     Bonn,  1870,  p.  598. 


226  THE    BILE. 

near  its  inner  end,  which  might  be  left  open  or  kept  closed  by  shifting 
the  position  of  an  inner  tube  fitting  closely  in  the  canula.  Thus  the  bile 
might  be  at  will  either  discharged  externally  from  the  orifice  of  the 
canula,  or  allowed  to  pass  into  the  duodenum  by  its  lateral  opening.  It 
was  found  that,  after  being  discharged  externally  for  even  two  or  three 
hours  previously  to  the  examination,  its  rate  of  secretion  was  much  less 
than  if  it  had  been  allowed  to  pass  into  the  intestine.  The  results 
obtained,  in  a  dog  weighing  12  kilogrammes,  were  as  follows: 

CUBIC  CENTIMETRES  OF  BILE  OBTAINED  IN  TEN  MINUTES  AFTER  HAVING  BEEN, 
FROM  Two  TO  THREE  HOURS, 

Evacuated  externally.  Discharged  into  the  duodenum. 

2.2  6.0 

2.3  5.4 
2.1  5.6 
2.0  6.2 

1.8  6.5 

1.9  5.7 

Average    .        .     2.05  5.90 

Thus  the  quantity  of  bile  secreted,  when  it  has  been  allowed  to  follow 
its  natural  course  into  the  duodenum,  is  nearly  three  times  as  great  as 
when  it  has  been  evacuated  through  the  external  fistula.  It  does  not 
necessarily  follow  from  this  that  it  is  again  directly  used  for  secretion 
by  the  liver,  since  this  process  may  be  influenced  by  a  variety  of  sec- 
ondary conditions ;  but  it  is  difficult  to  avoid  the  conclusion  that  its 
ingredients  are  absorbed  from  the  intestinal  cavity,  and  supply  in  some 
way  the  materials  for  continued  secretion. 

Before  their  reabsorption,  however,  the  biliary  salts  undergo  certain 
alterations  in  the  alimentary  canal,  so  that  when  finally  taken  up  by  the 
bloodvessels,  they  have  already  assumed  a  different  form;  otherwise 
they  could  be  detected  in  the  blood  of  the  portal  vein.  But  such  re- 
searches have  constantly  led  to  a  negative  result.  Our  own  experiments 
on  this  point  were  performed  on  dogs,  by  examining  the  portal  blood 
obtained  at  different  periods  after  feeding.  The  animals  were  killed  by 
section  of  the  medulla  oblongata,  a  ligature  immediately  placed  on  the 
portal  vein,  while  the  circulation  was  still  active,  and  the  requisite 
quantity  of  blood  collected  by  opening  the  vein.  The  blood  was  some- 
times immediately  evaporated  to  dryness  by  the  water-bath.  Sometimes 
it  was  coagulated  by  boiling  in  a  porcelain  capsule  over  a  spirit  lamp, 
with  water  and  an  excess  of  sodium  sulphate,  and  the  filtered  watery 
solution  afterward  examined.  But  most  frequently  the  blood,  after 
being  collected  from  the  vein,  was  coagulated  by  the  gradual  addition 
of  three  times  its  volume  of  alcohol,  stirring  the  mixture  constantly,  so 
as  to  make  the  coagulation  gradual  and  uniform.  It  was  then  filtered, 
the  moist  mass  remaining  on  the  filter  subjected  to  strong  pressure  in  a 
linen  bag,  by  a  porcelain  press,  and  the  fluid  thus  obtained  added  to  that 
previously  filtered ,  The  entire  spirituous  solution  was  then  evaporated 


THE    BILE.  227 

to  dryness,  the  dry  residue  extracted  with  absolute  alcohol,  and  the 
alcoholic  solution  treated  as  usual  to  discover  the  presence  of  biliary 
matters.  In  every  instance,  blood  was  taken  at  the  same  time  from  the 
jugular  vein,  or  the  abdominal  vena  cava,  and  treated  in  the  same  way 
for  purposes  of  comparison. 

We  have  examined  the  blood,  in  this  way,  one,  four,  six,  nine,  eleven 
and  a  half,  twelve,  and  twenty  hours  after  feeding.  The  result  shows 
that  in  the  venous  blood,  both  of  the  portal  vein  and  of  the  general  circu- 
lation, there  exists  a  substance  soluble  in  water  and  in  absolute  alcohol, 
and  precipitable  by  ether  from  its  alcoholic  solution.  This  substance 
is  often  considerably  more  abundant  in  the  portal  blood  than  in  that 
taken  from  the  general  venous  system.  It  adheres  closely  to  the  sides 
of  the  glass  vessel  after  precipitation,  so  that  it  is  always  difficult,  and 
often  impossible,  to  obtain  enough  of  it,  mixed  with  ether,  for  micro- 
scopic examination.  It  dissolves,  also,  like  the  biliary  substances,  with 
great  readiness  in  water ;  but  in  no  instance  have  we  ever  been  able 
to  obtain  from  it  such  a  reaction  with  Pettenkofer's  test,  as  would 
indicate  the  presence  of  bile.  This  is  not  because  the  reaction  is 
masked  by  any  other  ingredient  of  the  blood ;  for  if,  at  the  same  time,  a 
little  bile  be  added  to  blood  taken  from  the  abdominal  vena  cava,  in  the 
proportion  of  one  drop  of  bile  to  seven  or  eight  cubic  centimetres  of 
blood,  and  the  two  specimens  treated  alike,  the  ether-precipitate  may 
be  considerably  more  abundant  in  the  case  of  the  portal  blood ;  and  yet 
that  from  the  blood  of  the  vena  cava,  dissolved  in  water,  will  give  Pet- 
tenkofer's reaction  for  bile  perfectly,  while  that  of  the  portal  blood  will 
give  no  such  reaction. 

Notwithstanding  the  evidence,  therefore,  that  the  biliary  matters  are 
absorbed  by  the  portal  blood,  they  cannot  be  recognized  there  by  Pet- 
tenkofer's test.  They  must  accordingly  have  passed  through  such 
changes,  in  the  intestine,  previously  to  their  absorption,  that  they  can 
no  longer  give  the  ordinary  reaction  of  the  biliary  salts.  We  cannot 
say  precisely  what  these  changes  are,  but  they  are  undoubtedly  depen- 
dent upon  the  action  of  the  intestinal  juices,  and  are  therefore  more  rapid 
while  the  process  of  digestion  is  going  on.  This  is  probably  the  ex- 
planation of  the  fact  that  the  bile,  though  a  continuous  secretion,  is  dis- 
charged into  the  alimentary  canal  in  greatest  abundance  immediately 
after  the  ingestion  of  food ;  since  it  is  not  so  much  needed  to  assist  the 
intestinal  juices  in  the  process  of  digestion,  as  to  be  itself  acted  on  by 
them  and  converted  into  other  materials. 

The  bile,  accordingly,  is  a  secretion  which  has  not  yet  accomplished 
its  function  when  it  is  discharged  from  the  liver  and  poured  into  the 
intestine.  While  in  the  cavity  of  the  alimentary  canal,  in  contact  with 
its  glandular  surface,  and  mingled  with  the  intestinal  juices,  its  ingre- 
dients lose  their  original  character  and  pass  into  the  form  of  new  com- 
binations. These  substances  again  enter  the  circulation  by  absorption 
from  the  intestinal  cavity,  and  are  carried  away  by  the  blood,  to  com- 
plete their  function  in  some  other  part  of  the  body. 


CHAPTEE  XI. 

PRODUCTION  OF  GLYCOGEN  AND  GLUCOSE  IN  THE 

LIVER. 

IP  the  liver  of  a  carnivorous  or  herbivorous  animal,  after  twenty-four 
hours'  fasting,  be  taken  from  the  body  immediately  after  death,  finely 
divided,  and  boiled  for  a  few  moments  in  water  with  animal  charcoal  or 
an  excess  of  sodium  sulphate,  to  eliminate  the  albuminous  and  coloring 
matters,  the  filtered  fluid  will  be  nearly  clear,  or  show  only  a  moder- 
ately opaline  tinge.  But  if  the  same  thing  be  done  within  a  few  hours 
after  the  ingestion  of  animal  or  vegetable  food,  the  watery  decoction  of 
the  liver  tissue  will  be  strongly  opalescent,  being  rendered  turbid  by 
the  presence  in  considerable  quantity  of  a  matter  which  communicates 
to  the  solution  a  partial  turbidity.  This  matter  is  glycogen,  which  is 
contained,  in  greater  or  smaller  quantity,  in  the  liver  extract  under  these 
two  conditions. 

This  substance,  first  discovered  by  Bernard,  has  so  strong  an  analogy, 
in  its  composition  and  properties,  with  the  ordinary  amylaceous  matter 
of  vegetable  tissues,  that  it  is  often  spoken  of  as  "animal  starch."  It 
is,  when  purified,  a  non-nitrogenous  body,  having  the  formula  C6H1005. 
It  is  accordingly  a  carbohydrate,  and  indentical  with  starch  in  its  ulti- 
mate chemical  composition. 

It  is  obtained  from  the  liver  by  first  cutting  the  organ  into  small 
pieces  and  immediately  coagulating  them  by  a  short  immersion  in  boil- 
ing water.  This  is  for  the  purpose  of  prevening  the  partial  transforma- 
tion of  the  glycogen  which  would  otherwise  take  place,  under  the  influ- 
ence of  a  moderate  temperature,  by  contact  with  the  albuminous  matters 
present  in  the  liver.  These  albuminous  matters  having  been  once 
coagulated  by  the  preliminary  boiling,  the  glycogen  can  afterward  be 
extracted  at  leisure.  The  liver  tissue  is  then  ground  to  pulp  in  a 
mortar  and  boiled  continuously  for  half  an  hour  with  a  small  quantity 
of  water,  just  sufficient  to  keep  the  mixture  fluid,  in  order  to  obtain  a 
decoction  as  concentrated  as  possible.  The  decoction  is  then  treated 
with  animal  charcoal,  to  remove  the  coloring  matters,  and  filtered.  The 
solution  is  distinctly  opaline,  and  if  allowed  to  fall  into  a  vessel  of  strong 
alcohol,  the  glycogen,  which  is  insoluble  in  this  fluid,  is  precipitated  in  the 
form  of  a  white  deposit.  This  deposit  is  still  contaminated  by  a  little 
glucose,  and  by  a  certain  quantity  of  biliary  salts  and  other  nitrogenous 
matters.  The  glucose  and  biliary  salts  are  removed  by  repeatedly 
washing  the  precipitate  with  alcohol.  The  deposit  is  then  boiled  for 
a  quarter  of  an  hour  with  a  concentrated  solution  of  potassium  hydrate, 
(  228  ) 


GLYCOGEN  AND  GLUCOSE  IN  THE  LIVER.      229 

which  dissolves  the  albuminous  matters,  but  does  not  affect  the  gly- 
cogen.  After  being  separated  by  filtration  it  is  again  dissolved  in 
water,  the  traces  of  alkali  removed  by  the  addition  of  a  little  acetic 
acid,  and  the  glycogen  then  precipitated  anew,  in  a  pure  form,  by 
alcohol  in  excess.  It  is  then  dried  and  may  be  kept  in  the  form  of  a 
white  pulverulent  mass,  which  retains  its  properties  for  an  indefinite 
time. 

Glycogen  thus  prepared  is  soluble  in  water,  its  solution  having  an 
opalescent  tinge.  Treated  with  iodine,  it  gives  a  violet  color,  inter- 
mediate between  the  blue  reaction  of  starch  and  the  red  of  dextrine. 
It  does  not  reduce  the  copper  salts  in  Trommer's  test,  nor  give  rise  to 
fermentation  with  yeast ;  but  it  is  converted  into  dextrine  and  glucose 
by  all  those  agencies  which  have  a  similar  effect  upon  starch — namely, 
prolonged  boiling  with  dilute  mineral  acids,  the  contact  of  vegetable 
diastase,  of  saliva,  the  pancreatic  juice,  and  the  serum  of  blood  at  a 
moderately  warm  temperature.  If  allowed  to  remain  in  the  liver  after 
death,  a  part  of  it  suffers  transformation  into  glucose  by  contact  with 
the  fluids  of  the  hepatic  tissue. 

Origin  and  Mode  of  Formation  of  Glycogen. — As  this  substance  is 
present  in  the  liver  tissue  of  both  carnivorous  and  herbivorous  animals, 
it  may  be  derived  from  the  materials  of  either  kind  of  food.  In  the 
carnivora,  at  least,  there  is  evidence  that  it  is  supplied  from  nitrogenous 
materials,  by  the  nutritive  changes  which  they  undergo  in  the  substance 
of  the  liver.  Under  some  circumstances  a  material  resembling  glycogen, 
or  identical  with  it,  may  be  present  in  the  muscles  of  the  herbivora. 
Bernard  has  found  it  in  the  muscular  tissue  in  rabbits,  and  especially  in 
pigeons,  when  fed  upon  the  cereal  grains,  and  in  horses  kept  upon  oats 
and  barley;  but  in  all  these  animals  it  disappears  when  the  food  is 
changed,  or  after  some  days'  fasting.  Lnchsinger1  has  also  found  it  to 
be  absent  from  the  muscles  of  the  rabbit  after  several  days'  fasting,  but 
to  continue  more  persistently  in  the  pectoral  muscles  of  the  fowl  under 
similar  conditions. 

It  is  accordingly  not  a  constant  but  only  an  occasional  ingredient  of 
muscular  flesh,  and  when  present  is  usually  found  in  very  small  quan- 
tity. Poggiale,2  in  very  many  experiments  instituted  for  this  purpose 
by  a  Commission  of  the  French  Academy  of  Sciences,  found  glycogen 
present  in  ordinary  butcher's  meat  only  once.  We  have  also  found  it 
to  be  absent  from  the  fresh  meat  of  the  bullock's  heart,  when  examined 
in  the  manner  described  above.  Nevertheless,  in  dogs  fed  exclusively 
for  eight  clays  upon  this  food,  glycogen  may  be  abundant  in  the  liver, 
while  it  does  not  exist  in  the  other  internal  organs,  as  the  spleen,  lungs, 
and  kidneys. 

The  production  of  glycogen  from  nitrogenous  substances  is  also 
shown,  according  to  Bernard,  by  the  fact  that  it  makes  its  appearance 

1  Archiv  fur  die  Gesammte  Physiologie,  1873.     Band  viii.  p.  290. 

2  Journal  de  la  Physiologie.     Paris,  1858,  p.  558. 


230  PRODUCTION    OF 

in  the  bodies  of  maggots  during  the  course  of  their  development, 
although  neither  the  eggs  from  which  they  are  hatched,  nor  the  putrefy- 
ing meat  upon  which  they  feed,  contain  any  appreciable  traces  of  this 
substance. 

Glycogen  is  produced,  however,  in  especial  abundance  in  the  liver, 
after  the  ingestion  of  starchy  and  saccharine  food.  Bernard1  found  the 
decoction  of  the  liver  tissue  in  the  dog,  after  feeding  for  two  days  with 
bread  and  starch  paste,  very  turbid  and  milky  in  appearance.  Subse- 
quent experiments  by  the  same  observer2  have  shown  that  a  starchy 
diet  augments  notably  the  quantity  of  glycogen  existing  in  the  liver. 
This  fact  was  first  demonstrated  in  a  special  manner  by  the  observations 
of  Pavy,3  who,  by  comparative  experiments  upon  dogs  fed  with  animal 
and  vegetable  food,  found  that  the  influence  of  the  latter  was  to  increase 
very  decidedly  the  weight  of  the  whole  liver,  and  also  the  pencentage 
of  glycogen  which  it  contained.  The  same  effect  was  produced  by  a 
diet  of  animal  food  with  sugar  in  addition.  The  following  table  gives 
the  average  results  of  three  series  of  observations  by  Pavy : 

AVERAGE  PRODUCTION  OF  GLYCOGEN,  IN  DOGS,  UNDER  DIET  OF  ANIMAL  AND 
VEGETABLE  FOOD. 

Diet  for  "Weight  of  liver,  Glycogen  in  the 

several  days  in  percentage  of  fresh  liver, 

previously.  bodily  weight.  per  cent. 

Tripe 3.03  7.19 

Tripe  and  sugar        .        .         .         6.42  14.50 

Meal,  bread,  potatoes       .        .        6.06  17.23 

Experiments  on  the  rabbit  also  showed  that  in  this  animal  both  the 
weight  of  the  liver  and  its  percentage  in  glycogen  are  much  diminished 
by  several  days'  fasting,  but  are  maintained  at  the  maximum  standard, 
for  a  time  at  least,  by  a  diet  consisting  exclusively  of  the  carbohydrates. 
The  average  results  were  as  follows : 

AVERAGE  PRODUCTION  OF  GLYCOGEN  IN  RABBITS,  TN  THE  FASTING  CONDITION  AND 
WHEN  FED  ON  CARBOHYDRATES. 

Diet  for  Absolute  weight  Glycogen  in  the 

three  days  of  liver  fresh  liver 

previously.  (grammes).  (per  cent.). 

No  food 34.02  1.35 

Starch  and  sugar      .         .        .       73.71  16.15 

The  quantity  of  glycogen  found  in  the  liver  by  Pavy  is  considerably 
greater  than  that  obtained  by  subsequent  observers  under  similar  cir- 
cumstances, and  is  attributed  to  his  having  employed  an  imperfect 
method  of  purification ;  but  the  principal  fact  of  the  increase  of  glycogen 
under  the  use  of  the  carbohydrates  has  been  confirmed  by  several  other 

1  LeQons  de  Physiologic  Experimentale.     Paris,  1855,  p.  159. 

2  Revue  des  Sciences  Medicales.     Paris,  1874,  torn.  iii.  p.  34. 

3  On  the  Nature  and  Treatment  of  Diabetes.     London,  1862. 


GLYCOGEN  AND  GLUCOSE  IN  THE  LIVER.      231 

experimenters.  Dock  found,  in  his  experiments  on  the  rabbit,1  that  after 
from  3  to  5  days'  fasting  the  glycogen  in  the  entire  liver  was  reduced 
to  a  very  minute  quantity,  or  more  frequently  was  entirely  absent. 
But  if,  in  this  condition,  a  solution  of  glucose  were  introduced  into  the 
stomach  through  a  catheter,  and  the  animal  killed  from  19  to  24  hours 
afterward,  the  quantity  of  glycogen  contained  in  the  liver  amounted  to 
from  0.650  to  1.243  grammes.  After  even  t  days'  fasting,  followed  by 
an  injection  of  glucose  into  the  stomach,  so  short  a  time  as  four  hours 
was  sufficient  to  produce  an  abundance  of  glycogen  in  the  liver.  The 
deposit  of  this  substance  accordingly  takes  place  so  rapidly  after  the 
ingestion  of  this  kind  of  food,  that  no  doubt  can  remain  of  its  being 
directly  produced  from  the  materials  of  the  saccharine  or  starchy  sub- 
stances. 

Tscherinow  showed,  by  his  observations  on  fowls,2  both  the  production 
of  glycogen  from  animal  food,  and  also  its  more  abundant  deposit  under 
a  vegetable  diet.  He  found  that,  in  this  species,  two  days7  fasting  was 
sufficient  to  reduce  the  quantity  of  glycogen  to  a  minimum.  After 
being  subjected  to  a  preliminary  fast  of  this  duration,  the  fowls  were 
fed  for  two  or  three  days  with  different  kinds  of  food,  and  then  killed 
and  examined.  The  average  results  were  as  follows : 

PRODUCTION  OF  GLYCOGEN  IN  FOWLS  UNDER  DIFFERENT  KINDS  OF  DIET. 
Diet  previous  to  the  Glycogen  in  the  fresh 

experiment.  liver,  per  cent. 

Fasting,  2  days 0.57 

Lean  meat,  2  to  4  days  .......  1.40 

Barley,  2  days 5.41 

Kice,  2  days 7.21 

Fibrine  and  sugar,  2  to  3  days 10.20 

It  appears  furthermore  from  the  experiments  of  Weiss  and  Luch- 
singer3  that  a  similar  increase  of  glycogen  will  take  place  in  the  liver 
after  the  ingestion  of  glycerine  (C3H8O3),  a  substance  closely  related  in 
chemical  composition  to  the  carbohydrates,  but  not  under  the  use  of  fat 
or  of  the  alkaline  tartrates  or  lactates. 

There  is  accordingly  every  reason  for  the  belief  that  the  carbohydrates, 
when  taken  in  with  the  food,  are  at  once  transported  to  the  liver  by  the 
portal  circulation,  and  there  fixed  in  its  substance  under  the  form  of 
glycogen.  It  makes  no  difference,  in  this  respect,  whether  these  sub- 
stances be  taken  as  starch  or  as  sugar ;  since  starchy  matters  are  always 
transformed  into  glucose  by  the  process  of  digestion,  to  be  afterward 
absorbed  by  the  bloodvessels  of  the  intestine.  It  is  under  the  form  of 
glucose,  therefore,  that  they  all  enter  the  portal  circulation  and  thus 
reach  the  tissue  of  the  liver.  The  process  of  the  conversion  of  this  sub- 

1  Archiv  fur  die  Gesammte  Physiologic.     Bonn,  1872,  Band  v.  571. 

2  Archiv  fur  Pathologische  Anatomic  und  Physiologic,  1869,  Band  xlvii.  p.  102. 

3  Archiv  flir  die  Gesammte  Physiologic,  1873,  Band  viii.  p.  290. 


232  PRODUCTION    OF 

stance  into  glycogen  is  a  dehydration;  that  is,  the  separation  from  it 
of  the  elements  of  water,  as  follows : 

Glucose.      Water.      Glycogen. 

C6H1206  -  H20  =  CCH1005. 

It  is  not  possible  to  say  in  what  manner  or  by  what  influence  this 
change  takes  place ;  but  it  is  one  of  the  simplest  actions  manifested  by 
organic  substances,  and  is  known  to  occur,  as  well  as  the  opposite  change 
of  hydration,  in  many  of  the  phenomena  of  both  animal  and  vegetable 
nutrition.  The  formation  of  glycogen  from  albuminous  materials  is  a 
more  complicated  process,  and  is  necessarily  accompanied  by  the  appear- 
ance of  another  secondary  product  containing  nitrogen  ;  but  we  have  no 
certain  knowledge  as  to  what  this  substance  may  be,  or  whether  there 
may  not  be  several  new  compounds  formed  at  the  same  time. 

Transformation  of  Glycogen  into  Sugar. — One  of  the  most  marked 
characters  of  glycogen,  as  extracted  from  the  liver  tissue,  is  its  ready 
convertibility  into  glucose  by  contact  with  certain  organic  matters  con- 
tained in  the  secretions  and  in  the  blood.  This  change  takes  place 
partially  in  the  liver  itself;  and  the  consequence  is  that  in  a  state  of 
health  the  tissue  of  the  organ  always  contains  glucose  as  well  as  gly- 
cogen. In  fact,  the  existence  and  production  of  sugar  in  the  liver  was 
a  discovery  anterior  to  that  of  glycogen,  having  been  demonstrated  b}' 
Bernard1  in  1848.  The  experiments  of  this  observer,  the  most  important 
of  which  have  been  repeatedly  confirmed  by  others,  show  that  the  glu- 
cose found  in  the  liver  of  both  carnivorous  and  herbivorous  animals  has 
an  internal  origin,  and  that  it  first  makes  its  appearance  in  the  hepatic 
tissue  itself. 

If  a  dog,  cat,  or  other  carnivorous  animal,  be  fed  for  several  days 
exclusively  upon  meat  and  then  killed,  the  liver  alone  of  all  the  internal 
organs  is  found  to  contain  glucose.  For  this  purpose,  a  portion  of  the 
organ  should  be  cut  into  small  pieces,  reduced  to  a  pulp  by  grinding  in 
a  mortar  with  a  little  water,  and  the  mixture  coagulated  by  boiling  with 
an  excess  of  sodium  sulphate.  The  filtered  fluid  will  then  reduce  the 
oxide  of  copper,  with  great  readiness,  on  the  application  of  Trommer's 
test.  A  decoction  of  the  same  tissue,  mixed  with  a  little  yeast,  will 
also  give  rise  to  fermentation,  producing  alcohol  and  carbonic  acid,  as 
is  usual  with  saccharine  solutions.  On  the  contrary,  the  tissues  of 
the  spleen,  the  kidneys,  the  lungs,  and  the  muscles,  treated  in  the  same 
way,  give  no  indication  of  sugar,  and  do  not  reduce  the  salts  of  copper. 
Every  other  organ  in  the  body,  as  well  as  the  blood  of  the  portal  vein 
by  which  the  liver  is  supplied,  may  be  destitute  of  sugar,  while  the  liver 
always  contains  it,  provided  the  animal  be  healthy. 

The  presence  of  sugar  in  the  liver  is  common  to  all  species  of  animals, 
so  far  as  yet  known.  Bernard  found  it  invariably  in  monkeys,  dogs, 
cats,  rabbits,  the  horse,  the  ox,  the  goat,  the  sheep,  in  birds,  in  reptiles, 

1  Comptes  Rendus  de  1'Academie  des  Sciences.     Paris,  1850,  tome  xxxi.  p.  571. 


GLYCOGEN  AND  GLUCOSE  IN  THE  LIVER.      233 

and  in  most  kinds  of  fish.  '  It  was  only  in  two  species  of  fish,  namely,  the 
eel  and  the  ray  (Muraena  anguilla  and  Eaia  batis),  that  he  sometimes 
failed  to  discover  it ;  but  the  failure  in  these  instances  was  apparently 
owing  to  the  commencing  putrescence  of  the  tissue,  by  which  the  sugar 
had  probably  been  destroyed.  In  the  fresh  liver  of  the  human  subject, 
examined  after  death  from  accidental  violence,  sugar  was  found  to  be 
present  in  the  proportion  of  1.10  to  2.14  per  cent,  of  the  entire  weight 
of  the  organ. 

The  following  list  shows  the  average  percentage  of  sugar  present  in 
the  healthy  liver  of  man  and  different  species  of  animals,  according  to 
the  examinations  of  Bernard : 

PERCENTAGE  OF  GLUCOSE  IN  THE  LIVER. 

In  man    .  .  .  1.68  In  ox       .         .        .         .  2.30 

"  monkey  .  .  .  2.15  "  horse           .         .        .  4.08 

«  dog     .  .  .  .  1.69  "  goat    ....  3.89 

"  cat     .  .  .  .  1-94  "  birds  ....  1.49 

"  rabbit  .  .  .  1.94  "  reptiles        .         .        .  1.04 

"  sheep  .  .  .  2.00  "  fish     .        .        .        .  1.45 

The  glucose  thus  found  in  the  liver  originates  by  transformation  of 
the  glycogen  of  the  hepatic  tissue.  As  glycogen  diminishes  in  quantity 
or  disappears  altogether  by  continued  fasting,  and  is  again  produced 
from  the  ingestion  of  animal  food,  the  glucose  which  is  derived  from  it 
exhibits  similar  fluctuations.  In  the  carnivorous  animals,  sugar  is  pre- 
sent in  the  liver,  although  no  carbohydrates  have  been  given  with  the 
food  for  an  indefinite  time.  Bernard  kept  a  dog  under  observation 
for  three  months  upon  an  exclusive  diet  of  boiled  calves'  heads,  and 
another  for  eight  months  upon  scalded  tripe.  At  the  end  of  that 
time  the  liver  in  each  case  contained  the  usual  quantity  of  glucose. 
We  have  also  found  that  in  the  dog,  after  an  exclusive  diet  for  eight 
days  of  the  fresh  meat  of  the  bullock's  heart,  the  liver  contains  both 
glycogen  and  sugar,  while  neither  of  these  substances  exists  in  the 
blood  of  the  portal  vein.  The  diminution  of  glucose  by  fasting,  and  its 
reappearance  under  the  influence  of  animal  food,  were  shown  by  Ber- 
nard in  the  following  way :  Nine  rats,  taken  in  the  sewers  beneath  the 
College  of  France,  were  used  for  experiment.  Three  of  them  were  at 
once  killed  and  their  livers  found  to  be  highly  saccharine.  The  remainder 
were  then  kept  without  food  for  four  days.  At  the  end  of  that  time 
three  of  them  were  killed,  and  their  livers,  upon  examination,  found  to 
be  nearly  destitute  of  sugar,  only  slight  traces  being  discovered,  too 
small  for  quantitative  determination.  The  glucose  which  existed,  ac-' 
cordingly,  in  the  livers  of  these  animals  at  the  time  of  their  capture, 
had  disappeared  during  their  four  days'  period  of  fast.  The  remaining 
three  were  then  supplied  with  a  meal  of  raw  beef,  and  when  killed,  six 
hours  afterward,  their  livers  contained  an  abundance  of  sugar. 

The  most  distinct  proof  that  the  saccharine  matter  of  the  liver  origi- 
16 


234  PRODUCTION    OF 

nates  in  the  tissue  of  the  organ  itself,  by  transformation  of  the  glycogen, 
is  that  it  continues  to  be  formed  for  a  certain  length  of  time  after  death, 
provided  the  liver  "contain  glycogen.  This  fact  also  was  first  shown  by 
Bernard,1  and  is  easily  verified.  If  the  liver  of  a  healthy  dog  be  taken 
out  of  the  body  immediately  after  death,  and  injected  with  water  by  the 
portal  vein,  the  watery  injection  which  escapes  by  the  hepatic  vein,  after 
traversing  the  liver-tissue,  will  be  found  to  contain  sugar.  But,  as  the 
injection  is  continued,  the  quantity  of  glucose  extracted  by  it  from  the 
liver  grows  constantly  less,  until,  in  from  half  an  hour  to  an  hour,  it  is 
completely  exhausted,  and  at  the  end  of  this  time  neither  the  injected 
fluid  nor  the  hepatic  tissue  contains  any  trace  of  glucose.  If  such  a 
liver  be  kept  in  a  moderately  warm  place  for  some  hours  it  will  again 
be  found  abundantly  saccharine.  The  glucose  may  be  again  exhausted 
by  a  fresh  injection  and  again  reproduced,  until  all  the  glycogen  has 
been  transformed  or  until  the  changes  of  decomposition  begin  to  be 
established.  The  glycogen  itself,  being  less  soluble  than  the  sugar, 
remains  behind  after  such  an  injection,  and  produces  a  new  supply  of 
glucose  by  a  new  transformation. 

Immediately  after  death,  accordingly,  if  the  liver  be  allowed  to  remain 
saturated  with  its  natural  organic  juices,  the  transformation  of  its  gly- 
cogen takes  place  at  first  with  considerable  rapidity ;  approximating,  no 
doubt,  the  rate  at  which  this  transformation  takes  place  during  life. 
Within  the  first  hour,  according  to  our  own  observations  in  the  dog, 
the  glucose  in  the  liver  tissue  is  increased  to  between  4.81  and  5.66 
times  its  original  amount.  After  this  the  change  goes  on  more  slowly, 
its  rate  diminishing  with  the  lapse  of  time,  so  that  at  the  end  of  twelve 
hours  the  sugar  may  have  increased  to  not  more  than  5.73  times  its 
former  quantity.  The  following  table  gives  the  results  of  three  ex- 
periments in  this  direction. 

PROPORTION  OF  GLUCOSE  IN  THE  LIVER  OF  THE  DOG,  AT  DIFFERENT  PERIODS  AFTER 

DEATH. 


No.  1. 

No.  2. 

No.  3. 


In  the  tables  of  Bernard  (page  234),  the  results  are  drawn  mostly  from 
livers  examined  some  time  after  death,  and  according^  represent,  not 

1  Gazette  Hebdomadaire.     Paris,  5  Octobre,  1855. 


At  the  end  of 

Per  thousand  parts. 

810 

15  minutes    . 

.....            792 

1  hour 

10.260 

3.850 

6  hours 

11.458 

4  seconds     . 

2.675 

11.888 

4  hours 

13.361 

12  hours     •  . 

.       15.351 

GLYCOGEN  AND  GLUCOSE  IN  THE  LIVER.      235 

only  the  glucose  present  in  the  organ  at  the  moment  of  death,  but  also 
that  which  accumulates  afterward.  The  proportion  found  in  the  dog  at 
the  end  of  twelve  hours  corresponds  very  closely  in  both  tables. 

It  has  been  doubted  by  some  observers  (Pavy,  Meissner,  Hitter, 
SchifF),  whether  glucose  be  really  produced  in  the  liver  during  life  ;  its 
presence  in  the  liver  tissue,  in  ordinary  examinations,  being  attributed 
entirely  to  a  post-mortem  production  by  transformation  of  the  glycogen. 
It  is  true,  as  these  experimenters  have  found,  that  if  a  small  portion  of 
the  liver  substance  be  cut  out  from  the  body  of  the  living  animal  and 
instantly  plunged  into  a  freezing  mixture,  boiling  water,  or  strong 
alcohol,  so  as  to  arrest  the  transformation  of  the  glycogen,  its  subse- 
quent examination  may  not  show  the  presence  of  glucose  by  Trom- 
mer's  test,  as  applied  in  the  usual  way.  Professor  Flint,  Jr.,1  by  ope- 
rating in  this  way  with  boiling  water,  found  in  two  instances,  where 
the  time  employed  in  the  extraction  and  coagulation  of  the  liver  sub- 
stance was  respectively  28  seconds  and  22  seconds,  there  was  no  marked 
or  certain  evidence  of  sugar.  In  another  instance,  where  the  time  em- 
ployed was  only  10  seconds,  the  liver  extract  presented  no  trace  of 
sugar  whatever;  and  yet  the  blood  of  the  hepatic  vein,  obtained  within 
a  minute  after  the  first  operation,  showed  a  well-marked  saccharine  reac- 
tion by  the  copper  test.  We  have  also  found,  that  under  similar  con- 
ditions, the  liver  tissue  may  yield  no  reduction  by  the  copper  test  at  the 
end  of  17  or  of  22  seconds,  though  it  is  distinct  in  50  seconds  after  its 
extraction  from  the  living  body.  Harley,2  by  killing  the  animal  by 
section  of  the  medulla  oblongata,  immediately  placing  a  portion  of  the 
liver  in  a  freezing  mixture  and  afterward  slicing  it  directly  into  boiling 
acidulated  water,  has  shown  that  glucose  may  be  demonstrated  to  exist 
in  the  organ  within  20  seconds  after  the  death  of  the  animal. 

But  the  failure  to  demonstrate  the  presence  of  glucose,  even  within 
the  shortest  time  after  the  extraction  of  the  liver,  is  only  owing  to  the 
use  of  too  small  a  quantity  of  the  liver  tissue  and  an  imperfect  purifica- 
tion of  its  watery  extract.  If  these  sources  of  error  be  avoided,  glucose 
will  always  be  found  in  the  liver  at  the  instant  of  its  extraction,  or  as 
soon  afterward  as  the  necessary  test  can  be  applied.  In  order  to  demon- 
strate this,  a  portion  of  the  liver  is  to  be  taken  out  of  the  abdomen  of 
the  living  animal  by  an  instantaneous  incision,  reduced  to  a  pulpy  mass 
by  passing  it  between  two  fluted  rollers,  and  at  once  dropped  into  a 
vessel  of  boiling  water  or  of  strong  alcohol.  By  this  means  all  further 
change  of  the  glycogen  is  arrested,  and  the  time  which  elapses  between 
the  extraction  of  the  liver  substance  and  its  immersion  in  the  coagulating 
liquid  may  be  reduced  to  a  very  few  seconds.  A  watery  extract  is  finally 
to  be  made  of  the  liver  substance,  which  must  be  completely  purified  by 
the  repeated  use  of  animal  charcoal  until  it  is  absolutely  transparent 

1  New  York  Medical  Journal,  January,  1869. 

2  Proceedings  of  the  Royal  Society  of  London,  vol.  x.  p.  289. 


236 


PRODUCTION    OF 


and  colorless  1  after  which  it  is  tested  for  glucose  l)y  the  use  of  Fehling's 
solution. 

We  have  experimented,  in  the  manner  above  described,  upon  twenty 
dogs.  In  four  of  the  cases,  the  method  employed  was  that  by  boiling 
water ;  in  the  remaining  sixteen  cases,  that  by  alcohol.  The  animals 
were  examined  four,  eight,  twelve,  and  twenty-four  hours  after  feeding ; 
the  food  consisting  always  of  the  fresh  or  cooked  meat  of  the  bullock's 
heart.  The  longest  time  which  elapsed  from  the  separation  of  the  liver 
to  its  immersion  in  alcohol  or  boiling  water  was  thirteen  seconds ; 
the  shortest  time  was  three  seconds.  The  average  time  was  six  and  a 
quarter  seconds.  In  every  instance  the  final  watery  solution  gave  a 
distinct  and  perfectly  unmistakable  sugar  reaction  by  the  copper  test. 
In  one-half  the  cases,  the  presence  of  sugar  alone  was  determined  by 
this  method ;  in  the  remainder,  its  proportion  to  one  thousand  parts  of 
the  liver  tissue  was  also  ascertained. 

The  following  is  a  list  of  these  experiments,  with  their  results  : 

GLUCOSE  FOUND  IN  THE  LIVER  OF  THE  DOG  IMMEDIATELY  AFTER  ITS  EXTRACTION. 


Experiment. 

Time  after 
feeding. 

Time  consumed  in 
taking  out  liver. 

Process 
of  treatment. 

Proportion  of  glucose 
per  thousand  parts. 

No.    1 

4  hours 

13  seconds 

Alcohol 

Glucose 

No.    2 

4  hours 

7  seconds 

No.    3 

4  hours 

10  seconds 

< 

No.    4 

4  hours 

4  seconds 

« 

No.    5 

8  hours 

7  seconds 

i 

No.    6 

8  hours 

6  seconds 

< 

No.    7 

4  hours 

5  seconds 

Boiling  Water 

No.    8 

12  hours 

6  seconds 

11           '                      U 

No.    9 

12  hours 

8  seconds 

«            (« 

No.  10 

12  hours 

5  seconds 

"            " 

No.  11 

4  hours 

9  seconds 

Alcohol 

•      2.093 

No.  12 

4  hours 

5  seconds 

0.804 

No.  13 

8  hours 

7  seconds 

1.750 

No.  14 

8  hours 

3  seconds 

1.510 

No.  15 

12  hours 

5  seconds 

1.810 

No.  16 

12  hours 

5  seconds 

4.175 

No.  17 

12  hours 

7  seconds 

1.830 

No.  18 

12  hours 

3  seconds 

4.375 

No.  19 

24  hours 

5  seconds 

3.850 

No.  20 

24  hours 

4  seconds 

2.675 

It  appears  from  these  results,  that  when  the  requisite  precautions  are 
adopted,  glucose  is  found  in  the  liver  at  the  earliest  period  at  which  it 
is  possible  to  examine  the  organ  after  its  separation  from  the  body  of 
the  living  animal ;  the  average  quantity  of  sugar  existing  in  the  liver 
tissue,  at  this  time,  being  at  least  two  and  a  half  parts  per  thousand. 
The  exact  proportion  of  sugar  thus  present  in  the  liver  at  the  instant 
of  death,  or  within  a  few  seconds  afterward,  varies  from  0.804  to  4.375 


1  All  the  necessary  details  of  this  process  are  given  in  the  New  York  Medical 
Journal  for  July,  1871. 


GLYCOGEN  AND  GLUCOSE  IN  THE  LIVER.      237 

parts  per  thousand.  These  variations  appear  to  depend  upon  individual 
differences  in  the  animals  employed  for  experiment ;  in  the  same  man- 
ner as  other  ingredients  of  the  tissues  and  fluids  are  founcl  to  vary, 
within  physiological  limits,  in  different  individuals. 

As  sugar  is  found,  under  some  circumstances,  in  minute  quantity  in 
the  blood  of  the  general  circulation,  there  might  be  room  for  doubt 
whether  the  glucose,  present  in  the  liver  at  the  moment  of  death,  be  not 
due  to  the  arterial  blood  with  which  the  organ  is  supplied,  rather  than 
an  ingredient  of  the  hepatic  tissue.  This,  however,  is  not  the  case,  as 
is  shown  by  examining,  at  the  same  time  with  the  liver  or  immediately 
afterward,  some  other  abdominal  organ  equally  well  supplied  with  arte- 
rial blood.  In  the  experiments  above  described,  the  spleen  in  three 
cases  was  taken  out  within  ten  minutes  after  the  excision  of  the 
liver,  treated  in  the  same  manner  by  the  alcohol  process,  and  examined 
for  glucose  with  the  following  result: 


PROPORTION  OF  GLUCOSE  PER  THOUSAND  PARTS. 
At  the  end  of  In  the 

Exp.  No.  14.  |    3  seconds Liver    .        . 

(  10  minutes  ;  Spleen  . 

Exp.  No.  I9.l5seconds ^er    •        • 

1 10  minutes          '.  Spleen  .        .    0. 


Exp.No.20.{    4seconds ^yer    •        •    2'675 

(30  minutes  ....     Spleen  .         .     0. 

It  is  evident,  accordingly,  that  the  liver  sugar  does  not  belong  to  the 
arterial  blood  with  which  the  organ  is  supplied,  but  is  a  normal  ingre- 
dient of  the  hepatic  tissue. 

The  sugar  formed  in  tho  liver  is  similar  in  most  of  its  properties  to 
the  glucose  derived  from  other  sources.  Its  solution  readily  reduces 
the  salts  of  copper  in  Trommer's  or  Fehling's  test,  and  is  colored  brown 
when  boiled  with  a  solution  of  caustic  alkali.  It  rapidly  enters  into 
fermentation  if  mixed  with  yeast  and  kept  at  a  temperature  of  from  21° 
to  38°  (700  to  1000  F.).  It  is  distinguished  from  other  varieties  of  sugar, 
according  to  Bernard,1  by  the  readiness  with  which  it  becomes  decom- 
posed in  the  blood — since  cane  sugar,  if  injected  into  the  circulation  of 
a  living  animal,  passes  through  the  system  without  sensible  decomposi- 
tion, and  is  discharged  unchanged  with  the  urine;  sugar  of  milk,  and 
glucose  prepared  artificially  from  starch,  if  injected  in  moderate  quan- 
tity, are  decomposed  in  the  blood,  but  if  introduced  in  greater  abund- 
ance, make  their  appearance  also  in  the  urine ;  while  a  solution  of  liver- 
sugar,  though  injected  in  much  larger  quantity  than  either  of  the  others, 
may  disappear  altogether  in  the  circulation,  without  passing  off  by  the 
kidneys. 

Absorption  and  final  Disappearance  of  the  Liver-sugar. — The  glu- 
cose produced  in  the  liver  by  transformation  of  the  glycogen  does  not 

1  Lemons  de  Physiologic  Experimental.     Paris,  1855,  p.  213. 


238 


PKODUCTION    OF 


remain  at  the  place  of  its  formation.  It  is  constantly  absorbed  by  the 
blood  traversing  the  capillaries  of  the  organ,  and  carried  away  in  the 
current  of  the  circulation.  This  is  shown  by  the  fact  that  not  only  the 
liver  tissue,  but  also  the  blood  of  the  hepatic  vein  contains  glucose  in 
appreciable  quantity,  although  it  may  not  exist  in  the  portal  blood  by 
•which  the  organ  is  supplied.  As  the  blood  accordingly,  before  its  en- 
trance into  the  liver,  in  these  cases,  is  destitute  of  sugar,  and  yet  con- 
tains this  substance  after  its  passage  through  the  organ,  it  must  acquire 
its  saccharine  ingredients  by  the  absorption  of  glucose  in  the  liver 
itself.  Bernard  has  shown1  that  if  two  specimens,  of  portal  and  hepatic 
blood,  be  taken  from  the  same  dog,  when  in  a  fasting  condition  or  after 
an  exclusive  diet  of  animal  food,  the  former  will  show  no  trace  of  sugar, 
while  the  latter  will  be  distinctly  saccharine.  Lehmamr  has  obtained 
similar  results  by  experimenting  upon  both  dogs  and  horses.  In  these 
animals,  nourished  with  vegetable  matters,  glucose  was  found  in  the 
blood  of  the  portal  vein,  though  often  in  very  small  quantities.  In 
dogs,  when  under  a  diet  of  animal  food,  the  portal  blood  contained  no 
glucose,  while  this  substance  was  present  in  the  blood  of  the  hepatic 
vein.  The  following  table  gives  the  results  of  Lehmann's  experiments : 

QUANTITY  OF  GLUCOSE  IN  THE  BLOOD  OF  THE  HEPATIC  VEIN.  AS  COMPARED  WITH 

THAT  OF  THE  PORTAL 


Species 
of  animal. 

, 

Regimen  previous  to  the 
experiment. 

Proportion  of  glucose  per  thousand  parts 
in  the  blood  of  the 

Portal  vein. 

Hepatic  vein. 

.     Dog 

« 

Fasting  for  two  days 

tt          tt          tt 

0 
0 

7.640 
6.380 

H 

a          it          tt 

0 

8.040 

tt 

Meat 

0 

8.140 

» 

(4 

0 

7.990 

tt 

U 

0 

9.460 

It 
It 

Boiled  potatoes 

it            tt 

Traces 

9.810 
8.540 

Horse 

Bran,  hay,  and  straw 

0.550 
0.052 

8.950 
6.350 

Glucose,  accordingly,  although  constantly  produced  in  the  liver,  does 
not  accumulate  in  the  organ  during  life,  owing  to  its  being  absorbed 
by  the  blood,  and  carried  away  nearly  as  rapidly  as  it  is  formed.  It  is 
only  after  death,  when  the  circulation  has  come  to  an  end  and  the  trans- 
formation of  glycogen  still  goes  on  for  a  time,  that  the  proportion  of 
glucose  in  the  liver  tissue  becomes  notably  increased.  The  circulation 
of  blood  through  the  organ,  so. long  as  it  continues,  acts  like  an  artificial 
watery  injection  of  the  hepatic  vessels,  and  extracts  from  its  substance 
the  sugar  which  has  been  produced  at  the  expense  of  the  glycogen. 


1  Lecjons  de  Physiologic  Bxperimentale.     Paris,  1855,  p.  265,  469. 

2  Comptes  Kendus  de  1*  Academie  des  Sciences.     Paris,  1855.     Tome  xi.  p.  585. 


GLYCOGEN  AND  GLUCOSE  IN  THE  LIVER.      239 

Unless,  therefore,  a  new  supply  of  food  be  taken,  all  the  glycogen  of  the 
liver,  as  shown  by  experiments  cited  above,  becomes  after  a  time  ex- 
hausted ;  having  gradually  undergone  the  saccharine  transformation  and 
absorption  by  the  bloodvessels. 

Owing  to  these  processes  going  on  in  the  hepatic  tissue,  the  blood 
beyond  the  liver,  that  is,  the  blood  in  the  hepatic  vein,  the  inferior  vena 
cava  above  the  diaphragm,  and  the  right  side  of  the  heart,  contains 
traces  of  glucose.  The  proportion  of  sugar  in  the  blood,  however,  con- 
stantly diminishes  as  it  recedes  from  the  point  of  its  origin,  since  the 
saccharine  blood  coming  from  the  liver  is  diluted  with  that  of  the  inferior 
vena  cava,  and  this  mixture  again  with  that  of  the  superior  vena  cava, 
before  reaching  the  right  cavities  of  the  heart.  Beyond -the  pulmonary 
circulation,  under  ordinary  circumstances,  it  has  disappeared  altogether, 
so  that  no  sugar  is  to  be  found,  as  a  rule,  in  the  blood  of  the  general 
circulation. 

The  changes,  therefore,  which  take  place  in  the  liver,  so  far  as  regards 
the  carbohydrates,  consist,  first,  in  a  deposit  of  glycogen,  derived  from 
the  ingredients  of  the  blood.  This  glycogen  acts  as  a  reserve  material, 
which  is  afterward  used  for  the  purposes  of  nutrition.  The  vegetable 
starch  and  sugar  of  the  food,  after  digestion,  are  absorbed  under  the 
form  of  glucose  and  taken  up  by  the  vessels  of  the  portal  system.  This 
glucose  does  not  at  once  enter  the  general  circulation,  but  on  reaching 
the  liver  undergoes,  for  the  most  part,  a  conversion  and  deposit  as 
glycogen,  or  animal  starch.  It  then  gradually  again  passes  into  the 
form  of  glucose  by  a  secondary  transformation,  and  in  this  form  is 
carried  away  by  the  hepatic  blood,  to  be  finally  decomposed  or  assimi- 
lated in  some  unknown  manner  for  the  maintenance  of  the  vital  phe- 
nomena. The  final  product  of  its  metamorphosis  or  destruction  in  the 
animal  body  is  undoubtedly  carbonic  acid  and  the  elements  of  water ; 
but  how  far  this  is  accomplished  by  direct  oxidation,  or  what  other 
intermediate  changes  may  occur  in  the  act  of  nutrition,  cannot  as  yet  be 
determined  with  certainty. 

Similar  successive  transformations  of  the  starchy  and  saccharine 
carbohydrates  are  already  known  to  take  place  in  vegetables.  In  the 
growing  plant,  under  various  conditions,  the  starch,  first  formed  in  the 
green  leaves,  passes  into  the  condition  of  a  saccharine  fluid  to  be  trans- 
ported into  organs  of  reserve,  such  as  tuberous  roots,  grains,  and  fruits, 
where  it  is  again  deposited  as  starch ;  and  from  these  it  is  subsequently 
taken  up  at  the  requisite  time  as  glucose,  and  carried  by  the  vascular 
channels  into  the  growing  organs  for  its  final  destruction  or  assimila- 
tion.1 Starch  and  sugar,  therefore,  in  animals  as  well  as  in  vegetables, 
are  to  be  regarded  as  two  different  forms  of  the  same  nutritive  substance, 
one  of  which  is  in  the  condition  of  temporary  deposit,  the  other  in  that 
of  solution  and  activity. 

1  Mayer,  Lehrbuch  der  Agrikultur  Chemie.    Heidelberg,  1871,  Band  i.  pp.  76, 

78,  81. 


240  PRODUCTION    OF 

Accumulation  of  Glucose  in  the  Blood,  and  its  discharge  by  the  Urine. 
— The  sugar  formed  from  the  glycogen  of  the  liver,  and  discharged  little 
by  little  into  the  circulation,  is  not  usually  recognizable  at  a  distance 
from  the  organ,  owing  to  the  changes  which  it  undergoes  in  the  blood. 
But  under  certain  conditions  its  quantity,  or  the  rapidity  of  its  dis- 
charge by  the  liver,  may  be  increased  ;  so  that,  its  decomposition  no 
longer  keeping  pace  with  its  production,  it  is  diffused  to  a  greater  dis- 
tance from  the  point  of  its  origin.  Bernard  has  observed  this  to  take 
place,  in  an  appreciable  degree,  during  ordinary  digestion.  In  this  pro- 
cess, the  circulation  through  the  liver  being  increased  in  intensity,  after 
a  time  the  glucose  derived  from  its  substance  may  become  perceptible 
in  small  quantity  beyond  the  lungs,  and  traces  of  it  may  appear  in  the 
arterial  blood.  At  the  same  time  its  alteration  continues  to  be  effected, 
so  that  the  venous  blood,  after  passing  through  the  capillaries  of  the 
general  system,  is  no  longer  saccharine.  This  condition  lasts  but  for  a 
short  time.  As  the  digestive  process  comes  to  an  end,  and  the  hepatic 
circulation  returns  to  its  ordinary  standard  of  activity,  the  glucose 
which  it  supplies  to  the  blood  is  again  reduced  to  such  a  proportion,  that 
it  disappears  altogether  from  the  vascular  system  beyond  the  right  side 
of  the  heart. 

If,  however,  from  any  cause,  the  quantity  of  glucose  in  the  blood  of 
the  general  circulation  be  increased  beyond  a  certain  proportion,  it  then 
fails  to  be  completely  decomposed  or  assimilated,  and  a  part  of  it  is  dis- 
charged by  the  kidneys.  Under  these  circumstances  the  urine  becomes 
saccharine,  and  the  animal  is  placed  in  a  condition  of  diabetes.  The 
proportion  of  glucose  which  the  blood  must  contain,  in  order  that  it  may 
be  discharged  by  the  kidneys,  lias  been  determined  in  several  instances. 
Yon  Becker  found1  that  in  rabbits,  if  glucose  be  present  in  the  blood  in 
the  proportion  of  5  parts  per  thousand,  it  passes  off  by  the  urine,  where 
it  may  be  distinctly  recognized  by  the  copper  test ;  but  if  less  abundant 
than  this,  the  indications  of  its  presence  in  the  urine  are  faint  and  un- 
certain. Bernard  ascertained,2  by  injecting  in  the  same  animal  a  solu- 
tion of  glucose  into  the  veins,  that  in  general  a  condition  of  diabetes 
was  produced  when  glucose  was  injected  in  larger  quantity  than  one  part 
per  thousand  of  the  entire  bodily  weight.  The  appearance  of  glucose  in 
the  urine  is  therefore  dependent  upon  the  proportion  in  which  it  exists 
in  the  blood.  If  its  quantity  be  below  a  certain  point,  it  is  all  decom- 
posed by  contact  with  the  ingredients  of  the  blood ;  if  it  be  above  this 
point,  some  of  it  escapes  this  change  and  is  then  eliminated  as  an  in- 
gredient of  the  urine.  According  to  the  experiments  of  Von  Becker,  a 
solution  of  glucose,  injected  into  the  jugular  vein  of  the  rabbit  in  suffi- 
cient quantity,  may  cause  the  appearance  of  sugar  in  the  urine  in  less 
than  three  hours ;  but  at  the  end  of  from  six  to  seven  hours  the  whole 

1  Zeitschrift  fiir  Wissenschaftliche  Zoologie,  Band  v.  p.  176. 

2  LeQons  sur  les  Liquides  de  1'Organisme.     Paris,  1859,  tome  ii.  p.  73. 


GLYCOGEN  AND  GLUCOSE  IN  THE  LIVER.      241 

of  it  may  be  eliminated,  so  that  it  is  no  longer  to  be  found  as  an  ingre- 
dient of  the  excretions. 

There  are  a  variety  of  circumstances  which  may  so  increase  the  pro- 
portion of  glucose  in  the  blood  as  to  cause  a  saccharine  condition  of  the 
urine. 

I.  One  of  these  causes  is  an  unusually  abundant  and  rapid  absorption 
of  sugar  from  the  intestine.     The  sugar  taken  in  with  the  food,  or  pro- 
duced in  the  intestine  by  the  transformation  of  starch,  is  usually  changed 
into  glycogen  by  the  hepatic  tissue,  and  is  afterward  only  slowly  recon- 
verted into  glucose  and  discharged  under  this  form  into  the  blood.     But 
where  a  very  large  quantity  of  sugar  is  suddenly  absorbed  by  the  blood- 
vessels of  the  intestine   and  at  once  carried  by  the  portal  vein  to  the 
liver,  the  tissue  of  the  organ  is  not  capable  of  immediately  converting 
the  whole  of  it  into  glycogen.     Thus  a  portion  of  the  sugar  taken  up 
in  this  way  passes  through  the  hepatic  circulation  unchanged,  and,  reach- 
ing the  general  circulation  in  unusual  quantity,  is  accordingly  discharged 
with  the  urine.     Yon  Becker  observed  that  when  concentrated  solutions 
of  glucose  are  introduced  in  abundance  into  the  intestinal  canal  of  the 
rabbit,  it  may  appear  subsequently  in  the  urine.     Bernard  has  also  found 
that,  in  the  rabbit  after  one  or  two  days'  fasting,  if  sugar  in  large  amount 
be  injected  into  the  stomach,  the  urine  becomes  diabetic;  and  that  the 
same  result  may  follow,  if  the  animal,  in  a  similar  fasting  condition,  be 
made  to  eat  a  considerable  quantity  of  carrots,  which  are  highly  saccha- 
rine.    The  same  thing  has  been  observed  by  Bernard  in  the  human  sub- 
ject, in  consequence  of  taking  a  large  supply  of  sugar  in  solution  when 
the  stomach  has  been  empty  for  several  hours.     This  result  is  produced, 
however,  only  when  a  much  greater  abundance  of  sugar  is  present  in 
the  intestine  than  occurs  in  ordinary  digestion,  and  depends  upon  the 
excessive  quantity  absorbed  within  a  given  time. 

II.  A  diabetic  condition  may  also  be  induced  by   anything  which 
hastens  the  circulation  of  blood  through  the  liver,  or  increases  its  supply 
of  blood.     Many  observers  have  met  with  this  result,  as  produced  by  a 
variety  of  causes.     Bernard  has  found   that  in   dogs  the  blood  of  the 
venous  system  generally  may  present  traces  of  glucose  after  the  abdo- 
men of  the  animal  has  been  subjected  to  pressure  or  manipulation  over 
the  region  of  the  liver,  and  after  any  continued  struggles  or  convulsive 
muscular  action,  by  which  the  abdominal  organs  are  forcibly  compressed 
In  the  same  animal,  according  to  the  experiments  of  Harley,  the  injec- 
tion of  weak  solutions  of  ammonia  or  of  ether  into  the  portal  vein  may 
be  followed  by  a  saccharine  condition  of  the  urine.     This  condition  has 
also  been  seen  in  the  human  subject  after  a  bruise  received  upon  the 
right  hypochondriac  region.     The  resistance  of  an  animal  to  the  inhala- 
tion of  ether  and  the  subsequent  muscular  relaxation,  general  paralysis 
from  a  fracture  of  the  skull  with  cerebral  hemorrhage,  and  the  action  of 
woorara,  or  the  South  American  arrow-poison,  which  also  causes  complete 
muscular  paralysis,  are  all  known  to  be. sometimes  followed  by  the  ap- 


242  GLYCOGEN    AND    GLUCOSE    IN    THE    LIVER. 

pearance  of  sugar  in  the  urine.  Schiff1  has  even  found  that  in  various 
animals,  by  simply  compressing  the  abdominal  aorta  for  ten  minutes,  or 
by  tying  the  principal  bloodvessels  of  one  limb,  he  has  induced,  for  the 
time,  a  condition  of  diabetes.  These  diiferent  causes  may  all  operate 
by  accelerating  the  hepatic  circulation  as  well  as  that  of  the  abdominal 
organs  generally. 

III.  A  saccharine  condition  of  the  blood  and  urine  may  also  be  in- 
duced by  puncture  of  the  medulla  oblongata  in  the  floor  of  the  fourth 
vertricle.  This  remarkable  fact,  which  was  first  discovered  by  Bernard,2 
may  be  demonstrated  in  both  carnivorous  and  herbivorous  animals.  It 
is  best  shown  in  the  rabbit  by  introducing  a  narrow  chisel-shaped 
instrument,  with  the  cutting  edge  directed  transversely,  through  the 
back  part  of  the  skull  and  the  cerebellum,  so  that  it  shall  pierce  the  pos- 
terior part  of  the  medulla  exactly  in  the  median  line,  without  passing 
completely  through  its  substance.  Glucose  appears  in  the  urine  after 
from  one  to  two  hours  and  continues  to  be  present  for  two  or  three  days. 
The  immediate  effect  of  this  operation,  according  to  the  direct  observa- 
tions of  Bernard,  is  to  increase  the  activity  of  the  abdominal  and 
hepatic  circulation.  It  is  not  due  to  a  direct  influence  conveyed  by  the 
pneumogastric  nerve,  since  the  result  follows,  as  usual,  although  the 
pneumogastric  nerves  may  have  been  divided,  and  neither  division  nor 
irritation  of  these  nerves  produces  a  similar  effect.  When  successfully 
performed,  the  operation  causes  no  serious  disturbance  of  the  vital 
functions,  and  the  animal  recovers  after  a  few  days  without  suffering 
permanent  injury. 

In  all  the  instances  above  mentioned,  the  appearance  of  sugar  in  the 
urine  is  only  temporary,  depending  upon  an  occasional  disturbance  of 
the  circulation.  When  in  the  human  subject  this  condition  becomes 
permanent,  it  constitutes  the  disease  known  as  Diabetes  mellitus.  In 
this  affection,  which  is  generally  progressive  and  fatal,  the  urine  is 
increased  in  quantity,  of  greater  specific  gravity  than  natural,  and 
continuously  charged  with  sugar,  sometimes  in  excessive  abundance. 
Fluctuations  are  observable  in  the  quantity  of  glucose  discharged  at 
different  periods  of  the  digestive  process,  but  it  may  continue  to  appear, 
even  when  no  starchy  or  saccharine  matter  is  taken  with  the  food. 

1  Journal  de  1' Anatomic  et  de  la  Physioloerie.     Paris.  1866.  No.  iv.  p.  365. 

2  LeQons  de  Physiologie  Experimeutale.     Paris,  1855,  p.  290. 


CHAPTEE    XII. 

THE    BLOOD. 

THE  blood,  in  its  natural  condition,  while  circulating  in  the  vessels, 
is  a  thick  opaque  fluid,  varying  in  different  parts  of  the  body  from  a 
brilliant  scarlet  to  a  dark  purple  or  nearly  black  color.  It  has  a  slightly 
alkaline  reaction,  and  a  specific  gravity  of  1055.  It  consists,  first,  of  a 
nearly  colorless,  transparent,  alkaline  fluid,  termd  ihQ  plasma,  containing 
water,  fibrine,  albumen,  and  salts,  in  a  fluid  condition;  and,  secondly,  of 
a  large  number  of  distinct  cells,  or  corpuscles,  the  blood-globules,  swim- 
ming freely  in  the  liquid  plasma.  The  globules  form  about  40  per  cent., 
and  the  plasma  about  60  per  cent.,  by  volume,  of  the  entire  mass.  The 
specific  gravity  of  the  two  ingredients  is  somewhat  different.  That  of 
the  plasma  is  about  1030 ;  that  of  the  globules,  1088.  Their  relative 
quantities  by  weight  are  therefore  more  nearly  equal  to  each  other  than 
when  estimated  by  volume;  the  exact  proportions,  according  to  Robin, 
being  nearly  45  per  cent,  of  globules  and  55  per  cent,  of  plasma. 

Notwithstanding  the  difference  in  specific  gravity  between  the  blood- 
globules  and  the  plasma,  the  natural  movement  of  the  blood  in  the 
vessels  keeps  them  thoroughly  mingled ;  and  even  when  the  blood  is 
allowed  to  remain  at  rest  in  a  glass  jar,  the  globules  subside  only  very 
slowly  and  imperfectly.  Thus  the  globules,  disseminated  uniformly 
throughout  the  plasma,  give  to  the  entire  mass  of  the  blood  an  opaque 
aspect  and  a  deep  red  color. 

The  globules  of  the  blood  are  of  two  kinds,  namely,  red  and  white; 
of  these  the  red  are  by  far  the  most  numerous. 

Red  Globules  of  the  Blood. 

The  red  globules  of  human  blood  are  so  abundant  that,  in  the  thinnest 
layer  under  the  microscope,  they  appear  crowded  together  in  such  profu- 
sion as  to  cover  or  touch  each  other  in  every  direction.  According  to 
the  estimates  of  Welcker  and  Vierordt  about  5  millions  of  them  are  con- 
tained in  each  cubic  millimetre  of  blood.  On  account  of  their  quantity 
therefore,  as  well  as  their  peculiar  properties,  it  is  evident  that  they 
form  a  most  important  constituent  of  the  circulating  fluid. 

Physical  Properties  of  the  Red  Globules.— The  red  globules  of  hu- 
man blood  present,  under  the  microscope,  a  perfectly  circular  outline 
and  a  smooth  exterior.  According  to  the  most  recent  and  careful  mea- 
surements of  various  observers,  they  have,  on  the  average,  a  transverse 
diameter  of  from  7.50  to  7.75  mmm.  Their  size  varies  more  or  less, 
but  this  variation  is  not  very  marked  for  the  greater  number  of  the 

(243) 


THE    BLOOD. 


Fig.  76. 


HUMAN  BLOOD-GLOBULES.  —  a,  Red  glob- 
ules, seen  flatwise,  b.  Red  globules,  seen  edge- 
wise, c.  White  globule. 


globules ,  and,  according  to  the  observations  of  Schmidt,  over  90  per 
cent,  of  those  contained  in  a  single  specimen  have  the  same  dimensions. 
The  smallest  size  observed  is  4.50  mmm.  (Harting),  and  the  largest  9.3 

mmm.;  while  their  average  di- 
ameter, as  found  in  different 
individuals,  varies  from  6.70  to 
8,20  mmm. 

The  form  of  the  red  globule 
is  that  of  a  spheroid,  very  much 
flattened  on  its  opposite  sur- 
faces, somewhat  like  a  thick 
piece  of  money  with  rounded 
edges.  The  globule  accordingly, 
if  seen  flatwise,  presents  a  com- 
paratively broad  surface  and  a 
circular  outline  (Fig.  76,  o); 
but  if  it  be  made  to  roil  over, 
it  will  present  itself  edgewise 
during  its  rotation,  and  assume 
the  flattened  form  indicated 
at  b.  The  thickness  of  the 
globule,  seen  in  this  position, 
is  about  one-fifth  of  its  transverse  diameter.  When  the  globules  are 
examined  lying  upon  their  broad  surfaces,  it  can  be  seen  that  these 

surfaces  are  not  exactly  flat, 
but  that  there  is  on  each  side  a 
slight  central  depression,  so  that 
the  rounded  edges  of  the  blood- 
globule  are  evidently  thicker 
than  its  middle  portion.  This 
inequality  produces  a  remarka- 
ble optical  effect.  The  substance 
of  which  the  blood-globule  is 
composed  refracts  light  more 
strongly  than  the  fluid  plasma. 
Therefore,  when  examined  with 
the  microscope  by  transmitted 
light,  the  thick  edges  of  the 
globules  act  as  double  convex 
lenses,  and  concentrate  the  light 
above  the  level  of  the  fluid,, 
Consequently,  if  the  object-glass 
be  carried  upward  by  the  ad- 
justing screw  of  the  microscope,  and  lifted  away  from  the  stage,  so  that 
the  blood-globules  fall  beyond  its  focus,  their  edges  will  appear  brighter. 
But  the  central  portion  of  each  globule,  being  excavated  on  both  sides, 
acts  as  a  double  concave  lens,  and  disperses  the  light  from  a  point  be- 


Fig.  77. 


RED  GLOBULES  OF  THE  BLOOD,  seen  a  little 
beyond  the  focus  of  the  microscope. 


RED  GLOBULES  OF  THE  BLOOD. 


245 


Fig.  78. 


low  the  level  of  the  fluid.  It  thus  becomes  brighter  as  the  object- 
glass  is  carried  downward,  and  the  object  falls  within  its  focus.  An 
alternating  appearance  of  the 
blood-globules  may,  therefore, 
be  produced  by  viewing  them 
first  beyond  and  then  within  the 
focus  of  the  instrument.  When 
beyond  the  focus,  the  globules 
will  be  seen  with  a  bright  rim 
and  a  dark  centre  (Fig.  77). 
When  within  it,  they  will  appear 
with  a  dark  rim  and  a  bright 
centre.  (Fig.  78.) 

Within  a  minute  after  being 
placed  under  the  microscope, 
the  blood-globules,  after  a  fluc- 
tuating movement  of  short  du- 
ration, often  arrange  themselves 
in  slightly  curved  rows  or  chains, 
in  which  they  adhere  to  each 
other  by  their  flat  surfaces,  presenting  an  appearance  which  has  been 
aptly  compared  with  that  of  rolls  of  coin.  This  is  probably  owing  to 
the  coagulation  of  the  blood, 
which  takes  place  very  rapidly 
when  spread  out  in  thin  layers 
and  in  contact  with  glass  sur- 
faces ;  and  which,  by  compress- 
ing the  globules,  forces  them 
into  such  a  position  that  they 
occupy  the  least  possible  space. 

The  color  of  the  blood-glob- 
ules, when  viewed  by  transmit- 
ted light  and  in  a  thin  layer,  is 
a  light  amber  or  pale  yellow. 
It  is  deep  red  when  seen  by  re- 
flected light,  or  in  thick  layers. 
The  blood-globules  have  a  con- 
sistency which  is  very  nearly 
fluid  They  are  exceedingly 

a      ..  .  °~        RED  GLOBULES  OP  THE  BLOOD,  adhering 

flexible,    and   easily  elongated,  together,  like  roils  of  coin, 

bent,   or  distorted  by  pressure 

in  passing  through  the  narrow  currents  of  fluid  which  often  establish 
themselves  in  a  drop  of  blood  under  microscopic  examination ;  but  re- 
gain their  original  shape  as  soon  as  the  pressure  is  taken  off. 

So  far  as  immediate  observation  can  show,  the  red  globules  of  the 
blood,  in  man  and  the  mammalians,  are  homogeneous  in  structure.  The 
most  careful  examination  fails  to  show,  with  any  certainty,  the  evidence 


THE  SAME,  seen  a  little  within  the  focus. 


Fijr.  79. 


246 


THE    BLOCD. 


Fig.  80. 


RED   GLOBULES   OP    THE  BLOOD,    shrunken, 
with  their  margins  crenated. 


of  an  external  envelope,  distinct  from  the  parts  contained  within  it ; 
and  although  some  microscopists  of  high  authority  (Kolliker,  Richard- 
son) continue  to  regard  the  existence  of  such  a  cell-membrane  as  proba- 
ble, it  is  not  generally  admitted,  and  cannot  be  directly  demonstrated. 

Each  globule  appears  to  con- 
sist of  a  mass  of  organic  sub- 
stance, presenting  the  same 
color,  consistency,  and  compo- 
sition throughout. 

The  appearance  of  the  blood- 
globules  is  altered  by  various 
physical  and  chemical  reagents- 
If  a  drop  of  blood,  when  placed 
under  the  microscope,  be  not 
protected  from  evaporation,  the 
globules  near  the  edges  of  the 
preparation  often  diminish  in 
size,  becoming  shrivelled  and 
crenated,  presenting  an  appear- 
ance as  if  minute  granules  were 
projecting  from  their  surfaces  ; 
an  effect  apparently  produced 
by  the  loss  of  a  part  of  their 

watery  ingredients.  This  distortion  of  the  globules  sometimes  takes 
place  with  great  rapidity,  and  care  is  requisite  not  to  confound  a  change 
produced  by  external  physical  causes  with  morbid  alteration  of  the  in- 
gredients of  the  blood.  According  to  the  observations  of  Kolliker,  this, 
as  well  as  certain  other  abnormal  forms  presented  by  the  blood-globules, 
is  never  to  be  seen  in  the  blood  while  circulating  in  the  vessels. 

If  water,  on  the  other  hand,  be  added  to  the  blood,  so  as  to  dilute  the 
plasma,  the  red  globules  absorb  it  by  imbibition,  lose  the  central  con- 
cavity of  their  flat  surfaces,  assume  the  spherical  form,  and  become 
paler.  If  a  larger  quantity  of  water  be  added,  it  may  dissolve  out  com- 
pletely the  coloring  matter,  leaving  the  globules  as  pale,  colorless  circles, 
which  are  almost  invisible  on  account  of  their  tenuity.  They  may  still, 
however,  be  brought  into  view  by  the  addition  of  an  iodine  solution, 
which  stains  them  of  a  yellowish  color.  If  the  water  added  to  the 
blood  be  moderate  in  quantity,  just  sufficient  to  be  taken  up  by  imbibi- 
tion by  the  globules,  but  not  to  extract  their  coloring  matter,  a  special 
change  in  their  form  is  exhibited.  The  edges  of  the  globules,  being 
thicker  than  the  central  portions,  and  absorbing  water  more  abun- 
dantly, become  turgid,  and  encroach  gradually  upon  the  central  part. 
(Fig.  81.)  It  is  very  common  to  see  the  central  depression,  under  these 
circumstances,  disappear  on  one  side  before  it  is  lost  on  the  other,  so 
that  the  globule,  as  it  swells  up,  curls  over  toward  one  side,  and 
assumes  a  peculiar  cup-shaped  form.  (Fig.  81,  a,  a.)  This  figure  may 
often  be  seen  in  blood-globules  after  soaking  for  some  time  in  the  urine, 


RED  GLOBULES  OF  THE  BLOOD, 


247 


Fig.  81. 


RED   GLOBULES   OF   THK   BLOOD,  after  the 
imbibition  of  water. 


or  other  animal  fluids  of  less  density  than  the  plasma  of  the  blood. 
Dilute  acetic  acid,  added  to  the  blood,  instantly  extracts  the  coloring 
matter  of  the  red  globules,  reducing  them  to  the  condition  of  pale  and 
nearly  invisible  colorless  bodies. 
After  the  action  of  water, 
however,  these  colorless  cells 
remain  for  a  long  time,  and  are 
dissolved  very  slowly  in  com- 
parison with  the  coloring  mat- 
ter. 

Dilute  alkaline  solutions,  on 
the  contrary,  dissolve  readity 
the  whole  substance  of  the 
blood-globules.  A  solution  of 
potassium  hydrate,  in  the  pro- 
portion of  ten  per  cent.,  acts 
most  rapidly  in  this  manner. 
Solutions  of  soda  and  ammonia 
have  a  similar  effect,  although 
less  promptly  than  the  preced- 
ing- 
Solutions  of  sodium  glycocholate  or  taurocholate,  in  any  grade  of 
concentration,  or  of  the  fresh  bile  itself,  as  shown  by  Kiihne,  have  also 
the  property  of  dissolving  completely  the  red  globules  of  the  blood. 

Composition  of  the  Red  Globules. — The  red  globules  are  composed  of 
an  albuminous  and  a  coloring  matter,  together  with  mineral  salts  and  a 
certain  proportion  of  water.  According  to  Lehmann,  the  water  of  the 
red  globules  amounts  to  688  per  thousand  parts,  and  a  little  over  8 
parts  per  thousand  consist  of  mineral  salts,  namely,  sodium  and  potas- 
sium chlorides,  phosphates,  and  sulphates,  together  with  lime  and  mag- 
nesium phosphates. 

By  far  the  most  important  ingredient  of  the  red  globules  is  undoubt- 
edly their  coloring  matter,  or  hemoglobine,  the  main  characters  of  which 
have  been  described  in  Chapter  Y.  According  to  the  estimates  of 
Preyer,1  founded  upon  the  observed  quantity  of  iron  as  an  ingredient, 
the  average  proportion  of  hemoglobine  in  healthy  human  blood  is  12.34 
per  cent.  As  the  globules  themselves  constitute  45  per  cent  of  the 
whole  blood,  the  quantity  of  hemoglobine  in  each  blood  globule  is 
about  27  per  cent,  of  its  entire  mass,  or  86  per  cent,  of  its  solid  ingre- 
dients. It  is,  accordingly,  as  regards  its  quantity,  the  principal  substance 
of  which  the  globules  are  composed. 

In  the  fresh  globule,  the  hemoglobine  is  united  with  another  substance 
which  is  colorless  and  undoubtedly  albuminous  in  its  nature,  and  which 
forms  a  substratum  for  the  other  ingredients  of  the  globules.  This 
colorless  matter  is  less  soluble  in  water  than  the  hemoglobine,  and  it  is 


Die  Blutkrystalle,  Jena,  1871,  p.  117. 


218 


THE    BLOOD. 


owing  to  this  fact,  already  mentioned,  that  when  water  is  added  to 
the  blood  in  sufficient  quantity,  the  hemoglobine  may  be  entirely  ex- 
tracted from  the  globules  in  a  state  of  solution,  leaving  behind  the 
colorless  substratum,  much  reduced  in  volume,  but  still  remaining 
undissolved  for  a  considerable  time.  The  exact  physical  condition  of 
the  hemoglobine  in  the  blood-globule  and  its  mode  of  union  with  the 
colorless  substratum  are  not  positively  known.  Preyer  calculates  that 
the  water  of  the  blood-globule  is  quite  insufficient  in  quantity  to  hold  in 
solution,  by  itself,  the  hemoglobine  which  is  present ;  and,  according  to 
the  same  observer,  it  cannot  exist  in  the  blood-globules  in  a  solid  form, 
since  the  crystals  of  hemoglobine  are  always  doubly  refracting,  while 
the  fresh  globules  themselves  are  never  so.  So  far  as  we  can  judge,  the 
two  substances  are  united  uniformly  throughout  the  mass,  in  a  condition 
of  thick  or  tenacious  semi-fluidity ;  but  the  hemoglobine  is  more  easily 
affected  by  various  artificial  dissolving  agents,  and  by  this  means  may  be 
extracted  from  the  mass  of  the  globule. 

Hemoglobine  is  remarkable  for  the  avidity  with  which  it  absorbs 
oxygen  whenever,  either  as  constituent  of  the  blood-globules  or  in  the 
form  of  solution,  it  is  brought  in  contact  with  this  gas  or  with  atmo- 
spheric air.  The  brilliant  red  color  presented  by  its  solutions  depends 
upon  the  quantity  of  oxygen  present ;  for  if  this  substance  be  exhausted 
by  means  of  the  air-pump,  the  application  of  heat,  or  the  displacing 
action  of  an  indifferent  gas,  the  clear  scarlet  hue  of  the  solution  dis- 
appears and  is  replaced  by  a  dull  red  or  purple  color. 

Solutions  of  pure  hemoglobine,  as  well  as  the  blood-globules  them- 
selves, or  diluted  mixtures  of  blood  and  water,  in  the  aerated  condition, 
exhibit  a  well-marked  and  peculiar  spectrum.  This  spectrum  is  dis- 
tinguished by  the  existence  of  two  absorption  bands  between  the  lines 
D  and  E,  and  situated,  the  one  in  the  yellow,  the  other  at  the  commence- 
ment of  the  green.  The  first  of  these  absorption  bands  is  comparatively 

Pig.  82. 


BC        D 


Red     Or.   Yel.  Green     Blue 


Violet 


SPECTRUM  OF  HEMOOLOBINE,  in  Aerated  Blood. 

narrow,  well  defined,  and  dark,  and  is  placed  at  about  one-fifth  the  dis- 
tance from  D  to  E.  The  second  is  double  the  width  of  the  first,  but  is 
less  dark,  and  not  so  well  defined ;  it  occupies  nearly  the  last  half  of 
the  space  between  D  and  E.  Beyond  the  second  band  the  light  of  the 


RED    GLOBULES    OF    THE    BLOOD.  249 

spectrum  gradually  diminishes,  and  ceases  altogether  about  the  termina- 
tion of  the  blue,  midway  between  F  and  G. 

If  the  solution  or  mixture  be  much  concentrated,  or  be  viewed  in  a 
very  deep  layer,  it  is  too  opaque  for  spectroscopic  examination,  and 
may  shut  off  all  the  light  of  the  spectrum  except  a  little  of  the  red  and 
orange;  if  it  be  too  dilute,  it  will  fail  to  exhibit  the  distinguishing 
characters  of  hemoglobine.  A  solution  of  a  certain  grade  of  strength, 
which  allows  an  abundance  of  light  to  pass  through,  and  is  yet  sufficient 
to  cause  its  marked  absorption  at  particular  points  of  the  spectrum,  is 
to  be  used  for  examination.  With  pure  hemoglobine,  according  to 
Preyer,  a  solution  of  about  1.5  parts  per  thousand  gives  the  most  marked 
results.  With  fresh  blood,  if  one  volume  of  the  defibrinated  blood  be 
diluted  with  one  hundred  volumes  of  water,  and  the  mixture  viewed  in 
a  layer  of  one  centimetre,  all  the  characteristic  traits  of  the  spectrum 
will  be  distinctly  shown. 

The  spectroscopic  characters  above  described  form  a  very  delicate 
test  for  the  coloring  matter  of  blood.  According  to  Preyer,  with  a 
solution  of  pure  hemoglobine  in  water,  of  4  parts  per  ten  thousand,  the 
absorption  bands  may  still  be  seen,  though  the  second  one  is  very  faint. 
Fresh  dog's  blood,  if  diluted  with  1000  parts  of  water  and  viewed  in  a 
layer  of  3  centimetres'  thickness,  will  show  a  spectrum  in  which  both 
absorption  bands  are  distinctly  perceptible  though  not  very  strong.  If 
diluted  with  10,000  parts  of  water  and  viewed  in  a  layer  of  4.5  centi- 
metres, the  first  band  is  still  visible,  though  very  faint ;  the  second  is 
entirely  imperceptible. 

These  characters  are  also  of  value  in  showing  that  hemoglobine,  as 
extracted  in  the  crystalline  form,  is  identical  with  the  normal  coloring 
matter  of  the  fresh  globules.  A  solution  of  crystallized  hemoglobine 
gives  the  same  spectrum  with  solutions  of  fresh  blood  or  with  the  dried 
globules.  EA^en  the  blood  while  still  circulating  in  the  vessels  may  be 
made  to  exhibit  the  same  appearances.  If  a  spectroscope  eye-piece  with 
two  prisms  be  attached  to  the  body  of  a  microscope  in  such  a  way  that 
two  spectra  may  be  seen  in  the  field,  one  above  another,  one  of  them 
formed  by  the  light  coming  through  the  body  of  the  instrument,  the 
other  by  that  coming  through  a  lateral  opening  in  the  eye-piece ;  and  if 
the  mesentery  of  a  living  frog  be  placed  before  the  objective  of  the  micro- 
scope, while  a  solution  of  human  blood  is  placed  at  the  lateral  opening, 
it  will  be  seen  that  the  absorption  bands  in  the  two  spectra  are  the  same, 
and  exactly  correspond  with  each  other. 

In  all  the  above  cases  the  blood  which  yields  the  characteristic  spec- 
trum already  described  is  in  the  aerated  condition.  Even  if  venous  blood 
be  taken  for  examination,  the  process  of  extracting  it  and  placing  it  in 
a  suitable  vessel  for  examination  brings  it  in  contact  with  the  atmosphere 
and  thus  restores  it  to  the  condition  of  arterial  blood.  In  the  mesentery 
of  the  living  frog,  when  extracted  from  the  abdomen  and  spread  out 
under  the  microscope,  the  free  access  of  air  to  the  peritoneal  surface 
constantly  supplies  the  circulating  blood  with  oxygen  ;  and  accordingly 
17 


250  THE    BLOOD. 

no  marked  difference,  either  of  color  or  of  spectroscopic  characters,  is 
to  be  seen  between  the  blood  in  the  arteries  and  capillaries,  and  that  in 
the  veins.  But  if  by  any  means  the  blood  or  a  solution  of  hemoglobine 
be  deprived  of  its  oxygen,  and  examined  in  that  condition,  it  at  once 
shows  a  decided  change  both  in  color  and  spectroscopic  appearances. 

This  reduction  or  deoxidation  of  the  coloring  matter  of  the  blood  may 
be  effected  in  either  of  two  ways,  namely,  first,  by  the  addition  of  deoxi- 
dizing agents,  and  secondly  by  keeping  the  blood  for  a  time  excluded 
from  the  access  of  air.  According  to  the  experiments  of  Stokes,  the 
addition  of  iron  protosulphate  to  fresh  blood  reduces  the  hemoglobine, 
and  changes  its  color  from  bright  red  to  dark  purple ;  the  scarlet  color 
being  again  restored  by  agitating  the  blood  with  oxygen  or  atmospheric 
air.  Other  observers  have  accomplished  the  reduction  of  the  hemoglo- 
bine by  continued  treatment  of  the  blood  or  its  solutions  with  a  stream 
of  carbonic  acid.  The  second  method,  however,  is  more  easily  applied. 
If  a  solution  of  fresh  blood,  of  a  bright  scarlet  color,  which  yields  a 
spectrum  with  the  absorption  bands  of  aerated  hemoglobine  fully  devel- 
oped, be  inclosed  in  a  securely  stoppered  test-tube,  the  whole  of  which 
it  completely  fills,  and  be  kept  in  this  condition  secluded  from  the  air 
for  twenty-four  or  forty-eight  hours,  the  hemoglobine  at  the  end  of  that 
time  will  have  lost  its  oxygen  which  has  entered  into  other  combinations. 
If  now  placed  before  the  spectroscope,  the  solution  will  show  a  spectrum 
in  which  the  two  absorption  bands  above  described  have  disappeared, 
and  which  shows  in  place  of  them  a  single  wide  and  comparatively  ill- 
defined  band  covering  about  three-quarters  of  the  distance  from  D  to  E, 
and  extending  usually  toward  the  red  a  little  beyond  the  situation  of 
the  line  I).  The  darkest  part  of  this  absorption  band  occupies  exactly 
the  space  which  intervened  between  the  two  former  bands. 

Fig.  83. 


SPECTRUM   OF   REDUCED   HEMOGLOBIXE. 

If  the  solution  be  now  shaken  up  for  a  few  instants  with  atmospheric 
air.  its  bright  color  is  at  once  restored,  and  at  the  same  time  the  single 
absorption  band  of  reduced  hemoglobine  disappears,  and  is  replaced  by 
the  two  normal  bands  of  oxidized  or  aerated  blood.  These  changes 
may  be  repeated  until  the  blood  begins  to  show  the  effect  of  putrefaction. 

Red  Globules  of  the  Blood  in  different  Classes  of  Animals. — In  all 
vertebrate  animals  the  blood  contains  red  globules,  of  which  the  color- 


RED    GLOBULES    OF    THE    BLOOD.  251 

ing  matter  is  identical  with  that  in  the  human  species.  Even  in  Am- 
phioxus,  a  kind  of  fish  of  very  low  grade  of  organization,  which  was 
long  regarded  as  exceptional  in  this  respect,  the  existence  of  faintly 
colored  globules  has  been  demonstrated  of  late  years.  That  th'e  coloring 
matter  of  these  globules  consists  of  hemoglobine  has  been  demonstrated 
in  such  different  animals  as  the  dog,  fox,  cat,  horse,  sheep,  pig,  lion, 
cougar,  baboon,  bat,  hedge-hog,  rat,  guinea-pig,  squirrel,  mole,  goose, 
pigeon,  lark,  owl,  crow,  lizard,  python,  tortoise,  frog,  carp,  perch,  her- 
ring, and  pike.  It  has  been  discovered,  in  all,  in  22  species  of  mam- 
malians, 7  birds,  5  reptiles,  and  12  fish;  and  has  been  found  to  exist  in 
every  species  of  vertebrate  animal  which  has  been  examined  for  that 
purpose.  Even  in  several  invertebrate  species  where  the  blood  is  of  a 
red  color,  although  it  exhibits  no  distinct  globules,  it  has  been  found  to 
contain  hemoglobine  in  a  state  of  solution.  Preyer  found  that  the  red 
circulating  fluid  of  the  earthworm,  when  examined  by  the  spectroscope, 
yielded  a  spectrum  with  two  absorption  bands  identical  with  those  of 
human  hemoglobine.  It  has  also  been  discovered  in  the  blood  of  the 
pond-snail,  the  horse-leech,  and  the  fresh-water  shrimp. 

But  although  in  all  these  cases  the  red  globules  contain  the  same 
coloring  matter,  they  present,  in  different  animals,  variations  of  form, 
size,  and  structure,  which  are  more  or  less  characteristic  of  the  different 
classes,  families,  and  species,  to  which  they  belong. 

In  the  mammalians,  or  warm-blooded  quadrupeds,  the  red  globules 
of  the  blood  have  without  exception  the  same  homogeneous  structure  as 
in  man.  They  have  also  invariably  the  same  disk-like  figure,  with  a 
circular  outline,  except  in  the  species  belonging  to  the  family  of  the 
camelidse  (camel,  dromedary,  lama),  where  the  disks  have  an  oval  form. 
The  size  of  the  red  globules  in  the  mammalians  varies  much  in  extreme 
cases;  the  smallest  known  being  those  of  the  Java  musk-deer,  an  animal 
not  larger  than  a  rabbit,  which  have  a  diameter  of  2.50  mmm.,  while  the 
largest  are  those  of  the  elephant,  which  measure  9.20  mmm.  The  rela- 
tive size  of  the  globules,  however,  in  different  species,  does  not  con- 
stantly correspond  with  that  of  the  animal  itself;  since  those  of  the  cat 
are  larger  than  those  of  the  sheep,  and  those  of  the  rabbit  larger  than 
either.  The  following  list  gives  the  size  of  the  red  globules  in  various 
species  of  mammalians,  according  to  the  measurements  of  Gulliver  and 
Welcker: 


DIAMETER  OF  THE  CIRCULAR  RED  GLOBULES  OF  MAMMALIANS, 

in  micro-millimetres. 

•  .        .        7.35  Horse  ....  5.43 

f>og      .  7.30  Sheep  ....  5.00 

Wolf    ....        6.94  Red  deer     .        .        .  5.00 

Rabbit          .        .        .        6.90  Goat    ....  4.10 

Cat       ....        6.50  Elephant     .         .        .  9.20 

Fox      ....         6.10  Two-toed  sloth     .         .  8.93 

Ox       ....        5.95  Java  musk  deer  .  2.50 


252 


THE    BLOOD 


In  animals  where  the  red  globules  are  of  comparatively  smaller  size 
they  are  proportionally  more  numerous.  It  is  estimated  by  Kolliker  that 
the  entire  volume  or  mass  of  all  the  red  globules  together,  in  any  deter- 
minate quantity  of  blood,  does  not  vary  much  in  different  species ;  and 
that  accordingly,  in  blood  containing  the  smaller  and  more  abundant 
globules,  the  extent  of  their  surface,  and  probably  their  functional 
activity,  is  greater  than  where  they  are  larger  and  less  numerous.  This 
will  apply  also  to  the  inferior  groups  of  vertebrate  animals,  in  which  the 
globules  are  often  very  much  larger  and  at  the  same  time  less  abundant 
than  in  man. 

In  the  birds,  reptiles,  and  fish,  comprising  all  the  oviparous  verte- 
brata,  as  well  as  some  which  are  viviparous,  the  red  globules  are  distin- 
guished by  two  very  marked  characters  of  shape  and  structure :  namely, 
an  oval  form  and  the  presence  of  a  granular,  colorless  nucleus.  The 
only  known  exception  is  in  two  species  of  fish  belonging  to  the  family 
of  the  Lampreys,  in  which  the  globules  have  a  circular  outline;  but  here 
also  they  are  provided  with  a  nucleus,  and  accordingly  readily  distin- 
guishable from  the  circular  globules  of  mammalia. 

It  is  among  the  Batrachians,  or  naked  reptiles,  that  the  red  globules 
present  the  largest  size  and  exhibit  most  distinctly  their  structural 
character.  They  are  of  a  regularly  oval  form,  their  short  diameter 

being  between  one-half  and 
three-quarters  the  long  one,  a 
little  thicker  toward  the  edges 
and  thinner  in  the  middle  ;  the 
round  or  oval  nucleus  project- 
ing slightly  from  the  lateral 
surface  at  its  central  portion 
In  their  reactions  toward  dif- 
ferent physical  and  chemical 
agents,  they  resemble  the  red 
blood-globules  of  mammalians. 
In  the  frog,  the  red  globules 
have  a  long  diameter  of  22 
mmm.,  or  nearly  three  times 
that  of  the  human  globules  ;  in 
Proteus  anguinus,  the  blind 
water-lizard  of  the  Carniola 
grottoes,  58  mmm. ;  in  Meno- 
branchns,  an  allied  species  inhabiting  the  northern  lakes  of  the  United 
States,  62.5  mmm.  ;  and  in  Amphiuma  tridactylum,  the  great  water- 
lizard  of  Louisiana,  according  to  Dr.  Riddell,  the  red  globules  are  one- 
third  larger  than  in  Proteus,  or  about  77  mmm.  The  following  list 
gives  the  size  of  different  globules  of  the  oval  form. 


BLOOD-OLOBULKS   OF    FROG.  —  a.  Blood-glo 
bule  seen  edgewise,    b.  White  globule. 


BED  GLOBULES  OF  THE  BLOOD.  253 

LONG  DlAMKTEK  OF  THE  OVAL  RED  GLOBULES  OF  BlRDS,  REPTILES,  AND  FlSH, 

in  micro-millimetres. 

Pigeon        ....  147  Frog       ......  22.0 

Fowl  .        .        .        .        .  12.1  Triton 29.3 

Duck 12.9  Menobranchus        .        .         .  62.5 

Tortoise       ....  20.0  Carp 13.1 

Lizard         ....  16.4  Sturgeon         ....  13.4 

Alligator 19.2  Perch 12.0 

Diagnosis  of  Blood,  and  the  distinction  between  Human  Blood  and  that 
of  Animals. — It  is  often  of  consequence  to  recognize  the  existence  of 
blood  in  various  animal  fluids  in  physiological  experiments,  and  it  some- 
times becomes  important  in  medico-legal  investigations.  For  this 
purpose,  in  the  fresh  fluids,  nothing  can  be  more  satisfactory  than 
spectroscopic  examination ;  a  very  small  quantity  of  hemoglobine,  as 
already  shown,  being  sufficient  to  yield  a  spectrum  with  the  character- 
istic absorption  bands.  There  is  a  further  advantage  in  this  method, 
namely,  that  it  will  enable  us  to  detect  the  presence  of  blood  in  fluids 
where  the  red  globules  have  been  dissolved  and  the  coloring  matter 
reduced  to  a  fluid  condition.  The  washings  of  a  blood  spot  or  stain 
may  therefore  show  the  spectrum  of  hemoglobine,  although  they  may 
not  contain  any  red  globules  perceptible  by  the  microscope.  This,  how- 
ever, only  shows  the  presence  of  the  coloring  matter  of  blood,  and  thus 
allows  us  to  distinguish  blood  from  other  colored  fluids ;  it  does  not 
enable  us  to  make  a  distinction  between  the  blood  of  man  and  that  of 
animals,  since  the  hemoglobine  is  the  same  in  all. 

But  by  microscopic  examination  of  the  red  globules,  either  when 
fresh  or  after  having  been  dried  and  again  moistened,  we  can  often  dis- 
tinguish the  blood  of  an  inferior  animal  from  that  of  the  human  subject. 
According  to  the  observations  of  Prof.  J.  G,  Richardson,1  a  fragment  of 
a  blood  spot,  weighing  less  than  r-|^  of  a  milligramme,  which  had  been 
kept  in  the  dried  condition  for  five  years,  when  decolorized  with  a  weak 
watery  solution  (0.15  per  cent.)  of  sodium  chloride,  and  afterward  tinted 
with  a  solution  of  aniline,  exhibited  the  blood-globules  in  such  a  condi- 
tion that  their  size  could  be  accurately  measured. 

If  a  blood  stain,  accordingly,  which  in  a  watery  solution  gives  the 
common  spectrum  of  hemoglobine,  be  found  to  contain  oval  nucleated 
globules,  this  would  show  it  to  be  the  blood  of  a  bird,  reptile,  or  fish ; 
and  the  oval  form  alone  would  show  that  it  is  not  human  blood.  The 
question,  therefore,  whether  a  particular  specimen  be  composed  of  human 
blood  may  often  be.  decided  with  certainty  in  the  negative  by  microscopic 
examination.  But  if  the  specimen  contain  circular  globules,  without 
nuclei,  it  will  be  impossible  to  say  positively,  in  any  instance,  that  they 
belong  to  human  blood,  and  not  to  that  of  some  animal,  such  as  the  ape 
or  the  dog,  whose  red  globules  nearly  approach  the  human  in  size.  In 
most  of  the  domesticated  quadrupeds,  the  globules  are  smaller  than  in 

1  Monthly  Microscopical  Journal.     London,  September  1,  1874,  p.  140. 


THE    BLOOD. 

human  blood;  but  in  both  the  sloth  and  the  elephant,  they  are  larger. 
If  it  were  only  required  to  decide  whether  a  given  specimen  of  fresh 
blood  belonged  to  man  or  to  the  musk  deer,  for  example,  or  even  to  the 
goat,  no  doubt  the  difference  in  size  of  the  globules  would  be  sufficient 
to  determine  the  question. 

But  within  nearer  limits  of  resemblance  it  would  be  doubtful,  because 
the  size  of  the  red  globules  varies  to  some  extent  in  each  kind  of  blood ; 
and  in  order  to  be  certain  that  a  particular  specimen  were  human  blood, 
it  would  be  necessary  to  show  that  the  smallest  of  its  globules  were 
larger  than  the  largest  of  those  belonging  to  the  animal  in  question,  or 
vice  versa.  The  limits  of  this  variation  have  been  tolerably  well  defined 
for  human  blood,  but  not  sufficiently  so  for  many  of  the  lower  animals 
to  make  an  absolute  distinction  possible. 

In  the  examination  of  stains  or  blood  spots,  the  difficulty  is  increased 
by  the  fact  that  the  drying  and  subsequent  moistening  of  the  globules 
introduces  another  element  of  uncertainty  as  to  their  exact  original  size. 

Physiological  Function  of  the  Bed  Globules. — There  is  no  doubt  that 
the  red  globules  of  blood  serve  mainly  as  the  carriers  of  oxygen.  The 
extreme  readiness  with  which  they  absorb  this  substance  from  the 
atmosphere  or  from  any  other  gaseous  mixture  containing  it,  their  im- 
mediate change  of  color  depending  upon  the  supply  or  withdrawal  of 
oxygen,  corresponding  with  the  change  of  color  in  the  blood  as  it  tra- 
verses the  lungs  or  the  capillaries  of  the  general  circulation,  all  indicate 
that  they  have  a  special  relation  to  the  introduction  and  distribution  of 
oxygen  in  the  living  body.  As  a  general  rule,  in  those  animals  where 
the  red  globules  are  of  large  size  and  few  in  number,  the  activity  of  the 
vital  functions  is  below  the  average  ;  while  in  the  species  where  they  are 
smaller  and  more  numerous,  the  processes  of  respiration,  circulation, 
nutrition,  and  movement  are  increased  in  rapidity  to  a  similar  degree. 
The  strongly  marked  physical  and  chemical  characters  of  the  red  glo- 
bules correspond  with  their  importance  in  the  functions  of  vitality. 

White  Globules  of  the  Blood. 

Beside  the  red  globules  above  described,  the  blood  contains  a  certain 
number  of  other  cellular  bodies,  which  differ  from  the  former  in  several 
important  particulars.  These  are  the  white  or  colorless  corpuscles.  As 
their  name  implies,  they  are  destitute  of  red  or  other  coloring  matter, 
but  under  many  circumstances  present  under  the  microscope  a  glistening 
appearance,  and  when  collected  in  large  quantity  may  give  to  the  fluid 
or  clot  which  contains  them  a  whitish  hue.  They  are  much  less  abun- 
dant than  the  red  globules,  the  average  proportion  in  healthy  human 
blood  being  one  white  globule  to  300  red.  They  are  nearly  spherical 
in  form,  and  measure,  on  the  average,  11  mmm.  in  diameter.  They  are 
accordingly,  in  human  blood,  distinctly  larger  than  the  red  globules. 
(Fig.  76,  c.)  As  regards  their  structure,  they  consist  of  a  soft,  some- 
what viscid,  colorless,  finely  granular  substance,  containing  in  its 
interior  one,  two,  or  three  ovoid  nuclei.  They  are  less  yielding  and 


WHITE    GLOBULES    OF    THE    BLOOD. 


255 


Fig.  85. 


slippery  than  the  red  globules,  and  have  a  tendency  to  adhere  more 
readily  to  the  surfaces  with  which  they  are  in  contact ;  so  that  if  a 
small  quantity  of  a  watery  fluid  be  added  to  the  drop  of  blood  under 
examination,  the  red  globules  will  be  hurried  away  by  the  currents  pro- 
duced, while  the  white  globules  lag  behind,  and,  if  the  irrigation  be  con- 
tinued, may  finally  be  left  alone  in  the  field  of  the  microscope.  Their 
transparency  is  such  that,  when  slowly  rolling  over  with  the  current, 
the  granules  in  their  interior  may  often  be  perceived  to  rotate  past 
each  other,  above  and  below,  with  the  motion  of  the  globule.  The 
nuclei  are  sometimes  visible  in  the  perfectly  fresh  globule,  but  may 
always  be  brought  into  view  by  the  addition  of  pure  water  or  of  dilute 
acetic  acid.  The  action  of  these  fluids  is  to  cause  a  slight  swelling  of 
the  globule  and  to  increase  the 
transparency  of  its  substance, 
by  which  the  nuclei  become 
perceptible  as  sharply  defined 
ovoid  or  vesicular  bodies  in  or 
near  the  central  part  of  the 
mass.  By  the  prolonged  ac- 
tion of  acetic  acid,  a  portion 
of  the  cell  substance  becomes 
condensed  about  the  nuclei  in 
various  irregular  forms,  while 
the  remainder  appears  as  a  per- 
fectly transparent  and  homo- 
geneous material,  surrounded 
by  a  very  delicate  circular  out- 
line. The  final  effect  of  both 
water  and  acetic  acid  is  to  dis- 
integrate the  white  globules 
and  cause  their  disappearance.  Dilute  alkalies  dissolve  them  with  great 
readiness. 

Amoeboid  Movements  of  the  White  #Zo6u/es.— These  movements  are 
so  called  from  their  resemblance  to  the  motions  of  Amoeba,  a  minute 
gelatinous  creature,  of  very  simple  organization,  living  in  fresh-water 
pools  and  ditches.  They  are  never  to  be  seen  while  the  blood  is  circu- 
lating in  a  normal  manner  within  the  bloodvessels,  where  the  white 
globules  always  present  their  natural  rounded  form  and  uniformly 
granular  appearance.  But  within  a  short  time  after  the  blood  has  been 
withdrawn  from  the  vessels,  provided  it  be  maintained  at  or  near  the 
normal  temperature  of  the  animal,  the  white  globules  may  be  seen  to 
alter  their  shape  in  a  very  remarkable  way.  The  first  indication  of  the 
change  is  that  a  certain  portion  of  the  rounded  outline  of  the  globule 
becomes  faint  and  irregular,  its  substance  at  this  point  flattening  out 
and  extending  itself  into  one  or  more  transparent  and  homogeneous 
looking  prolongations.  These  prolongations  are  alternately  protruded 
and  retracted,  sometimes  extending  into  long  filamentous  processes, 


WHITK  GLOBULES  OP  THE  BLOOD;  altered 
by  dilute  acetic  acid. 


256  THE    BLOOD. 

sometimes  into  shorter  expansions  with  rounded  ends.  Variations  in 
the  form  of  the  globule  are  thus  produced  which  succeed  each  other  with 
different  degrees  of  rapidity  according  to  circumstances.  In  man  and 
the  warm-blooded  animals,  the  blood  under  examination  requires  to  be 
kept  at  about  the  normal  temperature  of  the  body,  in  order  that  these 
appearances  may  be  exhibited;  but  in  the  cold-blooded  animals  they 
may  be  shown  at  the  ordinary  temperature  of  the  air. 

Fig.  86. 


CHANGES  IN  FORM  OF  A  SINGLE  WHITE  GLOBULE  of  the  blood  of  the  Newt  (Triton 
millepunctatus)  occurring  in  an  interval  of  seven  minutes,  and  within  half  an  hour  after  its 
extraction  from  the  living  body. 

Besides  showing  these  changes  of  form,  the  white  globules  of  the 
blood  may  sometimes  be  seen,  by  a  similar  mechanism,  to  move  from 
place  to  place.  In  these  cases,  the  globule  first  sends  out  the  pale  pro- 
longations of  its  substance  as  above  described.  The  granulations  of  the 
remaining  portion  are  then  propelled,  by  a  kind  of  flowing  movement, 
into  the  prolongations,  which  thus  become  granular,  and  at  the  same 
time  assume  a  more  rounded  form.  The  remaining  portion  is  subse- 
quently drawn  after  and  into  the  part  previously  expanded ;  and  by  a 
continuance  of  this  process  the  whole  mass  makes  a  slow  progression 
from  one  point  to  another  in  the  field  of  the  microscope. 

These  movements  are  accomplished,  like  those  of  the  amoeba,  by  alter- 
nate local  contractions  and  relaxations  of  the  substance  of  the  globule. 
In  Amoeba  princeps  the  movement  of  progression  may  take  place  at  the 
rate  of  73  micro-millimetres  per  minute,  and  in  some  forms  of  gelatinous 
animalcules  is  occasionally  so  active  that  it  may  be  followed  continuously 
by  the  eye.  But  in  the  white  globules  of  the  blood  it  is  much  more 
slowly  performed,  and,  like  that  of  the  hour  hand  of  a  clock,  is  to  be 
distinguished  only  by  noting  their  change  of  position  after  a  certain 
interval  of  time.  The  white  globules  of  the  frog,  when  upon  the  free 
surface  of  the  mesentery,  may  be  seen  to  move  at  a  rate,  as  measured 
by  the  micrometer,  of  13  micro-millimetres  per  minute  ;  and  similar 
granular  corpuscles,  in  the  meshes  of  the  connective  tissue  of  the  mesen- 
tery itself,  may  progress  at  the  rate  of  3.5  micro-millimetres  in  the  same 
time.  Certain  changeable  cells  in  the  tissue  of  the  frog's  cornea,  which 
are  regarded  by  some  observers  as  identical  in  character  with  the  white 
globules  of  the  blood,  may  change  their  position  in  the  substance  of  the 
cornea  at  the  rate  of  2.5  micro-millimetres  per  minute. 

The  amoeboid  movements  of  the  white  globules  of  the  blood  are  also 
sometimes  to  be  seen  in  the  interior  of  the  capillary  bloodvessels  or 


PLASMA    OF    THE    BLOOD.  257 

small  veins,  when  imprisoned  in  a  stagnant  portion  of  the  blood-plasma. 
But  if  the  circulation  be  re-established,  and  the  globules  again  move 
with  the  blood  current,  they  cease  to  be  distorted,  and  resume  their 
original  rounded  form. 

The  precise  physiological  properties  and  functions  of  the  white  cor- 
puscles cannot  be  determined  so  distinctly  as  in  the  case  of  the  red 
globules.  Their  great  inferiority  in  number  shows  that  they  are  less 
important  for  the  immediate  continuance  of  the  vital  operations ;  and 
the  same  thing  may  be  inferred  from  their  want  of  strongly  marked  spe- 
cific characters.  For  while  the  red  globules  of  the  blood  vary  in  ap- 
pearance to  a  marked  degree  in  different  classes  and  orders  of  animals, 
the  white  globules  present  nearly  the  same  general  features  of  size,  form, 
and  structure  throughout  the  series  of  vertebrate  animals. 

Plasma  of  the  Blood. 

The  plasma  of  the  blood  is  the  transparent,  colorless,  homogeneous 
liquid,  in  which  the  blood-globules  are  held  in  suspension.  It  consists 
of  water,  holding  in  solution  various  mineral  salts,  and  of  certain  albu- 
minous matters,  which  are  distinguished  by  their  modes  of  coagulation, 
the  principal  of  which  are  known  as  fibrine  and  albumen. 

Ths  plasma  of  the  blood,  according  to  the  estimates  of  Lehmann  and 
Robin,  has,  on  the  average,  the  following  constitution : 

COMPOSITION  OF  THE  BLOOD-PLASMA. 

Water 902.00 

Albumen        ..........       75.00 

Fibrine 3.00 

Fatty  matters 2.50 

Crystallizable  nitrogenous  matters 4.00 

Other  organic  ingredients .        5.00 

Sodium  chloride 

Potassium  chloride 

Sodium  carbonate 

Sodium  and  potassium  sulphates 

Sodium  and  potassium  phosphates 

Lime  and  magnesium  phosphates     j 


Mineral  salts  8.50 


1000.00 

The  above  ingredients  are  all  intimately  mingled  in  the  blood-plasma, 
in  a  fluid  form,  by  mutual  solution ;  but  they  may  be  separated  from 
each  other  for  examination  by  appropriate  means.  The  two  ingredients 
which  on  account  of  their  nature  and  properties  have  received  the 
greatest  attention,  are  the  fibrine  and  the  albumen. 

The  fibrine  cannot  be  obtained  for  examination  under  the  form  in 
which  it  naturally  exists  in  the  blood,  since  it  is  only  to  be  separated 
from  the  other  albuminous  ingredients  by  undergoing  the  process  of 
coagulation.  Notwithstanding  that  this  substance,  or  the  material  from 
which  it  is  derived,  is  present  in  the  blood  in  so  small  a  quantity  as 
three  parts  per  thousand,  it  is  evidently  an  important  element  in  the 


258 


THE    BLOOD. 


Fig.  87. 


constitution  of  the  circulating  fluid,  since  it  is  upon  its  power  of  spon- 
taneous solidification  that  the  coagulability  of  the  entire  blood  depends. 
This  process  takes  place,  under  all  ordinary  conditions,  soon  after  the 
blood  has  been  withdrawn  from  the  circulation ;  and  the  fibrine  may  be 
obtained  in  a  state  of  tolerable  purity  by  continuously  stirring  freshly- 
drawn  blood  with  glass  rods  or  a  bundle  of  twigs.  When  coagulation 
occurs,  the  fibrine  solidifies  in  the  form  of  thin  layers  adherent  to  the 
surface  of  the  rods  or  twigs.  It  at  first  contains,  entangled  with'  it, 
some  of  the  red  globules  of  the  blood  with  their  coloring  matter ;  but 
these,  as  well  as  other  foreign  substances,  may  be  removed  by  subjecting 
the  mass  for  a  few  hours  to  the  action  of  running  water.  The  fibrine 
then  presents  itself  under  the  form  of  nearly  white  threads  and  flakes, 
having  a  semi-solid  consistency  and  a  considerable  degree  of  elasticity. 
Coagulated  fibrine,  if  examined  in  thin  layers,  is  seen  to  have  a  fibroid 
or  filamentous  texture.  The  filaments  of  which  it  is  composed  are 

colorless  and  elastic,  and  when 
isolated  are  seen  to  be  exceed- 
ingly minute,  being  not  more 
than  0.5  mmm.  in  diameter. 
They  are  partly  so  placed  as  to 
lie  parallel  with  each  other,  and 
this  is  probably  their  arrange- 
ment throughout  the  undis- 
turbed fibrinous  laj^er;  but 
when  torn  up  for  microscopic 
examination,  its  filaments  are 
seen  to  be  in  many  spots  inter- 
laced with  each  other  in  a  kind 
of  irregular  network.  On  the 
addition  of  dilute  acetic  acid 
the  filaments  become  swollen, 
transparent,  and  fused  into  a 
homogeneous  mass,  but  do  not 
dissolve.  They  are  often  in- 
terspersed with  minute  granules,  which  render  their  outlines  more  or  less 
obscure. 

Once  coagulated,  fibrine  is  insoluble  in  water  and  can  only  be  again 
liquefied  by  the  action  of  an  alkaline  or  strongly  saline  solution,  by  pro- 
longed boiling  at  a  very  high  temperature,  or  by  digesting  with  gastric 
juice  or  an  acidulated  solution  of  pepsine.  These  agents,  however,  pro- 
duce a  permanent  alteration  in  the  properties  of  the  fibrine,  and  after 
being  subjected  to  their  influence  it  is  no  longer  the  same  substance  as 
before. 

The  quantity  of  fibrine  which  may  be  extracted  from  the  blood  varies 
in  different  parts  of  the  body.  According  to  most  observers,  venous 
blood  in  general  yields  less  fibrine  than  arterial  blood.  A  portion  of  it 
therefore  disappears  in  passing  through  the  capillary  circulation.  In 


COAGULATED  FIBRINE,  showing  its  flbrillatod 
condition. 


PLASMA    OF    THE    BLOOD.  259 

the  liver  and  the  kidneys  this  disappearance  is  so  complete  that  no 
fibrine  is  to  be  obtained,  as  a  general  rule,  from  the  blood  of  the  renal 
or  the  hepatic  veins.  On  this  account,  also,  the  blood  in  the  large  veins 
near  the  heart  is  more  deficient  in  fibrine  than  in  those  at  a  distance ; 
since  the  venous  blood  coming  from  the  general  circulation,  and  con- 
taining a  moderate  quantity  of  fibrine,  is  mingled,  on  approaching  the 
heart,  with  that  of  the  renal  and  hepatic  veins,  in  which  the  coagulating 
material  is  entirely  absent. 

The  albumen  of  the  plasma  is  undoubtedly  the  most  important  of  its 
ingredients  in  regard  to  the  process  of  nutrition,  since  it  is  by  far  the 
most  abundant  of  the  albuminous  matters  present.  It  coagulates  at 
once  on  being  heated  to  72°  (162°  F.),  or  by  contact  with  alcohol,  the 
mineral  acids,  or  their  metallic  salts,  or  with  potassium  ferrocyanide  in 
an  acidulated  solution.  It  exists  naturally  in  the  plasma  in  a  fluid  form 
by  reason  of  its  union  with  the  water.  The  greater  part  of  the  water 
of  the  plasma  being  united  with  the  albumen,  when  this  latter  substance 
coagulates,  the  water  remains  in  combination  with  it,  and  assumes  at 
the  same  time  the  solid  form.  If  the  plasma  of  the  blood,  accordingly, 
after  removal  of  the  fibrine,  be  exposed  to  a  boiling  temperature,  it 
solidifies  almost  completely,  so  that  only  a  few  drops  of  water  can  be 
drained  away  from  the  coagulated  mass.  The  earthy  phosphates  are 
also  retained  by  the  solidified  albuminous  mass. 

The  substance  existing  in  the  blood  plasma,  however,  and  designated 
as  albumen,  appears  to  consist  really  of  two  different  ingredients,  of 
which  one  is  about  double  the  quantity  of  the  other.  Both  of  them  are 
coagulable  by  heat ;  and  on  this  account  the  whole  albuminous  ingredient 
of  the  plasma  solidifies  when  exposed  to  a  boiling  temperature.  But  one 
of  them  is  coagulable  also  by  magnesium  sulphate  added  in  excess. 
This  substance  is  termed  metalbumen,  and  is  present  in  the  plasma  in 
the  proportion  of  about  22  parts  per  thousand.  It  may  be  separated 
from  the  remainder  by  filtering  the  plasma  through  magnesium  sulphate, 
which  retains  the  metalbumen  in  a  coagulated  form  and  allows  the 
remaining  liquid  to  pass  through.  The  second  substance,  which  has 
passed  through  the  filter,  and  which  is  coagulable  by  heat  but  not  by 
magnesium  sulphate,  is  albumen  proper.  It  has  been  called  "  serine" 
by  Denis  and  Robin,  to  indicate  that  it  is  the  kind  of  albumen  present 
in  blood-serum.  It  exists  in  the  plasma  in  the  proportion  of  about  53 
parts  per  thousand,  being  accordingly  rather  more  than  twice  as  abun- 
dant as  the  metalbumen.  It  is  not  known  whether  these  two  substances 
are  mutually  convertible,  or  if  so,  which  of  them  is  produced  by  trans- 
formation of  the  other. 

A  certain  quantity  of  albuminose  is  also  to  be  found  in  the  blood, 
probably  derived  from  the  products  of  digestion.  Its  quantity,  accord- 
ing to  Robin,  varies  from  1  to  4  parts  per  thousand.  As  it  is  absorbed 
from  the  intestine  during  digestion,  and  neither  accumulates  in  the 
blood  nor  appears  in  any  of  the  excretions,  it  is  no  cloubt  transformed 
into  some  other  substance  after  being  taken  into  the  blood. 


260  THE    BLOOD. 

ThQ  fatty  matters  exist  in  the  blood  mostly  in  a  saponified  form,  ex- 
cepting soon  after  the  digestion  of  food  rich  in  fat.  At  that  period,  the 
emulsioned  fat  finds  its  way  into  the  blood,  and  circulates  for  a  time 
unchanged.  Afterward  it  disappears  as  free  fat,  but  remains  partly  in 
the  saponified  condition. 

The  saline  substances  of  the  plasma  are  principally  sodium  and  potas- 
sium chlorides,  phosphates,  and  sulphates,  together  with  lime  and  mag- 
nesium phosphates.  Of  these  the  sodium  chloride  is  the  most  abundant, 
constituting  nearly  40  per  cent,  of  all  the  mineral  ingredients.  The 
sodium  and  potassium  phosphates  are  of  great  importance  in  providing 
for  the  alkalescence  of  the  blood  plasma,  a  property  which  is  essential 
to  the  performance  of  the  functions  of  nutrition  and  even  to  the  im- 
mediate continuance  of  life ;  since  it  is  the  alkaline  condition  of  the 
plasma  which  enables  it  to  absorb  from  the  various  tissues  the  car- 
bonic acid  produced  in  their  substance  and  return  it  to  the  centre  of  the 
circulation,  for  elimination  by  the  lungs.  The  sodium  and  potassium 
carbonates  also  take  part  in  the  production  of  this  alkalescence,  and  in 
the  herbivorous  animals  are  its  principal  cause;  while  in  the  carnivora 
the  alkaline  phosphates  alone  are  to  be  found  in  the  plasma  in  appre- 
ciable quantity.  In  the  human  subject,  under  the  use  of  an  ordinary 
mixed  animal  and  vegetable  diet,  both  the  alkaline  phosphates  and  car- 
bonates are  present  in  varying  proportions. 

The  earthy  phosphates  of  the  plasma,  which  are  by  themselves  in- 
soluble in  alkaline  or  neutral  fluids,  are  held  in  solution  in  the  blood  by 
union  with  its  albuminous  ingredients. 

Coagulation  of  the  Blood. 

A  few  moments  after  the  blood  has  been  withdrawn  from  the  vessels, 
a  remarkable  phenomenon  presents  itself,  namely,  its  coagulation  or 
clotting.  This  process  commences  at  nearly  the  same  time  throughout 
the  whole  mass  of  the  blood,  which  becomes  first  somewhat  diminished 
in  fluidity,  so  that  it  will  not  run  over  the  edge  of  the  vessel,  when 
slightly  inclined ;  while  its  surface  may  be  gently  depressed  with  the 
end  of  the  finger  or  a  glass  rod.  It  then  becomes  rapidly  thicker,  and 
at  last  solidifies  into  a  uniformly  red,  opaque,  consistent,  gelatinous 
mass,  which  takes  the  form  of  the  vessel  in  which  the  blood  was  received. 
The  process  usually  commences,  in  man,  in  about  fifteen  minutes  after 
the  blood  has  been  drawn,  and  is  completed  in  about  twenty  minutes. 

The  coagulation  of  the  blood  is  dependent  upon  the  presence  of  its 
fibrine.  This  fact  may  be  demonstrated  in  various  ways.  In  the  first 
place,  if  freshly  drawn  frog's  blood  be  mixed  with  a  solution  of  sugar, 
of  the  strength  of  one-half  per  cent.,  and  placed  upon  a  filter,  the  blood- 
globules  will  be  retained  upon  the  filter,  while  a  transparent  colorless 
liquid  passes  through,  which  after  a  time  coagulates  like  fresh  blood. 
Secondly,  if  horse's  blood,  which  coagulates  more  slowly  than  that  of 
most  other  warm-blooded  animals,  be  drawn  from  the  veins  into  a  cylin- 
drical glass  vessel  and  allowed  to  remain  at  rest,  by  the  time  coagulation 


COAGULATION    OF    THE    BLOOD. 


261 


Fig.  88. 


takes  place  the  blood-globules  have  subsided  from  the  upper  part  of  the 
fluid,  leaving  a  layer  at  the  surface  which  is  colorless  and  partly  trans- 
parent, but  which  is  as  firmly  coagulated  as  the  rest.  Thirdty,  if  horse's 
blood  be  freshly  drawn  into  such  a  vessel,  surrounded  by  a  freezing 
mixture  and  kept  at  the  temperature  of  0°  (32°  F.),  coagulation  is  for 
the  time  altogether  suspended,  and  the  globules  sink  toward  the  bottom, 
leaving  a  transparent  colorless  fluid  above.  If  this  colorless  fluid  be 
removed  by  decantation,  and  allowed  to  rise  in  temperature  a  few  de- 
grees, it  coagulates  firmly  like  fresh  blood. 

These  facts  show  that  the  blood-globules  take  no  direct  part  in  the 
process  of  coagulation;  and  that,  when  present,  they  are  simply  en- 
tangled mechanically  in  the  solidifying  clot. 

Finally,  if  the  freshly  drawn  blood  of  man,  or  of  any  of  the  warm- 
blooded animals,  be  briskly  stirred  with  a  bundle  of  twigs  or  glass  rods, 
the  fibrine  coagulates  in  comparatively  small  mass  upon  the  surface  of  the 
foreign  bodies  ;  and  the  red  globules  which  it  entangles  may  be  removed 
by  washing,  without  changing  in  any  way  its  essential  characters. 

It  is  the  fibrine,  therefore,  which,  by  its  own  coagulation,  induces  the 
solidification  of  the  entire  blood.  As  it  is  uniformly  distributed  before- 
hand throughout  the  blood,  when  coagulation 
takes  place  the  minute  filaments  which  make 
their  appearance  in  it  entangle  in  their  meshes 
the  globules  and  the  albuminous  fluids  of  the 
plasma.  A  very  small  quantity  of  fibrine, 
therefore,  is  sufficient  to  include  in  its  solidifi- 
cation all  the  fluid  and  semi-fluid  ingredients 
which  were  before  mingled  with  it,  and  to 
convert  the  whole  into  a  voluminous,  trem- 
bling, jelly-like  mass  of  coagulated  blood. 

As  soon  as  the  coagulum  has  fairly  formed, 
it  begins  to  contract,  increasing  somewhat  in 
consistency  as  it  diminishes  in  size.  By 
means  of  this  contraction  the  albuminous  liquids  begin  to  be  pressed 
out  from  th^e  meshes  in  which  they  were  entangled.  A  few  isolated 
drops  first  appear  on  the  surface  of  the  clot, 
which  soon  increase  in  size  and  also  become 
more  numerous.  After  a  time  they  enlarge  so 
much  as  to  come  in  contact  with  each  other 
at  various  points,  when  they  coalesce,  extend- 
ing in  all  directions  as  the  exudation  increases, 
until  the  whole  surface  of  the  clot  is  covered 
with  a  thin  layer  of  fluid.  The  clot  at  first  ad- 
heres pretty  strongly  to  the  sides  of  the  vessel 
into  which  the  blood  was  drawn;  but  as  its 
contraction  goes  on,  its  edges  are  separated, 

and  the  fluid  continues  to  exude  between  it  and    showing  the  clot  contracted 
the  sides  of  the  vessel.     This  process  continues 


Bowl  of  recently  OOAGTT- 
LATKD  BLOOD,  showing  the 
whole  mass  uniformly  solidi- 
fied. 


Fig.  89. 


262  THE    BLOOD.. 

for  ten  or  twelve  hours  ;  the  clot  growing  constantly  smaller  and  firmer, 
and  the  expressed  fluid  more  abundant 

The  globules,  owing  to  their  greater  consistency,  do  not  escape  with 
the  albuminous  fluids,  but  remain  entangled  in  the  fibrinous  coagulum. 
At  the  end  of  ten  or  twelve  hours  the  whole  of  the  blood  has  usually 
separated  into  two  parts,  namely,  the  clot,  which  is  a  red,  opaque,  semi- 
solid  mass,  consisting  of  the  fibrine  and  the  blood-globules  ;  and  the 
serum,  which  is  a  transparent,  nearly  colorless  fluid,  containing  the 
water,  albumen,  and  saline  matters  of  the  plasma. 

The  change  of  the  blood  in  coagulation  may  be  expressed  as  follows  : 

Before  coagulation  the  blood  consists  of 

f  Fibrine, 

1st.  GLOBULES  ;  and  2d.  PLASMA  —  containing      .         .  \  en' 

I 


Salts. 
After  coagulation  it  is  separated  into 

1st.  CLOT,  containing  \    .         f  an        and  2d.  SERUM,  containing  j  Water 
lW°buleS;  ' 


Salts. 

Conditions  favoring  or  retarding  Coagulation.  —  The  coagulation  of 
the  blood  is  influenced  by  various  physical  conditions.  In  the  first 
place  it  is  suspended  by  a  freezing  temperature.  If  the  blood  be  drawn 
into  a  narrow  vessel  surrounded  by  a  freezing  mixture,  so  that  the  whole 
of  it  is  rapidly  cooled  down  to  0°  (32QF.)t  coagulation  does  not  occur, 
and  the  blood  remains  fluid  indefinitely,  so  long  as  the  temperature  is 
not  allowed  to  rise  above  this  point.  A  variety  of  other  changes,  such 
as  fermentation,  putrefaction,  and  many  chemical  combinations  or  de- 
compositions, are  also  prevented,  as  it  is  well  known,  by  special  condi- 
tions of  temperature. 

Secondly,  the  coagulation  of  the  blood  is  prevented  by  certain  of  the 
neutral  salts.  If  fresh  blood  be  allowed  to  mingle  with  a  concentrated 
watery  solution  of  sodium  sulphate,  no  coagulation  takes  place.  This 
is  not  because  the  coagulable  material  has  been  decomposed  or  chemi- 
cally altered  ;  because  if  the  mixture  be  diluted  with  six  or  seven  times 
its  volume  of  water,  so  as  to  reduce  the  concentration  of  the  saline  solu- 
tion, the  fibrine  solidifies  in  a  few  moments  in  the  usual  manner. 

Coagulation  of  the  blood  may  also  be  hastened  or  retarded  by  varia- 
tions in  the  manner  of  its  withdrawal  from  the  veins,  or  in  the  surfaces 
with  which  it  afterward  comes  in  contact.  If  drawn  rapidly  from  a 
large  orifice,  it  remains  fluid  for  a  comparatively  long  time  ;  if  slowly, 
from  a  narrow  orifice,  it  coagulates  quickly.  The  shape  of  the  vessel 
into  which  the  blood  is  received,  and  the  condition  of  its  internal  sur- 
face, also  exert  an  influence.  The  greater  the  extent  of  surface  over 
which  the  blood  comes  in  contact  with  the  vessel,  the  more  is  its  coagu- 
lation hastened.  If  the  blood  be  allowed  to  flow  into  a  tall,  narrow, 
cylindrical  vessel,  or  into  a  shallow  plate,  it  coagulates  more  rapidly 


COAGULATION  OF  THE  BLOOD.  263 

than  if  received  into  a  hemispherical  bowl,  in  which  the  extent  of  sur- 
face is  less,  in  proportion  to  the  quantity  of  blood  which  it  contains. 
For  the  same  reason,  coagulation  takes  place  more  rapidly  in  a  vessel 
with  a  roughened  internal  surface  than  in  one  which  is  smooth ;  and 
blood  coagulates  most  rapidly  when  spread  out  in  thin  layers,  or  entan- 
gled among  the  fibres  of  cloth  or  sponges.  Hemorrhage,  accordingly, 
continues  longer  from  an  incised  wound  than  from  a  lacerated  one ;  be- 
cause the  blood,  in  flowing  over  the  ragged  edges  of  lacerated  tissues, 
solidifies  upon  them,  and  thus  blocks  up  the  wound. 

In  all  cases  there  is  an  inverse  relation  between  the  rapidity  of  coagu- 
lation and  the  firmness  of  the  clot.  When  coagulation  takes  place  slowly, 
the  clot  afterward  becomes  small  and  dense,  and  the  serum  is  abundant- 
When  it  is  rapid,  there  is  but  little  contraction  of  the  coagulum,  an  im- 
perfect separation  of  the  serum,  and  the  clot  remains  large,  soft,  and 
gelatinous. 

The  blood  coagulates  also  in  the  interior  of  the  vessels  after  stoppage 
of  the  circulation.  Under  these  circumstances  coagulation  takes  place 
less  rapidly  than  if  the  blood  were  wholly  withdrawn  from  the  body. 
In  man,  as  a  general  rule,  the  blood  is  found  coagulated  in  the  cavities 
of  the  heart  and  large  vessels  in  from  twelve  to  twenty -four  hours  after 
death.  In  the  lower  animals,  coagulation  occurs  earlier  than  this, 
namely,  from  four  to  ten  hours  after  death. 

Coagulation  of  the  blood  takes  place  also  in  the  interior  of  the  body, 
during  life,  from  local  arrest  or  impediment  of  the  circulation.  Thus,  if 
blood  be  accidentally  extravasated  into  the  connective  tissue,  the  sub- 
stance of  the  brain  or  spinal  cord,  or  a  serous  cavity,  it  coagulates  after 
a  short  time,  and  forms  a  clot  which  takes  the  shape  of  the  cavity  occu- 
pied by  it.  If  a  ligature  be  placed  upon  an  artery  in  the  living  subject, 
the  blood  which  stagnates  above  the  ligatured  spot  coagulates  as  it 
would  do  if  removed  from  the  circulation.  The  clot  extends  from  the 
ligature  backward  to  the  situation  of  the  next  collateral  branch,  that  is, 
to  the  point  at  which  the  movement  of  the  circulation  still  continues. 
In  an  Arterial  aneurism,  during  life,  the  blood  in  the  dilated  portion  of 
the  artery,  which  is  sufficiently  removed  from  the  centre  of  the  current, 
gradually  coagulates  upon  the  inner  surface  of  the  sac.  In  these  cases, 
as  well  within  as  outside  the  body,  and  during  life  as  well  as  after 
death,  the  stoppage  or  retardation  of  the  circulatory  movement  induces, 
after  a  time,  the  coagulation  of  the  blood. 

It  is  asserted,  however,  by  some  observers,  that  simple  stoppage  of 
the  circulation  during  life  will  not  induce  coagulation,  unless  the  inner 
membrane  of  the  bloodvessels  be  wounded  or  irritated.  According  to 
Burdon  Sanderson,  if  blood  be  imprisoned  in  the  jugular  vein  of  the 
living  rabbit  by  carefully  compressing  the  vessel  at  two  points  between 
transverse  needles,  so  arranged  as  not  to  wound  or  bruise  the  vascular 
coats,  it  will  remain  fluid  in  this  situation  for  two  clays ;  while  if  ordi- 
nary ligatures  be  placed  immediately  around  the  vessel,  a  coagulum  is 
formed  in  the  isolated  portion  of  the  vein. 


264:  THE    BLOOD. 

The  coagulation  of  fibrine  is  not  a  commencement  of -organization. 
It  is  simply  the  passage  of  an  albuminous  ingredient  of  the  blood  from 
its  normal  fluid  condition  to  a  state  of  solidity.  The  coagulable  ingre- 
dient of  the  blood,  when  solidified,  has  lost  its  natural  properties  as  a 
constituent  of  the  liquid  plasma,  and  cannot  afterward  be  restored  to 
its  original  condition.  The  clot,  therefore,  when  once  formed,  even  in 
the  interior  of  the  system,  as  in  cases  of  ligature,  apoplexy,  or  extrava- 
sation, becomes  a  foreign  body,  and  is  reabsorbed  by  the  neighboring 
parts  during  convalescence.  At  first  the  clot  is  comparatively  volumi- 
nous, soft,  and  of  a  deep  red  color.  Its  more  fluid  parts  are  then  reab- 
sorbed, and  the  clot  becomes  smaller  and  denser.  The  red  coloring 
matter  gradually  diminishes  as  absorption  goes  on,  and  finally  altogether 
disappears.  The  time  required  for  complete  reabsorption  varies  from  a 
few  days  to  several  months,  according  to  the  size  of  the  clot  and  the 
situation  in  which  extravasation  has  taken  place. 

Nature  of  the  Process  of  Coagulation. — The  difficulty  in  fully  under- 
standing the  nature  of  coagulation  depends  upon  the  fact  that  the  blood 
naturally  continues  fluid  under  all  ordinary  conditions  while  circulating 
in  the  vessels,  but  coagulates  inevitably  within  a  few  minutes  after  its 
removal.  Properly  speaking,  the  fibrine  which  we  obtain  at  the  time  of 
coagulation,  either  by  itself  or  as  forming  a  part  of  the  clot,  does  not 
pre-exist  in  the  blood  with  the  same  constitution  and  properties,  other- 
wise it  would  coagulate  within  the  vessels  during  life.  It  must  be  de- 
rived from  some  ingredient  of  the  blood,  which,  on  being  withdrawn  from 
the  current  of  the  circulation,  suffers  a  change  by  which  it  becomes 
spontaneously  coagulable.  It  is  not  easy  to  understand  what  this 
change  may  be,  or  what  are  the  immediate  influences  which  produce  it. 

There  are  two  theories  in  existence  as  to  the  nature  of  coagulation. 
According  to  one  of  them  (Denis),  the  coagulable  fibrine  is  produced  by 
the  spontaneous  decomposition  of  a  liquid  substance  pre-existing  in  the 
blood.  This  substance  is  termed  plasmine,  and  is  thought  to  be  present 
in  the  plasma  of  the  blood  in  the  proportion  of  25  parts  per  thousand. 
When  withdrawn  from  the  circulation  it  decomposes  or  separates  into 
two  new  substances.  One  of  these  is  fibrine  (3  parts  per  thousand), 
which  immediately  coagulates ;  the  other  is  metalbumen  (22  parts  per 
thousand),  which  remains  fluid.  The  basis  of  this  theory  is,  that  if 
fresh  blood  be  drawn  into  a  concentrated  solution  of  sodium  sulphate, 
as  above  stated,  no  coagulation  takes  place.  But  if  sodium  chloride  in 
powder  be  added  to  this  mixture  in  the  proportion  of  ten  per  cent.,  it 
precipitates  a  white  pasty  substance,  which  is  thrown  down  because  it 
is  insoluble  in  a  sodium  chloride  solution  of  that  strength.  This  sub- 
stance, the  so-called  "  plasmine,"  represents  25  parts  per  thousand  of 
the  original  plasma.  After  its  separation  it  may  be  readily  dissolved 
again  by  the  addition  of  water;  but  in  a  few  moments  its  solution  coagu- 
lates, yielding  3  parts  of  a  solid  matter  like  ordinary  fibrine,  and  22 
parts  of  a  liquid  substance  having  the  properties  of  metalbumen.  The 
albumen  proper  of  the  blood  remains  behind  in  the  sodium  sulphate 


COAGULATION  OF  THE  BLOOD.  265 

solution,  not  having  been  precipitated  by  the  addition  of  sodium  chlo- 
ride. 

According  to  the  other  theory  (Schmidt),  the  coagulable  fibrine  is 
produced  by  the  union  of  two  previously  existing  substances,  neither 
of  which  is  coagulable  by  itself.  One  of  these  is  termed  fibrino-plastic 
matter,  because  it  has  the  property  of  inducing  coagulation  in  a  liquid 
containing  the  other  material.  This  second  material  is  named  fibri- 
nogen,  being  considered  as  more  directly  the  generator  of  the  coagulable 
fibrine.  The  plasma  of  the  blood  is  supposed  to  contain  both  these 
substances,  but  in  very  different  quantities ;  the  fibrino-plastic  matter 
being  abundant,  the  fibrinogen  comparatively  scanty.  When  the  fibri- 
nogen,  accordingly,  has  all  been  converted  into  fibrine  and  has  coag- 
ulated, a  surplus  of  fibrino-plastic  matter  still  remains  in  the  serum, 
and  may  be  used  to  induce  coagulation  in  other  liquids  which  would  not 
coagulate  of  themselves.  This  last  fact  forms  the  basis  of  the  theory. 
If  the  clear  serum  from  coagulated  blood  be  added,  at  the  temperature 
of  the  living  body,  to  filtered  hydrocele  fluid,  after  some  minutes  the 
mixture  coagulates  into  a  transparent  gelatinous  mass,  which  afterward 
exudes  a  colorless  serum.  Both  fibrino-plastic  matter  and  fibrinogen 
are  obtained  from  the  liquids  containing  them,  by  dilution  with  water 
and  by  passing  though  them  for  a  considerable  time  a  continuous  stream 
of  carbonic  acid.  Fibrinogen  is  also  precipitable  by  the  addition  of 
sodium  chloride  to  the  point  of  saturation. 

This  theory  not  having  been  found  sufficient  to  account  for  all  the 
phenomena  of  coagulation,  its  author  has  modified  it1  by  supposing  that, 
while  fibrino-plastic  matter  and  fibrinogen  by  their  combination  furnish 
the  material  of  the  coagulable  fibrine,  they  need,  in  order  to  effect  their 
union,  the  influence  of  a  third  substance,  which  does  not  itself  form  any 
part  of  the  fibrine,  but  which  acts  as  a  ferment  to  excite  the  combina- 
tion of  the  two  others.  A  fluid  accordingly  may  contain  both  fibrino- 
plastic  matter  and  fibrinogen,  and  yet  will  not  coagulate  unless  the 
ferment  be  also  present.  The  ferment  is  supposed  to  be  generated  in 
the  blood  only  after  its  withdrawal  from  the  vessels ;  and  this  accounts 
for  its  fluid  condition  while  the  circulation  is  going  on. 

Neither  of  the  foregoing  explanations  rests  upon  complete  demonstra- 
tion. The  plasmine  of  Denis  may  be,  from  the  first,  a  mixture  of  two 
different  substances,  both  of  which  are  precipitable  by  sodium  chloride 
from  the  sodium  sulphate  solution ;  and  the  union  of  the  twro  fibrine 
generators  of  Schmidt,  under  the  influence  of  a  "  ferment,"  still  leaves 
it  quite  unknown  how  or  by  what  causes  this  ferment  is  generated  when 
the  blood  coagulates  after  removal  from  the  vessels.  The  only  thing 
which  seems  absolutely  certain  is  that  a  substance  exists  in  the  blood 
in  small  quantity  which  becomes  coagulable  by  a  spontaneous  change 
soon  after  it  is  withdrawn  from  the  influences  of  the  circulation. 

If  we  endeavor  to  explain  why  this  change  and  the  consequent  coagu- 

1   Archiv  fur  die  Gesammte  Physiologic,  1872,  Band  vi.  p  413. 
18 


266  THE    BLOOD. 

lation  of  the  blood  do  not  occur  normally  in  the  bloodvessels  during  life, 
the  most  important  facts  bearing  on  this  point  are  that  the  blood  of  the 
renal  and  hepatic  veins  yields  no  fibrine,  or  much  less  than  arterial  blood. 
The  substance  which  causes  coagulation,  therefore,  is  decomposed  and 
disappears  from  the  blood  while  passing  through  the  liver  and  the  kidneys. 
This  is  established  by  the  observations  of  Simon,  Lehmann,  and  Brown- 
Sequard.  While  an  abundance  of  fibrine  may  be  obtained  from  either 
arterial  or  portal  blood,  none  or  only  feeble  traces  of  it  are  to  be  found 
in  that  of  the  hepatic  or  the  renal  veins.  This  substance,  being  con- 
stantly eliminated  from  the  blood  in  this  way  by  the  liver  and  kidneys,  is 
necessarily  produced  afresh  elsewhere  at  the  same  time,  since  its  quan- 
tity in  the  blood  remains  unchanged ;  and  the  new  material  thus  formed 
is  also  rapidly  altered  by  a  continuation  of  the  same  process.  -By 
calculating  approximately  the  quantity  of  blood  contained  in  the  whole 
body  and  that  passing  daily  through  the  liver  and  kidneys,  it  appears 
that  a  quantity  of  fibrine  equal  to  that  in  the  entire  blood  must  be  de- 
stroyed and  reproduced  several  times  over  in  the  course  of  a  single  day. 
Thus  the  fibrine  which  appears  in  a  specimen  of  blood  drawn  from  the 
vessels  at  any  one  time,  and  which  causes  its  coagulation,  is  derived 
from  a  substance  of  very  recent  formation  ;  and,  if  allowed  to  remain  in 
the  bloodvessels,  it  would  have  disappeared  by  metamorphosis  before 
arriving  at  the  stage  of  coagulation. 

Usefulness  of  Fibrine  and  of  its  property  of  Coagulation. — Although 
the  fibrine  of  the  blood,  from  its  small  quantity  and  the  general  charac-  t 
ter  of  its  properties,  does  not  seem  to  take  a  direct  part  in  the  more 
essential  phenomena  of  nutrition,  it  is  still  a  very  important  ingredient 
of  the  circulating  fluid.  Upon  the  presence  of  this  substance  depends 
the  process  by  which  nature  effects  the  arrest  of  hemorrhage  from 
divided  or  ruptured  bloodvessels.  Whenever  a  wound  is  accidentally 
made  in  vascular  tissues,  the  blood  at  first  flows  freely  from  the  external 
orifice.  But  a  portion  of  the  blood  coagulates  upon  the  edges  of  the 
wound,  and  after  a  time  the  successive  deposits  of  cogulated  fibrine 
become  sufficient  to  effectually  close  the  opening  and  prevent  further 
loss  of  blood.  The  proper  treatment  for  wounds  of  moderate  size,  in 
which  only  the  veins  and  capillaries,  or  small  arteries,  have  been  divided, 
is  simply  to  apply  compression  and  to  keep  the  edges  of  the  wound  in 
contact  continuously  for  fifteen  or  twenty  minutes.  By  this  time  the 
thin  layer  of  blood  between  the  wounded  surfaces,  thus  kept  at  rest,  has 
coagulated,  and  the  hemorrhage  does  not  reappear  when  the  artificial 
compression  is  removed.  If  a  larger  artery  be  opened,  the  force  with 
which  the  blood  is  expelled  prevents  local  coagulation,  or  is  sufficient 
to  detach  the  coagula  after  they  are  formed.  In  such  cases  accordingly 
the  surgeon  places  a  ligature  upon  the  wounded  artery  itself,  and  in  this 
way  effectually  controls  the  hemorrhage.  But  even  in  this  instance  the 
ligature  is  only  a  means  of  applying  compression  for  a  longer  time,  and 
is  still  temporary,  as  it  must  come  away  again  when  it  ulcerates  through 
the  coats  of  the  vessel.  The  immediate  and  essential  means  of  stopping 


COAGULATION  OF  THE  BLOOD.  267 

the  flow  of  blood,  even  in  a  ligatured  artery,  is  the  coagulum  which 
forms  within  the  vessel  behind  the  ligature;  and  which,  by  the  time  the 
ligature  is  detached  by  ulceration,  has  become  sufficiently  firm  and  adhe- 
rent to  resist  the  impulse  of  the  blood. 

The  importance  of  fibrine  in  this  respect  is  shown  by  the  difficulties 
which  follow  in  cases  where  it  is  deficient.  In  some  instances  of  the 
ligature  of  large  arteries,  in  patients  much  exhausted  by  injury  or  by 
previous  loss  of  blood,  the  surgeon  finds  that  when  the  ligature  comes 
awajr  the  bleeding  begins  again,  no  internal  clot  having  been  formed  ; 
and  a  second  ligature,  applied  above  the  situation  of  the  former  one,  is 
again  followed  by  secondary  hemorrhage.  In  certain  persons  also  there 
appears  to  be  a  congenital  deficiency  of  the  coagulating  ingredient  of 
the  blood,  a  peculiarity  sometimes  observed  in  several  members  of  the 
same  family ;  and  in  these  cases,  any  slight  accidental  wound,  or  tri- 
vial surgical  operation,  may  be  followed  by  long-continued  or  even  fatal 
hemorrhage. 

Entire  Quantity  of  Blood  in  the  Body. — The  estimation  of  the  whole 
mass  of  the  blood  in  the  living  body  is  surrounded  with  many  difficul- 
ties. The  first  and  simplest  method  adopted  for  this  purpose  was  by 
suddenly  dividing  all  the  vessels  of  the  neck  in  the  living  animal  and 
collecting  all  the  blood  which  escaped.  This  method,  however,  was 
found  to  be  quite  faulty,  since  the  flow  of  blood  ceases,  in  such  an 
experiment,  not  because  the  whole  of  it  has  been  discharged,  but  because 
coagula  have  formed  about  the  orifices  of  the  divided  vessels  and  because 
the  force  of  the  heart's  action  is  no  longer  sufficient  to  overcome  the 
obstruction.  A  certain  quantity  of  blood,  therefore,  always  remains  in 
the  body  after  death  by  hemorrhage ;  and  this  quantity,  as  shown  by 
subsequent  experiments,  may  even  amount  to  over  25  per  cent,  of  the 
whole  mass  of  blood.  The  animal  therefore  dies  before  he  has  lost  quite 
three-fourths  of  the  circulating  fluid. 

-Other  methods  have  been  adopted  by  various  experimenters,  none  of 
which  are  absolutely  free  from  all  possible  sources  of  error.  The  best 
is  that  by  which,  after  all  the  blood  is  discharged  which  can  be  made 
to  escape  spontaneously  from  divided  vessels,  the  circulatory  system 
is  immediately  injected  with  water  or  a  weak  saline  solution,  until  the 
fluid  of  injection,  after  traversing  the  vascular  channels,  returns  nearly 
or  quite  colorless.  The  quantity  of  blood  which  it  has  thus  washed  out 
of  the  vessels  is  then  ascertained,  either  by  a  comparison  of  its  color 
with  that  of  a  watery  dilution  of  blood  of  known  strength,  or  by  com- 
paring the  quantity  of  its  solid  ingredients  with  that  of  a  similar  watery 
dilution. 

The  most  accurate  of  these  processes  is  that  employed  by  Steinberg,1 
who,  after  bleeding  the  animal  to  death,  injected  the  aorta  with  a  watery 
solution  of  sodium  chloride,  of  the  strength  of  one-half  per  cent.,  until 
the  fluid  of  injection  returned  colorless.  The  whole  of  the  fluid  which 

1  Archiv  fur  die  Gesammte  Physiologic,  1873,  Band  vii.  p.  101. 


268  THE    BLOOD. 

had  been  used  for  injection  being  then  mingled,  a  small  quantity  of  it 
was  taken,  and  the  proportion  of  hemoglobine  contained  in  it  determined 
by  the  spectroscopic  test  as  follows  :  Equal  quantities  of  pure  blood  were 
placed  in  two  similar  test-tubes,  and  diluted,  one  of  them  with  pure 
water,  the  other  with  the  fluid  of  injection,  until  each  of  them,  placed 
before  the  slit  of  the  spectroscope,  just  allowed  the  green  light  of  the 
spectrum  to  become  visible.  From  the  relative  quantities  of  the  two 
liquids  which  must  be  added  to  produce  this  result,  the  amount  of 
hemoglobine,  and  consequently  of  blood,  extracted  by  the  injection  could 
be  readily  calculated.  This  quantity,  added  to  that  which  had  escaped 
spontaneously  from  the  vessels,  gave  the  entire  amount  of  blood,  as 
follows : 

QUANTITY  OF  BLOOD,  IN  VARIOUS  ANIMALS,  AS  COMPARED  WITH  THE  WEIGHT  OF  THE 

WHOLE  BODY. 

In  Dogs,  from  8.00  to  8.93  per  cent. 

"   Cats,  "     8.40  "  9.61 

"  Guinea-pigs,    "     8.13  "  8.33 
"  Babbits,  "     7.50  "  8.13 

There  is  evidence,  however,  that  the  quantity  of  blood  varies  naturally, 
in  the  same  animal^  according  to  the  condition  of  the  system  at  large, 
and  especially  according  to  that  of  the  digestive  process.  Steinberg 
found  that  in  the  cat,  while  fasting,  the  percentage  of  blood  was  reduced 
from  8.40  to  5.61  per  cent.  Bernard1  has  observed  that  if  two  animals 
of  the  same  weight,  one  of  which  is  in  full  digestion  while  the  other  is 
fasting,  be  suddenly  decapitated,  the  quantity  of  blood  discharged  from 
the  former  is  much  greater  than  that  from  the  latter.  He  has  also 
shown  that,  in  a  rabbit  during  digestion,  twice  as  much  blood  can  be 
withdrawn  without  causing  death,  as  in  one  of  the  same  weight  but 
in  the  fasting  condition.  The  volume  of  the  blood,  therefore,  contained 
in  the  body,  fluctuates,  within  certain  limits,  with  the  alternate  intro- 
duction of  nutritious  matter  by  digestion  and  its  expenditure  during 
the  interval  of  fasting. 

The  most  satisfactory  determination  of  the  quantity  of  blood  in  the 
human  subject  is  that  by  Weber  and  Lehmann.2  These  observers 
operated  upon  two  criminals  who  suffered  death  by  decapitation ;  the 
methods  and  results  being  essentially  the  same  in  both  cases.  In  one 
of  them  the  body  weighed  before  decapitation  60.14  kilogrammes  ;  and 
the  blood  which  escaped  from  the  vessels  at  the  time  of  decapitation 
amounted  to  5540  grammes.  In  order  to  estimate  the  quantity  of  blood 
which  remained  in  the  vessels,  the  experimenters  injected  the  arteries 
of  the  head  and  trunk  with  water  until  it  returned  from  the  veins  of  a 
pale  red  or  yellow  color,  collected  the  fluid  thus  returned,  and  ascer- 
tained how  much  solid  matter  it  held  in  solution.  This,  amounted  to 

1  LeQons  sur  les  Liquides  de  TOrganisme.     Paris,  1859,  tome  i.  p.  419. 

2  Physiological  Chemistry,  Cavendish  edition.     London,  1853,  vol.  ii.  p.  269. 


COAGULATION  OF  THE  BLOOD.  269 

37.24  grammes,  corresponding  to  1980  grammes  of  blood.     The  result 
of  the  experiment  is  therefore  as  follows : 

Blood  which  escaped  from  the  vessels    ....     5540  grammes, 
remained  in  the  body         ....     1980         '' 

Whole  quantity  of  blood  in  the  living  body,  7520        " 

The  blood,  accordingly,  in  these  cases  amounted  .to  12.54  percent,  of 
the  entire  bodily  weight ;  and  the  body  of  a  healthy  man,  weighing  65 
kilogrammes  (143  pounds  avoirdupois)  will  contain  on  the  average  8127 
grammes  (18  pounds)  of  blood. 


CHAPTEE    XIII. 

RESPIRATION. 

THE  most  constant  and  striking  phenomenon  presented  by  living 
organisms,  both  animal  and  vegetable,  is  the  absorption  of  oxygen.  A 
supply  of  this  substance,  either  in  the  gaseous  form  as  a  constituent 
part  of  the  atmospheric  air,  or  dissolved  in  water  or  other  liquids,  is 
indispensably  requisite  for  the  maintenance  of  life  and  the  manifestation 
of  vital  phenomena.  Oxygen  exists  diffused  everywhere  over  the  sur- 
face of  the  earth,  forming  rather  more  than  one-fifth  part  of  the  volume 
of  the  atmosphere,  and  it  is  dissolved  in  greater  or  less  abundance  in 
the  water  of  springs,  rivers,  lakes,  and  seas.  Animals  and  plants,  ac- 
cordingly, whether  living  in  the  air  or  in  the  water,  are  surrounded  by 
media  in  which  this  substance  is  constantly  present.  Even  parasitic 
organisms,  inhabiting  the  interior  of  other  living  bodies,  and  the  foetus 
during  the  period  of  its  intra-uterine  development,  though  not  imme- 
diately in  contact  with  oxygen,  are  supplied  with  nutritious  fluids  which 
have  themselves  been  exposed  to  its  influence.  The  function  of  respi- 
ration consists  in  the  process  by  which  oxygen  penetrates  the  substance 
of  living  organisms,  together  with  the  changes  which  accompany  and 
follow  its  introduction. 

Respiration  in  Vegetables. — In  regard  to  the  phenomena  of  respira- 
tion in  vegetables,  a  distinction  is  to  be  made  between  respiration  proper 
and  the  absorption  of  gaseous  matter  for  the  production  of  organic 
material.  It  is  well  known  that  all  green  plants,  under  the  influence 
of  the  solar  light,  have  the  power  of  absorbing  carbonic  acid  and  water, 
and  of  partially  deoxidizing  these  substances,  to  form,  with  their  re- 
maining elements,  starch,  cellulose,  and  fat.  The  oxygen  thus  sepa- 
rated from  its  inorganic  combinations  is  exhaled  by  the  plant  in  a  free 
form ;  while,  as  a  result  of  the  process,  an  accumulation  of  organic  ma- 
terial takes  place  in  the  vegetable  fabric,  which  increases  in  substance, 
and  may  afterward  serve  for  the  nutrition  of  animal  bodies.  This  ac- 
cordingly is  not  a  process  of  respiration,  but  one  of  organic  production. 
It  is  peculiar  to  vegetables,  animals  having  no  power  to  produce  organic 
material,  and  therefore  depending  upon  vegetables  for  their  supply  of  food. 

Animals,  on  the  other  hand,  consume  the  organic  material  thus  pro- 
duced, at  the  same  time  absorbing  oxygen  and  exhaling  carbonic  acid 
and  water.  In  this  respect  there  is  an  opposition  between  the  actions 
of  animal  and  vegetable  life,  by  which  they  stand  in  a  complementary 
relation  to  each  other.  Vegetables  produce  organic  matter  by  a  process 
of  deoxidation ;  animals  consume  it  with  the  phenomena  of  oxidation. 
(270) 


ORGANS    OF    RESPIRATION.  27i 

But  this  apparent  opposition  between  the  phenomena  of  animal  and 
vegetable  life  only  exists  because  plants  have  the  special  power  of  pro- 
ducing organic  matter,  by  which  they  become  the  source  of  nourish- 
ment for  the  entire  living  creation.  The  organic  substances  so  pro- 
duced do  not  immediately  take  part  in  the  more  active  phenomena  even 
of  vegetable  life.  They  are,  on  the  contrary,  deposited  in  a  more  or  less 
quiescent  form,  and  constitute  a  reserve  material,  to  be  afterward  trans- 
formed and  assimilated  by  the  plant,  or  consumed  by  herbivorous  ani- 
mals. In  vegetables,  as  well  as  in  animals,  a  true  respiration  also  takes 
place,  which  is  marked  in  both  instances  by  the  absorption  of  oxygen. 
The  deoxidizing  process,  by  which  organic  matter  is  produced,  occurs 
only  in  green  vegetables,  and  under  the  influence  of  the  solar  light ; 
while  the  absorption  of  oxygen  is  a  constant  phenomenon,  taking  place 
in  both  green  and  colorless  plants,  and  in  darkness  as  well  as  in  the 
light. 

The  more  active  phenomena  of  vegetation,  moreover,  are  immediately 
dependent  upon  the  absorption  of  oxygen,  and  cannot  go  on  without  it. 
When  the  starch  which  has  been  stored  up  in  the  seed  becomes  liquefied 
and  converted  into  sugar,  and  the  process  of  germination  and  growth 
begins,  the  absorption  of  oxygen  is  necessary  to  its  continuance.  This 
is  seen  not  only  in  germinating  seeds,  but  also  in  expanding  leaf  and 
flower  buds,  all  of  which  organs  consume  in  a  short  period  several  times 
their  volume  of  oxygen.  The  processes  of  germination,  growth,  and 
flowering,  as  well  as  the  intra-cellular  movement  of  the  vegetable  plasma, 
the  motions  of  the  sensitive-plant  in  response  to  stimulus,  and  the  pe- 
riodical movements  of  the  leaves  in  certain  other  vegetable  species,  all 
cease  in  an  atmosphere  deprived  of  oxygen.1  The  function  of  respira- 
tion is  accordingly  a  universal  one,  and  essential  to  all  forms  of  vital 
activity. 

Organs  of  Respiration. 

The  process  of  respiration  takes  place  very  actively  in  the  mamma- 
lians and  birds,  less  so  in  reptiles  and  fishes ;  and  in  these  different 
classes  the  organs  by  which  it  is  accomplished  vary  in  size  and  struc- 
ture according  to  the  activity  of  the  function  itself.  Its  necessary  con- 
ditions everywhere  are  that  the  circulating  fluid  should  be  exposed  in 
some  way  to  the  influence  of  the  atmospheric  air  or  of  an  aerated  fluid. 
The  respiratory  apparatus,  accordingly,  consists  essentially  of  a  moist 
and  permeable  animal  membrane,  termed  the  respiratory  membrane, 
with  bloodvessels  on  one  side  of  it,  and  air  or  an  aerated  fluid  on  the 
other.  The  blood  and  the  air,  consequently,  do  not  come  in  direct  con- 
tact with  each  other,  but  absorption  and  exhalation  take  place  through 
the  respiratory  membrane  which  lies  between. 

1  Mayer,  Lehrbuch  der  Agrikultur-Chemie.  Heidelberg,  1871,  Band  i.  pp. 
91-95. 


272 


RESPIRATION. 


90- 


In  most  aquatic  animals,  the  respiratory  organs  have  the  form  of 
gills  or  branchiae;  that  is,  filamentous  prolongations  of  some  part  of  the 
integument  or  mucous  membranes,  which  contain  an  abundant  supply 
of  bloodvessels,  and  which  hang  out  freely  into  the  surrounding  water. 
In  many  kinds  of  amphibious  reptiles,  as,  for  example,  in  Menobranchus 

(Fig.  90),  there  are  upon  each 
side  of  the  neck  feathery  tufts  or 
prolongations  from  the  mucous 
membrane  of  the  pharynx,  which 
pass  out  through  lateral  fissures 
in  the  neck.  Each  filament  con- 
sists of  a  thin  fold  of  mucous 
membrane,  containing  in  its  in- 
terior a  network  of  minute  blood- 
vessels. The  venous  blood,  as  it 

enters  the  filament,  is  exposed  to 
HEAD  AND  G-ILLS  OF   MENOBRANCHUS. 

the  influence  of  the  surrounding 

water,  and  is  thus  converted  into  arterial  blood.  The  apparatus  is 
further  supplied  with  a  cartilaginous  framework  and  a  set  of  muscles, 
by  which  the  gills  are  kept  in  motion,  and  constantly  brought  into  con- 
tact with  fresh  portions  of  the  aerated  fluid. 

In  terrestrial  and  air-breathing  animals,  the  respiratory  apparatus  is 
situated  internally.  In  salamanders  and  newts,  for  example,  which, 
though  partly  aquatic  in  their  habits,  are  air-breathing  animals,  the 
lungs  are  cylindrical  sacs,  running  nearly  the  entire  length  of  the  body, 
commencing  anteriorly  by  a  communication  with  the  pharynx,  and  ter- 
minating by  rounded  extremities  at  the  posterior  part  of  the  abdomen. 
These  air-sacs  have  a  smooth  internal  surface  ;  and 
the  blood  which  circulates  through  their  vessels  is 
arterialized  by  exposure  to  the  air  contained  in  their 
cavities.  The  air  is  forced  into  the  lungs  by  a  kind 
of  swallowing  movement,  and  is  after  a  time  regur- 
gitated and  discharged,  to  make  room  for  a  fresh 
supply. 

In  frogs,  turtles,  and  serpents,  the  cavity  of  the 
lung,  instead  of  being  simple,  is  divided  by  incom- 
plete partitions  into  a  number  of  smaller  cavities  or 
"  cells."    The  cells  all  communicate  with  the  central 
pulmonary  cavity  ;  and  the  partitions,  which  join 
each  other  at  various  angles,  are  composed  of  thin, 
projecting  vascular  folds  of  the  lining  membrane. 
(Fig.  91.)     By  this  arrangement,  the  extent  of  sur- 
face presented  to  the  air  by  the  pulmonary  membrane  is  increased,  and 
the  arterialization  of  the  blood  takes  place  with  a  corresponding  degree 
of  rapidity. 

In  man,  and  in  the  warm-blooded  quadrupeds,  the  lungs  are  constructed 
on  a  plan  essentially  similar  to  the  above,  but  which  differs  from  it  in 


Fig.  91. 


Li  TING       OF      FROG, 

cut  open,  showing  its 
internal  surface. 


ORGANS    OF    RESPIRATION.  273 

the  greater  extent  to  which  the  pulmonary  cavity  is  subdivided.  The 
respiratory  apparatus  in  man  (Fig.  92)  commences  with  the  larynx, 
which  communicates  with  the  pharynx  at  the  upper  part  of  the  neck. 

Fig.  92. 


HUMAN  LARYNX,  TRACHEA,  BRONCHI,  AND   LUNGS;   showing  the  ramification  of 
the  bronchi,  and  the  division  of  the  lungs  into  lobules. 

Then  follows  the  trachea,  a  membranous  tube  with  cartilaginous  rings, 
which,  upon  its  entrance  into  the  chest,  divides  into  the  right  and  left 
bronchi.  These  divide  successively  into  secondary  and  tertiary  bronchi ; 
the  subdivision  continuing,  while  the  bronchial  tubes  grow  smaller  and 
more  numerous,  and  separate  constantly  from  each  other.  As  they 
diminish  in  size,  the  tubes  grow  more  delicate  in  structure,  and  the  car- 
tilaginous rings  and  plates  disappear  from  their  walls.  They  are  finally 
reduced,  according  to  Kolliker,  to  the  size  of  0.3  millimetre  in  diameter ; 
and  are  composed  only  of  a  thin  mucous  membrane,  lined  with  pave- 
ment epithelium,  resting  upon  an  elastic  fibrous  layer.  They  are  then 
known  as  the  "  ultimate  bronchial  tubes." 

Each  ultimate  bronchial  tube  terminates  in  a  pyramidal  division  or 
islet  of  the  pulmonary  tissue,  about  2  millimetres  in  diameter,  which  is 
termed  a  "  pulmonary  lobule."  Each  lobule  may  be  considered  as  rep- 
resenting the  entire  frog's  lung  in  miniature.  It  consists  of  a  vascular 
membrane  in  the  form  of  a  pyramidal  sac,  the  cavity  of  which  is  divided 
into  secondary  compartments  by  thin  septa  or  partitions  which  project 
from  its  internal  surface.  These  secondary  cavities  are  the  "  pulmonary 


274  RESPIRATION. 

vesicles."  They  have,  according  to  Kolliker,  an  average  diameter  of 
about  0.25  millimetre  ;  but  owing  to  the  elasticity  of  their  walls,  each 
vesicle  is  capable  of  dilating  to  double  or  triple  its  former  size,  and 
returning  to  its  original  dimensions  when  the  distending  force  is  re- 
moved. There  is  every  reason  to  believe  that  during  life  they  are  alter- 
nately enlarged  and  diminished  in  size,  as  the  lungs  are  filled  and  emptied 
with  the  movements  of  respiration. 

Fig.  93.  Fig.  94. 


SINGLE  LOBULE  OF  HUMVN  LUNO.  NKTWOKK  OF  CAPILLARY  BLOOD- 
— a.  Ultimate  bronchial  tube.  b.  Cavity  of  VESSELS  in  the  Pulmonary  Vesicles  of  the 
lobule.  c,c,c.  Pulmonary  vesicles.  Horse.  (Frey.) 

Each  pulmonary  vesicle  is  covered  upon  its  exterior  with  a  'close  net- 
work of  capillary  bloodvessels,  which  penetrate  into  the  septa  between  it 
and  the  adjacent  cavities,  and  which  are  thus  exposed  on  both  sides  to 
the  influence  of  the  atmospheric  air.  In  the  walls  of  the  vesicles,  and 
also  in  the  interspaces  between  the  lobules,  there  is  an  abundance  of 
elastic  tissue,  which  gives  to  the  pulmonary  structure  its  property  of 
resiliency.  The  thin  layer  of  pavement  epithelium  lining  the  ultimate 
bronchial  tubes  extends  into  the  cavities  of  the  lobules  and  vesicles, 
forming,  according  to  the  observations  of  Kolliker,  a  continuous  invest- 
ment of  their  internal  surface. 

The  abundant  involution  of  the  respiratory  membrane,  effected  by  the 
subdivision  of  the  bronchial  tubes  and  the  multiplication  of  the  vascular 
septa  between  the  vesicles,  existing  in  the  lungs  of  man  and  the  mam- 
malians, evidently  increases  to  an  extraordinary  degree  the  functional 
activity  of  the  organs  of  respiration.  The  entire  extent  of  the  respira- 
tory surface  in  the  human  lungs  has  been  estimated  at  130  square 
metres,  which  is  probably  not  an  exaggeration.  The  blood,  accordingly, 
in  the  pulmonary  capillaries,  distributed  in  thin  layers  over  so  large  a 
surface,  in  immediate  proximity  to  the  air  in  the  cavity  of  the  vesicles, 
is  placed  under  the  most  favorable  conditions  for  its  rapid  and  complete 
arterialization. 


MOVEMENTS    OF    KESP1RATION. 


275 


Movements  of  Respiration. 

The  air  which  is  contained  in  the  pulmonary  lobules  and  vesicles, 
being  used  for  the  purpose  of  arterializing  the  blood,  becomes  rapidly 
vitiated  in  the  process  of  respiration,  and  requires  accordingly  to  be  as 
rapidly  expelled  and  replaced  by  a  fresh  supply.  This  exchange  or 
renovation  of  the  air  is  effected  by  alternate  movements  of  the  chest,  of 
expansion  and  collapse,  which  follow  each  other  in  regular  succession, 
and  which  are  known  as  the  "  movement  of  inspiration,"  and  the  "  move- 
ment of  expiration." 

Movement  of  Inspiration. — The  expansion  of  the  chest  is  effected  by 
two  sets  of  muscles,  namely,  the  diaphragm  and  the  intercostals. 
While  the  diaphragm  is  relaxed,  it  has  the  form  of  a  vaulted  partition, 
the  edges  of  which  are  attached  to  the  inferior  extremity  of  the  sternum, 
the  inferior  costal  cartilages,  the  borders  of 
the  lower  ribs  and  the  bodies  of  the  lumbar 
vertebrae,  while  its  convexity  rises  into  the 
cavity  of  the  chest,  as  high  as  the  level  of 
the  fifth  rib.  When  the  fibres  of  the  dia- 
phragm contract,  their  curvature  is  neces- 
sarily diminished;  and  they  approximate  a 
straight  line,  in  proportion  to  the  extent  of 
their  contraction.  Consequently,  the  entire 
convexity  of  the  diaphragm  is  diminished  in 
the  same  proportion,  and  it  descends  to- 
ward the  abdomen,  enlarging  the  cavity  of 
the  chest  from  above  downward.  At  the 
same  time  the  intercostal  muscles  enlarge  it 
in  a  lateral  direction.  For  the  ribs,  articu- 
lated behind  with  the  bodies  of  the  vertebrae, 
and  attached  to  the  sternum  by  the  flexible 
and  elastic  costal  cartilages,  are  so  arranged 
that,  in  a  position  of  rest,  their  convexities 
look  obliquely  outward  and  downward. 
When  the  movement  of  inspiration  is  about 
to  commence,  the  first  rib  is  fixed  by  the 
contraction  of  the  scaleni  muscles,  and,  the 
intercostal  muscles  then  contracting  simul- 
taneously, the  ribs  are  drawn  upward.  In 
this  movement,  as  each  rib  rotates  upon  its 
articulations  with  the  spinal  column  at  one 
extremity  and  with  the  sternum  at  the 
other,  its  convexity  is  necessarily  carried 
outward  at  the  same  time  that  it  is  drawn 
upward,  and  the  parietes  of  the  chest  are 
expanded  laterally.  The  sternum  rises  slightly  with  the  same  move- 
ment, and  enlarges  to  some  extent  the  antero-posterior  diameter  of  the 


DIAGRAM  ILLUSTRATING 
THE  RESPIRATORY  MOVE- 
MENTS.—a.  Cavity  of  the  chest. 
6.  Diaphragm.  The  dark  out- 
lines  show  the  figure  of  the  chest 
when,  collapsed  ;  the  dotted  lines 
show  the  same  when  expanded. 


276  RESPIRATION. 

thorax.  By  the  simultaneous  action  of  the  diaphragm  which  descends, 
and  of  the  intercostal  muscles  which  lift  the  ribs  and  the  sternum,  the 
cavity  of  the  chest  is  expanded  in  every  direction,  and  the  air  passes 
inward,  through  the  trachea  and  bronchial  tubes,  by  the  force  of  aspira- 
tion. 

The  action  of  these  two  sets  of  respiratory  muscles  is  indicated  exter- 
nally by  two  different  motions,  visible  to  the  eye;  namely,  an  expansion 
of  the  chest,  due  to  the  action  of  the  intercostals,  and  a  protrusion  of 
the  abdomen,  caused  by  the  descent  of  the  diaphragm.  In  children,  as 
well  as  in  the  adult  male,  in  the  ordinary  quiescent  condition,  the  dia- 
phragm performs  most  of  the  work  in  the  act  of  inspiration ;  and  the 
movements  of  the  abdomen  are  the  only  ones  which  are  especially 
marked.  Any  muscular  exertion,  however,  produces  an  increased  expan- 
sion of  the  chest ;  and  the  movement  of  the  ribs,  accordingly,  becomes 
more  plainly  visible  after  walking  or  running.  In  the  female  the  move- 
ments of  the  chest,  and  particularly  of  its  upper  half,  are  habitually 
more  prominent  than  those  caused  by  the  action  of  the  diaphragm; 
and  this  difference  in  the  mechanism  of  respiration  is  a  characteristic 
mark  of  the  two  sexes. 

In  certain  abnormal  conditions  the  activity  of  either  the  intercostal 
muscles  or  the  diaphragm  may  be  separately  suspended,  leaving  the 
entire  work  of  respiration  to  be  performed  by  the  remaining  set  of 
muscles.  If  the  intercostal  muscles  be  paralyzed,  by  disease  or  injury 
of  the  spinal  cord  in  the  lower  cervical  or  upper  dorsal  region,  the 
thorax  remains  quiescent  in  respiration,  while  the  protrusion  of  the 
abdomen  is  increased  in  extent  to  a  corresponding  degree.  This  mode 
of  breathing  is  called  abdominal  respiration. 

In  cases  of  peritonitis,  on  the  other  hand,  or  any  local  inflammation 
within  the  abdominal  cavity,  the  movements  of  the  diaphragm  are  some- 
times restrained,  owing  to  the  pain  which  they  excite  in  the  inflamed  sur- 
faces. This  is  known  as  thoracic  respiration  ;  since  the  expansion  of 
the  chest  becomes  more  active  than  usual,  and  is  the  only  visible  move- 
ment performed. 

Movement  of  Expiration. — After  the  movement  of  inspiration  is 
accomplished  and  the  lungs  have  been  filled  with  air,  the  diaphragm 
and  intercostal  muscles  relax,  and  a  movement  of  expiration  takes  place, 
by  which  the  chest  is  partially  emptied,  and  a  portion  of  the  air  con- 
tained in  the  pulmonar}''  cavity  is  expelled.  While  the  movement  of 
inspiration,  however,  is  an  active  one,  accomplished  by  means  of  mus- 
cular contraction,  that  of  expiration  is  a  passive  one,  resulting  from  a 
combination  of  several  forces.  The  principal  one  of  these  forces  is  the 
elastic  reaction  of  the  lungs  themselves,  due  to  the  numerous  fibres  of 
elastic  tissue  which  enter  into  the  structure  of  the  walls  of  the  pul- 
monary vesicles  and  smaller  bronchial  tubes,  and  are  disseminated  gene- 
rally between  the  lobules.  The  existence  of  this  elastic  force  in  the 
pulmonary  tissue  is  readily  demonstrated  by  removing  the  lungs  from 
the  chest  of  a  recently  killed  animal,  distending  them  by  artificial 


MOVEMENTS    OF    RESPIRATION.  277 

insufflation  through  a  tube  inserted  into  the  trachea,  and  then  relieving 
them  from  pressure.  They  at  once  react  with  sufficient  power  to  expel 
the  larger  portion  of  the  air  which  had  been  forced  into  their  cavities. 
The  same  elasticity  being  constantly  present  during  life,  the  air  is  sub- 
jected to  its  pressure,  and  is  consequently  expelled  as  soon  as  the  mus- 
cles of  inspiration  cease  to  act.  Other  organs,  however,  aid  in  the 
same  process.  The  costal  cartilages,  which  are  also  elastic,  having 
been  twisted  slightly  out  of  position  by  the  elevation  of  the  ribs,  resume 
their  original  form,  and,  drawing  the  ribs  down  again,  thus  serve  to  com- 
press the  sides  of  the  chest.  Lastly,  the  abdominal  organs,  which  have 
been  displaced  by  the  descent  of  the  diaphragm,  are  forced  backward 
by  the  elasticity  of  the  abdominal  walls  and  of  their  own  fibrous  attach- 
ments, carrying  the  relaxed  diaphragm  before  them.  By  the  constant 
recurrence  of  these  alternating  movements  of  inspiration  and  expiration, 
fresh  portions  of  air  are  incessantly  introduced  into  and  expelled  from 
the  chest. 

All  the  air,  however,  contained  in  the  lungs,  is  not  changed  at  each 
movement  of  respiration.  On  the  contrary,  a  considerable  quantity 
remains  in  the  pulmonary  cavity  after  the  most  complete  expiration ; 
and  even  when  the  lungs  have  been  removed  from  the  chest,  they  still 
contain  a  certain  amount  of  air,  which  cannot  be  entirely  displaced  by 
any  violence  short  of  disintegrating  the  pulmonary  tissue.  It  is  evi- 
dent, therefore,  that  only  a  comparatively  small  portion  of  the  air  in 
the  lungs  passes  in  and  out  with  each  respiratory  movement ;  and  it 
will  require  several  successive  respirations  before  it  can  be  entirely 
changed.  The  proportion  existing  between  the  air  which  is  changed  at 
each  respiration  and  the  entire  quantity  contained  in  the  chest  varies 
considerably  with  the  different  conditions  of  the  respiratory  function ; 
but  the  average  results  obtained  by  different  observers  show  that,  in 
general,  the  volume  of  the  inspired  and  expired  air  is  from  10  to  13  per 
cent,  of  that  contained  in  the  whole  of  the  pulmonary  cavity.  Thus  it 
will  require  from  eight  to  ten  respirations  to  renovate  completely  the 
air  in  the  lungs. 

Respiratory  Movements  of  the  Glottis. — Beside  the  movements  of 
expansion  and  collapse  already  described,  belonging  to  the  chest,  there 
are  similar  movements  of  respiration  which  take  place  in  the  larynx. 
If  the  respiratory  passages  be  examined  in  the  state  of  collapse  in  which 
they  are  usually  found  after  death,  it  will  be  observed  that  the  opening 
of  the  glottis  is  smaller  in  calibre  than  the  cavity  of  the  trachea  below. 
The  glottis  presents  the  appearance  of  a  narrow  chink,  while  the  passage 
for  the  inspired  air  widens  in  the  lower  part  of  the  larynx,  and  in  the 
trachea  constitutes  a  spacious  tube,  nearly  cylindrical  in  shape,  and  over 
12  millimetres  in  diameter.  We  have  found  that  in  the  human  subject 
the  space  included  between  the  vocal  chords  has  an  area,  on  the  aver- 
age, of  only  one  square  centimetre ;  while  the  calibre  of  the  trachea  in 
the  middle  of  its  length  is  2.81  square  centimetres.  This  disproportion, 
which  is  so  evident  after  death,  does  not  exist  during  life.  While 


278 


RESPIKATION. 


respiration  is  going  on,  there  is  a  regular  movement  of  the  vocal  chords, 
synchronous  with  the  inspiratory  and  expiratory  movements  of  the 
chest,  by  which  the  size  of  the  glottis  is  alternately  enlarged  and  dimin- 
ished. At  inspiration,  the  glottis  opens  and  allows  the  air  to  pass  freely 

Fig.  96. 


HUMAN  LARVNX,  viewed  from  above 
in  its  ordinary  post-mortem  condition.— a. 
Vocal  chords,  b.  Thyroid  cartilage,  c,  c. 
Arytenoid  cartilages.  o.  Opening  of  the 
glottis. 


The  same,  with  the  glottis  opened  by  sepa- 
ration of  the  vocal  chords. — a.  Vocal  chords. 
b.  Thyroid  cartilage,  c,  c.  Arytenoid  carti- 
lages, o.  Opening  of  the  glottis. 


Fig.  98. 


into  the  trachea ;  at  expiration  it  collapses,  and  the  air  is  driven  out 
from  below.  These  movements  are  the  "  respiratory  movements  of  the 
glottis."  They  correspond  in  every  respect  with  those  of  the  chest,  and 
are  excited  or  retarded  by  similar  causes.  Whenever  the  general  move- 
ments of  respiration  are  hurried,  those  of  the  glottis  become  accelerated 

at  the  same  time ;  and  when  the  movements 
of  the  chest  are  slower  or  fainter  than 
usual,  those  of  the  glottis  are  diminished 
in  the  same  proportion. 

In  the  respiratory  motions  of  the  glottis, 
as  in  those  of  the  chest,  the  movement  of 
inspiration  is  an  active  one,  and  that  of  ex- 
piration passive.  In  inspiration,  the  glottis 
is  opened  by  contraction  of  the  posterior 
crico-arytenoid  muscles.  These  muscles 
originate  from  the  posterior  surface  of  the 
cricoid  cartilage,  near  the  median  line ;  and 
their  fibres,  running  upward  and  outward, 
are  inserted  into  the  external  angles  of  the 
arytenoid  cartilages.  By  the  contraction 
of  these  muscles,  during  the  movement  of 
HUMAN  LARYNX,  POSTERIOR  inspiration,  the  arytenoid  cartilages  are 

VIEW.— a.  Thyroid   cartilage,     b.  ,.     .  *        ..       .    ,. 

Epiglottis,  c,  c.  Arytenoid  carti-  rotated  upon  their  articulations,  so  that 
lages.  d.  Cricoid  cartilage,  e,  e.  their  anterior  extremities  are  carried  out- 
Posterior  crico-arytenoid  muscles.  ,  .  ,  .  t  •,  i 

/.  Trachea,  ward,  and  the  vocal  chords  stretched  and 


MOVEMENTS    OF    RESPIRATION.  279 

separated  from  each  other.  In  this  way,  the  orifice  of  the  glottis  may 
be  nearly  doubled  in  size,  being  increased  from  0.94  to  1.69  square  cen- 
timetre. 

At  the  time  of  expiration,  the  posterior  crico-arytenoid  muscles  are 
relaxed,  and  the  elasticity  of  the  vocal  chords  brings  them  back  to  their 
former  position. 

The  motions  of  respiration  consist,  therefore,  of  two  sets  of  move- 
ments, namely,  those  of  the  chest  and  those  of  the  glottis.  These  move- 
ments, in  the  natural  condition,  correspond  with  each  other  both  in  time 
and  intensity.  It  is  at  the  same  time  and  by  the  same  nervous  influence, 
that  the  chest  expands  to  inhale  the  air,  while  the  glottis  opens  to  admit 
it ;  and  in  expiration,  the  muscles  of  both  chest  and  glottis  are  relaxed, 
while  the  elasticity  of  the  tissues  restores  the  parts  to  their  original 
condition. 

Rapidity  of  the  Movements  of  Respiration. — The  movements  of  res- 
piration in  the  human  subject  follow  each  other  in  general  with  great 
regularity,  and,  according  to  the  results  obtained  from  the  most  exten- 
sive and  varied  observations,  are  performed  on  the  average  with  a 
rapidity  of  20  inspirations  per  minute.  This  rate  varies  considerably 
under  the  influence  of  different  conditions,  one  of  the  most  important  of 
which  is  age.  It  is  well  known  that  respiration,  as  a  rule,  is  more  rapid 
in  young  children  than  in  the  adult,  and  Quetelet  has  found,  as  the 
average  of  a  large  number  of  observations,  that  in  the  newly  born  infant 
the  rate  is  44  per  minute,  and  at  the  age  of  5  years  26  per  minute ;  be- 
coming reduced  to  the  standard  rapidity  of  20  per  minute  between  the 
ages  of  fifteen  and  twenty  years.  Even  in  the  adult,  a  condition  of  rest 
or  activity  readily  influences  the  number  of  respirations ;  as,  according 
to  the  same  observer,  they  are  less  frequent  during  sleep  than  in  the 
waking  condition.  Even  a  difference  in  position  has  been  found  to  have 
a  perceptible  effect,  the  number  of  respirations  being,  in  the  same  indi- 
vidual, 19  per  minute  while  lying  down,  and  22  per  minute  when  standing 
up.1  Any  especial  muscular  activity,  as  the  rapid  motion  of  walking 
or  running,  at  once  increases  the  frequency  of  respiration,  which  returns 
to  its  ordinary  regularity  soon  after  the  exertion  has  ceased. 

In  all  cases  the  movements  of  respiration  are  involuntary  in  character, 
and  even  their  acceleration  or  diminution  is  regulated  by  influences 
beyond  our  control.  It  is  possible  for  a  short  time  to  increase  or  retard 
the  rate  of  respiration,  within  certain  limits,  by  voluntary  effort ;  but 
this  cannot  be  done  continuously.  If  we  intentionally  arrest  or  diminish 
the  respiratory  movements,  after  a  short  interval  the  nervous  impulse 
becomes  too  strong  to  be  controlled,  and  the  movements  necessarily 
resume  their  regular  frequency.  If  on  the  other  hand  we  endeavor  to 
breathe  much  more  rapidly  than  twenty  times  per  minute,  the  exertion 
soon  becomes  too  fatiguing  to  be  continued,  and  the  rate  of  movement 
returns  to  its  normal  standard.  The  movements  of  respiration,  accord- 

1  Milne-Edwards,  Legons  sur  la  Physiologic.     Paris,  1857,  tome  ii.  p.  483. 


280  RESPIRATION. 

ingly,  as  they  are  actually  performed,  in  infancy  and  childhood,  during 
sleep,  and  for  the  greater  part  of  the  waking  condition,  when  the  atten- 
tion is  not  directed  to  them,  are  purely  automatic  in  character,  like  the 
pulsations  of  the  heart,  and  do  not  require  the  expenditure  of  an}T 
voluntary  exertion. 

Quantity  of  Air  used  in  Respiration. — Like  all  the  quantitative  esti- 
mates connected  with  respiration,  that  of  the  volume  of  air  habitually 
inspired  and  expired  with  the  breath,  varies  considerably  as  given  by 
different  observers.  The  differences  incident  to  the  different  individuals 
subjected  to  observation,  and  to  the  conditions  of  rest  or  activity,  pre- 
vent our  arriving  at  an  absolutely  invariable  standard.  The  average 
result,  however,  which  most  nearly  conforms  to  the  truth,  as  derived 
from  several  of  the  most  trustworthy  experimenters,  as  well  as  from 
our  own  observations,  is  that  which  gives  the  amount  of  air  taken  into 
and  expelled  from  the  lungs  with  each  inspiration  and  expiration  as  320 
cubic  centimetres.  It  is  certain  that  this  estimate  is  not  above  the 
reality.  If  we  take,  accordingly,  eighteen  respirations  per  minute  as 
the  mean  rapidity  between  the  sleeping  and  waking  hours,  this  would 
amount  to  5760  cubic  centimetres  of  inspired  air  per  minute,  345,600 
per  hour,  and  8,294,400  cubic  centimetres,  or  8294.4  litres  per  day.  But 
as  the  breathing  is  increased,  both  in  rapidity  and  extent,  by  every 
muscular  exertion,  the  entire  quantity  of  air  daily  used  in  respiration  is 
not  less  than  10,000  litres,  or  a  little  over  350  cubic  feet. 

The  quantity  of  air  daily  used  in  respiration  is  sometimes  employed 
as  a  basis  for  calculating  the  air-space  necessary  to  allow  for  each  in- 
mate of  a  hospital  or  school-room.  This  estimate  alone,  however,  can 
never  give  sufficient  data  for  the  purpose.  The  successful  ventilation 
of  a  room  depends  not  so  much  on  the  quantity  of  air  which  it  contains 
at  any  one  time  as  upon  the  quantity  of  fresh  air  introduced,  and  of 
vitiated  air  expelled,  within  a  certain  period.  The  air  of  a  small  room 
which  is  thoroughly  ventilated  may  be  amply  sufficient  for  respiration, 
while  that  of  a  large  room,  if  allowed  to  remain  stagnant,  will  gradually 
become  unfit  for  use.  A  large  air-space,  in  any  occupied  apartment, 
will  render  ventilation  more  easy  of  accomplishment  by  ordinarj- 
methods,  because  the  air  will  not  be  so  rapidly  vitiated  by  the  same 
number  of  persons  as  if  it  were  in  smaller  volume ;  but  the  air  must 
still  be  changed  with  a  rapidity  proportionate  to  that  of  its  contamina- 
tion, in  order  to  maintain  the  apartment  in  a  wholesome  condition. 

Changes  in  the  Air  by  Respiration. 

The  atmospheric  air,  as  it  is  drawn  into  the  cavity  of  the  lungs,  is  a 
mixture  of  oxygen  and  nitrogen  in  the  proportion,  by  volume,  of  about 
21  parts  of  oxj^gen  to  79  parts  of  nitrogen.  It  also  contains  about  .05 
per  cent,  of  carbonic  acid,  a  varying  quantity  of  watery  vapor,  and 
some  traces  of  ammonia.  The  last  named  ingredients,  so  far  as  animal 
respiration  is  concerned,  are  quite  insignificant  in  comparison  with  the 
oxygen  and  nitrogen  which  form  the  principal  part  of  its  mass. 


CHANGES    IN    THE    AIR    BY    RESPIRATION.  281 

If  collected  and  examined,  after  passing  through  the  lungs,  the  air  is 
found  to  have  become  altered  in  the  following  particulars:  first,  it  has 
lost  oxygen;  secondly,  it  has  gained  carbonic  acid;  and  thirdly,  it  has 
absorbed  the  vapor  of  water.  The  most  important  of  these  changes  are 
its  diminution  in  oxygen  and  its  increase  in  carbonic  acid. 

Diminution  of  Oxygen. — According  to  the  researches  of  Valentin, 
Yierordt,  Regnault,  and  Reiset,  the  air  loses  during  respiration,  on  an 
average,  five  per  cent,  of  its  volume  of  oxygen.  At  each  inspiration, 
therefore,  about  16  cubic  centimetres  of  oxygen  are  removed  from  the 
air  and  absorbed  by  the  blood ;  and,  as  we  have  seen  that  the  daily 
quantity  of  air  used  in  respiration  is  about  10,000  litres,  the  entire  quan- 
tity of  oxygen  thus  consumed  in  twenty-four  hours  is  not  less  than  500 
litres.  This  is,  by  weight,  715  grammes,  or  rather  more  than  one  pound 
and  a  half  avoirdupois. 

In  consequence  of  this  diminution  in  oxygen,  air  which  has  once  been 
breathed  is  less  capable,  both  of  supporting  combustion  and  of  serving 
for  respiration,  than  before.  If  an  animal  be  confined  in  a  limited  space, 
the  air  becomes  poorer  in  oxygen  as  respiration  goes  on ;  and  when  its 
proportion  has  been  reduced  to  a  certain  point,  the  animal  dies  by  suf- 
focation, because  the  substance  which  is  essential  to  life  is  no  longer 
present  in  sufficient  quantity.  Different  kinds  of  animals  are  affected  in 
different  degrees  of  intensity  by  a  given  diminution  in  the  proportion  of 
atmospheric  oxygen.  Cold-blooded  animals,  in  which  respiration  is 
naturally  a  comparatively  slow  process,  may  continue  to  breathe  when 
only  a  very  small  quantity  of  oxygen  is  present ;  and  it  has  been  found 
that  electrical  fishes,  as  well  as  slugs  and  snails,  may  continue  respira- 
tion until  they  have  completely  exhausted  the  oxygen  in  the  water  or 
the  air  in  which  they  are  confined.  But  in  species  where  the  respira- 
tion and  circulation  are  carried  on  with  activity,  as  in  birds,  in  quad- 
rupeds, and  in  man,  a  partial  reduction  of  the  oxygen  is  sufficient  to 
cause  death.  If  the  carbonic  acid  exhaled  be  absorbed  by  an  alkaline 
solution,  so  that  the  purity  of  the  air  be  maintained,  it  is  found  that 
a  sparrow  dies  in  an  hour  when  its  proportion  of  oxygen  has  been 
gradually  reduced  to  15  per  cent. ;  and  a  mouse  dies  in  five  minutes 
when  the  oxygen  is  reduced  to  10  per  cent.;1  the  remainder  of  the  air 
in  both  cases  consisting  of  nitrogen.  In  man,  also,  asphyxia  is  almost 
immediately  produced  when  the  proportion  of  oxygen  has  fallen  to  10 
per  cent. 

As  a  candle  flame  is  also  extinguished  in  an  atmosphere  deprived  of 
oxygen,  this  is  sometimes  employed  as  a  test  to  determine  whether  it 
be  safe  to  enter  an  atmosphere  the  composition  of  which  is  doubtful. 
In  bread-rooms  and  beer-vats,  where  the  process  of  fermentation  has 
been  going  on,  in  old  wells  which  have  been  for  a  long  time  closed,  or 
in  any  newly  opened  underground  cavity  or  passage,  the  atmosphere  is 
frequently  so  poor  in  oxygen  that  suffocation  would  at  once  follow  if 

1  Milne-Edwards,  Lec.ons  sur  la  Physiologie.     Paris,  1857,  tome  ii.  p,  638. 
19 


282  RESPIRATION. 

they  were  to  be  entered  without  precaution.  A  lighted  candle  is  accord- 
ingly first  let  down  into  the  suspected  cavity,  and  if  a  sufficient  quantity 
of  oxygen  be  present,  it  continues  to  burn ;  if  not,  it  is  immediately 
extinguished. 

This  test  is  the  more  valuable,  because  it  is  found  that  the  proportion 
of  oxygen  necessary  to  support  the  combustion  of  a  candle  is  a  little 
greater  than  that  required  for  the  immediate  continuance  of  respiration. 
A  candle  is  extinguished  when  the  air  contains  only  It  per  cent,  of  its 
volume  of  oxygen,  while  a  little  less  than  this  may  still  serve  a  short 
time  for  respiration.  According  to  Milne-Edwards,  a  man  may  still 
keep  up  respiration  in  an  atmosphere  which  is  insufficient  to  support 
combustion ;  and  we  have  repeatedly  seen  pigeons  continue  to  breathe, 
though  with  difficulty,  in  air  in  which  a  candle  flame  was  immediately 
extinguished. 

Although,  however,  an  atmosphere  containing  from  10  to  IT  per  cent, 
of  oxygen  is  not  immediately  fatal  to  man  by  suffocation,  it  is  still  unfit 
for  continued  breathing.  The  deficiency  is  not  sufficient  to  stop  respira- 
tion at  once,  but  after  a  time  its  deleterious  effects  become  manifest, 
and  increase  in  intensity  with  each  repetition.  A  complete  renewal  of 
the  deteriorated  atmosphere  is  essential  to  the  perfect  performance  of 
the  respiratory  process. 

The  absorption  of  oxygen  by  different  species  of  animals  varies 
according  to  their  general  state  of  functional  activity ;  and  this  differ- 
ence may  be  manifested  even  between  species  belonging  to  the  same 
class.  Thus  it  has  been  found  that  in  the  sparrow  the  amount  of 
oxygen  absorbed,  in  proportion  to  the  weight  of  the  body,  is  ten  times 
as  great  as  in  the  common  fowl ;  and  in  a  carp  the  quantity  consumed 
in  the  course  of  an  hour  would  hardly  be  sufficient  for  the  respiration 
of  a  pigeon  for  a  single  minute. 

In  the  same  individual,  also,  a  temporary  increase  of  muscular  activity 
augments  in  a  marked  degree  the  absorption  of  oxygen  by  the  lungs. 
In  the  human  subject  it  was  found  by  Lavoisier  and  Seguin  that  a  man, 
who  in  the  ordinary  quiescent  condition  absorbed  a  little  over  19,000 
cubic  centimetres  of  oxygen  per  hour,  consumed  nearly  13,000  cubic 
centimetres  of  the  same  gas  during  fifteen  minutes  of  active  muscular 
exercise ;  the  rapidity  of  absorption  being  thus  increased  to  more  than 
2J  times  its  former  rate.  On  the  other  hand,  the  same  process  is  dimin- 
ished in  activity  during  sleep ;  and  in  the  hibernating  animals,  and  in 
insects  which  undergo  transformation,  at  the  time  of  their  most  pro- 
found lethargy  is  reduced  to  a  mere  vestige  as  compared  with  its  usual 
activity.  Spallanzani  observed  that  in  insects  the  amount  of  oxygen 
consumed  in  a  given  time  by  the  chrysalis  was  far  less  than  that  ab- 
sorbed before  or  afterward  by  the  caterpillar  or  the  butterfly ;  and  in 
the  experiments  of  Kegnault  and  Reiset  upon  the  marmot,  at  the  com- 
mencement of  the  cold  season,  the  consumption  of  oxygen  by  this 
animal  was  about  500  cubic  centimetres  per  hour  for  every  kilogramme 


CHANGES    IN    THE    AIR    BY    RESPIRATION.  283 

of  bodily  weight,  while  after  hibernation  was  fully  established  it  was 
reduced  to  26  cubic  centimetres  per  kilogramme  per  hour. 

The  absorption  of  oxygen,  accordingly,  in  the  process  of  respiration, 
is  directly  associated,  so  far  as  regards  its  rapidity  and  amount,  with  the 
physiological  activity  of  the  living  organism. 

Increase  of  Carbonic  Acid. — The  expired  air  usually  contains,  in 
man,  about  4  per  cent,  of  its  volume  of  carbonic  acid,  which  it  has  ab- 
sorbed in  its  passage  through  the  lungs.  Rather  less  than  13  cubic 
centimetres  of  this  gas  are  accordingly  given  off  with  each  ordinary 
expiration ;  and  as  we  have  found  that  10,000  litres  of  air  are  habitually 
inhaled  and  discharged  during  twenty-four  hours,  this  will  give  400 
litres  of  carbonic  acid  as  the  amount  expired  per  day.  This  quantity 
is,  by  weight,  186  grammes,  or  rather  less  than  one  pound  and  three- 
quarters  avoirdupois. 

The  rate  of  exhalation  of  carbonic  acid  by  respiration  varies  in  the 
same  manner  and  according  to  the  same  conditions  as  the  absorption 
of  oxygen.  In  a  general  way  it  may  be  said,  as  the  result  of  many 
trustworthy  observations,  both  in  animals  and  man,  that  the  quantity 
of  carbonic  acid  exhaled  during  a  given  time,  in  proportion  to  the  weight 
of  the  body,  is  increased  by  muscular  exertion  or  by  any  physiological 
activity  of  the  system,  and  is  diminished  by  quietude,  during  sleep,  and 
in  a  state  of  inanition. 

These  facts  have  been  established  more  particularly  for  the  human 
subject,  in  a  special  series  of  investigations  by  Prof.  Scharling,1  who 
found  that  the  quantity  of  carbonic  acid  exhaled  was  greater  during 
digestion  than  in  the  fasting  condition.  It  was  greater  in  the  waking 
state  than  during  sleep ;  and  in  a  state  of  activity  than  in  one  of  repose. 
It  was  diminished  by  fatigue,  and  ~by  most  conditions  which  interfere 
with  perfect  health. 

It  is  also  known  that  in  man  the  habitual  rate  of  exhalation  varies 
according  to  age,  sex,  constitution,  and  development.  These  variations 
were  very  fully  investigated  by  Andral  and  Gavarret,  who  found  them 
to  be  very  marked  in  different  individuals,  notwithstanding  that  the 
experiments  were  made  at  the  same  period  of  the  day,  and  with  the 
subject  as  nearly  as  possible  in  the  same  condition.  Thus  they  found 
that  the  quantity  of  carbonic  acid  exhaled  per  hour  in  five  different  per- 
sons was  as  follows : 

QUANTITY  OP  CARBONIC  ACID  PER  HOUR. 
In  subject  No.  1     ......     19,770  cubic  centimetres. 

"    2 15,888      " 

"    3     ,         .         .         .         .         .     20,475      " 

"    4 20,475      " 

11    5 26,060      " 

With  regard  to  the  difference  produced  by  age,  it  was  found  that  from 
the  period  of  eight  years  up  to  puberty  the  quantity  of  carbonic  acid 

1  Annales  de  Chimie  et  de  Physique.     Paris,  1843,  tome  viii.  p.  490. 


284  KESPIRATION. 

increases  constantly  with  the  age.  Thus  a  boy  of  eight  years  exhales, 
on  the  average,  9238  cubic  centimetres  per  hour ;  while  a  boy  of  fifteen 
years  exhales  16,168  cubic  centimetres  in  the  same  time.  Boys  exhale 
during  this  period  more  carbonic  acid  than  girls  of  the  same  age.  In 
males  this  augmentation  of  the  quantity  of  carbonic  acid  continues 
till  the  twenty-fifth  or  thirtieth  year,  when  it  reaches,  on  the  average, 
22,899  cubic  centimetres  per  hour.  Its  quantity  then  remains  stationary 
for  ten  or  fifteen  years ;  then  diminishes  slightly  from  the  fortieth  to 
the  sixtieth  year ;  and  after  sixty  years  diminishes  in  a  marked  degree, 
so  that  it  may  fall  as  low  as  IT, 000  cubic  centimetres.  In  one  superan- 
nuated person,  102  years  of  age,  Andral  and  Gavarret  found  the  hourly 
quantity  of  carbonic  acid  to  be  less  than  11,000  cubic  centimetres. 

In  women,  the  increase  of  carbonic  acid 'ceases  at  the  period  of 
puberty;  and  its  production  then  remains  constant  until  the  cessation 
of  menstruation,  about  the  fortieth  or  forty-fifth  year.  At  that  time  it 
increases  again  until  after  fifty  years,  when  it  subsequently  diminishes 
with  the  approach  of  old  age,  as  in  men.  Pregnancy,  occurring  at  any 
time  in  the  above  period,  produces  a  temporary  increase  in  the  quantity 
of  carbonic  acid. 

The  strength  of  the  constitution,  and  particularly  the  development  of 
the  muscular  system,  was  found  to  have  a  great  influence  in  this  respect. 
The  largest  production  of  carbonic  acid  observed  was  in  a  young  man, 
26  years  of  age,  whose  frame  presented  a  remarkably  vigorous  and 
athletic  development,  and  who  exhaled  26,060  cubic  centimetres  per 
hour.  On  the  other  hand,  an  unusually  large  skeleton,  or  an  abundant 
deposit  of  adipose  tissue,  is  not  accompanied  by  any  similar  increase  of 
the  carbonic  acid. 

Andral  and  Gavarret  sum  up  the  results  of  their  investigation  as 
follows : 

1.  The  quantity  of  carbonic  acid  exhaled  from  the  lungs  in  a  given 
time  varies  with  the  age,  the  sex,  and  the  constitution  of  the  subject. 

2.  In  the  male,  as  well  as  in  the  female,  the  quantity  of  carbonic  acid 
varies  according  to  age. 

3.  During  all  periods  of  life,  the  male  and  female  may  be  distinguished 
by  the  different  quantities  of  carbonic  acid  exhaled  in  a  given  time. 
Other  things  being  equal,  the  male  exhales  a  larger  quantity  than  the 
female.     This  difference  is  particularly  marked  between  the  ages  of  16 
and  40  years,  during  which  period  the  male  usually  exhales  twice  as 
much  carbonic  acid  as  the  female. 

4.  In  the  male,  the  quantity  of  carbonic  acid  increases  constantly  from 
eight  to  thirty  years ;  and  the  rate  of  this  increase  undergoes  a  rapid 
augmentation  at  the  period  of  puberty.     Beyond  forty  years  the  exha- 
lation of  carbonic  acid  begins  to  decrease,  and  its  diminution  is  more 
marked  as  the  individual  approaches  extreme  old  age,  so  that  near  the 
termination  of  life,  the  quantity  of  carbonic  acid  produced  may  be  no 
greater  than  at  the  age  of  ten  years. 

5.  In  the  female,  the  exhalation  of  carbonic  acid  increases  according 


CHANGES    IN    THE    AIR    BY    RESPIRATION.  285 

to  the  same  law  as  in  the  male,  from  the  age  of  eight  years  until  puberty. 
But  at  the  period  of  puberty,  at  the  appearance  of  menstruation,  the 
exhalation  ceases  to  increase  ;  and  it  afterward  remains  stationary  so 
long  as  the  menstrual  periods  recur  with  regularity.  At  the  cessation 
of  the  menses,  the  quantity  of  carbonic  acid  increases  in  a  notable 
manner ;  then  it  decreases  again,  as  in  the  male,  toward  old  age. 

6.  During  the  whole  period  of  pregnancy,  the  exhalation  of  carbonic 
acid  rises,  for  the  time,  to  the  same  standard  as  in  women  whose  menses 
have  ceased. 

7.  In  both  sexes,  and  at  all  ages,  the  quantity  of  carbonic  acid  is 
greater,  as  the  constitution  is  stronger  and  the  muscular  system  more 
fully  developed. 

The  process  of  respiration  is  not  altogether  confined  to  the  lungs, 
but  the  discharge  of  carbonic  acid  takes  place  also,  to  a  slight  extent, 
both  by  the  urine  and  the  perspiration.  Morin1  has  found  that  the 
urine  always  contains  gases  in  solution,  of  which  carbonic  acid  is  con- 
siderably the  most  abundant.  The  mean  result  of  fifteen  observations 
showed  that  urine  excreted  during  the  night  contains  about  1.96  per 
cent,  of  its  volume  of  carbonic  acid.  During  the  day  the  quantity  of 
this  gas  contained  in  the  urine  varied  considerably,  according  to  the 
condition  of  muscular  repose  or  activity.;  since  after  remaining  quiet  for 
an  hour  or  two,  it  was  only  1.19  per  cent,  of  the  volume  of  the  urine, 
while  after  continued  exertion  for  the  same  space  of  time,  not  only  was 
the  urine  augmented  in  quantity,  but  the  proportion  of  carbonic  acid 
contained  in  it  was  nearly  doubled,  amounting  to  2.29  per  cent,  of  its 
volume. 

An  equal  or  even  greater  activity  of  gaseous  exhalation  takes  place 
by  the  skin.  It  has  been  found,  by  inclosing  one  of  the  limbs  in  an  air- 
tight case,  that  the  air  in  which  it  is  confined  loses  oxygen  and  gains 
carbonic  acid.  From  an  experiment  of  this  sort,  Prof.  Scharling  esti- 
mated that  the  carbonic  acid  given  off  from  the  whole  cutaneous  surface, 
in  man,  is  from  one-sixtieth  to  one-thirtieth  of  that  discharged  during 
the  same  period  from  the  lungs.  In  the  more  recent  and  complete  obser- 
vations of  Aubert  upon  this  subject,  the  whole  body  without  clothing 
was  confined  in  an  air-tight  case,  leaving  only  the  head  exposed.  A 
continuous  ventilation  of  the  space  was  kept  up  during  the  course 
of  the  experiment  with  air  free  from  carbonic  acid,  while  the  carbonic 
acid  exhaled  from  the  surface  of  the  body  was  absorbed  by  baryta- 
water.  Each  observation  lasted  for  two  hours,  and  the  average  result 
obtained  was  that,  for  the  entire  day  of  twenty-four  hours,  198  cubic 
centimetres  of  carbonic  acid  were  exhaled  from  the  skin ;  a  quantity 
representing  rather  less  than  0.5  per  cent,  of  that  given  off  by  the  lungs 
in  the  same  time. 

In  the  amphibious  reptiles,  as  frogs,  newts,  and  salamanders,  which 

1  Recherches  sur  les  Gaz  libres  de  1'Uriue.  Journal  de  Pbarmacie  et  de  Chinrie. 
Paris,  1864,  tome  xlv.  p.  396. 


286  RESPIRATION. 

breathe  by  lungs,  and  yet  can  remain  under  water  for  a  considerable 
time,  the  thin,  moist,  and  flexible  integument  takes  a  still  more  active 
part  in  the  process  of  respiration.  The  skin  in  these  animals  is  covered, 
not  with  dry  cuticle,  but  with  a  delicate  layer  of  epithelium.  It  accord- 
ingly presents  all  the  conditions  necessary  for  the  accomplishment  of 
respiration ;  and  while  the  animal  remains  beneath  the  surface  of  the 
water,  though  the  lungs  are  in  a  state  of  comparative  inactivity,  the 
exhalation  and  absorption  of  gases  continue  to  take  place  through  the 
skin,  and  respiration  goes  on  without  interruption. 

Relation  between  the  Oxygen  absorbed  in  respiration  and  the  Car- 
bonic Acid  given  off. — It  has  been  seen  that,  in  the  human  subject,  with 
each  respiration,  on  the  average,  16  cubic  centimetres  of  oxygen  are 
taken  into  the  system  by  absorption,  and  13  cubic  centimetres  of  car- 
bonic acid  given  off.  As  the  oxygen  thus  taken  in  weighs  rather  less 
than  .023  gramme,  while  the  carbonic  acid  discharged  weighs  .025 
gramme,  it  is  evident  that  the  gross  result  of  the  process  is  a  loss  of 
weight  to  the  system,  and  this  loss  of  substance  by  continued  respira- 
tion amounts  on  the  average  to  a  little  over  70  grammes  per  day.  This 
is  one  of  the  most  important  facts  connected  with  the  plvysiology  of 
respiration.  It  shows  that  this  function  is  carried  on  at  the  expense  of 
the  substance  of  the  animal  body,  since  the  oxygen  and  carbon  dis- 
charged under  the  form  of  carbonic  acid,  weigh  more  than  the  oxygen 
which  is  absorbed  in  a  free  state.  This  difference  in  quantity  must 
accordingly  be  supplied  in  some  way  by  the  ingredients  of  the  food; 
and  if  this  be  withheld,  the  progress  of  respiration  alone  will  be  suffi- 
cient to  diminish  gradually  the  weight  of  the  body,  and  to  bring  it  to  a 
state  of  more  or  less  complete  emaciation. 

If  we  endeavor  to  ascertain  what  becomes  of  the  oxygen  itself,  it  is 
found  that  the  quantity  of  this  gas  which  disappears  from  the  inspired 
air  is  not  entirely  replaced  in  the  carbonic  acid  exhaled ;  that  is,  there 
is  less  oxygen  in  the  carbonic  acid  which  is  returned  to  the  air  by  expi- 
ration than  has  been  lost  by  it  during  inspiration. 

The  proportion  of  ox}-gen  which  disappears  in  the  interior  of  the 
body,  over  and  above  that  returned  in  the  breath  under  the  form  of 
carbonic  acid,  varies  in  different  kinds  of  animals.  In  the  herbivora  it 
is  about  10  per  cent,  of  the  whole  amount  of  oxygen  inspired;  in  the 
carnivora,  20  or  25  per  cent.;  and  even  in  the  same  animal,  the  propor- 
tion of  oxygen  absorbed,  to  that  of  carbonic  acid  exhaled,  varies  accord- 
ing to  the  kind  of  food  upon  which  he  subsists.  In  clogs,  while  fed  on 
meat,  according  to  the  experiments  of  Regnault  and  Reiset,1  25  per 
cent,  of  the  inspired  oxygen  disappeared  in  the  body  of  the  animal ; 
but  when  fed  on  starchy  substances,  all  but  8  per  cent,  reappeared  in 
the  expired  carbonic  acid.  Under  some  circumstances,  a  difference  may 
show  itself  in  the  opposite  direction ;  that  is,  more  oxygen  may  be  con- 
tained in  the  carbonic  acid  exhaled  than  is  absorbed  in  a  free  state  from 

1  Annales  de  Chimie  et  de  Physique,  tome  xxvi.  p.  428. 


CHANGES    IN    THE    AIR    BY    RESPIRATION.  287 

the  atmosphere.  In  some  of  the  experiments  of  Regnault  and  Reiset,1 
where  rabbits  and  fowls  had  been  led  exclusively  upon  bread  and  grain, 
the  proportion  of  oxygen  in  the  expired  carbonic  acid  was  101  or  102 
per  cent,  of  that  taken  in  by  respiration ;  and  even  in  the  human  sub- 
ject, according  to  the  observations  of  Doyere,  the  quantity  of  oxygen 
eliminated  by  the  breath  as  carbonic  acid,  may  be  considerably  greater 
than  that  absorbed.  But,  as  a  general  rule,  it  is  the  reverse ;  the  quan- 
tity of  oxygen  which  is  not  to  be  accounted  for  in  the  expired  carbonic 
acid  being  habitually  greater  in  the  carnivorous  animals  than  in  the 
Jierbivora. 

These  facts  have  been  established  by  direct  observation,  and  without 
any  reference  to  the  supposed  manner  in  which  the  internal  changes  of 
respiration  take  place.  Nevertheless,  they  are  susceptible  of  so  ready 
an  explanation  that  there  can  be  little  doubt  as  to  their  significance. 
The  simplest  case  for  examination  would  be  that  of  an  herbivorous  ani- 
mal living  exclusively  upon  the  carbo-hydrates,  as  starch  or  sugar. 
Since  these  substances,  as  their  name  implies,  already  contain  hydrogen 
and  oxygen  in  the  proportions  to  form  water,  any  further  oxidation 
which  they  undergo  must  result  in  the  production  of  carbonic  acid ; 
and  in  this  case  exactly  the  same  quantity  of  oxygen  as  that  taken  in 
must  necessarily  be  returned  to  the  atmosphere  as  a  constituent  of  the 
carbonic  acid  exhaled ;  the  remainder  of  the  substance  being  separated 
from  its  combinations  in  the  form  of  water.  This  process  is  represented 
in  the  following  formula : 

Starch.  Carbonic  acid.         Water. 

C6H100-  +  012    =     CG012    +     H1005. 

In  an  animal  supported  upon  this  food,  therefore,  the  whole  of  the 
oxygen  taken  in  by  respiration  would  reappear  in  the  expired  carbonic 
acid.  But  in  an  animal  feeding  also  upon  fatty  substances,  the  propor- 
tions would  be  changed.  As  these  matters  no  longer  contain  oxj^gen 
in  the  requisite  quantity  to  form  water  with  the  hydrogen  present,  more 
oxygen  must  be  taken  in  with  the  breath  than  is  sufficient  to  unite  with 
the  carbon  under  the  form  of  carbonic  acid  ;  and  consequently  a  portion 
of  it  will  disappear  from  the  gaseous  products  of  respiration.  The 
change  in  this  instance  is  as  follows : 

Oleine.  Carbonic  acid.       Water. 

Cor^oA  H-  0160  =  C3701U  +  H104052. 

In  effecting,  therefore,  the  complete  disappearance  of  a  fatty  sub- 
stance, 160  parts  of  oxygen  will  be  absorbed,  and  only  114  parts  re- 
turned in  the  form  of  carbonic  acid.  This  will  also  take  place  where 
albuminous  matters  are  used  as  food,  since  it  is  known  that  all  the 
nitrogen  of  these  substances  is  expelled  from  the  body  under  the  form 
of  urea ;  and  after  the  separation  of  urea  from  albumen,  a  body  must  be 
left  which  is  analogous  in  composition  to  fat ;  that  is,  which  contains 

1  Annales  de  Chimie  et  de  Physique,  tome  xxvi.  pp.  409-451. 


288 


RESPIRATION. 


less  oxjrgen  than  would  be  required  to  convert  all  its  hydrogen  into 
water. 

It  is  no  doubt  for  these  reasons  that,  in  herbivorous  animals,  feeding 
largely  on  the  carbohydrates,  the  quantity  of  oxygen  exhaled  in  the 
carbonic  acid  should  be  nearly  equal  to  that  taken  in  with  the  breath  ; 
while  in  the  carnivora,  which  consume  only  fats  and  albuminous  matters, 
a  larger  proportion  of  oxygen  should  disappear  from  the  products  of 
respiration. 

Finally,  some  kinds  of  vegetable  food,  as  fruits  and  green  tissues, 
contain  certain  substances  in  which  the  oxygen  is  more  than  sufficient 
to  form  water  with  the  hydrogen  present.  Such  are  the  salts  of  vegeta- 
ble acids,  like  oxalic,  citric,  gallic,  malic,  and  tartaric  acid.  The  result 
of  the  internal  consumption  of  tartaric  acid,  for  example,  would  be  as 
follows  • 


Tartaric  acid. 


Carbonic  acid. 

=    c,o8    4- 


Water. 

H603. 


In  this  instance  more  oxygen  will  be  exhaled,  in  the  carbonic  acid 
produced,  than  was  absorbed  from  the  atmosphere;  because  a  super- 
abundance already  existed  in  the  material  used  as  food. 

The  relative  proportions  of  oxygen  and  carbonic  acid,  absorbed  and 
expired  in  respiration,  will  therefore  vary,  as  has  been  well  shown  by 
Mayer,1  not  only  with  the  nature  of  the  food,  but  also  according  to  the 
transformations,  in  the  interior  of  the  living  organism,  of  one  nutritive 
substance  into  another,  as  of  a  carbohydrate  into  a  fat,  or  of  either  into 
an  organic  acid.  In  the  fermentation  of  a  saccharine  solution  there  is 
even  an  elimination  of  carbonic  acid  without  the  absorption  of  any 
oxygen  whatever ;  this  process  being  one,  not  of  direct  oxidation,  but 
of  the  rearrangement  of  the  elements  already  present  in  the  sugar,  a 
portion  of  them  being  exhaled  as  carbonic  acid,  while  the  rest  remain 
behind  in  the  form  of  alcohol. 

In  the  animal  body  the  function  of  respiration  consists,  first  in  the 
absorption  of  oxygen,  and  secondly  in  the  exhalation  of  carbonic  acid. 
It  is  evidently,  therefore,  so  far  as  its  consequences  are  concerned,  an 
act  of  oxidation.  But  the  elements  of  the  food  are  in  no  case  subjected 
to  immediate  oxidation.  They  are  digested  in  the  alimentary  canal  and 
taken  up  into  the  circulating  fluid  under  other  forms  of  organic  com- 
bination. These  undergo  still  further  transformations,  both  in  the  blood 
and  in  the  tissues,  passing  through  a  series  of  successive  metamorphoses, 
until  they  finally  leave  the  body,  principally  under  the  forms  of  urea, 
carbonic  acid,  and  water.  Oxidation,  accordingly ?  as  it  occurs  in  the 
living  body,  is  not  so  much  the  immediate  process  as  the  result  of  the 
vital  operations,  and  is  very  different  from  the  direct  combustion  of 
hydrocarbonaceous  matters  in  the  atmosphere. 

Exhalation  of  Watery  Vapor  in  Respiration. — The  watery  vapor, 
exhaled  with  the  breath,  is  given  off  by  the  pulmonary  mucous  mem- 


1  Lehrbuch  der  Agrikultur-Chemie.     Heidelberg,  1871,  p.  101. 


CHANGES    IN    THE    AIR    BY    RESPIRATION.  289 

brane,  by  which  it  is  absorbed  from  the  blood.  At  ordinary  tempera- 
tures it  is  transparent  and  invisible ;  but  in  cold  weather  it  becomes 
partly  condensed  on  leaving  the  lungs,  and  appears  under  the  form  of  a 
cloudy  vapor  in  the  breath.  According  to  the  researches  of  Valentin, 
the  average  quantity  of  water  exhaled  from  the  lungs  is  about  500 
grammes  per  day. 

The  exhalation  of  watery  vapor  by  the  lungs  is  a  purely  physical 
process,  dependent  upon  the  moist  and  permeable  structure  of  the  pul- 
monary mucous  membrane  and  the  volatility  of  the  watery  fluid,  by 
which  it  necessarily  becomes  vaporized  under  the  requisite  conditions 
of  temperature  at  the  ordinary  pressure  of  the  atmosphere.  Any  moist 
animal  membrane,  after  death  as  well  as  during  life,  loses  water  by 
evaporation  and  thus  becomes  gradually  desiccated.  Experiments  upon 
recently  killed  frogs  have  shown  that  the  spontaneous  desiccation  goes 
on  rapidly  at  first,  and  afterward  more  slowly,  as  the  proportion  of  water 
contained  in  the  tissues  becomes  diminished.  In  the  lungs  of  a  warm- 
blooded animal  during  life  all  the  requisite  conditions  are  present  for 
rapid  and  continuous  evaporation,  namely,  a  moderately  elevated  tem- 
perature, a  constant  renewal  of  atmospheric  air  by  the  movements  of 
respiration,  and  a  continuous  supply  of  fresh  moisture  to  the  pulmonary 
membrane  by  the  blood  circulating  in  its  vessels.  The  quantity  of 
watery  vapor  exhaled  by  the  lungs  in  a  given  time  is  therefore  increased 
or  diminished  by  corresponding  changes  in  the  rapidity  of  respiration, 
by  greater  dryness  or  humidity  of  the  atmosphere,  and  by  increase  or 
diminution  of  the  pulmonary  circulation. 

In  some  species  of  animals,  as  in  the  dog,  where  the  integument  is 
comparatively  destitute  of  perspiratory  glands,  the  pulmonary  trans- 
piration becomes  much  more  active ;  and  it  is  not  uncommon  to  see 
these  animals,  in  hot  weather,  lying  at  rest  with  their  tongues  protruded, 
and  the  movements  of  respiration  doubled  or  trebled  in  frequency,  for 
the  purpose  of  increasing  the  watery  exhalation  from  the  lungs. 

In  the  human  subject  the  precise  physiological  value  of  the  pulmonary 
transpiration  is  not  known.  Though  subject  to  fluctuations  according 
to  variation  in  the  physical  conditions  above  mentioned,  it  is  a  continu- 
ous process,  and  even  at  ordinary  temperatures  the  expired  breath 
directed  upon  a  polished  glass  or  metallic  surface  will  always  produce 
an  immediate  dimness  by  the  condensation  of  its  watery  vapor.  It  is 
very  possible  that  the  vapor  thus  exhaled,  beside  being  complementary 
to  the  perspiration  by  the  skin,  may  serve  as  a  vehicle  for  the  discharge 
of  certain  other  substances  from  the  pulmonary  cavity.  • 

Exhalation  of  Organic  Matter  by  the  Breath. — Beside  carbonic  acid 
and  water,  the  expired  air  also  contains  a  small  amount  of  an  organic 
ingredient,  which  communicates  a  faint  but  perceptible  odor  to  the 
breath.  This  substance  is  discharged  in  the  vaporous  form,  probably 
entangled  in  the  watery  vapor  exhaled  by  respiration.  Under  ordinary 
circumstances  it  is  present  in  so  small  a  quantity  as  to  be  hardly  notice- 
able ;  but  if  a  large  number  of  persons  be  confined  in  a  small  apartment 


290  RESPIRATION. 

x 

with  insufficient  ventilation,  the  organic  matter  accumulates  in  the 
atmosphere,  and  after  a  few  hours  its  odor  becomes  exceedingly  offen- 
sive. According  to  Carpenter,  if  the  fluid  condensed  from  the  expired 
air  be  kept  in  a  closed  vessel  at  ordinary  temperatures,  a  putrescent 
odor  is  after  a  time  exhaled,  which  could  only  come  from  some  organic 
substance  in  a  state  of  decomposition. 

When  perfectly  fresh  and  in  the  healthy  condition,  the  organic  in- 
gredient of  the  expired  breath  is  not  offensive  and  appears  to  have  no 
unwholesome  qualities.  It  is  only  when  accumulated  in  undue  quantity, 
and  allowed  to  stagnate  in  the  atmosphere,  that  its  disagreeable  properties 
become  manifest.  It  appears  to  be  distinct  in  character  for  each  species 
of  animal,  and  it  is  liable  to  be  absorbed  and  retained  for  a  time  by  any 
porous  material,  as  wood,  rough  plaster,  or  woven  fabrics.  It  is  easy 
to  distinguish  by  its  odor  the  breath  of  cattle  from  that  of  sheep  or 
swine,  and  the  odor  remains  perceptible  in  any  small  inclosure  or  trans- 
portation-car in  which  these  animals  have  been  recently  confined.  The 
organic  ingredient  of  the  expired  air  which  communicates  these  quali- 
ties to  the  breath  has  not  been  isolated  in  sufficient  quantity  to  deter- 
mine its  exact  composition. 

Vitiation  of  the  Air  by  Continued  Respiration. — From  what  has  pre- 
ceded it  is  seen  that  the  air,  after  being  exhaled  from  the  lungs,  has 
become  altered  in  its  constitution  by  diminution  of  its  oxygen  and  the 
addition  of  certain  other  materials  derived  from  the  breath.  Under 
ordinary  conditions,  this  deteriorated  air  is  at  once  diffused  in  the  sur- 
rounding atmosphere,  rising  to  a  higher  level  on  account  of  its  increased 
temperature,  and  being  readily  dispersed  by  the  aerial  currents  which 
are  always  more  or  less  in  motion  ;  so  that  a  fresh  supply  of  air,  with 
its  normal  constitution,  is  taken  into  the  lungs  with  each  successive 
inspiration.  But  when  breathing  is  carried  on  in  a  confined  space,  the 
air  necessarily  becomes  vitiated ;  and  this  effect  is  produced  with  rapidity 
in  proportion  to  the  small  extent  of  the  air  space  and  the  number  of 
men  or  animals  confined  in  it. 

This  vitiation  of  the  atmosphere  by  respiration  is  accordingly  the 
result  of  several  different  changes  taking  place  at  the  same  time,  and  its 
effects  are  a  combination  of  those  due  to  all  these  alterations. 

So  far  as  regards  immediate  danger  to  life,  the  diminution  of  oxygen 
is  no  doubt  the  most  important  change  in  the  vitiated  air,  when  carried 
to  a  sufficient  extent.  We  have  already  seen  that  for  man  and  the 
mammalians,  the  air  is  completely  irrespirable  when  its  proportion  of 
oxygen  is  diminished  to  10  per  cent.  In  these  experiments,  however, 
the  carbonic  acid  exhaled  was  removed,  as  fast  as  produced,  by  the 
action  of  an  alkaline  solution,  so  that  the  air  was  retained  in  a  state  of 
purity  except  for  its  loss  of  oxygen.  In  the  experiments  of  Leblanc,  a 
dog  and  a  pigeon,  breathing  in  a  confined  space,  were  both  reduced  to 
extremities  when  the  air  still  contained  16  per  cent,  of  oxygen  but  was 
also  contaminated  with  30  per  cent,  of  carbonic  acid.  The  different 


CHANGES    IN    THE    AIR    BY    RESPIRATION.  291 

modifications  of  the  atmosphere  in  respiration,  therefore,  react  upon 
each  other  and  combine  to  produce  a  common  result. 

The  second  element  in  the  vitiation  of  the  respired  air  is  that  due  to 
the  presence  of  carbonic  acid.  The  effect  of  this  gas,  as  produced  by 
respiration,  cannot  be  ascertained  from  that  of  an  atmosphere  consisting 
of  carbonic  acid  alone.  A  man  or  an  animal,  introduced  suddenly  into 
an  atmosphere  of  pure  carbonic  acid,  as  sometimes  happens  in  beer-vats 
and  old  wells,  dies  at  once  by  suffocation.  But  this  result  is  not  due  to 
the  influence  of  carbonic  acid.  It  is  simply  the  consequence  of  the 
absence  of  oxygen ;  and  death  would  take  place  as  promptly,  in  the 
warm-blooded  animals,  by  exposure  to  an  atmosphere  of  pure  nitrogen 
or  any  other  indifferent  gas.  It  may  be  said  that,  as  a  general  rule,  for 
birds  and  small  mammalians,  the  atmosphere  becomes  incapable  of 
supporting  life  when,  in  addition  to  its  normal  proportion  of  oxygen,  it 
contains  20  per  cent,  of  its  volume  of  carbonic  acid ;  that  is,  five  times 
as  much  as  is  present,  in  man,  in  the  expired  breath.  But  Regnault 
and  Reiset  found  that  dogs  and  rabbits  could  continue  to  breathe  with- 
out difficulty  in  an  atmosphere  containing  even  23  per  cent  of  carbonic 
acid,  provided  its  proportion  of  oxygen  were  at  the  same  time  increased 
to  30  or  40  per  cent.  Thus  a  part  at  least  of  the  influence  of  carbonic 
acid,  when  present  exclusively  or  in  large  quantity  in  the  atmosphere, 
is  evidently  due  to  its  physical  action  in  excluding  or  interfering  with 
the  absorption  of  oxygen. 

When  pure  carbonic  acid  is  gradually  mingled  with  atmospheric 
air,  its  immediate  effects  are  not  so  fatal  as  they  have  sometimes  been 
represented.  If  a  pigeon  be  confined  in  a  glass  receiver  with  a  wide 
open  mouth,  and  carbonic  acid  be  introduced  through  a  tube  placed  just 
within  the  edge  of  the  vessel,  so  that  it  will  not  completely  displace  the 
air  but  gradually  mingle  with  it,  its  effect  is  to  produce  a  rapid  and 
laborious  respiration,  gradually  increasing  in  intensity ;  and  in  a  few 
moments  the  pigeon  falls  in  a  state  of  complete  insensibility.  But  if 
the  glass  receiver  be  removed  and  fresh  air  allowed  access,  the  insen- 
sibility rapidly  passes  off,  and  in  a  few  moments  longer  the  animal  is 
again  breathing  in  a  natural  manner,  without  having  suffered  any  per- 
ceptible permanent  injury.  The  effect  of  carbonic  acid  alone,  thus 
mingled  with  the  atmosphere,  is  very  similar  to  that  of  an  anaesthetic 
vapor,  like  ether  or  chloroform,  with  the  addition  of  strong  symptoms 
of  dyspnoea. 

There  is  evidence  that  in  man  the  immediate  effects  of  carbonic  acid 
in  respiration  are  of  a  similar  nature.  From  personal  experiments  upon 
this  subject  we  have  found  that  the  inhalation  of  pure  carbonic  acid 
from  a  gasometer  is  at  first  extremely  difficult,  owing  to  the  stimulant 
effect  of  the  gas  upon  the  mucous  membrane  of  the  larynx,  which  pro- 
duces a  spasmodic  stricture  of  the  glottis.  If  the  gas,  however,  be 
allowed  to  remain  in  contact  with  the  mucous  membrane  for  a  short 
time,  this  effect  passes  off,  the  glottis  may  be  gently  opened,  and  the 
carbonic  acid  drawn  into  the  lungs,  by  a  full,  deep  inspiration,  to  the 


292  RESPIRATION. 

amount  of  from  800  to  1200  cubic  centimetres.  At  first  it  produces  in 
the  chest  only  a  sensation  of  warmth  and  moderate  stimulus.  But  at 
the  end  of  two  or  three  seconds  there  comes  on  very  suddenly  a  sense 
of  extreme  dyspnoea,  with  rapid  and  laborious  respiration,  accompanied 
immediately  by  dimness  of  vision,  slight  confusion  of  mind,  and  partial 
insensibility,  all  of  which  are  soon  terminated,  as  respiration  returns  to 
its  normal  condition,  leaving  only  a  feeling  of  quietude  and  tendency  to 
sleep. 

Notwithstanding,  however,  the  intense  feeling  of  dyspnoea  produced 
by  such  an  inhalation  of  pure  carbonic  acid,  the  external  signs  of  actual 
suffocation  are  very  slight,  and  bear  no  proportion  to  the  severity  of 
the  sensations.  They  are  confined  to  a  little  suffusion  of  the  face  with 
partial  lividity  of  the  lips ;  and  the  pulse  is  but  little  if  at  all  affected. 

A  mixture  of  carbonic  acid  and  atmospheric  air  in  equal  volumes  pro- 
duces a  perceptible  feeling  of  warmth  and  pungency  at  the  glottis,  but 
may  still  be  readily  drawn  into  the  lungs.  After  two  or  three  deep 
inspirations,  the  strong  sense  of  want  of  air,  and  the  access  of  rapid  and 
laborious  respiration,  come  on  as  before.  The  dyspnoea,  suffusion  of 
the  face,  and  lividity  are  all  less  marked  than  after  breathing  pure 
carbonic  acid,  but  the  subsequent  condition  of  quiescence  and  partial 
anaesthesia  is  more  decided  and  of  longer  continuance. 

A  mixture  of  one  volume  of  carbonic  acid  with  three  volumes  of 
atmospheric  air  may  be  inspired  without  difficulty,  producing  a  rather 
agreeable  sensation  by  contact  with  the  lungs.  After  about  3000  cubic 
centimetres  have  been  inhaled  in  successive  inspirations,  a  sense  of 
dyspnoea  comes  on,  which  however  is  not  particularly  increased  by  con- 
tinuing the  inspiration  of  the  mixture  to  6000  cubic  centimetres.  The 
nervous  symptoms  produced  are  moderate  in  degree,  but  similar  to  the 
preceding. 

On  the  other  hand,  pure  nitrogen  has  no  taste  or  odor,  nor  does  it 
have  any  stimulating  effect  on  the  mucous  membrane.  It  may  be  inspired 
from  the  gasometer  to  the  amount  of  6000  cubic  centimetres,  without 
producing  any  sense  of  dyspnoea,  or  any  perceptible  effect  on  the  nervous 
system. 

These  results  indicate  that  the  presence  of  carbonic  acid  in  the  lungs 
acts  as  a  stimulus  to  respiration  by  causing  a  sense  of  the  want  of  air ; 
and  that  furthermore  its  principal  toxic  effect,  when  in  abnormal  quan- 
tity, is  that  of  producing  more  or  less  insensibility  or  anaesthesia.  The 
sense  of  drowsiness  and  inattention  experienced  by  an  audience  in  an 
imperfectly  ventilated  lecture-room  or  theatre  is  probabry  due  to  this 
cause,  especially  as  the  burning  gas-lights  are  at  the  same  time  contribu- 
ting to  the  formation  of  carbonic  acid.  The  temporary  nature  of  these 
sensations,  and  their  immediate  relief  on  coming  into  the  open  air,  are 
matters  of  common  observation. 

The  third  element  in  the  vitiation  of  air  by  the  breath  is  the  accumu- 
lation of  its  organic  vapor.  This  is  the  least  understood,  but  probably 
the  most  deleterious  ingredient  of  the  atmosphere  produced  by  respira- 


CHANGES    IN    THE    BLOOD    BY    RESPIRATION.  293 

tion  in  a  crowded  and  ill-ventilated  apartment.  It  is  this  which  causes 
the  offensive  odor  and  the  sense  of  oppression  on  entering  any  confined 
space,  where  too  great  a  number  of  persons  have  remained  for  a  time 
without  sufficient  renewal  of  the  air.  It  is  most  marked  when  such  con- 
tinued respiration  and  neglect  of  ventilation  have  been  going  on  over 
night,  as  in  a  crowded  dormitory  or  sleeping-car;  since  the  organic 
emanations  have  then  had  time  not  only  to  accumulate  but  also  to  pass 
into  a  state  of  incipient  decomposition.  They  are  then  in  the  condition 
in  which  they  belong  to  the  class  of  animal  poisons ;  and  there  is  reason 
to  believe  that,  once  introduced  into  the  system,  they  may  cause  dis- 
turbances which  last  for  a  considerable  time.  It  is  certain  that  the  con- 
tagion of  many  febrile  diseases,  as  scarlatina,  meases,  and  smallpox,  is 
communicated  through  the  air  by  the  products  of  respiration ;  and  the 
normal  organic  exhalations  of  the  pulmonary  mucous  membrane,  when 
altered  by  concentration,  the  accumulation  of  moisture,  and  an  elevated 
temperature,  are  undoubtedly  capable  of  producing  morbid  effects  of  an 
analogous  kind. 

All  the  above  causes  of  vitiation  of  the  atmosphere  in  respiration, 
notwithstanding  the  differences  in  their  nature  and  effects,  are  to  be 
obviated  by  the  same  means ;  that  is,  a  sufficient  renewal  of  the  air  by 
ventilation. 

Changes  in  the  Blood  by  Respiration. 

The  blood  as  it  circulates  in  the  arterial  system  has  a  bright  scarlet 
color;  but  as  it  passes  through  the  capillaries  it  gradually  becomes 
darker,  and  on  arriving  in  the  veins  it  is  deep  purple,  or  in  some  situ- 
ations nearly  black.  There  are,  therefore,  two  kinds  of  blood  in  the 
body  ;  arterial  blood,  which  is  of  a  bright  color,  and  venous  blood,  which 
is  dark.  The  dark-colored  venous  blood,  which  has  been  thus  altered 
by  passing  through  the  capillaries,  is  incapable,  in  this  state,  of  supply- 
ing the  organs  with  their  healthy  stimulus  and  nutrition,  and  has  lost  its^ 
value  as  a  circulating  fluid.  It  is  accordingly  returned  to  the  heart  by 
the  veins,  and  is  thence  sent,  through  the  pulmonary  artery,  to  the  lungs. 
In  passing  through  the  pulmonary  circulation  it  reassumes  its  scarlet 
hue,  and  is  again  converted  into  arterial  blood.  Thus  the  most  striking 
physical  effect  produced  upon  the  blood  by  respiration  is  its  change  of 
color  from  venous  to  arterial. 

This  change  is  accomplished  by  the  influence  of  the  air  in  the  pulmo- 
nary cavities.  For  if  defibrinated  venous  blood,  recently  drawn  from 
the  veins  of  the  living  animal,  be  shaken  up  in  a  glass  vessel  with 
atmospheric  air,  it  at  once  changes  its  color  and  acquires  the  bright  hue 
of  arterial  blood.  If  injected  through  the  vessels  of  the  lungs  them- 
selves after  removal  from  the  body,  the  lungs  being  filled  with  air,  the 
same  change  takes  place.  If  a  dog  be  rendered  insensible  by  a  narcotic 
injection  or  other  similar  means,  the  thorax  opened,  and  artificial  re- 
spiration kept  up  by  the  nozzle  of  a  bellows  inserted  into  the  trachea, 
the  dark  venous  blood  can  be  seen  in  the  great  veins  and  in  the  right 


294  EESPIRATION. 

auricle  of  the  heart,  while  that  returning  from  the  lungs  to  the  left 
auricle  is  bright  red.  But  if  artificial  respiration  be  stopped,  the  circu- 
lation through  the  lungs  continuing,  the  blood  soon  ceases  to  be  arteri- 
alized  in  the  pulmonary  capillaries,  and  returns  to  the  left  auricle  of  a 
dark  venous  hue.  On  recommencing  artificial  respiration,  arterialization 
of  the  blood  is  again  produced,  and  its  red  color  is  restored  in  the  pul- 
monary yeins  and  the  left  cavities  of  the  heart. 

At  the  same  time,  in  passing  through  the  pulmonary  circulation,  the 
blood  undergoes  a  change  in  its  gaseous  constituents,  the  converse  of 
that  which  is  produced  in  the  air ;  that  is,  it  absorbs  oxygen  and  exhales 
carbonic  acid. 

Passage  of  Oxygen  into  the  Blood  in  Respiration. — The  oxygen  which 
is  absorbed  from  the  air  in  the  lungs  is  taken  up  by  the  blood  circulating 
in  the  pulmonary  capillaries.  It  does  not  at  once  enter  into  intimate 
chemical  union  with  other  elementary  substances,  but  is  still  in  the  form 
of  solution  or  of  such  loose  combination  that  it  may  be  removed  from 
the  blood  by  means  of  the  air-pump,  by  a  current  of  hydrogen  or  nitro- 
gen, and  especially  by  the  action  of  carbonic  oxide  (CO),  which  expels 
it  completely.  According  to  a  large  number  of  observations  which  have 
been  made  on  this  point,  its  quantity,  in  the  fresh  arterial  blood  of  the 
dog,  may  vary  from  a  little  over  10  per  cent,  to  22  per  cent,  of  the 
volume  of  the  blood ;  the  average  in  the  experiments  of  Schoeffer  and 
Ludwig1  being  about  15  per  cent. 

Nearly  the  whole  of  the  oxygen  is  taken  up  by  the  blood-globules; 
the  hemogiobine  of  which  has  been  shown  to  possess  so  remarkable  a 
power  of  absorption  for  this  gas  that  one  gramme  of  hemogiobine  in 
solution  will  absorb  more  than  one  cubic  centimetre  of  oxygen.  Ac- 
cording to  the  experiments  of  Magnus,  while  the  blood  contains  more 
than  twice  as  much  oxygen  as  water  could  hold  in  solution  at  the  same 
temperature,  the  serum  alone  has  no  more  solvent  power  for  this  gas 
'than  pure  water ;  and  on  the  other  hand,  defibrinated  blood,  that  is,  the 
serum  and  globules  mingled,  dissolves  as  much  oxygen  as  the  fresh  blood 
itself.  Pfliiger  also  found,  as  the  average  of  six  observations  on  the  arte- 
rial blood  of  the  dog,  that  the  oxygen  contained  in  the  entire  blood  was, 
by  volume,  15.6  per  cent.,  while  in  the  serum  alone  he  found  only  0.2  per 
cent.  According  to  the  same  observer,  the  arterial  blood  in  the  carotids 
contains  nearly  though  not  quite  all  the  oxygen  it  is  capable  of  holding  in 
solution ;  since  a  specimen  of  dog's  blood  drawn  directly  from  the  artery 
already  contained  18.8  per  cent,  of  oxygen,  and  after  being  shaken  up 
with  atmospheric  air  contained  rather  less  than  20  per  cent.  The  blood, 
therefore,  either  does  not  become  fully  saturated  with  oxygen  in  passing 
through  the  lungs,  or  else  a  little  of  this  gas  has  already  passed  into 
some  other  form  of  combination  on  reaching  the  carotid  arteries. 

The  color  of  the  blood  depends  solely  on  the  presence  or  absence  of 
oxygen,  not  on  that  of  carbonic  acid.  Yenous  blood,  shaken  up  with 

1  Archiv  fur  die  Gesammte  Physiologic,  1868,  Band  1,  p.  279. 


CHANGES    IN    THE    BLOOD    BY    RESPIRATION.  295 

oxygen  or  atmospheric  air,  at  once  assumes  the  arterial  tint,  although 
its  carbonic  acid  may  remain.  According  to  Pfliiger's  experiments,  if 
defibrinated  dog's  blood  be  placed  in  two  flasks,  and  shaken  up,  one  with 
pure  oxygen,  the  other  with  a  mixture  of  oxygen  and  carbonic  acid,  both 
specimens  will  present  the  same  bright  color ;  both  of  them  being  found 
on  analysis  to  contain  nearly  the  same  quantities  of  oxygen,  while  their 
proportions  of  carbonic  acid  are  very  different.  Also  the  recently  drawn 
blood  of  these  animals,  after  they  have  been  made  to  breathe  either  pure 
oxygen,  or  oxygen  and  carbonic  acid  mingled,  is  of  the  same  color  in 
each  instance ;  the  percentage  of  oxygen  which  it  contains  being  the 
same,  but  that  of  carbonic  acid  being  different  in  the  two  cases. 

It  is  the  oxygen,  therefore,  which,  on  being  taken  up  by  the  blood- 
globules,  changes  their  color  from  dark  purple  to  bright  red.  It  passes 
off  with  the  arterial  blood  in  this  condition,  and  is  then  distributed  to 
the  capillary  circulation.  Here,  as  the  blood  comes  in  contact  with  the 
tissues,  its  oxygen  in  great  measure  disappears,  and  its  color  is  again 
changed  from  arterial  to  venous. 

The  loss  of  oxj^gen  by  the  blood,  in  traversing  the  capillaries,  is  due 
to  its  transfer  from  the  blood-globules  to  the  substance  of  the  tissues. 
Nearly  all  the  tissues,  in  fact,  exert  an  absorbent  power  upon  oxygen, 
when  exposed  to  this  gas  or  to  atmospheric  air  containing  it.  The  ex- 
periments of  Paul  Bert1  have  shown  that  the  following  tissues,  extracted 
from  the  body  of  the  recently  killed  dog  and  exposed  to  the  contact  of 
atmospheric  air  in  closed  vessels,  absorb  oxygen,  with  different  degrees 
of  intensity,  in  the  following  order,  namely :  muscles,  brain,  kidneys, 
spleen,  testicle,  and  pounded  bones.  Of  these  the  muscles  are  the  most 
active,  absorbing  50  cubic  centimetres  of  oxygen  for  every  100  grammes 
of  muscular  tissue;  while  the  bones  absorb  only  a  little  over  Jt  cubic 
centimetres  for  the  same  weight  of  substance. 

The  tissues  have  even  a  greater  absorbent  power  for  oxygen  than  the 
blood-globules  themselves.  This  is  shown  by  the  experiments  of  Spal- 
lanzani,  and  still  more  completely  by  those  of  Bert.  In  these  experi- 
ments, three  equal  portions  of  recently  drawn  defibrinated  dog's  blood 
are  placed  in  test-tubes,  a  piece  of  fresh  muscular  tissue  from  the  same 
animal  being  introduced  into  one  of  them,  a  portion  of  the  spleen-tissue 
into  another,  while  the  third  is  left  to  itself.  After  a  time  it  is  found 
that  the  solid  tissues  have  abstracted  oxygen  from  the  blood  with  which 
they  are  in  contact,  so  that  in  these  two  specimens  the  blood,  on 
analysis,  contains  less  oxygen  than  in  the  third  specimen,  which  has 
remained  by  itself.  The  result  obtained  by  Bert  was  as  follows : 

QUANTITY  OF  OXYGEN  BY  VOLUME  REMAINING  IN 

Blood  left  to  itself 18  per  cent. 

Blood  containing  spleen  tissue      .         .  12       " 

Blood  containing  muscular  tissue  6       " 

1  Lecjons  sur  la  Physiologic  compare  de  la  Respiration.     Paris,  1870,  p.  46. 


296  RESPIKATION. 

Finally,  successive  analyses  of  the  blood,  as  it  passes  from  the  arte- 
rial into  the  venous  system,  shows  that  it  loses  oxygen  in  proportion  as 
it  has  been  subjected  to  the  influence  of  the  capillary  circulation.  Ber- 
nard1 found  that  the  blood  of  the  same  dog,  from  different  parts  of  the 
circulatory  system,  3delded,  by  the  action  of  carbonic  oxide,  the  follow- 
ing quantities  of  oxygen  : 

QUANTITY  OP  OXYGEN  BY  VOLUME  IN 

Arterial  blood 18.93  per  cent. 

Yenous  blood  from  right  side  of  heart     .         .         .       9.93       '; 
Yenous  blood  from  hepatic  veins     ....       2.80       " 

The  average  quantity  of  oxygen  existing  in  venous  blood  generally  is 
8  per  cent. ;  that  is,  it  is  reduced  about  one-half  from  its  proportion  in 
arterial  blood. 

Thus  the  blood-globules  serve  as  carriers  of  oxygen  from  the  lungs 
where  it  is  absorbed,  to  the  tissues  where  it  is  consumed ;  and  the  first 
object  of  respiration  is  to  supply  oxygen  to  the  blood,  in  order  that  the 
blood  may  supply  it  to  the  tissues. 

Exhalation  of  Carbonic  Acid  by  the  Blood. — The  venous  blood,  as  it 
returns  to  the  right  side  of  the  heart,  is  already  charged  with  carbonic 
acid  to  such  an  extent  that  a  portion  of  this  gas  is  exhaled  through  the 
pulmonary  membrane,  and  discharged  with  the  breath.  Its  absolute 
quantity  in  the  blood  has  not  been  determined  with  the  same  accuracy 
as  that  of  the  oxygen.  Carbonic  oxide,  which  is  so  efficient  for  the 
extraction  of  oxygen  from  the  blood,  displaces  only  a  portion  of  its 
carbonic  acid  ;  and  in  the  experiments  of  Bernard,  the  maximum  quan- 
tity of  carbonic  acid  obtained  from  venous  blood  by  this  means  was 
only  about  6.5  per  cent,  by  volume.  A  much  larger  proportion  may  be 
extracted  by  the  mercurial  air-pump,  amounting  on  the  average,  in  the 
experiments  of  Ludwig,  to  about  28  per  cent,  for  arterial  blood,  and 
about  31  per  cent,  for  venous  blood.  But  a  large  part  of  the  carbonic- 
acid  obtainable  in  this  way  does  not  exist  in  a  free  form  in  the  blood, 
but  in  a  state  of  combination  with  the  alkaline  phosphates  and  carbon- 
ates of  the  plasma;  since  it  is  known  that  a  wratery  solution  of  sodium 
bicarbonate  will  lose  a  portion  of  its  carbonic  acid,  and  become  reduced 
to  the  condition  of  a  carbonate  by  being  subjected  to  the  influence  of  a 
vacuum,  or  even  by  agitation  with  pure  hydrogen  at  the  temperature 
of  the  ~body.  Lehmann  found2  that  after  the  expulsion  from  ox's  blood 
of  all  the  carbonic  acid  removable  by  the  air-pump  and  a  current  of 
hydrogen,  there  still  remained  0.1628  per  cent,  of  sodium  carbonate, 
with  wThich  a  certain  quantity  of  the  carbonic  acid  previously  given  off 
must  have  been  united  in  the  form  of  bicarbonate. 

It  is  estimated  by  Bert,  according  to  the  experiments  of  Fernet,  that 
a  portion  of  the  carbonic  acid  of  the  blood  is  in  simple  solution  and  a 

1  Liquides  de  1'Organisme.     Paris,  1859,  tome  i.  p.  394. 

2  Physiological  Chemistry,  Cavendish  edition.     London,  1854,  vol.  i.  p.  438. 


CHANGES    IN    THE    BLOOD    BY    RESPIRATION.  297 

portion  combined  with  the  alkaline  salts ;  the  blood,  when  artificially 
saturated  with  this  gas,  containing  about  three-fifths  in  a  state  of  solu- 
tion and  about  two-fifths  in  a  state  of  combination.  We  do  not  know, 
however,  what  this  proportion  is  in  the  venous  blood  as  it  exists  in  the 
living  body ;  and  the  large  amount  of  carbonic  acid  removable  by  the 
action  of  a  vacuum  does  not  represent  that  which  is  capable  of  being 
exhaled  from  the  blood  through  the  pulmonary  membrane.  This  quan- 
tity is  very  much  smaller.  We  know  that,  on  the  average,  13  cubic 
ceniirnetres  of  carbonic  acid  are  discharged  from  the  lungs  in  man  with 
each  expiration ;  and  during  this  interval,  judging  from  the  capacity 
of  the  left  auricle  and  the  frequency  of  its  pulsations,  there  can  hardly 
be  less  than  400  cubic  centimetres  of  blood  passing  through  the  pulmo- 
nary circulation.  This  would  give  only  a  little  over  3  per  cent,  as  the 
volume  of  carbonic  acid  discharged  from  a  given  quantity  of  blood  in 
respiration.  The  average  results  obtained  by  extraction  with  the  mer- 
curial air-pump,  in  the  experiments  of  Ludwig,  give  this  quantity  as 
the  actual  difference  between  venous  and  arterial  blood,  as  follows : 

AVERAGE  QUANTITY  OF  CARBONIC  ACID  REMOVABLE  BY  THE  AIR-PUMP,  FROM 

Venous  blood 31.27  per  cent. 

Arterial  blood 27.99       " 

Difference 3.28 

All  the  different  modes  of  analysis,  whether  by  carbonic  oxide,  other 
indifferent  gases,  or  the  air-pump,  though  differing  in  the  quantity  of 
gas  extracted,  show  that  there  is  less  carbonic  acid  in  arterial  than  in 
venous  blood,  and  accordingly  that  this  gas  is  exhaled  from  the  circu- 
lating fluid  during  its  passage  through  the  lungs. 

Unlike  the  oxygen,  the  carbonic  acid  of  the  blood  is  principally  con- 
tained in  the  plasma^  and  not  in  the  blood  globules ;  since  the  capacity 
of  absorption  for  this  gas  is  not  essentially  different  for  the  serum  and 
for  the  entire  blood. 

Source  of  the  Carbonic  Acid  of  the  Blood — The  source  of  the  car- 
bonic acid  of  the  blood,  as  well  as  the  destination  of  its  oxygen,  is  in 
the  tissues  themselves.  From  the  experiments  of  various  observers  it 
is  found  that  every  organized  tissue,  in  the  recent  condition,  has  the 
power  of  absorbing  oxygen  and  exhaling  carbonic  acid.  G.  Liebig, 
for  example,  showed  that  frogs'  muscles,  recently  prepared  and  com- 
pletely freed  from  blood,  will  continue  to  absorb  oxygen  and  discharge 
carbonic  acid.  Similar  experiments  with  other  tissues  have  led  to  the 
same  result.  It  is  in  the  substance  of  the  tissues,  accordingly,  that  the 
oxygen  becomes  fixed  and  assimilated,  and  that  the  carbonic  acid  takes 
its  origin.  These  two  phenomena,  however,  are  not  immediately  de- 
pendent upon  each  other.  This  is  shown  by  the  fact  that  animals  and 
fresh  animal  tissues  will  continue  to  exhale  carbonic  acid  in  an  atmo- 
sphere of  hydrogen  or  of  nitrogen,  or  even  when  placed  in  a  vacuum. 
Marchand  found  that  frogs  would  live  for  from  half  an  hour  to  an  hour 
20 


298  RESPIRATION. 

in  pure  hydrogen  gas ;  and  that  during  this  time  they  exhaled  even 
more  carbonic  acid  than  in  atmospheric  air,  owing  probably  to  the 
superior  displacing  power  of  hydrogen  for  carbonic  acid.  For  while 
1000  grammes'  weight  of  frogs  exhaled  about  0.071  gramme  of  carbonic 
acid  per  hour  in  atmospheric  air,  they  exhaled  during  the  same  time  in 
pure  hydrogen  as  much  as  0.263  gramme.  The  same  observer  found 
that  frogs  would  recover  on  the  admission  of  air  after  remaining  for 
about  half  an  hour  in  a  nearly  complete  vacuum  ;  and  that  if  they  were 
killed  by  total  abstraction  of  the  air,  1000  grammes'  weight  of  the  ani- 
mals were  found  to  have  eliminated  0.600  gramme  of  carbonic  acid. 
Similar  facts  were  previously  observed  by  Spallanzani ;  and  Paul  Bert 
found  that  while  a  certain  quantity  of  fresh  muscular  tissue,  in  atmo- 
spheric air,  exhaled  in  a  given  time  30  cubic  centimetres  of  carbonic  acid, 
the  same  quantity,  in  pure  hydrogen,  exhaled  23  cubic  centimetres  during 
the  same  time.  He  even  found  that  the  exhalation  of  carbonic  acid 
would  continue  to  go  on,  in  an  atmosphere  of  nitrogen,  from  muscular 
tissue  which  had  previously  been  subjected  for  a  quarter  of  an  hour  to 
the  action  of  a  vacuum.1 

It  is  furthermore  evident  that  in  this  process  of  internal  respiration 
by  the  tissues,  as  in  the  external  phenomena  of  respiration  by  the  lungs, 
the  quantities  of  oxygen  absorbed  and  of  carbonic  acid  exhaled  do  not 
always  bear  the  same  relation  to  each  other.  This  is  shown  by  the  ex- 
periments of  Paul  Bert  on  the  gases  absorbed  and  discharged  by  the 
different  tissues  of  the  dog  in  contact  with  atmospheric  air,  where  in 
some  instances  the  volume  of  carbonic  acid  produced  was  greater,  and 
in  others  less  than  that  of  the  oxygen  consumed  ;  the  proportions  of 
the  two  varying  considerably  in  each  case. 

The  following  list  gives  the  result  of  a  series  of  these  experiments : 

QUANTITY  OP  0  AND  C0a  ABSORBED  AND  EXHALED  DURING  24  HOURS, 

IN  CUBIC  CENTIMETRES. 
By  100  grammes  of  Oxygen  absorbed.  Carbonic  acid  exhaled. 

Muscle 50.8  56.8 

Brain 45.8  42.8 

Kidneys 37.0  15.6 

Spleen 27.3  15.4 

Testicles 18.3  27.5 

Pounded  bones       ....  17.2  8.1 

The  production  of  carbonic  acid  by  the  tissues  is  not,  therefore,  di- 
rectly connected  with  the  absorption  of  oxygen.  The  precise  chemical 
action  by  which  carbonic  acid  originates  in  the  solid  organs  is  unknown ; 
but  it  is  probably  by  some  mode  of  decomposition  in  which  a  portion 
of  the  carbon  and  oxygen  present  in  the  tissues  separate  from  their 
previous  combinations  in  this  form,  while  the  remaining  elements  at  the 
same  time  unite  to  produce  other  substances  of  different  composition. 

The  process  of  respiration  consists,  accordingly,  in  an  interchange  of 

1  LeQons  sur  la  Physiologic  comparee  de  la  Kespiration.     Paris,  1870,  p.  49. 


CHANGES    IN    THE    BLOOD    BY    RESPIRATION.  299 

gases  between  the  blood  and  the  lungs.  The  blood  coming  to  the  lungs 
comparatively  poor  in  oxygen  and  charged  with  carbonic  acid,  the  for- 
mer gas  is  absorbed  from  the  air  in  the  pulmonary  vesicles,  while  the 
latter  is  discharged  at  the  same  time,  to  be  exhaled  with  the  breath. 
These  changes,  however,  are  neither  of  them  complete,  but  only  partial, 
both  for  the  air  and  for  the  blood.  The  expired  air  is  never  deprived 
of  the  whole  of  its  oxygen,  and  contains  only  about  4  per  cent,  of  its 
volume  of  carbonic  acid.  On  the  other  hand,  the  venous  blood  coming 
to  the  lungs  still  contains  a  moderate  percentage  of  oxygen ;  and  a  cer- 
tain quantity  of  carbonic  acid  is  also  present  in  arterial  blood.  It  is 
only  the  proportion  of  -these  gases  which  is  changed  in  respiration,  the 
carbonic  acid  of  the  blood  being  diminished,  and  its  oxygen  increased, 
by  its  passage  through  the  pulmonary  circulation. 

The  office  of  the  respiratory  apparatus  is  therefore  to  afford  ingress 
and  egress  to  the  two  substances  which  enter  and  leave  the  body  in 
the  gaseous  form.  These  two  substances  have  no  immediate  relation 
with  each  other,  excepting  as  to  the  organ  by  which  they  are  absorbed 
and  exhaled.  They  represent  the  beginning  and  the  end  of  a  series  of 
internal  combinations  and  decompositions,  which  are  among  the  most 
essential  of  the  changes  contributing  to  the  maintenance  of  life. 


CHAPTER  XIV. 

ANIMAL    HEAT. 

ONE  of  the  characteristic  properties  of  living  creatures  is  that  of 
maintaining,  more  or  less  constantly,  a  standard  temperature,  notwith- 
standing the  external  changes  of  heat  or  cold  to  which  they  are  sub- 
jected. If  a  bar  of  iron  or  a  vessel  of  water  be  heated  to  a  temperature 
above  that  of  the  external  air,  and  then  left  to  itself,  it  will  at  once 
begin  to  lose  heat  by  radiation  and  conduction ;  and  this  loss  of  heat 
will  continue  until,  after  a  certain  time,  the  temperature  of  the  heated 
body  has  been  reduced  to  that  of  the  surrounding  atmosphere.  It  then 
remains  stationary  at  this  point,  unless  the  atmosphere  should  become 
warmer  or  cooler ;  in  which  case  a  similar  change  takes  place  in  the 
inorganic  body,  its  temperature  remaining  constant  or  varying  with 
that  of  the  surrounding  medium. 

With  man  and  many  animals  the  case  is  strikingly  different.  If  a 
thermometer  be  introduced  into  the  stomach  or  rectum  of  a  dog,  or 
placed  under  the  tongue  of  the  human  subject,  it  will  indicate  a  tem- 
perature of  from  37°  to  38°  (about  100°  F.),1  whether  the  surrounding 
atmosphere  at  the  time  be  warm  or  cool.  This  internal  temperature  of 
the  body  is  sensibly  the  same  in  summer  and  in  winter.  Although  the 
external  air  may  be  at  the  freezing  point,  the  internal  parts  of  the  body, 
in  a  condition  of  health,  will  indicate  their  usual  standard  of  warmth 
when  examined  by  the  thermometer;  and  even  in  ordinary  summer 
weather  the  temperature  of  the  air  is,  for  the  most  part,  many  degrees 
below  that  of  the  living  body.  As  the  body,  however,  by  exposure  to 
such  an  atmosphere  must  be  constantly  losing  heat  by  radiation  and 
conduction,  like  any  inorganic  mass,  and  yet  maintains  a  standard  tem- 
perature, it  is  plain  that  a  certain  amount  of  heat  must  be  generated  in 
its  interior,  sufficient  to  compensate  for  the  external  loss.  The  internal 
-heat,  so  produced,  is  known  by  the  name  of  vital  or  animal  heat. 

Thus  it  is  by  its  own  internal  heat  that  the  body  is  warmed.  The 
clothing  used  by  man,  and  the  fur,  wool,  or  feathers  by  which  the 
bodies  of  animals  are  protected,  have,  of  course,  no  warmth  in  them- 
selves ;  they  simply  prevent  the  body  from  losing  heat  too  rapidly  and 
thus  becoming  cooled  down  below  its  normal  standard.  Even  the  fur- 
naces and  fires  of  a  dwelling  house  only  serve  in  a  similar  way  to 
moderate  the  cooling  influence  of  the  air ;  for  the  atmosphere,  even  in 

• 

1  To  convert  any  given  number  of  degrees  of  the  Centigrade  scale  into  the 
corresponding  value  for  the  Fahrenheit  scale,  multiply  by  1.8  and  add  32  to  the 
product. 

(300) 


ANIMAL    HEAT.  301 

the  warmest  apartment,  never  rises  to  the  heat  of  the  living  body,  which 
is  still  the  only  source  of  its  own  vital  temperature. 

Differences  of  Temperature  in  Different  Classes  of  Animals. — The 
intensity  of  the  production  of  internal  heat  varies  in  different  classes 
of  animals.  As  a  rule,  it  is  most  active  in  birds,  whose  temperature  is 
in  general  45°.  In  the  mammalians  it  is  37°  to  40°;  in  man  about 
ST. 5.  As  in  these  two  classes  the  internal  organs  and  the  blood  are 
nearly  always  much  above  the  temperature  of  the  air  or  of  the  surface 
of  the  skin,  and  accordingly  feel  warm  to  the  touch,  they  are  called  the 
"warm-blooded  animals."  In  reptiles  and  fish,  on  the  other  hand,  the 
production  of  heat  is  much  less  rapid,  and  preponderates  so  little  over 
that  of  the  air  or  water  which  they  inhabit,  that  no  marked  difference  is 
perceptible  on  cursory  examination ;  and  as  their  internal  organs  have 
a  lower  temperature  than  our  own  integument,  and  consequently  feel 
cool  to  the  touch,  they  are  called  the  "cold-blooded  animals."  This 
difference,  however,  is  only  one  in  degree  and  not  in  kind.  Reptiles 
and  fish  also  generate  heat  within  their  bodies,  which  may  be  measured 
by  the  thermometer.  The  temperature  of  frogs,  serpents,  tortoises, 
water-lizards,  and  fish  has  thus  been  found  to  be  from  1.7°  to  4.5° 
above  that  of  the  surrounding  air  or  water. 

In  the  invertebrate  animals,  as  insects  and  the  like,  the  heat  produced 
is  still  less  easily  perceptible  because,  from  the  great  extent  of  the  sur- 
face presented  by  their  bodies  in  proportion  to  their  mass,  the  warmth 
is  more  rapidly  dissipated.  But  when  many  of  them  are  collected  in  a 
small  air-space,  or  when  they  are  in  a  state  of  activity,  it  is  still  distin- 
guishable by  thermometric  measurement.  The  temperature  of  the  butter- 
fly after  active  motion  has  been  found  to  be  from  2.77°  to  5°  above  that 
of  the  air;  that  of  the  humble-bee  from  1.5°  to  5.5°  higher  than  the 
exterior.  According  to  the  experiments  of  Newport,  the  interior  of  a 
hive  of  bees  may  have  a  temperature  of  9°  when  the  external  atmos- 
phere is  at  1.4°,  even  while  the  insects  are  quiet ;  but  if  they  be  excited 
to  activity  by  tapping  on  the  outside  of  the  hive,  it  may  rise  to  38.8°. 
Thus,  while  the  insects  are  at  rest,  the  thermometer  indicates  a  very 
moderate  temperature ;  but  if  kept  in  rapid  motion  in  a  confined  space, 
they  may  generate  a  sufficient  amount  of  heat  to  produce  a  sensible 
elevation  in  the  course  of  a  few  minutes. 

The  production  of  heat  is  not  confined  to  animal  organisms,  but  takes 
place  also  in  vegetables.  Here,  however,  it  is  still  more  rapidly  dissi- 
pated than  in  insects,  owing  to  the  great  extent  of  surface  presented 
by  the  ramifications  and  foliage,  and  to  the  abundant  evaporation  of 
moisture  from  the  leaves,  by  which  the  heat  generated  is  in  great 
measure  consumed  without  becoming  perceptible  by  the  ordinary  ther- 
mometer. If  this  loss  of  heat  from  the  plant  be  diminished  by  keeping 
the  air  charged  with  watery  vapor  and  thus  preventing  evaporation,  the 
elevation  of  temperature  becomes  sensible  and  may  be  measured.  Du- 
trochet1  first  demonstrated,  by  the  use  of  the  thermo-electric  needle,  that 

1  Annales  des  Sciences  naturelles.     Paris,  2me  S6rie,  tome  xii.  p.  277. 


302  ANIMAL    HEAT. 

nearly  all  parts  of  a  living  plant,  such  as  the  green  stems,  the  leaves, 
the  buds,  and  even  the  roots  and  fruit,  generate  a  certain  amount  of 
heat;  the  maximum  temperature  thus  detected  being  about  0.28°  above 
that  of  the  surrounding  atmosphere.  Subsequent  observations  have 
shown  that  in  certain  periods  of  vegetative  activity,  as  in  the  processes 
of  germination  and  flowering,  the  development  of  heat  is  much  more 
rapid.  In  the  malting  of  barley,  when  a  considerable  quantity  of  the 
germinating  grain  is  piled  in  a  mass,  its  elevation  of  temperature  may 
be  readily  distinguished,  both  by  the  hand  and  the  thermometer.  The 
most  striking  example  of  heat-production  in  flowers  is  presented  by 
those  of  the  Aracese  (Calla,  Indian  turnip,  Sweet  flag)  at  the  time  of 
fecundation,1  which  in  warm  weather  ma}^  show  a  temperature  of  4°, 
5°,  or  even  10°  above  that  of  the  surrounding  air. 

The  generation  of  heat  is  accordingly  a  phenomenon  common  to  all 
living  organisms,  whether  animal  or  vegetable.  When  the  mass  of  the 
organized  body  is  large  in  proportion  to  its  extent  of  surface,  the  heat 
thus  produced  is  readily  distinguishable  both  by  the  touch  and  by  the 
thermometer.  When  rapidly  dissipated  by  increased  extent  of  surface, 
and  especially  by  the  evaporation  of  moisture,  it  is  less  easily  detected, 
but  it  exists  in  each  case.  In  birds  and  mammalians  it  is  more  active 
than  in  reptiles  and  fish ;  and  even  in  different  species  of  animals  belong- 
ing to  the  same  class,  it  is  usually  found  that  the  normal  temperature 
of  the  body,  like  the  other  physiological  phenomena,  differs  slightly, 
according  to  the  special  organization  of  the  animal  and  the  general 
activity  of  its  functions. 

Quantity  of  Heat  in  the  Living  Body. — The  quantity  of  heat  produced 
in  the  body  within  a  given  time  is  best  measured  by  the  increase  of 
temperature  which  it  will  produce  in  a  certain  volume  of  water.  Prof. 
John  C.  Draper2  found  that  the  human  body,  having  a  volume  of  about 
85  litres  (3  cubic  feet)  and  a  weight  of  81.65  kilogrammes  (180  pounds 
avoirdupois),  by  remaining  at  rest  in  the  bath  for  one  hour,  could  raise 
the  temperature  of  212  kilogrammes  of  water  1.1 1° ;  which  he  estimates, 
assuming  the  specific  heat  of  the  body  to  be  about  the  same  with  that 
of  water,  would  be  capable  of  warming  the  body  itself  2.11°.  But  as 
the  temperature  of  the  body,  in  the  observation  quoted,  was  lowered 
0.55°  while  in  the  bath,  the  heat  actually  generated  would  be  capable 
of  warming  the  body  itself,  or  an  equal  volume  of  water,  2.22°.  This 
would  be  equivalent  to  188.7  heat  units,3  produced  by  the  human  body 
in  the  course  of  one  hour,  or  2.31  heat  units  for  every  kilogramme  of 
bodily  weight. 

The  experiments  of  Senator4  on  the  heat-producing  power  in  dogs 

1  Sachs,  Traite  de  Botanique.     Paris,  1874,  p.  847. 

2  American  Journal  of  Science  and  Arts.     New  Haven,  1872,  vol.  ii.  p.  445. 

3  A  heat  unit  is  the  quantity  of  heat  required  to  raise  the  temperature  of  one 
kilogramme  of  water  from  0°  to  1°  of  the  centigrade  scale. 

4  Archiv  fur  Anatomic,  Physiologic,  und  Wissenschaftliche  Medicin.     Leipzig, 
1872. 


ANIMAL    HEAT.  303 

were  performed  with  much  accuracy.  The  animals  were  inclosed  in  a 
copper  cage,  through  which  ventilation  was  kept  up  at  a  known  rate, 
the  temperature  of  the  incoming  and  outgoing  volumes  of  air  being  noted 
at  intervals  of  ten  minutes.  The  cage  containing  the  animal  was  sur- 
rounded by  a  known  volume  of  water,  at  from  26.5°  to  29°,  and  the 
whole  apparatus  inclosed  in  an  outer  case  made  as  nonconducting  as 
possible ;  the  quantity  of  heat  actually  lost  from  it  by  external  cooling 
being  determined  by  preliminary  observations.  The  internal  tempera- 
ture of  the  animal  having  been  taken,  he  was  introduced  into  the  cage 
and  allowed  to  remain  there  a  certain  time.  The  heat  produced  within 
this  time  was  mainly  ascertained  by  the  increase  of  temperature  in  the 
water  surrounding  the  cage,  the  result  being  corrected  by  that  of  the 
air  used  for  ventilation,  as  well  as  by  the  variation  in  temperature  of  the 
animal  himself,  and  the  loss  from  the  apparatus  by  external  cooling. 
By  this  method  the  experimenter  found,  as  the  average  result  of  five 
observations,  that  a  dog  of  5.392  kilogrammes'  weight,  at  rest  and  in 
the  fasting  condition,  produced  in  one  hour  12.63  heat  units;  that  is, 
2.34  heat  units  for  every  kilogramme  of  bodily  weight.  According  to 
these  experiments,  the  heat-producing  power  in  the  dog  and  that  in  the 
human  subject  are  nearly  the  same;  while  that  of  the  dog  is  rather  the 
more  active  of  the  two. 

Normal  Variations  of  Temperature  in  the  Living  Body. — The  tem- 
perature of  the  body  is  not  the  same  in  its  different  regions,  but  increases 
for  a  certain  distance,  from  the  exterior  toward  the  central  parts.  This 
is  because  the  living  body  is  subjected  to  a  constant  loss  of  heat  from 
the  surface,  like  any  other  solid  substance  of  higher  temperature  than 
the  surrounding  air.  Consequently  the  integument  and  the  parts  im- 
mediately subjacent  to  it,  being  more  exposed  to  this  cooling  influence 
than  the  internal  organs,  have  habitually  a  temperature  slightly  below 
that  of  the  body  in  general.  Accordingly,  whenever  the  external  air 
rises  to  the  neighborhood  of  3t°  or  3f.5°  it  feels  uncomfortably  warm ; 
because,  although  this  is  exactly  the  normal  temperature  of  the  blood 
and  the  internal  organs,  it  is  considerably  above  that  of  the  skin,  which 
is  readily  sensitive  to  variations  of  cold  or  warmth.  The  cooling  influ- 
ence of  the  external  atmosphere  upon  the  skin  is  considerably  moderated 
by  the  movement  of  the  circulation ;  since  the  warmer  blood  coming 
from  the  internal  parts  constantly  supplies  the  integument  with  fresh 
quantities  of  heat  and  thus  tends  to  compensate  for  its  external  loss. 

Notwithstanding  this  compensation,  however,  the  difference  in  tem- 
perature between  the  external  and  internal  parts  of  the  body  is  always 
perceptible  during  health.  If  the  bulb  of  a  thermometer  be  held  for 
some  minutes  between  the  folds  of  skin  in  the  palm  of  the  hand,  it  will 
stand  at  36.4°  ;  in  the  axilla,  at  36.6°  ;  under  the  tongue,  it  will  reach 
37.2°;  in  the  rectum,  31.5°;  and  Dr.  Beaumont  found,  in  the  case  of 
Alexis  St.  Martin,  that  the  thermometer,  introduced  into  the  stomach 
through  the  gastric  fistula,  often  indicated  a  temperature  of  31.8°.  It 
is  evident  therefore  that,  in  order  to  ascertain  the  real  internal  tempera- 


304  ANIMAL    HEAT. 

ture  of  the  body,  the  bulb  of  the  thermometer  should  be  inserted  so 
deeply  as  to  pass  beyond  the  superficial  zone  affected  by  the  process  of 
external  cooling.  Even  when  placed  beneath  the  tongue  it  is  in  contact 
with  parts  which  are  themselves  slightly  cooled  by  the  passage  of  the 
air  in  inspiration  and  expiration,  and  accordingly  does  not  reach  the 
maximum  temperature  of  the  body.  To  accomplish  this,  it  must  be  in- 
serted into  the  abdominal  cavity  or  the  rectum,  so  deeply  that  a  further 
introduction  produces  no  increase  in  the  indicated  temperature.  This 
is  the  method  usually  adopted  in  physiological  observations. 

Beside  the  differences  observable  from  the  above  cause  between  the 
superficial  and  the  deep-seated  parts,  there  is  a  real  variation  within 
narrow  limits  of  the  internal  temperature  of  the  body,  according  to  dif- 
ferent physiological  conditions.  Jiirgensen  has  shown1  that  in  the  human 
subject  there  is  a  diurnal  variation,  the  temperature  during  the  day 
being  a  little  higher  than  at  night,  even  when  both  periods  are  passed 
in  complete  repose.  A  series  of  observations  upon  the  same  individual 
in  a  state  of  rest  gave  the  following  averages : 

TEMPEKATURE  OF  THE  HUMAN  BODY  WHEN  AT  REST. 
By  day.  By  night. 

37.34°  36.91° 

The  difference  between  the  two  averages  amounts  to  0.43°.  There 
are  also  temporary  variations  of  small  extent  during  each  of  the  above 
periods  ;  the  greatest  variation  during  the  day  being  0.21° ;  that  during 
the  night  0.15°. 

The  temperature  of  the  body  is  also  increased  by  muscular  activity. 
It  is  a  matter  of  common  observation,  both  in  man  and  animals,  that 
temporary  exertion  produces  an  increase  of  bodily  warmth.  Jurgensen 
observed  in  the  same  individual  that  while  during  a  day  of  absolute 
rest  the  maximum  temperature  attained  was  37.7°,  under  the  influence 
of  exercise  it  reached  38.8°.  A  much  more  striking  difference,  corre- 
sponding with  muscular  repose  or  activity,  has  already  been  mentioned 
as  observable  in  insects. 

The  animal  temperature  is  furthermore  increased  or  diminished  by  a 
condition  of  digestion  or  abstinence.  This  was  indicated  in  several 
instances  by  the  observations  of  Jurgensen  upon  man,  but  is  shown  in 
a  very  marked  degree  by  those  of  Senator  upon  the  dog,  in  which  the 
average  production  of  heat  was  sensibly  diminished  by  continued  fast- 
ing and  increased  by  the  digestion  of  food.  The  following  table  shows 
the  quantity  of  heat  produced  by  the  same  animal,  in  the  conditions  of 
abstinence  and  digestion. 

QUANTITY  OF  HEAT  PRODUCED  BY  THE  DOG  IN  ONE  HOUR. 
After  two  days'  fasting     ....         10.90  heat  units. 
After  one  day's  fasting      ....        12.63 
Fed  one  hour  previously   ....        18.87 

1  Die  Korperwarme  des  gesundcn  Menscben.     Leipzig,  1873. 


MODE  OF  PRODUCTION  OF  ANIMAL  HEAT.     305 

As  the  production  of  heat  in  the  body  can  only  take  place  by  the  con- 
sumption or  change  of  combination  of  its  ingredients,  it  is  evident  that 
in  continued  abstinence  from  food,  the  materials  susceptible  of  this 
change  must  be  constantly  diminishing  in  quantity  ;  and  the  animal 
temperature  accordingly,  like  other  vital  phenomena,  becomes  depressed 
from  a  deficiency  in  the  sources  of  its  supply. 

Mode  of  Production  of  Animal  Heat. 

In  all  instances,  so  far  as  observation  has  gone,  the  production  of 
heat  in  living  organisms  is  in  proportion  to  the  activity  of  the  internal 
changes  going  on  in  the  body.  These  changes  are  more  especially  and 
constantly  indicated  by  the  absorption  of  oxygen  and  the  exhalation 
of  carbonic  acid  in  respiration.  Even  in  the  vegetable  kingdom,  it  is 
demonstrated  by  the  researches  of  physiological  botanists  that  the  ab- 
sorption of  oxygen  in  plants  is  always  accompanied  both  by  the  pro- 
duction of  carbonic  acid  and  by  the  evolution  of  heat ;  and  the  quantity 
of  heat  produced  is  greatest  at  the  time  when  those  processes  are  going 
on  which,  like  germination  and  flowering,  are  accompanied  by  the  most 
active  absorption  and  exhalation  of  oxygen  and  carbonic  acid  respec- 
tively. 

The  same  thing  is  manifest  in  the  different  classes  of  the  animal  king- 
dom. Birds  and  mammalians,  where  respiration  is  most  active,  have 
also  the  highest  temperature;  while  in  reptiles  and  fish  the  respiratory 
process  is  more  sluggish,  and  the  production  of  heat  at  the  same  time 
less  abundant.  A  very  close  connection  between  the  two  phenomena  is 
observable  in  hibernating  animals,  in  which,  during  the  winter  sleep, 
respiration  becomes  comparatively  inactive  and  the  bodily  temperature 
is  also  reduced  to  a  very  low  standard.  In  the  observations  of  Horvath1 
on  the  respiration  of  marmots,  he  found  that  these  animals  during  cold 
weather  are  plunged  in  a  profound  stupor  in  which  the  movements  of 
respiration  are  exceedingly  infrequent  and  sometimes  hardly  perceptible. 
At  certain  intervals  the  animals  awake  for  a  short  time,  after  which 
they  again  return  to  the  state  of  insensibility.  Horvath  found  that  the 
internal  temperature  of  the  marmot,  when  awake,  was  from  35°  to  37°; 
while,  in  the  hibernating  condition,  it  was  reduced  to  10°,  9°,  or  even 
to  2°,  according  to  that  of  the  surrounding  air.  On  awakening,  the  tem- 
perature of  the  body  rapidly  rises.  In  one  animal,  the  internal  tempera- 
ture during  sleep  was  from  9°  to  10° ;  but  on  awakening  it  rose  at  the 
end  of  an  hour  to  12°,  in  two  hours  to  17°,  and  in  two  hours  and  a  half 
to  32°.  Respiration  also  becomes  increased  in  activity  to  a  similar 
degree.  A  marmot  weighing  153  grammes  produced,  while  in  the 
comatose  condition,  0.015  gramme  of  carbonic  acid  per  hour;  and  two 
days  afterward,  when  awake,  produced  0.513  gramme  in  the  same  time, 
that  is,  more  than  thirty  times  as  much  as  when  in  the  state  of  hiberna- 
tion. 

1  Revue  des  Sciences  Medicales.     Paris,  1873,  tome  i.  p.  59. 


306  ANIMAL    HEAT. 

These  and  similar  facts  point  to  so  close  a  relation  between  the 
intensity  of  respiration  and  that  of  heat-production,  that  the  one  of 
these  processes  may  be  taken,  in  general  terms,  as  the  measure  of  the 
other ;  particularly  as  respiration  consists  in  the  absorption  of  oxygen 
and  the  exhalation  of  carbonic  acid,  and  as  we  know  that  the  oxidation 
of  carbonaceous  matters,  outside  the  body,  is  one  of  the  readiest  means 
for  the  production  of  heat. 

This  connection,  however,  is  not  an  immediate  one,  nor  can  we  con- 
sider the  production  of  heat  in  the  living  body  as  a  result  of  simple 
oxidation.  We  have  already  seen  in  the  preceding  chapter  that  the 
formation  of  carbonic  acid  is  not  due  to  direct  oxidation,  since  it  will 
go  on  in  the  tissues  without  the  immediate  presence  of  oxygen.  Re- 
spiration is  essential  to  all  the  phenomena  of  animal  life,  and  may  be 
taken  as  the  criterion  of  vital  activity  in  general.  The  production  of 
heat  is  one  of  these  phenomena,  and,  like  the  rest,  increases  or  dimin- 
ishes in  intensity  with  that  of  respiration ;  but  it  cannot  be  said  to 
depend  upon  respiration  in  any  peculiar  or  exclusive  manner. 

The  Evolution  of  Heat  and  the  Products  of  Eespiration  not  strictly 
proportional.  —  Furthermore,  notwithstanding  the  general  relation  in 
activity  between  the  two  functions,  if  an  accurate  comparison  be  made 
between  the  quantity  of  heat  produced,  under  different  circumstances, 
and  that  of  oxygen  absorbed  or  of  carbonic  acid  exhaled,  they  are 
found  not  to  correspond  exactly  with  each  other.  In  the  experiments 
of  Senator  on  the  bodily  temperature  in  dogs,  it  was  shown  that  the 
evolution  of  heat  and  the  production  of  carbonic  acid  do  not  follow  the 
same  rate  of  increase.  They  are  both  augmented  during  digestion,  but 
the  production  of  carbonic  acid  never  in  the  same  degree  with  that  of 
heat.  An  examination  of  the  averages  obtained  in  three  series  of  obser- 
tions  gives  the  following  result : 


„      XT     ,  (  Fasting     . 
Dog  No.  1  {  In  d]gestioi 


QUANTITIES  OF  HEAT  AND  OF  CARBONIC  ACID  PRODUCED  BY  THE  DOG  IN  ONE  HOUR. 

Condition  Carbonic  acid  in  Proportion 

of  the  animal.  grammes.  Heat  units.  between  the  two. 

.     .     3.455  12.630  1  to  3.65 

ion  .     .     .     5.013  18.875  1  to  3.76 

( Fasting     ....    4405  16.500  1  to  3.72 

Dog  No.  2  j  In  digestion  m     t     m    4837  19  390  1  to  4.01 

f  Fasting     ....     3.154  16.880  1  to  5.35 

Dog  No.  3 1  In  digestion       ,     m    3,846  21.960  1  to  5.71 

Thus  the  proportion  of  carbonic  acid  formed  to  the  heat  produced  is 
different  in  the  three  animals  when  compared  with  each  other  in  the 
same  condition ;  and  it  also  varies  in  each  animal  under  the  different 
conditions  of  fasting  and  digestion. 

In  the  experiments  of  the  same  observer  on  the  effect  exerted  by  arti- 
ficial cooling  on  the  animal  body,  he  found  that  under  the  influence  of  a 
low  temperature  the  actual  production  of  heat  in  dogs  was  never  in- 
creased, but  was  usually  perceptibly  diminished;  while  that  of  carbonic 
acid  was  generally  somewhat  increased  and  never  diminished. 


MODE    OF    PRODUCTION    OF    ANIMAL    HEAT.  307 

It  is  evident,  accordingly,  that  the  evolution  of  heat  in  the  living 
animal  is  due  to  other  causes  than  those  which  result  in  the  immediate 
production  of  carbonic  acid.  Even  outside  the  body  a  notable  elevation 
of  temperature  may  be  produced  by  the  hydration  of  quicklime,  the 
mixture  of  alcohol  and  water,  or  of  sulphuric  acid  and  water,  as  well 
as  other  chemical  or  physical  actions  in  which  direct  oxidation  does  not 
take  part.  Many  analogous  changes  may  take  place  in  the  process  of 
internal  nutrition,  from  which  a  part,  at  least,  of  the  animal  heat  origin- 
ates in  the  living  body. 

Local  Production  of  Heat  in  the  Organs  and  Tissues — Although 
the  living  body,  as  a  whole,  presents  a  certain  standard  temperature, 
the  production  of  heat  takes  place  separately  in  each  organ  and  tissue 
by  the  changes  of  nutrition  which  go  on  in  its  substance.  This  is 
shown  by  the  fact  that  each  separate  organ  has  a  special  temperature 
of  its  own,  which  increases  or  diminishes  according  to  its  condition  of 
activity  or  repose.  A  very  considerable  quantity  of  heat  is  thus  pro- 
duced in  the  substance  of  the  muscles.  The  experiments  of  Becquerel 
and  Breschet  on  the  brachialis,  in  man,  showed  the  temperature  of  this 
muscle  in  repose  to  be  36.5°  ;  while,  after  repeated  and  energetic  flexion, 
it  was  from  37°  to  37.5°.  Bernard,1  by  placing  thermo-electric  needles 
in  the  two  gastrocnemii  muscles  of  the  dog,  after  section  of  the  spinal 
cord  to  prevent  voluntary  movements,  found  the  temperature  of  the 
muscles  on  the  two  sides  to  be  sensibly  equal ;  but  on  producing  con- 
traction by  galvanizing  one  of  the  sciatic  nerves,  the  temperature  of 
the  muscle  on  that  side  rose  from  0.1°  to  0.2°,  at  the  same  time  that 
the  venous  blood  of  the  muscle  became  darker  in  hue.  Since  the 
muscles  constitute  so  large  a  part  of  the  mass  of  the  body,  it  is  easy  to 
understand  how  continuous  muscular  exertion  should,  after  a  time, 
produce  a  general  elevation  of  temperature.  In  the  muscles,  during 
contraction,  the  increase  in  warmth  is  always  accompanied  by  a  greater 
consumption  of  oxygen,  and  consequently  by  a  darker  color  of  the 
venous  blood. 

Heat  is  also  produced  in  the  glandular  organs  when  in  active  secre- 
tion, as  shown  by  comparing  the  temperature  of  the  arterial  blood  enter- 
ing with  that  of  the  venous  blood  leaving  the  glandular  tissue.  Under 
these  circumstances  the  venous  blood  coming  from  the  gland  is  warmer 
than  the  arterial  blood  with  which  it  is  supplied.  According  to  the 
observations  of  Bernard  upon  the  submaxillary  gland  of  the  dog,  while 
the  gland  is  in  repose,  the  circulation  through  its  tissue  is  slow,  its 
venous  blood  scanty  and  very  dark-colored,  and  the  oxygen  of  the  arte- 
rial blood  is  reduced,  in  traversing  the  organ,  to  40  per  cent,  of  its 
original  quantity  ;  but  when  the  gland  is  excited  to  active  secretion,  its 
circulation  is  increased  in  rapidity,  its  venous  blood  is  more  abundant 
and  of  a  brighter  color,  its  oxygen  being  only  reduced  to  61  per  cent, 
of  that  contained  in  the  arteries.  At  the  same  time  its  temperature 

1  Revue  Scientifique.     Paris,  1871,  No.  I.,  p.  1064. 


308 


ANIMAL    HEAT. 


rises,  notwithstanding  the  consumption  of  oxy gen  is  less  than  in  the 
condition  of  glandular  repose. 

A  similar  elevation  of  temperature  is  shown  by  the  blood  while  tra- 
versing the  capillary  circulation  of  the  intestine  and  of  the  liver.  The 
following  tables  give  the  results  of  two  series  of  observations  by  Ber-, 
nard  on  the  temperature  of  the  blood  entering  and  leaving  these  two 
organs  in  the  dog: 

TEMPERATURE  OF  THE  BLOOD  IN  THE 
Aorta.  Portal  Vein. 

36.8°  38.8° 

40.3°  40.7° 

39.40  39.5° 

Portal  Vein.  Hepatic  Vein. 
40.2°  40.6° 

40.6°  40.9° 

40.7°  40.9° 

Thus  the  blood  of  the  hepatic  vein,  after  traversing  two  successive 
capillary  circulations,  is  warmer  than  that  drawn  from  any  other  part 
of  the  body. 

Even  in  the  kidneys,  when  the  secretion  of  urine  is  actively  going  on, 
there  is  a  rise  of  temperature  in  the  blood  of  the  renal  veins.  At  the 
same  time,  as  in  the  submaxillary  glands,  the  circulation  is  increased  in 
activitjr,  the  venous  blood  leaves  the  organ  of  a  bright  red  color,  and  its 
proportion  of  oxygen,  according  to  Bernard,  is  only  reduced  to  88  per 
cent,  of  that  contained  in  the  arteries,  while  in  the  condition  of  glandular 
repose  it  is  reduced  to  33  per  cent. 

The  production  of  heat,  therefore,  is  accomplished  in  the  different 
organs  of  the  body  with  different  degrees  of  intensity  according  to  the 
special  nature  of  the  act  of  nutrition  in  each  one.  In  the  muscles  it  is 
accompanied  by  an  increased  consumption  of  oxygen  and  a  deeper 
coloration  of  the  venous  blood ;  in  the  salivary  glands  and  the  kidneys 
by  a  diminished  consumption  of  oxygen  and  a  less  complete  change  in 
the  color  of  the  blood.  The  blood  coming  from  each  organ  has  a  higher 
temperature  in  proportion  to  the  activity  of  heat-production  in  the 
organ  itself;  and  thus  the  temperature  of  the  venous  blood  varies  in 
different  parts  of  the  circulatory  system,  while  that  of  the  arterial  blood 
is  everywhere  sensibly  the  same. 

Cooling  of  the  Blood  in  its  Passage  through  the  Lungs  and  Skin. — 
While  in  the  other  internal  organs  the  blood  is  warmed  during  its  pass- 
age through  the  capillary  vessels,  in  the  lungs  its  temperature  is  slightly 
diminished.  This  fact,  which  has  been  alternately  asserted  and  denied, 
owing  to  the  difficulties  of  exact  observation  without  introducing  other 
causes  of  a  change  of  temperature,  has  been  abundantly  confirmed  by  the 
more  recent  observations  of  Bering,  Bernard,  Heidenhain  and  Korner, 
and  Strieker  and  Albert.  That  of  Hering  was  made  upon  a  young  calf, 
otherwise  in  good  condition,  but  presenting  the  malformation  of  ectopia 


MODE    OF    PRODUCTION    OF    ANIMAL    HEAT.  309 

eorclis,  by  which  the  heart  was  withdrawn  from  the  immediate  contact 
of  other  organs,  and  in  which  case  the  blood  of  the  right  ventricle  had 
a  temperature  of  39.37°,  that  of  the  left  ventricle  38.75°.  Heidenhain 
and  Korner,1  in  94  observations  on  the  dog,  partly  with  the  use  of  thermo- 
electric needles  and  partly  with  the  mercurial  thermometer,  found  the 
temperature  of  the  blood  on  the  two  sides  of  the  heart  equal  in  only 
one  instance.  In  all  the  others,  it  was  higher  on  the  right  side  than  on 
the  left,  by  0.1°  to  0.6°.  Bernard,2  who  first  demonstrated  this  differ- 
ence by  the  mercurial  thermometer,  has  shown  it  also  by  the  use  of 
thermo-electric  needles,  introduced  into  the  right  and  left  ventricles  of 
the  dog's  heart,  through  the  jugular  vein  and  carotid  artery  respectively  ; 
always  finding  the  blood  in  the  right  ventricle  warmer  than  that  in  the 
left.  According  to  these  observations,  the  difference  in  temperature  may 
amount  in  the  fasting  animal  to  0.174°,  during  digestion  to  0.232°. 
Although  during  digestion  the  temperature  of  the  blood  generally  is 
higher  than  in  the  fasting  condition,  the  difference  between  the  two 
sides  of  the  heart  continues  to  show  itself  in  the  same  direction. 

The  diminution  in  temperature  of  the  blood  while  passing  through  the 
lungs  is  usually  attributed  to  the  physical  influence  of  the  cooler  air  in 
the  pulmonary  cavities  and  to  that  of  the  vaporization  of  watery  fluid. 
As  the  air  expelled  by  respiration  is  warmer  than  when  introduced  into 
the  lungs,  it  must  withdraw  a  certain  amount  of  heat  from  the  internal 
parts ;  and  as  it  contains,  furthermore,  watery  vapor  disengaged  from  the 
lungs,  the  vaporization  of  this  fluid  must  also  reduce  the  temperature  of 
the  respiratory  organs.  Whether  the  cooling  influence  of  these  causes 
is  more  or  less  than  sufficient  to  account  fully  for  the  difference  in  the 
blood  on  the  two  sides  of  the  heart  has  not  been  determined.  It  is  pos- 
sible that  heat  is  also  produced  in  the  lungs,  as  in  the  other  internal 
organs ;  but  that  the  wrhole  of  it,  and  a  little  more,  is  consumed  by  the 
influence  of  the  air  upon  the  pulmonary  membrane.  It  is  evident,  how- 
ever, that  physical  conditions  exist  in  the  lungs  which  must  cause  the 
disappearance  of  more  or  less  sensible  heat ;  and  it  is  certain  that  the 
blood,  in  point  of  fact,  diminishes  slightly  in  temperature  while  passing 
through  the  pulmonary  circulation. 

In  the  cutaneous  circulation  the  same  physical  causes  exist  for  a  cool- 
ing effect  on  the  blood  as  in  the  lungs ;  namely,  the  contact  of  the  skin 
with  the  cooler  air,  and  the  vaporization  of  the  watery  fluid  supplied  by 
perspiration.  It  is  for  this  reason,  as  already  mentioned,  that  the  super- 
ficial parts  of  the  body  have  a  normal  temperature  somewhat  below  that 
of  the  interior ;  and  accordingly  the  blood,  after  passing  through  the 
vessels  of  the  integument,  returns  to  the  centre  with  its  temperature 
slightly  diminished.  There  is  every  reason  to  believe  that  the  tissues 
of  the  skin  and  subjacent  parts  evolve  a  certain  amount  of  heat  by  their 
own  nutritive  changes  ;  but  the  heat  thus  produced,  as  in  the  case  of  the 

1  Archiv  fur  die  Gesammte  Physiologie.   Bonn,  1871,  Band  iv.  p.  558. 

2  Eevue  Scientifique.     Paris,  1871,  No.  1,  p.  946. 


310  ANIMAL    HEAT. 

lungs,  being  rather  more  than  counterbalanced  by  that  lost  from  the 
surface,  the  total  effect  upon  the  circulating  fluid  is  a  lowering  of  its 
temperature.  The  amount  of  warmth  thus  lost  will  vary  with  the  degree 
of  external  cold  and  other  conditions  of  the  atmosphere  which  influence 
the  rapidity  of  the  abstraction  of  heat. 

Local  Elevation  of  Temperature  by  increased  Circulation. — If  the 
circulation  be  increased  in  any  part  of  the  external  integument,  the 
immediate  effect  produced  is  a  local  rise  of  temperature.  This  was  first 
shown  by  Bernard  in  his  experiments  upon  division  of  the  sympathetic 
nerve  on  one  side  of  the  neck.  If  this  operation  be  performed  upon  the 
rabbit,  the  consequence  is  a  relaxation  of  the  bloodvessels  in  the  cor- 
responding side  of  the  head,  an  increased  vascularity  of  the  parts,  most 
readily  seen  in  the  semi-transparent  tissues  of  the  ear,  and  a  higher 
temperature,  readily  perceptible  both  by  the  touch  and  the  thermometer. 
In  a  rabbit,  after  section  of  the  sympathetic  nerve  upon  the  right  side 
of  the  neck,  the  temperature  of  the  corresponding  ear,  as  indicated  by 
the  thermometer,  was  increased  from  25°  to  32°;  and  the  difference 
between  the  two  sides  is  usually  more  marked  as  the  external  air  is 
colder.  Since  the  superficial  parts  of  the  body  are  habitually  cooler 
than  the  internal  on  account  of  their  exposure  to  the  air,  and  as  they 
are  constantly  supplied  with  warm  blood  from  the  interior,  their  actual 
temperature  will  be  increased  in  proportion  to  the  amount  of  blood  cir- 
culating through  their  vessels.  The  local  rise  of  temperature  in  these 
instances  is  a  passive  one,  the  exposed  tissues  being  warmed  at  the 
expense  of  the  blood  coming  from  the  internal  organs.  No  more  heat 
is  actually  produced  in  the  body  than  usual,  and  the  cooling  effect  of  the 
air  upon  the  whole  system  is  unchanged ;  but  it  is  less  perceptible  in 
the  part  subjected  to  experiment,  because  it  receives  a  larger  quantity 
of  heat  from  the  interior  owing  to  the  increased  volume  of  blood  passing 
through  it  in  a  given  time. 

This  influence  of  the  circulation  upon  the  temperature  of  the  external 
parts  has  been  shown  by  Dr.  Wier  Mitchell1  by  observations  upon  the 
human  subject.  If  the  hand  and  arm  be  held  for  some  moments  above 
the  head,  emptied  as  fully  as  possible  of  blood,  and  a  tourniquet  then 
applied  to  the  arm  in  such  a  way  as  to  check  the  circulation,  the  tem- 
perature of  the  hand  falls  0.55°.  If,  on  the  contrary,  the  circulation  be 
left  unimpeded,  and  a  freezing  mixture  applied  to  the  elbow,  sufficient 
to  chill  the  ulnar  nerve,  when  sensation  has  become  entirely  abolished 
the  temperature  of  the  corresponding  hand  rises  from  1.10°  to  2.20°. 
But  if  the  arm  be  first  emptied  of  blood  as  before,  the  tourniquet  applied, 
and  the  ulnar  nerve  then  chilled  to  insensibility,  the  temperature  of  the 
hand  no  longer  rises,  but  falls,  as  in  the  former  experiment,  0.55°. 

In  the  internal  or  glandular  organs,  on  the  other  hand,  when  ex- 
cited to  functional  activity,  the  rise  of  temperature  is  an  active  one, 
taking  place  in  the  substance  of  the  gland  itself;  since  the  blood 

1  Archives  of  Scientific  and  Practical  Medicine.     New  York,  1873,  vol.  i.  p.  354. 


REGULATION    OF    THE    ANIMAL    TEMPERATURE.        311 

passing  through  these  organs  becomes  warmer  instead  of  cooler,  and 
receives  heat  from  the  changes  taking  place  in  the  glandular  tissue. 

Equalization  of  Temperature  by  the  Circulation. — As  the  production 
of  heat  is  a  local  process  in  each  separate  organ  or  tissue,  varying  in 
intensity  with  the  nature  of  the  nutritive  changes  in  different  parts,  the 
blood,  as  we  have  seen,  acquires  a  higher  temperature  in  some  organs 
than  in  others ;  and  in  the  lungs  and  skin  its  heat  actually  diminishes 
instead  of  increasing.  If  it  remained  at  rest,  these  differences  of  tem- 
perature would  no  doubt  be  more  marked  than  they  are  at  present.  But 
as  the  blood  is  in  constant  motion,  passing  from  the  circumference  to 
the  centre,  and  being  again  distributed  from  the  centre  to  the  circum- 
ference, the  effect  of  this  movement  of  circulation  is  to  equalize  to  a 
considerable  degree  the  temperature  of  different  parts  of  the  body.  The 
venous  blood  coming  from  the  general  integument  with  a  diminished 
temperature  is  mingled  with  that  of  the  muscular  system,  which  has 
become  warmed  during  its  capillary  circulation.  The  blood  of  the 
hepatic  veins,  which  is  the  warmest  of  all,  joins  the  current  of  the  inferior 
vena  cava,  returning  from  the  pelvic  organs  and  the  inferior  extremities. 
This  is  again  mingled,  at  its  entrance  into  the  right  cavities  of  the  heart, 
with  the  slightly  cooler  column  of  blood  descending  from  the  head  and 
upper  extremities  by  the  superior  vena  cava.  The  whole  volume  of  the 
blood  then  passes  through  the  lungs,  with  the  effect  of  still  further 
moderating  its  temperature  ;  and  the  arterial  blood  is  then  distributed 
to  the  various  parts  of  the  body,  to  gain  warmth  in  some  of  them  and  to 
lose  it  in  others,  and  again  mingled  after  a  few  seconds  at  the  centre 
of  the  circulation.  Thus  the  superabundant  heat  of  certain  organs, 
where  its  production  is  most  active,  is  constantly  transferred  to  others 
by  the  moving  column  of  the  blood  ;  and  a  certain  equilibrium  or  standard 
of  temperature  is  thus  established  for  the  body  as  a  whole.  It  is  found, 
by  the  observations  of  Jurgensen,  that  this  standard  temperature  for 
the  human  body,  as  measured  in  the  rectum,  varies  within  very  narrow 
limits,  from  day  to  night,  and  even  at  successive  periods  of  each  division 
of  the  twenty-four  hours.  These  normal  fluctuations  are  no  doubt  owing 
to  the  greater  or  less  activity,  at  different  times,  of  different  internal 
organs ;  the  total  amount  of  heat  produced  being  increased  or  dimin- 
ished with  the  preponderating  influence  of  organs  in  which  it  is  more  or 
less  rapidly  generated. 

Regulation  of  the  Animal  Temperature. 

A  certain  temperature  is  .not  only  the  result  of  the  vital  actions;  it  is 
also  necessary  to  their  accomplishment.  Even  in  the  vegetable  king- 
dom this  temperature,  which  varies  within  moderate  limits  in  different 
kinds  of  plants,  is  requisite  for  all  the  phenomena  of  growth  and  vitality. 
A  seed  sown  in  the  most  productive  soil  does  not  germinate  until  it 
feels  the  influence  of  the  necessary  warmth ;  and  its  germination  is  also 
impossible  if  it  be  exposed  to  a  heat  which  is  too  intense.  The  degrees 
both  of  heat  and  cold  which  favor  or  arrest  the  functions  of  vegetation 


312  ANIMAL    HEAT. 

have  been  in  many  instances  accurately  determined.  According  to  the 
experiments  of  Sachs,  the  limits  of  germination  for  wheat  and  barley 
are  between  5°  and  38°,  and  for  Indian  corn  between  9°  and  42°.  The 
irritability  and  periodic  movements  of  the  sensitive-plant  do  not  show 
themselves  unless  the  temperature  of  the  surrounding  air  be  above  15°. 
In  air  at  48°  to  50°,  on  the  other  hand,  the  leaflets  become  rigid  in  a 
few  moments,  though  they  may  afterward  recover  if  the  temperature  be 
moderated;  while  a  heat  of  52°  permanently  destroys  their  vitality. 
Thus  no  vegetative  function  can  come  into  activity,  unless  the  tempera-, 
ture  of  the  plant  reaches  a  certain  degree  above  the  freezing  point ;  and 
it  ceases,  furthermore,  if  the  temperature  rise  above  another  determinate 
degree,  which  cannot  for  any  considerable  time  exceed  50°.  Within 
these  two  limits,  also,  every  vegetable  function  has  a  special  tempera- 
ture at  which  it  is  most  active;  diminishing  in  intensity  both  above 
and  below  this  point. 

Observation  shows  that  the  same  is  true  of  the  animal  functions. 
Each  species  of  animal  has  a  definite  bodily  temperature,  and  this  tem- 
perature cannot  be  raised  or  lowered  beyond  certain  limits  without 
arresting  the  phenomena  of  life.  Mammalians,  whose  normal  tempera- 
ture is  from  37°  to  40°,  become  insensible  and  soon  die,  when  cooled 
down  to  18°  or  20°,  which  is  the  natural  standard  for  reptiles  and  fish; 
while  a  frog  is  soon  killed  by  being  kept  in  water  at  38°.  On  the  other 
hand,  mammalians  die  when  their  blood  and  internal  organs  are  heated 
up  to  45°,  which  is  precisely  the  normal  temperature  of  birds;  and 
birds  themselves  are  fatally  affected  when  their  internal  temperature  is 
raised  to  48°  or  50°.  In  every  case  the  vital  functions  are  seriously 
disturbed  by  a  very  moderate  change  in  the  actual  temperature  of  the 
bodily  organs ;  and  in  the  mammalians,  as  a  general  rule,  death  follows 
when  this  change  amounts  to  an  elevation  of  6°  or  7°,  or  to  a  depres- 
sion of  20°. 

In  the  human  subject,  in  febrile  affections,  the  rise  of  temperature,  as 
measured  in  the  axilla,  yields  a  very  accurate  criterion  of  the  gravity  of 
the  disease.  An  increase  of  this  temperature  from  36.6°  to  37.5°  or  38° 
indicates  a  mild  form  of  the  malady;  but  an  increase  to  40°  or  40.5° 
shows  that  the  attack  is  severe.  Above  40.5°  it  is  a  symptom  of  great 
danger;  and  when  the  temperature  rises  to  42.5°  or  43°  a  fatal  result  is 
almost  inevitable.1 

Effects  of  Lowering  the  Temperature  of  the  Animal  Body. — If  a 
warm-blooded  animal  be  exposed  to  cold  in  such  a  way  as  to  abstract 
the  internal  heat  faster  than  it  can  be  produced,  the  effect  is  a  general 
and  continuous  depression  of  the  vital  functions.  After  a  short  period 
of  pain  in  the  more  exposed  and  sensitive  parts,  the  skin  becomes 
insensible,  the  muscles  lose  their  contractile  energy,  the  movements  of 
respiration  diminish  in  frequency,  and  the  nervous  system  becomes  more 
and  more  inactive.  In  the  human  subject  a  marked  sluggishness  of 

1  Flint,  Principles  and  Practice  of  Medicine.     Philadelphia,  1868,  p.  109. 


REGULATION  OF  THE  ANIMAL  TEMPERATURE.   313 

mind  and  a  disposition  to  sleep  have  been  observed  as  among  the  symp- 
toms of  long  continued  and  dangerous  exposure  to  unusually  low  tem- 
peratures. 

The  local  effects  of  cold  upon  the  nervous  tissues  in  man  have  been 
shown  by  the  experiments  of  Dr.  Weir  Mitchell,1  in  chilling  the  ulnar 
nerve  at  the  elbow  by  the  application  of  a  freezing  mixture.  This  at 
first  produces  pain  in  the  hand,  subsequently  followed  by  loss  of  sensi- 
bility and  motive  power  in  the  parts  corresponding  with  the  distribu- 
tion of  the  nerve. 

The  general  effects  of  a  lowered  temperature  result  from  its  combined 
influence  upon  all  the  separate  organs  and  tissues.  According  to  the 
observations  of  Bernard,  if  the  body  of  a  rabbit  or  a  guinea-pig  be  sur- 
rounded by  snow  or  ice  so  as  to  prevent  spontaneous  motion  and  to 
cause  a  continuous  abstraction  of  heat,  the  temperature,  as  taken  in 
the  rectum,  gradually  falls  from  38°  to  30°,  25°,  20°,  and  18°.  When 
the  depression  of  the  bodily  temperature  has  reached  this  point,  the 
animal  is  insensible  and  paralyzed,  and  the  respiration  feeble  and  infre- 
quent. The  heat-producing  power  is  also  lost,  so  that  if  the  animal  be 
withdrawn  from  the  cooling  mixture  and  kept  in  the  air  at  10°  or  12°, 
the  temperature  of  the  body  continues  steadily  to  diminish,  and  death 
takes  place  after  a  short  time. 

But  when  in  this  condition  of  depression  and  insensibility,  although 
most  of  the  vital  actions  are  suspended,  and  the  animal  has  lost  the 
power  of  maintaining  his  own  temperature,  if  he  be  supplied  with  arti- 
ficial warmth  up  to  a  certain  point,  he  may  regain  his  vitality,  and  the 
processes  of  life  be  again  put  in  operation.  The  respiration,  which 
was  reduced  to  a  minimum  by  the  continued  action  of  cold,  becomes 
increased  in  rapidity  as  the  body  is  artificially  warmed,  and  the  func- 
tions of  the  nervous  and  muscular  systems  are  also  finally  restored. 

A  striking  example  of  the  temporary  suspension  of  the  bodily  func- 
tions by  cold  is  presented  by  the  hibernating  animals,  as  marmots  and 
some  species  of  squirrels,  which  pass  into  a  condition  of  torpor  during 
the  winter,  becoming  insensible,  unconscious,  and  immovable,  while 
at  the  same  time  respiration  is  nearly  imperceptible,  and  the  bodily 
temperature  sinks  to  10°,  8°,  or  even  2°.  Life,  however,  is  not  abol- 
ished but  only  held  in  abeyance ;  and  with  the  return  of  spring  all  the 
functions  resume  their  activity.  A  hibernating  animal  is  accordingly 
somewhat  in  the  condition  of  a  seed,  which  remains  in  the  ground  over 
winter,  with  its  vitality  dormant,  but  ready  to  come  into  action  when 
supplied  with  the  requisite  degree  of  warmth. 

Effects  of  Elevating  the  Temperature  of  the  Animal  Body. — If  the 
temperature  of  the  body,  in  a  living  animal,  be  artificially  raised  some 
degrees  above  the  normal  standard,  the  effects  are  quite  different  from 
those  produced  by  cold.  In  the  experiments  of  Bernard,  the  animals, 
both  birds  and  mammalians,  were  inclosed  in  a  cage  with  heated  air ; 

1  Injuries  of  Nerves  and  their  Consequences.     Philadelphia,  1872,  p.  59. 
21 


314  ANIMAL    HEAT. 

the  air  being  sometimes  dry  and  sometimes  loaded  with  moisture,  but 
renewed  by  due  ventilation.  The  primary  effects  were  increased  fre- 
quencjr  of  respiration  and  an  appearance  of  discomfort  and  agitation ; 
and  finally  death  took  place  usually  with  convulsive  movements,  some- 
times accompanied  by  an  audible  cry.  The  fatal  result  was  more  rapidly 
produced  in  birds  than  in  mammalia.  Thus,  a  rabbit  placed  in  the  cage 
with  dry  air  at  65°,  died  in  twenty  minutes;  and  a  bird,  in  air  at  the 
same  temperature,  died  in  four  minutes.  This  difference  is  no  doubt 
partly  due  to  the  greater  activity  of  the  circulation  in  birds,  by  which 
external  heat  is  more  rapidly  transferred  to  the  internal  organs ;  since 
the  same  observer  found  that  of  two  rabbits,  one  living  and  one  dead, 
placed  in  the  warm  cage  at  100°,  the  internal  temperature  of  the  living 
animal  became  sensibly  raised  sooner  than  that  of  the  dead  one.  In  a 
medium  of  high  temperature,  therefore,  a  fatal  amount  of  heat  reaches 
the  internal  organs  more  rapidly  by  means  of  the  circulation  than  by 
simple  conduction  through  the  solid  tissues. 

After  death  from  exposure  to  too  warm  an  atmosphere,  the  internal 
temperature  is  found  to  be  5°  or  6°  above  the  normal  standard;  the 
heart  is  motionless ;  both  the  muscles  and  the  nerves  are  insensible  to 
the  stimulus  of  galvanism ;  and  lastly,  cadaveric  rigidity  is  established 
with  unusual  promptitude.  In  many  instances  the  blood  is  found  dark- 
colored  in  the  arterial  as  well  as  in  the  venous  system ;  but  this  is  a 
post-mortem  change,  since  observation  shows  that  the  arterial  blood 
continues  red  so  long  as  life  lasts,  while  its  oxygen  disappears  and  its 
color  darkens  with  great  rapidity  after  the  stoppage  of  respiration.  The 
appearances  indicate  that  an  unnaturally  high  temperature  produces 
death  by  hastening,  in  an  undue  degree,  the  chemical  changes  taking 
place  in  the  tissues  and  fluids,  in  such  a  manner  that  their  vitality  is 
rapidly  exhausted  and  can  no  longer  be  maintained  by  the  usual  pro- 
cesses of  nutrition. 

Resistance  of  the  Living  Body  to  Low  External  Temperature. — Since 
an  actual  depression  of  the  temperature  of  the  body  is  followed  by  such 
serious  results,  and  as,  in  point  of  fact,  its  temperature  is  maintained  in 
health  at  the  normal  standard,  notwithstanding  exposure  to  varying 
degrees  of  cold,  it  is  evident  that  the  living  organism  possesses  the 
power  of  increased  production  of  internal  heat,  to  compensate  for  the 
greater  loss  without.  In  the  experiments  of  Senator  on  the  abstraction 
of  warmth,  by  confining  dogs  in  close  cages  surrounded  by  a  cold  me- 
dium, it  was  found  that  the  total  amount  of  heat  produced  by  the  ani- 
mal was  not  increased.  But  in  these  cases  the  animals  were  placed 
under  conditions  by  which  their  natural  movements  were  prevented, 
and  the  results  obtained  were  due  to  simple  cooling  of  the  body,  with- 
out the  action  of  compensating  causes.  In  the  natural,  unconfined  con- 
dition, the  effect  is  different.  It  is  a  matter  of  common  observation, 
that  the  influence  of  moderate  external  cold,  if  not  too  long  continued, 
produces  a  sense  of  warmth  and  increased  vigor,  instead  of  depression. 
The  atmosphere  of  a  winter's  day,  or  a  cold  shower  bath,  acts  as  a 


REGULATION  OF  THE  ANIMAL  TEMPERATURE.   815 

stimulant  to  vital  processes ;  and,  even  although  the  exposed  parts  of 
the  skin  may  be  reduced  considerably  below  their  normal  temperature, 
the  body,  as  a  whole,  does  not  experience  a  loss  of  warmth,  but  main- 
tains its  natural  condition  of  vitality.  It  is  certain  that  under  these 
circumstances  more  heat  than  usual  must  be  produced  from  the  influ- 
ence of  external  cold. 

The  mode  in  which  this  result  is  accomplished  has  not  been  deter- 
mined with  precision  by  experimental  means.  It  is  plain  that  the 
nervous  system  has  its  share  in  the  mechanism  of  the  process,  perhaps 
by  directly  stimulating  the  molecular  changes  which  produce  the  evolu- 
tion of  animal  heat.  There  are,  however,  two  sources  of  heat  supply, 
which  evidently  play  an  important  part  in  maintaining  the  temperature 
of  the  body  when  exposed  to  cold. 

The  first  of  these  is  muscular  activity.  It  has  been  shown  that  the 
muscles  produce  a  considerable  quantity  of  heat  in  their  own  tissue,  and 
that  this  quantity  is  increased  by  the  contraction  of  the  muscular  fibres. 
The  total  production  of  heat,  therefore,  for  the  whole  body,  must  be 
considerably  augmented  when  all  the  voluntary  muscles  are  thrown  into 
a  condition  of  unusual  functional  activity.  Experience  shows  that  this 
is,  in  fact,  one  of  the  requisite  conditions  of  resistance  to  cold.  The 
stimulus  of  the  cool  air  upon  the  skin  excites  the  desire  for  active  move- 
ment, and  muscular  exercise  produces  a  compensating  quantity  of 
internal  heat.  But  if  the  body  be  exposed  to  even  moderate  winter 
weather  without  voluntary  motion,  it  must  either  be  protected  by  an 
unusual  quantity  of  clothing,  or  it  will  soon  feel  the  depressing  effect 
of  a  loss  of  its  animal  heat. 

Secondly,  the  increased  production  of  warmth,  when  required,  is  pro- 
vided for  by  an  increased  supply  of  food.  The  materials  for  the  chemical 
changes  requisite  for  heat-production  are  supplied  directly  by  the  tissues 
or  the  blood,  but  primarily,  of  course,  from  the  ingredients  of  the  food. 
Even  a  recent  ingestion  of  food,  as  shown  in  the  experiments  of  Senator, 
increases  perceptibly  the  amount  of  heat  generated,  in  the  dog,  within 
a  given  time ;  and  for  longer  periods,  the  influence  of  an  ample  or  a 
scanty  supply  is  abundantly  manifest.  In  animals  which  are  scantily 
fed  or  ill  nourished,  the  capacity  for  resistance  to  cold  is  much  less  than 
in  those  which  are  in  good  condition  and  which  have  received  a  suffi- 
cient quantity  of  food.  The  immediate  effect  of  a  moderate  exposure 
to  cold  in  the  healthy  condition,  is  to  increase  the  appetite.  A  larger 
quantity  of  food  is  habitually  taken  during  the  winter  than  during  the 
summer  season;  and  among  the  inhabitants  of  northern  and  arctic 
regions,  the  daily  consumption  of  food  is  much  greater  than  in  the 
temperate  and  tropical  climates. 

It  is  not  necessary  to  assume  that  the  food,  thus  required  for  main- 
taining a  greater  heat-production,  is  directly  employed  to  furnish  the 
necessary  warmth  by  its  consumption.  The  heat  is  no  doubt  generated 
from  the  activity  of  all  the  nutritive  changes  in  the  different  tissues  of 
the  body,  and  these  changes  are  enabled  to  continue  indefinitely  only  by 


316  ANIMAL    HEAT. 

a  supply  of  food  sufficiently  ample  to  provide  for  the  material  demands 
of  the  animal  system. 

Resistance  of  the  Living  Body  to  High  External  Temperature. — It 
has  been  seen  that,  in  the  human  subject  and  the  warm-blooded  animals 
generally,  an  actual  rise  in  the  bodily  temperature  of  6°  or  7°  is  certainly 
fatal ;  and  yet  the  body  may  be  exposed,  as  shown  by  repeated  observa- 
tions, to  much  higher  degrees  of  heat  without  any  injurious  result. 
According  to  Dr.  Carpenter,  the  temperature  of  the  air,  in  many  parts 
of  the  tropical  zone,  often  rises,  during  a  large  portion  of  the  year,  to 
43.3°,  and  in  some  regions  of  India  is  occasionally  above  50°;  while  it 
is  well  known  that  the  air  of  manufactory  dr3ring-rooms  and  of  the 
Turkish  bath  may  be  easily  endured  at  a  heat  of  considerably  more  than 
45°.  Either  of  these  temperatures  would  be  fatal  to  man,  if  they  indi- 
cated the  actual  warmth  of  the  internal  organs.  The  body  therefore 
must  either  possess  some  means  of  diminishing  its  own  production  of 
heat,  or  else  of  neutralizing,  to  a  certain  extent,  temperatures  which  are 
higher  than  that  of  the  normal  standard. 

The  most  direct  and  simplest  means  of  moderating  the  temperature 
of  the  body  is  that  by  the  cutaneous  perspiration.  This  fluid,  derived 
from  the  perspiratory  glands  of  the  skin,  is  a  clear,  colorless,  watery 
secretion,  with  a  distinctly  acid  reaction,  and  a  specific  gravity  of  1003 
or  1004.  Its  constitution  is  as  follows  : 

COMPOSITION  OF  THE  CUTANEOUS  PERSPIRATION. 

Water 

Sodium  chloride 

Potassium  chloride     ........ 

Sodium  and  potassium  sulphates          ..... 

Salts  of  organic  acids 

1000.00 

It  is  accordingly  a  fluid  of  very  simple  composition,  containing  more 
than  99^  per  cent,  of  water,  and  more  than  half  its  solid  ingredients 
consisting  of  the  inorganic  alkaline  chlorides.  There  are  also  present 
in  the  perspiration  traces  of  an  organic  substance  similar  to  albumen, 
and  a  free  volatile  acid,  which  gives  to  the  fluid  its  acid  reaction  and 
odor. 

The  perspiration  is  a  constant  secretion.  In  a  condition  of  repose  or 
of  moderate  bodily  activity,  it  is  exuded  in  so  gradual  a  manner  that  it 
is  at  once  carried  off  by  evaporation,  and  has  received  the  name,  under 
these  circumstances,  of  the  insensible  transpiration.  The  entire  quantity 
of  fluid  discharged  in  this  way,  according  to  the  observations  of  Lavoi- 
sier and  Seguin,  amounts  on  the  average  to  900  grammes  per  day.  In 
addition  to  this,  about  500  grammes  are  discharged  from  the  lungs, 
making  1400  grammes  of  daily  exhalation  from  the  whole  body.  The 
vaporization  of  this  quantity  of  water  will  consume  750  heat  units;  or 


REGULATION    OF    THE    ANIMAL    TEMPERATURE.       317 

about  one-fifth  of  all  the  heat  produced  in  the  body  during  twenty-four 
hours. 

The  cutaneous  secretion  may  be  greatly  increased  by  temporary  causes. 
An  elevated  temperature  or  unusual  muscular  exertion,  will  increase  the 
circulation  through  the  skin  and  largely  augment  the  amount  of  fluid 
discharged.  It  then  exudes  more  rapidly  than  it  can  be  carried  off  by 
evaporation,  and  collects  upon  the  skin  as  a  visible  moisture,  whence  it 
is  known  as  the  sensible  perspiration.  The  amount  of  perspiration  dis- 
charged during  violent  exercise  has  been  known  to  rise  as  high  as  350 
or  380  grammes  per  hour ;  and  Dr.  Southwood  Smith1  found  that  the 
laborers  employed  in  heated  gas-works  sometimes  lost,  by  both  cutane- 
ous and  pulmonary  exhalation,  nearly  1600  grammes  in  the  course  of  an 
hour.  The  evaporation  of  this  increased  quantity  of  fluid  consumes  a 
large  portion  of  the  caloric  derived  from  the  heated  atmosphere,  and 
thus  prevents  an  undue  rise  in  the  temperature  of  the  bodily  organs. 

It  is  possible  that  certain  influences  transmitted  through  the  nerves 
may  also  have  the  power  of  controlling  directly  the  molecular  activity 
of  the  tissues,  and  may  thus  diminish  the  amount  of  internal  heat  at 
the  source  of  its  production ;  but  the  experimental  evidence  of  this 
action  is  yet  incomplete,  and  its  mode  of  operation  comparatively 
obscure. 

The  production  of  heat  in  the  animal  body  and  the  regulation  of  its 
temperature,  by  which  it  is  maintained  at  or  near  a  normal  standard, 
are  two  of  the  most  important  phenomena  presented  by  the  living  organ- 
ism. They  are  the  result  of  an  associated  series  of  vital  actions,  and 
at  the  same  time  essential  conditions  for  the  continuance  of  life. 

1  Philosophy  of  Health.  London,  1838,  chap.  xiii. 


CHAPTER  XV. 

THE    CIRCULATION. 

THE  blood  is  a  nutritious  fluid,  holding  in  solution  the  ingredients 
necessary  for  the  formation  of  the  tissues.  In  all  the  higher  animals 
and  in  man,  the  structure  of  the  body  is  compound,  consisting  of  various 
organs,  with  widely  different  functions,  situated  in  different  parts  of  the 
frame.  In  the  intestine  the  process  of  digestion  is  accomplished,  and 
the  prepared  ingredients  of  the  food  are  thence  absorbed  into  the  blood- 
vessels, by  which  they  are  transported  to  distant  parts.  In  the  lungs 
the  blood  absorbs  oxygen,  which  is  afterward  appropriated  by  the 
tissues  ;  and  the  carbonic  acid  produced  in  the  tissues  is  finally  exhaled 
from  the  lungs.  In  the  liver,  the  kidneys,  and  the  skin,  other  substances 
are  produced  or  eliminated,  and  these  local  processes  are  all  necessary 
to  the  preservation  of  the  general  organization.  The  circulating  fluid 
is  therefore  a  means  of  transportation,  by  which  substances  produced  in 
particular  organs  are  dispersed  throughout  the  body,  or  by  which  sub- 
stances produced  in  the  tissues  generally  are  conveyed  to  particular 
organs,  in  order  to  be  eliminated. 

The  circulatory  apparatus  consists  of  four  different  parts,  namely,  1st. 
The  heart ;  a  hollow,  muscular  organ,  which  propels  the  blood.  2d.  The 
arteries  ;  a  series  of  branching  tubes,  which  convey  it  from  the  heart  to 
different  parts  of  the  body.  3d.  The  capillaries  ;  a  network  of  inoscu- 
lating tubules,  interwoven  with  the  substance  of  the  tissues,  which  bring 
the  blood  into  intimate  contact  with  their  component  parts ;  and  4th. 
The  veins ;  a  set  of  converging  vessels,  destined  to  collect  the  blood 
from  the  capillaries,  and  return  it  to  the  heart.  In  each  of  these  different 
parts  of  the  circulatory  apparatus,  the  movement  of  the  blood  is  peculiar 
and  dependent  on  special  conditions. 

The  Heart. 

The  structure  of  the  heart  and  of  the  adjacent  vessels  varies  in  dif- 
ferent classes  of  animals,  owing  to  the  different  arrangement  of  the 
respiratory  organs. 

In  man  and  the  mammalians  the  process  of  respiration  is  not  only 
much  more  active  than  in  cold-blooded  animals,  but  the  lungs  are  also 
the  only  special  organs  of  aeration.  The  whole  of  the  blood,  accord- 
ingly, after  returning  from  the  general  system,  passes  through  the 
lungs  before  it  is  again  distributed  to  the  system.  It  thus  traverses  in 
succession  the  general  circulation  for  the  whole  body,  and  the  special 
circulation  for  the  lungs.  The  mammalian  heart  (Fig.  99),  consists  of 
(318) 


THE    HEART. 


319 


Fig.  99. 


a  right  auricle  and  ventricle  (a,  6),  receiving  the  blood  from  the  vena 

cava  (i),  and  driving  it  to  the  lungs;  and  a  left  auricle  and  ventricle 

(/,  g)  receiving  the  blood  from 

the  lungs  and  propelling  it  out- 

ward  through   the  arterial  sys- 

tem. 

In  the  mammalian  heart,  the 
different  parts  of  the  organ  pre- 
sent certain  peculiarities  and  bear 
certain  relations  to  each  other, 
which  influence  its  action  and 
movements.  The  heart  itself  is 
suspended  somewhat  freely  in 
the  cavity  of  the  chest,  attached 
to  the  spinal  column  mainly  by 
the  great  bloodvessels  passing 
through  the  superior  and  pos- 
terior mediastinum.  It  is  of  a 
more  or  less  conical  form  ;  its  base, 
situated  upon  the  median  line, 

being  directed  upward  and  back- 

,,.,.,  .    ,      , 

Ward,  While  its  apex  points  down- 

ward,    forward,    and    to    the    left, 
,     ,    ,        ,,  .         ,. 

surrounded  by  the  pericardium, 

but  capable  of  a  certain  degree 

of  lateral  and  rotatory  motion.     The  auricles,  which  have  a  smaller 

capacity  and  thinner  walls  than  the  ventricles,  are  situated  at  the  upper 

and  posterior  part  of  the  organ  (Figs.  100  and  101);  while  the  ventri- 


CIRCULATION  IN  MAMMALIANS.—  a. 
Right  auricle.  b.  Right  ventricle,  c.  Pulmon- 
ary  artery,  d.  Lungs,  e.  Pulmonary  vein. 
/.  Left  auricle,  cr.  Left  ventricle,  h.  Aorta. 

<  Vena  cava> 


Fig.  100. 


Fig.  101. 


HUMAN  HEART,  anterior  view.— 
a.  Right  ventricle.  6.  Left  ventricle. 
c.  Right  auricle,  d.  Left  auricle,  e. 
Pulmonary  artery,  /.  Aorta. 


HUMAN  HEART,  posterior  view. — 
a.  Right  ventricle.  6.  Left  ventricle. 
c.  Right  auricle,  d.  Left  auricle. 


cles  occupy  its  anterior  and  lower  portions.     The  two  ventricles,  more- 
over, are  not  situated  on  the  same  plane.     The  right  ventricle  occupies 


320  THE    CIRCULATION. 

a  position  somewhat  in  front  and  above  that  of  the  left ;  so  that  in  an 
anterior  view  of  the  heart  the  greater  portion  of  the  left  ventricle  is  con- 
cealed by  the  right  (Fig.  100),  and  in  a  posterior  view  the  greater  por- 
tion of  the  right  ventricle  is  concealed  by  the  left  (Fig.  101) ;  while  in 
both  positions  the  apex  of  the  heart  is  constituted  altogether  by  the 
point  of  the  left  ventricle. 

The  different  cavities  of  the  heart  and  of  the  adjacent  bloodvessels  on 
each  side,  though  continuous  with  each  other,  are  partially  separated  by 
certain  constrictions.  The  orifices  by  which  they  communicate  are 
known  by  the  names  of  the  auricular,  auriculo-ventricular,  and  aortic 
and  pulmonary  orifices ;  the  auricular  orifices  being  the  passages  from 
the  venae  eavse  and  pulmonary  veins  into  the  right  and  left  auricles  ;  the 
auriculo-ventricular  orifices  leading  from  the  auricles  into  the  ventricles  ; 
and  the  aortic  and  pulmonary  orifices  leading  from  the  ventricles  into 
the  aorta  and  pulmonary  artery  respectively. 

The  auriculo-ventricular,  aortic,  and  pulmonary  orifices  are  furnished 
with  valves,  which  allow  the  blood  to  pass  readily  from  the  auricles  to 
the  ventricles,  and  from  the  ventricles  to  the  arteries,  but  shut  back  in 
such  a  manner  as  to  prevent  its  return  in  the  opposite  direction.  The 
course  of  the  blood  through  the  heart  is,  therefore,  as  follows  (Fig.  102) : 

Fig.  102. 


RIGHT  AURICLE  AND  VENTRICLE;  Auriculo-ventricular  Valves  open,  Arterial 

Valves  closed. 

From  the  vena  cava  it  passes  into  the  right  auricle ;  and  from  the  right 
auricle  into  the  right  ventricle.  On  the  contraction  of  the  right  ventri- 
cle, the  tricuspid  valves  shut  back,  preventing  its  return  into  the  auricle 
(Fig.  103) ;  and  it  is  thus  driven  through  the  pulmonary  artery  to  the 
lungs.  Returning  from  the  lungs,  it  enters  the  left  auricle,  thence 
passes  into  the  left  ventricle,  from  which  it  is  finally  delivered  into  the 
aorta,  and  distributed  throughout  the  body.  The  two  streams  of  blood, 


THE    HEART. 


321 


arterial  and  venous,  in  their  passage  through  the  heart,  follow  a  course 
which  is,  in  each  case,  curvilinear  and  more  or  less  spiral  in  direction ; 

Fig.  103. 


RIGHT  AURICLE  AND  VENTRICLE;  Auriculo-ventricular  Valves  closed,  Arterial 

Valves  open. 

the  axes  of  the  currents  crossing  each  other  in  the  right  and  left  cavi- 
ties of  the  organ  respectively  (Fig.  104).     The  venous  blood,  received 

Fig.  104. 


COURSE  OP  BLOOD  THROUGH  THE  HEAKT.  — a,  a.  Vena  cava,  superior  and  inferior. 
b.  Right  ventricle,    c.  Pulmonary  artery,    d.  Pulmonary  vein.    e.  Left  ventricle.   /.Aorta. 

by  the  right  auricle  from  the  two  venae  cavae,  passes  downward  and 
forward  from  the  auricle  into  the  ventricle.     In  the  body  of  the  right 


322  THE    CIRCULATION. 

ventricle  it  turns  upon  itself  and  then  follows  a  direction  from  below 
upward,  from  right  to  left  and  from  before  backward,  through  that  part 
of  the  right  ventricle  tying  in  front  of  the  heart  and  termed  the  "  conus 
arteriosus,"  to  the  commencement  of  the  pulmonary  artery.  On  return- 
ing from  the  lungs  to  the  left  auricle,  it  passes  from  above  downward 
into  the  cavity  of  the  left  ventricle,  when  it  makes  a  turn  like  that  upon 
the  right  side  and  is  directed  again  from  below  upward  and  from  left  to 
right,  behind  the  situation  of  the  conus  arteriosus,  and  crossing  it  at  an 
acute  angle,  to  the  commencement  of  the  aorta.  The  aorta  itself,  though 
its  point  of  origin  is  placed  somewhat  posteriorly  to  that  of  the  pulmo- 
nary artery,  soon  comes  more  to  the  front  in  its  arched  portion,  while 
the  pulmonary  artery  runs  almost  directly  backward.  Thus  the  two 
blood-currents  may  be  said  to  twist  spirally  round  each  other  in  their 
course  through  the  corresponding  auricles  and  ventricles. 

The  movement  of  the  blood  through  the  cardiac  cavities  is  not  a  con-    < 
tinuous  and  steady  flow,  but  is  accomplished  by  alternate  contractions   ' 
and  relaxations  of  the  muscular  walls  of  the  heart ;  by  which  successive 
portions  of  blood  are  delivered  from  the  auricles  into  the  ventricles,  and 
thence  discharged  into  the  arteries.     Each  one  of  these  successive  actions 
is  called  a  beat  or  pulsation  of  the  heart.     The  cardiac  pulsations  are 
accompanied  by  certain  physical  phenomena  dependent  upon  the  struc- 
ture of  the  heart  and  its  mode  of  action. 

Sourtds,  Movements,  and  Impulse  of  the  Heart. — The  sounds  of  the 
heart  are  two  in  number.  They  can  be  heard  by  applying  the  ear  over 
the  cardiac  region,  when  they  are  found  to  be  quite  different  from  each 
other  in  position,  tone,  and  duration.  They  are  distinguished  as  the 
first  and  second  sounds  of  the  heart.  The  first  sound  is  heard  with  the 
greatest  intensity  over  the  anterior  surface  of  the  heart,  and  particularly 
at  the  situation  of  the  apex  beat,  over  the  fifth  rib  and  the  fifth  inter- 
costal space.  It  is  comparatively  long,  dull,  and  smothered  in  tone, 
and  occupies  one-half  the  entire  duration  of  a  beat.  It  corresponds  in 
time  with  the  impulse  of  the  heart  in  the  precordial  region,  and  with  the 
stroke  of  the  large  arteries  in  the  immediate  vicinity  of  the  chest.  The 
second  sound  follows  almost  immediately  upon  the  first.  It  is  heard 
most  distinctly  at  the  situation  of  the  aortic  and  pulmonary  valves, 
namely,  over  the  sternum  at  the  level  of  the  third  costal  cartilage.  It 
is  short  and  distinct,  and  occupies  only  about  one-quarter  of  the  whole 
time  of  a  pulsation.  It  is  followed  by  an  equal  interval  of  silence ;  after 
which  the  first  sound  again  recurs.  The  whole  time  of  a  cardiac  pulsa- 
tion may  be  divided  into  four  quarters,  of  which  the  first  two  are  occu- 
pied by  the  first  sound,  the  third  by  the  second  sound,  and  the  fourth 
by  an  interval  of  silence,  as  follows : 

KELATIVE  TIME  AND  DURATION  OF  THE  HEART-SOUNDS. 

r  1st  quarter  ) 

I  2d        „       j  First  sound. 

Cardiac  pulsation  \  _ 

3d  Second  sound. 

1 4th       "          Interval  of  silence. 


THE    HEART.  323 

The  cause  of  the  second  sound  is  universally  admitted  to  be  the  sudden 
closure  and  tension  of  the  aortic  and  pulmonary  valves.  This  fact  is 
established  by  the  following  proofs :  1st.  The  sound  is  heard  with  per- 
fect distinctness,  as  mentioned  above,  directly  over  the  situation  of  these 
valves  at  the  base  of  the  heart ;  2d.  The  further  we  recede  in  any  direc- 
tion from  this  point,  the  fainter  becomes  the  sound ;  and  3d,  in  experi- 
ments upon  the  living  animal,  b}'  different  observers,  it  has  been  found 
that  if  a  curved  needle  be  introduced  into  the  base  of  the  large  vessels, 
so  as  to  hook  back  the  semilunar  valves,  the  second  sound  disappears, 
and  remains  absent  until  the  valve  is  again  liberated.  The  valves  con- 
sist of  fibrous  sheets,  covered  with  a  layer  of  endocardial  epithelium. 
They  have  the  form  of  semilunar  festoons,  the  free  edge  of  which  is 
directed  from  the  cavity  of  the  ventricle,  while  the  attached  edge  is 
fastened  to  the  inner  surface  of  the  base  of  the  artery.  While  the  blood 
is  passing  from  the  ventricle  to  the  artery,  the  valves  are  thrown  for- 
ward and  relaxed ;  but  when  the  artery  reacts  upon  its  contents  they 
shut  back,  and  their  fibres,  becoming  suddenly  tense,  yield  a  clear, 
characteristic,  snapping  sound.  The  character  of  this  valvular  sound 
may  be  closely  imitated  by  snapping  a  piece  of  tape  or  ribbon  (Fig.  105), 

Fig.  105. 


alternately  loosening  and  extending  it,  while  firmly  held  between  the 
fingers  of  the  two  hands.  A  short  piece  of  ribbon  by  this  sudden  tension 
will  give  out  a  sharp  and  distinct  sound ;  a  longer  one  will  yield  a  sound 
which  is  more  dull  and  prolonged. 

The  first  sound  of  the  heart  contains  two  elements,  which  are  mingled 
in  different  proportions  according  to  the  point  at  which  it  is  heard.  One 
of  these  elements  is  comparatively  dull  in  tone,  and  when  heard  over 
the  apex  or  front  of  the  heart  communicates  its  character  to  the  whole 
of  the  first  sound.  It  is  variously  attributed  to  the  muscular  contrac- 
tion of  the  cardiac  fibres  and  to  the  movement  of  the  surface  of  the 
heart  against  the  inner  walls  of  the  chest.  The  remaining  element  of 
the  first  sound  is  valvular  in  character,  and  is  caused  by  the  tension  of 
the  auriclo-ventricular  valves  at  the  time  of  the  ventricular  pulsation. 
It  gradually  predominates  over  the  other,  at  points  further  removed 
from  the  apex  of  the  heart,  toward  the  left  border  of  the  organ  and  the 


324  THE    CIRCULATION. 

left  nipple ;  and  still  further  to  the  left  it  is  heard  alone,  the  first  sound 
at  this  situation  being  purely  valvular,  like  the  second.1 

The  movements  of  the  heart  ma}'  be  observed  in  the  dog,  or  other 
warm-blooded  quadruped,  by  opening  the  cavity  of  the  chest  by  a  longi- 
tudinal incision  through  the  sternum,  and  separating  the  costal  cartilages, 
on  each  side,  at  their  junction  with  the  ribs;  artificial  respiration  being 
maintained  by  the  nozzle  of  a  bellows  inserted  in  the  trachea.  The 
animal  may  be  partially  narcotized  by  a  preliminary  subcutaneous  in- 
jection of  morphine,  after  which  complete  etherization  is  produced  and 
continued  with  great  facility.  The  operation  of  opening  the  chest  and 
exposing  the  thoracic  organs  increases  the  rapidity  of  the  heart's  move- 
ments and  diminishes  their  force ;  but  its  action  is  not  otherwise 
changed,  and  the  circulation  will  continue  for  several  hours,  provided 
artificial  respiration  be  maintained  with  regularity. 

When  exposed  to  view  under  these  conditions,  the  movements  of  the 
mammalian  heart  are  at  once  seen  to  be  complicated  to  such  a  degree 
that  close  examination  is  requisite  to  distinguish  their  different  elements. 
The  most  obvious  appearance  at  first  presented  is  the  rapid  succession 
of  two  alternating  conditions,  namely  a  condition  of  rest  and  a  condi- 
tion of  movement.  Furthermore,  if  the  heart  be  touched  or  gently 
grasped  between  the  fingers,  it  becomes  evident  that  the  two  states  of 
rest  and  movement  are  accompanied  by  corresponding  changes  in  the 
consistency  of  the  organ.  At  the  time  of  rest  it  is  comparatively  soft 
and  yielding  to  the  touch ;  at  the  time  of  its  movement,  it  becomesxhard 
and  tense.  Inspection  alone  cannot  determine  which  of  these  two  states 
corresponds  with  the  entrance  of  the  blood  into  the  ventricles  and  which 
with  its  exit ;  in  other  words,  which  represents  muscular  relaxation  and 
which  the  contraction  of  the  heart.  Different  observers,  while  watching 
the  movements  of  the  same  heart  in  the  living  animal,  will  often  be  led 
to  opposite  conclusions  in  this  respect.  The  only  method  of  directly 
determining  the  point  is  that  first  adopted  by  Harvey,  in  his  observa- 
tions upon  the  heart,  which  formed  the  basis  of  the  discovery  of  the 
circulation  of  the  blood.  If  we  insert  through  the  walls  of  the  left 
ventricle  a  silver  canula  from  one  to  two  millimetres  in  diameter,  so  as 
to  pierce  its  cavity,  the  blood  is  forcibly  projected  from  its  orifice  at  the 
time  of  the  tension  of  the  cardiac  walls,  while  its  flow  is  suspended  in 
the  intervals  of  repose. 

Thus  the  two  states  of  relaxation  and  tension  of  the  heart  correspond 
with  the  relaxation  and  contraction  of  its  muscular  fibres.  Like  mus- 
cular tissue  elsewhere,  that  of  the  heart  during  relaxation  is  compara- 
tively soft  to  the  touch ;  when  the  ventricles  contract  upon  their  contents 
and  forcibly  expel  the  blood,  they  become  tense  and  firm,  by  the  sudden 
rigidity  of  their  fibres.  By  this  means  the  two  opposite  conditions  of 
the  diastole  and  systole  of  the  ventricles  may  be  recognized  with  cer- 
tainty, and  connected  with  the  other  corresponding  phenomena  of  the 

1  Flint,  Treatise  on  Diseases  of  the  Heart.     Philadelphia,  1870,  pp.  61-62. 


THE    HEART. 


325 


heart's  action.  At  the  time  of  their  diastole,  the  blood  enters  the 
cavity  of  the  ventricles  through  the  auricular  orifice ;  at  the  time  of 
their  systole  it  is  expelled  into  the  arterial  trunks. 

Simultaneously  with  the  hardening  and  contraction  of  the  ventricles 
the  apex  of  the  heart  moves  slighly  from  left  to  right,  and  rotates  at 
the  same  time  upon  its  own  axis  in  a  similar  direction.  This  movement 
was  also  observed  by  Harvey,  who  describes  it  as  follows:1 — 

"  And  if  any  one,"  he  says,  u  bearing  these  things  in  mind,  will  care- 
fully watch  the  motions  of  the  heart  in  the  body  of  the  living  animal, 
he  will  perceive  not  only  all  the  particulars  I  have  mentioned,  namely, 
the  heart  becoming  erect  and  making  one  continuous  motion  with  its 
auricles ;  but,  further,  a  certain  obscure  undulation  and  lateral  inclina- 
tion in  the  direction  of  the  axis  of  the  right  ventricle,  the  organ  twisting 
itself  slightly  in  performing  its  work." 

Both  these  movements,  of  lateral  inclination  and  rotation,  result  from 
the  spiral  arrangement  of  the  muscular  fibres  on  the  exterior  of  the 

heart.     The  most  superficial  of  these  fibres 
Fig.  106.  start  from  the  base  of  the  organ  and  pass 

toward  its  apex,  following  an  obliquely 
spiral  course  over  its  anterior  surface,  from 
above  downward  and  from  right  to  left. 
The  contraction  of  this  superficial  portion 

Fig.  107. 


BULLOCK'S  HEAKT,  anterior 
view,  showing  the  superficial  mus- 
cular fibres. 


CONVERGING  SPIRAL  FIBRES  AT  THE  APKX 
OP  THE  HEART.  The  direction  of  the  arrows  indi- 
cates that  of  the  rotating  movement  of  the  heart  at 
the  time  of  the  ventricular  systole. 


of  the  muscular  fibres  accordingly  tilts  the  apex  of  the  heart  in  a  slight 
degree  bodily  from  left  to  right.  As  the  fibres,  however,  reach  the  point 
of  the  heart  they  curl  round  its  axis,  change  their  direction,  and  disap- 
pear from  sight,  becoming  deep  seated  and  passing  upward  along  the 
septum  and  internal  surface  of  the  ventricle,  to  a  termination  finally  in 
the  columnse  carneae  and  the  fibrous  border  of  the  auriculo-ventricular 
ring.  They  thus  form,  exactly  at  the  apex  of  the  heart,  a  kind  of  whorl 
or  vortex,  of  spiral  muscular  fibres  easily  distinguishable  when  the  organ 
is  in  active  motion.  Any  muscular  fibre  arranged  in  this  direction 


Works  of  William  Harvey,  M.D.,  Sydenham  Edition.     London,  1847,  p.  32. 


THE    CIRCULATION. 

necessarily  tends,  at  the  moment  of  its  contraction,  to  straighten  or 
untwist  the  spiral.  At  the  time  of  the  ventricular  contraction,  there- 
fore, the  apex  of  the  heart  rotates  upon  its  axis,  from  left  to  right  ante- 
riorly and  from  right  to  left  posteriorly.  This  twisting  movement  at 
the  apex  is  very  perceptible  at  each  pulsation  of  the  heart  when  exposed 
in  the  living  animal. 

The  impulse  of  the  heart  is  a  stroke,  more  or  less  forcible,  of  the 
apex  of  the  organ  against  the  walls  of  the  chest,  taking  place  at  the 
time  of  the  ventricular  systole.  This  impulse  is  readily  perceptible 
externally,  as  a  general  rule,  both  to  the  eye  and  to  the  touch.  In  the 
human  subject,  when  in  the  erect  position,  it  is  located  in  the  fifth  inter- 
costal space,  midway  between  the  left  edge  of  the  sternum  and  a  line 
drawn  perpendicularly  through  the  left  nipple ;  while  in  the  supine  posi- 
tion of  the  body,  the  heart  subsides,  in  a  measure,  from  the  anterior  part 
of  the  chest,  so  that  its  external  impulse  may  become  for  the  time  very 
faint,  or  may  even  disappear  altogether. 

This  alternate  recession  and  advance  of  the  apex  of  the  heart,  corre- 
sponding with  its  relaxation  and  contraction,  is  visible  in  the  organ  when 
exposed  by  opening  the  walls  of  the  chest.  According  to  the  descrip- 
tion given  by  Harvey,  at  the  time  of  its  motion  "  the  heart  is  erected, 
and  rises  upward  to  a  point,  so  that  at  this  time  it  strikes  against  the 
breast  and  the  pulse  is  felt  externally."  If  we  allow  the  end  of  the 
finger  to  rest  lightly  upon  the  apex  of  the  exposed  heart,  the  protrusion 
of  this  part  of  the  organ  at  the  time  of  the  ventricular  systole  is  dis- 
tinctly felt,  lifting  the  finger  at  each  beat  with  a  somewhat  forcible 
impulse ;  and  if  a  light  rider  of  white  paper  be  placed  upon  the  apex,  it 
is  also  seen  to  be  thrown  forward  and  backward  at  each  alternate  con- 
traction and  relaxation  of  the  heart. 

The  immediate  cause  of  the  protrusion  of  the  heart's  apex  at  the  time 
of  the  ventricular  systole  has  been  variously  regarded,  first  as  an  actual 
elongation  of  the  ventricle,  and  secondly,  as  a  forward  movement  of  the 
whole  heart,  due  to  a  recoil  from  the  blood  expelled  from  it  under  pres- 
sure, or  to  a  reaction  of  the  distended  arteries  at  its  base.  Galen,  who 
was  the  first  to  study  the  action  of  the  heart  by  inspection  in  the  living 
animal,  found  the  transverse  diameter  of  the  organ  increased  during 
relaxation  and  its  length  diminished,  while  during  the  systole  its  width 
was  diminished  and  its  length  increased.1  Of  subsequent  observers, 
some  believed  the  heart  to  be  lengthened,  others  that  it  was  shortened  at 
the  time  of  the  ventricular  systole.  Nearly  all  the  more  recent  physio- 
logical writers  of  eminence  (Longet,  Carpenter,  Flint,  Ranke,  Burdon- 
Sanderson)  are  of  the  opinion  that  the  ventricles  when  contracting 
diminish  in  size  in  every  direction,  that  the  apex  of  the  organ  approaches 
the  base,  but  that  the  whole  heart  is  thrown  forward  by  the  impulse  of 
recoil  above  mentioned.  Prof.  Flint2  cut  out  the  heart  suddenly  from 

1  Galen,  De  Usu  Partium,  vi.  8. 

2  Physiology  of  Man.     New  York,  1866,  p.  189. 


THE    HEART.  327 

the  dog,  and,  fastening  it  upon  a  table  by  needles  passed  through  its  base, 
found  the  ventricles  shortened  in  contraction ;  and  obtained  the  same 
result,  in  another  experiment,  by  pinning  the  heart,  in  the  chest  of  the 
living  animal,  to  a  thin  board  placed  underneath.  On  the  other  hand, 
Drs.  Pennock  and  Moore,  who  performed  a  series  of  very  careful  experi- 
ments upon  the  action  of  the  heart  in  sheep,  calves,  and  horses,1  observed 
an  elongation  of  the  organ  at  the  time  of  the  ventricular  systole.  They 
operated  by  stunning  the  animals  with  a  blow  upon  the  head,  opening 
the  chest,  and  keeping  up  artificial  respiration,  and  they  were  able  to 
measure  the  extent  of  elongation  by  means  of  a  shoemaker's  rule  applied 
to  the  heart. 

In  our  own  observations  on  this  point,  many  times  repeated,  we  have 
always  seen  reason  to  believe  that  the  heart  actually  elongates  in  the 
ventricular  systole,  and  that  it  is  not  simply  thrown  forward  by  an  im- 
pulse of  recoil.  The  appearances  presented,  when  viewing  the  front  of 
the  mammalian  heart,  as  it  lies  in  its  natural  position  in  the  chest,  are 
somewhat  complicated.  The  anterior  surface  of  the  organ  is  mainly 
occupied  by  the  right  ventricle  and  especially  by  that  portion  of  it 
known  as  the  conus  arteriosus.  This  is  in  reality  a  vaulted  channel 
running  obliquely  over  the  front  of  the  heart,  from  right  to  left  and  from 
below  upward,  toward  the  origin  of  the  pulmonary  artery.  Its  muscular 
fibres,  on  the  other  hand,  run  directly  across  it  and  at  right  angles  to 
the  axis  of  its  cavity,  namely,  from  right  to  left  and  from  above  down- 
ward, constituting  the  most  superficial  fibres  of  the  heart  in  this  situa- 
tion. At  the  time  of  ventricular  systole,  these  fibres  contract  across  the 
line  of  the  conus  arteriosus,  become  thickened  and  more  prominent  and 
approximate  the  base  of  the  heart  and  the  lower  -border  of  the  conus 
arteriosus  toward  each  other. 

But  the  right  ventricle  constitutes  a  comparatively  small  portion  of 
the  heart.  The  greater  part  of  its  mass  is  formed  by  the  thick  walls  of 
the  left  ventricle,  which  occupies  a  posterior  position,  and  is  not  fully 
seen  in  a  front  view  of  the  organ.  If  the  heart  be  tilted  up  and  viewed 
from  its  posterior  surface,  at  every  contraction  its  sides  will  be  seen  to 
approximate  and  its  point  to  elongate ;  in  other  words,  its  transverse 
diameter  diminishes,  while  its  longitudinal  diameter  increases.  Its  base 
may  be  firmly  held  by  the  fingers  placed  upon  the  large  vessels,  -while 
this  change  of  form  of  the  organ  is  observed.  Even  in  an  anterior  view, 
with  the  whole  heart  securely  held  in  this  position,  according  to  our 
observations,  the  apex,  at  each  systole,  will  rise  toward  an  ivory  rod 
placed  horizontally  above  it,  and  will  recede  in  the  same  degree  at  each 
diastole. 

If  this  be  true,  the  explanation  of  the  ventricular  elongation  is  readily 
found  in  the  arrangement  of  the  muscular  fibres  of  the  left  ventricle. 
The  left  ventricle  preponderates  so  much  in  mass  over  the  other  parts  of 
the  organ,  that  its  changes  of  figure  determine  those  of  the  entire  heart. 

1  Philadelphia  Medical  Examiner,  1839,  No.  44. 


328 


THE    CIRCULATION. 


Fig.  108. 


TRANSVERSE  SECTION  OF  THE 
BULLOCK'S  HEART  IN  THE  STATE 
OP  CADAVERIC  RIGIDITY. — a.  Cav- 
ity of  the  Left  Ventricle,  b.  Cavity  of 
the  Right  Ventricle. 


Fig.  109. 


A  transverse  section  of  the  heart,  in  its  contracted  condition,  shows  the 
relative  volume  of  the  muscular  walls  of  the  right  and  left  ventricles, 

and  the  difference  in  form  of  the  two 
cavities. 

The  left  ventricle  forms  a  thick 
muscular  tube,  with  its  cavity  nearly 
in  the  centre  of  the  cardiac  mass ; 
while  the  right  ventricle  has  the  ap- 
pearance of  a  comparatively  incon- 
siderable layer  of  fibres,  attached  to 
the  lateral  surface  of  the  organ,  and 
enclosing  a  cavity  of  a  more  linear 
and  flattened  form. 

The  surperficial  cardiac  fibres,  which 
make  the  visible  part  of  the  wall  of 
the  right  ventricle,  run  obliquely  from 
right  to  left  and  from  above  down- 
ward, toward  the  heart's  apex;  but  the  more  deeply  seated  layers, 
belonging  to  the  left  ventricle,  take  more  and  more  a  horizontal  or 
circular  course,  being  wrappped  round  the  ven- 
tricle, almost  like  those  of  the  small  intestine. 
Whenever   these   muscular  fibres  contract,  they 
must,  of  course,  swell  in  the  direction  of  their 
thickness ;  and  the  effect  produced  by  this  simul- 
taneous swelling  of  all  the  circular  fibres  is  to 
increase    the  longitudinal  diameter   of  the   ven- 
tricle, at  the  same  time  that  its  sides  are  drawn 
together  and  its  calibre  diminished.     In  the  sys- 
tole of  the  ventricle,  accordingly,  its  muscular 
fibres  contract  upon  its  contents,  like  the  fingers 
of  a  closed  hand,  and  the  blood  is  expelled  from 
its  cavity  very  much  as  the  fluids  of  the  intestinal 
canal  are  forced  onward  by  the  contracting  cir- 
cular fibres  of  the  muscular  coat. 

fihythm  of  the  Heart's  Action. — The  succession  of  phenomena  in  the 
heart's  action  is  peculiar  and  somewhat  complicated.  Each  pulsation 
is  made  up  of  a  double  series  of  contractions  and  relaxations.  The  two 
auricles  contract  together,  and  afterward  the  two  ventricles ;  and  in 
each  case  the  contraction  is  immediately  followed  by  a  relaxation.  The 
auricular  contraction  is  short  and  feeble,  and  occupies  the  first  part  of 
the  time  of  a  pulsation.  The  ventricular  contraction  is  longer  and  more 
powerful,  and  occupies  the  latter  part  of  the  same  period.  Following 
the  ventricular  contraction  there  comes  a  short  interval  of  repose,  after 
which  the  auricular  contraction  again  recurs.  The  auricular  and  ven- 
tricular contractions,  however,  do  not  alternate  distinctly  with  each 
other,  like  the  strokes  of  the  two  pistons  in  a  double  forcing-pump.  On 
the  contrary,  they  are  connected  and  continuous.  The  contraction, 


LEFT  VENTRICLE  OF 
BULLOCK'S  HEART, 
showing  its  deep  fibres. 


THE    HEAKT.  329 

which  commences  at  the  auricle,  is  immediately  propagated  to  the  ven- 
tricle, and  runs  rapidly  from  the  base  of  the  heart  to  its  apex,  very 
much  in  the  manner  of  a  peristaltic  motion,  excepting  that  it  is  more 
sudden  and  vigorous.  This  part  of  the  heart's  action  is  described  by 
Harvey  in  very  graphic  terms,  evidently  drawn  from  direct  study  of  the 
phenomena  in  the  living  animal. 

"•  First  of  all,"  he  says,  "the  auricle  contracts,  and  in  the  course  of  its 
contraction  throws  the  blood  (which  it  contains  in  ample  quantity  as 
the  head  of  the  veins,  the  storehouse  and  cistern  of  the  blood)  into  the 
ventricle,  which  being  filled,  the  heart  raises  itself  straightway,  makes 
all  its  fibres  tense,  contracts  the  ventricles,  and  performs  a  beat,  b}' 
which  beat  it  immediately  sends  the  blood,  supplied  to  it  by  the  auricle, 
into  the  arteries ;  the  right  ventricle  sending  its  charge  into  the  lungs 
by  the  vessel  which  is  called  vena  arteriosa,  but  which,  in  structure  and 
function,  and  all  things  else,  is  an  artery ;  the  left  ventricle  sending  its 
charge  into  the  aorta,  and  through  this  by  the  arteries  to  the  body  at 
large. 

"  These  two  motions,  one  of  the  ventricles,  another  of  the  auricles, 
take  place  consecutively,  but  in  such  a  manner  that  there  is  a  kind  of 
harmony  or  rhythm  preserved  between  them,  the  two  concurring  in 
such  wise  that  but  one  motion  is  apparent,  especially  in  the  warmer 
blooded  animals,  in  which  the  movements  in  question  are  rapid.  Nor 
is  this  for  any  other  reason  than  it  is  in  a  piece  of  machinery,  in  which, 
though  one  wheel  gives  motion  to  another,  yet  all  the  wheels  seem  to 
move  simultaneous^ ;  or  in  that  mechanical  contrivance  which  is 
adapted  to  fire-arms,  where,  the  trigger  being  touched,  down  comes  the 
flint,  strikes  against  the  steel,  elicits  a  spark,  which  falling  among  the 
powder,  it  is  ignited,  upon  which  the  flame  extends,  enters  the  barrel, 
causes  the  explosion,  propels  the  ball,  and  the  mark  is  attained  ;  all  of 
which  incidents,  by  reason  of  the  celerity  with  which  they  happen,  seem 
to  take  place  in  the  twinkling  of  an  eye." 

The  above  description  indicates  precisely  the  manner  in  which  the 
contraction  of  the  ventricle  follows  successively  and  yet  continuously 
upon  that  of  the  auricle.  The  contraction  begins,  as  already  stated,  at 
the  auricle.  Thence  it  runs  immediately  forward  to  the  apex  of  the 
heaVt.  The  entire  ventricle  contracts  vigorously,  its  walls  harden,  its 
apex  protrudes,  strikes  against  the  walls  of  the  chest,  and  twists  from 
left  to  right,  the  auriculo-ventricular  valves  shut  back,  the  first  sound 
is  produced,  and  the  blood  is  driven  into  the  aorta  and  pulmonary  artery. 
These  phenomena  occupy  about  one-half  the  time  of  pulsation.  Then 
the  ventricle  is  relaxed,  and  a  short  period  of  repose  ensues.  During 
this  period  the  blood  flows  from  the  large  veins  into  the  auricle,  and 
through  the  auriculo-ventricular  orifice  into  the  ventricle;  filling  the 
ventricle,  by  a  kind  of  passive  dilatation,  about  two-thirds  or  three- 
quarters  full.  Then  the  auricle  contracts  with  a  quick  motion,  forces 
the  last  drop  of  blood  into  the  ventricle,  distending  it  to  its  full  capa- 
22 


330  THE    CIRCULATION. 

city ;  and  lastly  the  ventricular  contraction  takes  place,  driving  the  blood 
into  the  large  arteries.  These  movements  continue  to  alternate  with 
each  other,  and  form,  by  their  recurrence,  the  successive  cardiac  pul- 
sations. 

ft* 

The  Arterial  Circulation. 

The  arteries  are  a  series  of  branching  tubes,  which  commence  with 
the  aorta  and  ramify  throughout  the  body,  distributing  the  blood  to  the 
various  vascular  organs.  They  consist  of  three  principal  coats,  namely, 
an  inner  coat,  composed  of  thin  elastic  laminae  lined  with  a  single  layer 
of  narrow,  elongated  and  flattened  epithelium  cells  ;  a  middle  coat,  com- 
posed of  elastic  tissue  and  imstriped  muscular  fibres,  running  trans- 
versely, or  in  a  circular  direction,  round  the  calibre  of  the  vessel;  and 
an  external  coat,  consisting  mainly  of  a  more  or  less  condensed  layer 
of  connective  tissue.  The  principal  anatomical  distinction  between  the 
larger  and  the  smaller  arteries  is  in  the  structure  of  their  middle  coat. 
In  the  smaller  arteries  this  coat  is  composed  exclusively  of  muscular 
fibres,  arranged  in  one  or  several  layers.  In  arteries  of  medium  size 
the  middle  coat  contains  both  muscular  and  elastic  tissue;  while  in 
those  of  the  largest  calibre  it  consists  of  elastic  tissue  alone.  The 
large  arteries,  accordingly,  possess  a  remarkable  degree  of  elasticity  and 
but  little  contractility;  while  the  smaller  are  contractile,  and  less  dis- 
tinctly elastic. 

Movement  of  the  Blood  through  the  Arterial  System. — The  movement 
of  the  blood  through  the  arteries  is  due  to  the  muscular  force  of  the 
heart  and  the  impulse  derived  from  the  ventricular  systole.  The  arte- 
rial system,  which  is  an  extensive  ramification  of  tubular  canals,  may 
be  regarded  as  a  great  vascular  cavity,  subdivided  from  within  outward 
by  the  successive  branching  of  its  vessels,  but  communicating  freely 
with  the  heart  and  aorta  at  one  extremity,  and  with  the  capillary  plexus 
at  the  other,  and  filled  everywhere  with  the  circulating  fluid.  At  the 
time  of  the  heart's  contraction,  the  muscular  walls  of  the  ventricle  close 
in  upon  its  cavity ;  and  as  the  auriculo-ventricular  valves  at  the  same 
time  shut  back  and  prevent  regurgitation,  the  blood  is  forced  out  from 
the  ventricle  through  the  aortic  orifice.  As  the  ventricle  relaxes  it  is 
again  filled  with  blood  from  the  auricle,  and  delivers  it,  as  before,  by 
a  new  contraction,  into  the  arteries.  It  is  by  these  impulses,  recurring 
at  short  intervals,  that  the  entire  blood  moves  in  a  direction  from  the 
heart  outward  through  the  arterial  system. 

Distension  of  the  Arteries  by  the  HearVs  Action;  Arterial  Pulse. — At 
each  ventricular  systole  a  charge  of  blood  is  driven  into  the  arteries, 
distending  their  walls  by  the  pressure  of  the  additional  quantity  of  fluid 
introduced  into  their  cavities.  When  the  ventricle  afterward  relaxes, 
this  active  distending  force  is  suspended ;  and  the  elastic  arterial  walls, 
reacting  upon  their  contents,  would  drive  the  blood  back  into  the  heart 
were  it  not  for  the  closure  of  the  semilunar  valves,  which  shut  together 


THE    AUTERIAL    CI  RCUL  ATTON.  331 

and  prevent  any  movement  in  a  backward  direction.  The  blood  is  thus 
urged  onward,  under  the  pressure  of  the  arterial  elasticity,  into  the 
capillary  system.  When  the  arteries  have  become  partially  emptied, 
and  have  returned  to  their  previous  dimensions,  they  are  again  dis- 
tended by  another  contraction  of  the  heart.  In  this  manner  a  succes- 
sion of  expansions  is  produced,  which  can  be  felt  throughout  the  body 
wherever  the  arterial  ramifications  penetrate.  This  phenomenon  is 
known  by  the  name  of  the  arterial  pulse. 

Since  each  arterial  expansion  is  produced  by  a  ventricular  systole, 
the  pulse,  as  felt  in  any  superficial  artery,  is  a  convenient  guide  for 
ascertaining  the  frequency  and  regularity  of  the  heart's  action.  The 
radial  artery  at  the  wrist,  owing  to  its  easily  accessible  situation,  is 
mainly  employed  for  this  purpose.  Any  increase  or  diminution  in  the 
frequency  of  the  heart's  action  is  accompanied  by  a  similar  change  in 
the  arterial  pulsations ;  and  alterations  in  the  force  or  regularity  of  the 
cardiac  movements  are  also  indicated  by  corresponding  modifications 
of  the  pulse  at  the  wrist. 

The  average  frequency  of  the  pulse  in  the  human  subject  is,  for  the 
adult  male  in  a  state  of  quiescence,  70  beats  per  minute.  This  rate 
may  be  more  or  less  accelerated  by  any  muscular  exertion.  Even  the 
difference  of  muscular  effort  between  the  positions  of  standing,  sitting, 
and  lying  down,  will  make  a  normal  difference  in  the  pulse  of  from  8  to 
10  beats  per  minute.  Age  has  a  very  marked  influence  on  the  rapidity 
of  the  pulse ;  it  being  found,  as  a  rule,  more  rapid  the  younger  the  sub- 
ject of  observation.  According  to  Dr.  Carpenter,  the  pulse  of  the 
foetus,  before  birth,  is  about  140,  and  that  of  the  newly-born  infant  130. 
During  the  first,  second,  and  third  years  it  gradually  falls  to  100;  by 
the  fourteenth  year  to  80 ;  and  is  only  reduced  to  the  adult  standard 
by  the  twenty-first  year.  At  every  age,  mental  excitement  may  pro- 
duce a  temporary  acceleration  of  the  pulse,  varying  in  degree  with  the 
peculiarities  of  the  individual. 

As  a  general  rule,  the  rapidity  of  the  heart's  action  is  in  inverse  ratio 
to  its  force ;  that  is,  a  slow  pulse,  within  physiological  limits,  is  a  strong 
one ;  a  rapid  pulse  is  a  feeble  one.  This  is  readily  noticeable  in  ex- 
periments upon  the  lower  animals,  where  the  force  of  the  heart's  action 
may  be  measured  by  the  arterial  impulse ;  and  where  an  increase  in  the 
frequency  of  the  cardiac  pulsations  is  almost  invariably  accompanied 
by  a  diminution  in  their  strength.  The  same  thing  is  true  in  cases  of 
increased  frequency  of  the  heart's  action  from  morbid  causes  ;  the  pulse 
in  febrile  or  chronic  affections  becoming  weaker  as  it  growls  more  rapid. 
An  excessive  rapidity  of  the  pulse  is  an  indication  of  great  danger ; 
and,  in  the  adult  male,  a  continuous  pulse  of  160  per  minute  is  almost 
invariably  a  fatal  symptom. 

Increased  Curvature  of  the  Arteries  in  Pulsation. — When  the  blood 
is  driven  by  the  ventricular  systole  into  the  arteries,  these  vessels  are 
not  only  distended  laterally,  but  are  elongated  as  well  as  widened, 


332 


THE    CIRCULATION. 


Elongation  and 
increased  curvature 
of  an  ARTERY  IN 
PULSATION. 


Fi«r.  110.  becoming  enlarged  in  every  direction.      Especially 

in  arteries  having  a  distinctly  curved  or  serpen- 
tine course,  this  elongation  and  increase  of  curva- 
ture may  be  observed  at  the  time  of  each  pulsa- 
tion. It  is  perceptible,  for  instance,  in  emaciated 
persons,  in  the  temporal  artery,  or  even  in  the  ra- 
dial at  the  wrist,  and  may  readily  be  seen  in  the 
mesenteric  arteries  in  the  abdomen  of  the  living 
animal.  At  every  contraction  of  the  heart,  the 
curves  of  the  vessel  on  each  side  become  more 
strongly  pronounced.  In  the  case  of  the  radial  or 
other  artery,  running  over  a  bony  surface,  the  vessel 
may  even  partially  rise  out  of  its  bed  at  each  pulsa- 
tion. In  old  persons  the  arterial  curvatures  become 
permanently  enlarged  from  frequent  distension ;  and 
all  the  arteries  tend  to  assume,  with  the  advance  of 
age,  a  more  serpentine  and  spiral  course. 
Time  of  the  Arterial  Pulse. — The  shock  of  an  arterial  pulsation,  as 
perceived  by  the  finger,  varies  a  little  in  time,  according  to  its  distance 
from  the  centre  of  the  circulation.  If  we  place  one  finger  upon  the 
chest  over  the  apex  of  the  heart,  and  another  over  the  carotid  artery  at 
the  middle  of  the  neck,  we  can  distinguish  little  or  no  difference  in  time 
between  the  two  impulses ;  the  distension  of  the  carotid  being  sensibly 
simultaneous  with  the  heart's  contraction.  But  if  the  second  finger  be 
placed  upon  the  temporal  artery,  instead  of  the  carotid,  there  is  a  per- 
ceptible interval  between  the  two  beats.  The  impulse  of  the  temporal 
artery  is  felt  to  be  a  little  later  than  that  of  the  heart.  The  pulse  of  the 
radial  artery  at  the  wrist  also  appears  to  be  a  little  later  than  that  of 
the  carotid,  and  that  of  the  posterior  tibial  at  the  ankle  joint  a  little 
later  than  that  of  the  radial.  The  greater  the  distance  from  the  heart 
at  which  the  artery  is  examined,  the  later  is  the  pulsation  perceived  by 
the  finger  laid  upon  the  vessel. 

But  it  has  been  conclusively  shown  that  this  difference  in  time  of  the 
arterial  pulsations,  in  different  parts  of  the  body,  is  rather  relative  than 
absolute.  The  impulse  is  communicated  at  the  same  instant  to  all  parts 
of  the  arterial  system  ;  but  the  apparent  difference  between  them,  in  this 
respect,  depends  upon  the  fact,  that,  although  all  the  arteries  begin  to 
be  distended  at  the  same  moment,  yet  those  nearest  the  heart  are  ex- 
panded suddenly,  while  for  those  at  a  distance  the  distension  takes  place 
more  gradually.  The  impulse  given  to  the  finger  marks  the  condition 
of  maximum  distension  of  the  vessel ;  and  this  condition  occurs  at  a 
later  period,  according  to  the  distance  of  the  artery  from  the  heart. 

The  contraction  of  the  left  ventricle  is  a  brisk  and  sudden  motion. 
The  blood  driven  into  the  arterial  system,  meeting  with  a  certain  amount 
of  resistance  from  that  already  filling  the  vessels,  does  not  instantly 
displace  a  quantity  equal  to  its  own  mass,  but  a  certain  proportion  of 
its  force  is  used  in  expanding  the  distensible  walls  of  the  vessels.  In 


THE    ARTERIAL    CIRCULATION.  333 

the  immediate  neighborhood,  therefore,  the  expansion  of  the  arteries  is 
sudden  and  momentary,  like  the  contraction  of  the  heart  itself.  But 
this  expansion  requires  for  its  completion  a  certain  expenditure,  both 
of  force  and  time ;  so  that  at  a  little  distance  farther  on,  the  vessel  is 
distended  neither  to  the  same  degree  nor  with  the  same  rapidity.  At 
the  more  distant  point  the  arterial  impulse  is  less  powerful  and  arrives 
more  slowly  at  its  maximum. 

On  the  other  hand,  when  the  heart  becomes  relaxed,  the  artery  in  its 
immediate  neighborhood  reacts  upon  the  blood  by  its  own  elasticity ; 
and  as  it  meets  with  no  other  resistance  than  that  of  the  blood  in  the 
smaller  vessels  beyond,  it  drives  a  portion  of  its  own  blood  into  them, 
and  thus  supplies  to  these  vessels  a  certain  degree  of  distending  force 
even  in  the  intervals  of  the  heart's  action.  Thus  the  difference  in  size 
of  the  carotid  artery,  at  the  two  periods  of  the  heart's  contraction  and 
relaxation,  is  ve^  marked ;  for  the  degree  of  its  distension  is  great 
when  the  heart  contracts,  and  its  own  reaction  afterward  empties  it  of 
blood  to  a  considerable  extent.  But  in  the  small  branches  of  the  radial 
or  the  ulnar  artery,  there  is  less  distension  at  the  time  of  the  cardiac 
impulse,  because  this  force  has  been  partly  expended  in  overcoming  the 
elasticity  of  the  larger  vessels ;  and  there  is  less  emptying  of  the  vessel 
afterward,  because  it  is  still  kept  partially  filled  by  the  reaction  of  the 
aorta  and  its  larger  branches. 

These  facts  have  been  illustrated  by  Marey,1  by  attaching  to  the  pipe 
of  a  small  forcing  pump,  worked  by  alternate  strokes  of  the  piston,  a 
long  elastic  tube  open  at  its  farther  extremity.  At  different  points 
upon  this  tube  are  placed  small  movable  levers,  which  are  raised  by  the 
distension  of  the  tube  whenever  water  is  driven  into  it  by  the  forcing 
pump.  Each  lever  carries  upon  its  extremity  a  small  pencil,  which 
marks  upon  a  strip  of  paper,  moving  with  uniform  rapidity,  the  lines 
produced  by  its  alternate  elevation  and  depression.  By  these  curves 
both  the  extent  and  rapidity  of  distension  of  different  parts  of  the  elastic 
tube  are  accurately  registered.  The  curves  thus  produced  are  as  follows : 

Fig.  111. 


CURVES  OF  PULSATION  IN  AN  ELASTIC  TUBE.  —  1.  Near  the  distending  force 
2.  At  a  distance  from  it.    3.  Still  farther  removed. 

From  these  experiments  it  is  shown  that  the  distension  produced  by 
the  stroke  of  the  forcing  pump  begins  at  the  same  moment  throughout 

1  Journal  de  la  Physiologie.     Paris,  Avril,  1859 


334  THE    CIRCULATION. 

the  entire  length  of  the  tube,  and  that  the  whole  time  of  a  pulsation  is 
everywhere  of  equal  duration.  But  near  the  commencement  of  the  tube, 
the  expansion  is  wide  and  sudden,  and  occupies  only  a  sixth  part  of  the 
entire  pulsation,  while  all  the  rest  is  taken  up  by  a  slow  reaction.  At 
more  remote  points  the  period  of  expansion  becomes  longer  and  that  of 
collapse  shorter ;  until  finally,  at  a  certain  distance,  the  amount  of  ex- 
pansion is  reduced  one-half,  and  at  the  same  time  the  two  periods  are 
completely  equalized. 

Automatic  Registration  of  the  Arterial  Pulse;  the  Sphygmograph. — 
The  frequency  and  characters  of  the  arterial  pulse  may  be  permanently 
recorded  by  the  use  of  a  movable  lever  capable  of  registering  its  own 
oscillations,  and  so  arranged  that  it  may  be  applied  to  any  of  the  super- 
ficial arteries  in  the  living  body.  This  instrument,  which  was  first  made 
practically  serviceable  by  the  improvements  of  Marey,  is  the  sphygmo- 
graph.  It  consists  of  a  small  ivory  plate,  which  is  gently  pressed  upon 
the  artery  by  means  of  a  fine  spring,  and  which  thus  rises  and  falls  with 
each  expansion  and  collapse  of  the  arterial  tube.  The  motion  of  the 
plate  is  communicated  to  a  vertical  metallic  rod  touching  the  under  sur- 
face of  the  registering  lever  near  its  attached  extremity.  The  oscillating 
extremity  of  the  lever,  when  the  instrument  is  in  operation,  thus  follows 
the  movements  of  the  ivory  plate,  and  registers  faithfully  upon  the  strip 
of  paper,  the  frequency  and  form  of  the  arterial  pulsations. 

The  advantage  of  this  instrument  is,  first,  that  the  length  of  the  lever 
magnifies  to  the  eye  the  extent  of  the  arterial  oscillations,  and  thus 
enables  us  to  perceive  movements  too  delicate  to  be  distinguished  by 
the  touch  alone ;  and,  secondly,  that,  each  part  of  a  pulsation  being 
permanently  registered  upon  paper,  the  most  evanescent  changes  in  the 
form  of  the  artery  may  be  afterward  studied  at  leisure  and  compared 
with  each  other. 

By  the  use  of  the  sphygmograph  it  is  shown,  that,  while  there  is  a 
general  resemblance  in  the  form  of  pulsation  of  different  arteries,  nearly 
every  vessel  to  which  the  instrument  can  be  applied  presents  certain 
peculiarities  dependent  on  its  size,  position,  and  distance  from  the 
heart.  In  the  radial  artery  at  the  wrist,  each  pulsation  consists  of  a 

Fi>.  112. 


TKACE  01-  THE  K  ADI  AL  PULSE,  taken  by  the  Sphygmograph. 

sudden  expansion  of  the  vessel,  indicated  by  a  rapid  upward  movement 
of  the  lever,  making,  in  the  trace,  a  straight,  nearly  A^ertical  line.  This 
is  followed  by  a  gradual  descent  corresponding  with  the  collapse  of  the 
artery,  until  it  reaches  the  lowest  point  of  the  trace,  when  the  move- 
ment of  ascension  again  takes  place,  and  so  on  alternately.  The  line 
of  descent,  however,  is  not  straight,  like  that  of  ascension,  but  is  marked 


THE    ARTERIAL    CIRCULATION. 


335 


by  one,  arid  sometimes  by  two  or  even  three  slight  undulations,  indi- 
cating a  corresponding  variation  in  the  tension  of  the  artery  during  its 
period  of  collapse. 

The  undulations  in  the  line  of  descent,  in  the  sphygmograph  tracing, 
are  due  to  an  oscillation  in  the  mass  of  the  blood,  subsequent  to  the 
impulse  of  the  heart,  and  during  the  reaction  of  the  arterial  system. 
Marey  has  shown,  by  a  series  of  well-conducted  experiments,1  that 
similar  oscillations  are  produced  when  any  incompressible  liquid  is 
driven  by  a  sudden  impulse  into  an  elastic  tube;  and  that  they  are  indi- 
cated by  a  similar  movement  of  the  index  of  the  sphygmograph.  When 
the  heart's  impulse  is  moderate,  and  the  tension  of  the  arterial  system 
fully  developed,  the  undulations  in  the  descending  line  of  the  pulse  are 
only  slightly  perceptible ;  but  when  the  heart's  impulse  is  more  rapid, 
and  the  arterial  tension  diminished,  the  undulations  become  more 
marked.  Marey  found  that  he  could  procure  upon  his  own  person 
traces  of  different  form,  in  this  respect,  by  simply  increasing  the  tem- 
perature of  the  body  by  the  addition  of  warmer  clothing.  The  following 
are  three  traces  of  the  radial  pulse  obtained  in  this  way,  by  increasing 
the  quantity  of  clothing  at  intervals  of  twenty  minutes. 

Fig.  11 3. 


Fi?.  114. 


Fig.  115. 


VARIATIONS  OF  THE  KADIAL  PULSE,  under  the  influence  of  increased  temperature. 

(Marey.) 

Dicrotic  Pulse. — In  certain  conditions,  accompanied  by  rapid  pulsa- 
tion of  the  heart  with  greatly  diminished  arterial  tension,  the  rebound 
or  oscillation  of  the  artery  becomes  so  marked,  in  proportion  to  the 
original  impulse,  that  it  is  easily  perceived  by  the  finger,  and  thus  the 
pulse  is  apparently  reduplicated;  that  is,  there  are  two  pulsations  of 
the  artery  for  each. contraction  of  the  heart,  namely,  one  due  to  the 
original  impulse,  and  another  due  to  the  oscillation  of  the  blood  in  the 

1  Physiologic  Medicale  de  la  Circulation  du  Sang.     Paris,  1863,  p.  266. 


836 


THE    CIRCULATION. 


feebly  distended  artery.     This  is  the   dicrotic   pulse,  which  is  often 
present  in  diseases  of  a  typhoid  character. 


116. 


DICROTIC  PULJSK  OF  TYPHOID  PNEUMONIA.    (Marey.) 
Fig.  117. 


DICROTIC  PULSE  OF  TYPHOID  FEVER      (Marey.) 

It  is  evident  that  the  dicrotic  character  of  the  pulse  is  not,  in  reality, 
peculiar  to  diseased  conditions,  since  the  sphygmograph  shows  that  it 
exists  more  or  less  perfectly  in  a  state  of  health ;  only  it  is  too  slight 
in  degree  to  be  appreciated  by  the  finger. 

Koschlakoff1  has  succeeded  in  verifying  the  results  obtained  from 
the  sphygmograph,  and  in  demonstrating  the  mechanism  of  the  dicrotic 
pulse.  He  shows  that  if  a  liquid  be  driven  by  a  rapid  impulse  through 
an  elastic  tube,  connected  with  two  separate  pressure  gauges,  one 
situated  near  the  point  of  entrance  of  the  liquid,  the  other  near  its  point 
of  exit,  the  liquid  will  rise  in  the  first  gauge  before  the  increased  pres- 
sure reaches  the  second ;  that  it  then  falls  while  the  second  is  rising, 
and  again  rises  while  the  second  falls ;  showing  an  alternate  increase 
and  diminution  of  pressure  in  the  two  extremities  of  the  elastic  tube. 
This  alternation  continues  until  the  pressure  is  equalized,  or  until  the 
tube  is  again  distended  by  a  new  impulse. 

Pulsating  Movement  of  the  Blood  in  the  Arterial  System. — Owing  to 
the  alternate  contraction  and  relaxation  of  the  heart,  the  blood  passes 
through  the  arteries  in  a  series  of  impulses  ;  and  the  hemorrhage  from 
a  wounded  artery  is  distinguished  from  venous  or  capillary  hemorrhage 
by  the  fact  that  the  blood  flows  in  successive  jets,  as  well  as  more 
rapidly  and  abundantly.  If  a  slender  canula  be  introduced  through  the 
walls  of  the  left  ventricle,  in  the  exposed  heart  of  a  living  animal,  the 
flow  of  blood  from  its  external  orifice  is  seen  to  be  completely  intermit- 
tent. A  strong  jet  takes  place  at  each  ventricular  contraction,  and  at  each 
relaxation  the  flow  is  interrupted.  If  a  puncture  be  made,  however,  in 
any  of  the  large  arteries  near  the  heart,  the  flow  of  blood  through  the 
opening  is  no  longer  intermittent,  but  continuous ;  only  it  is  much 
stronger  at  the  time  of  the  ventricular  contraction,  and  diminishes, 
though  it  does  not  entirely  cease,  at  the  time  of  relaxation.  If  the 
blood  were  driven  through  rigid  and  unyielding  tubes,  its  flow  would 

1  In  Lorain  Etudes  de  MSdecine  Clinique.     Paris,  1870,  p  75 


THE    ARTERIAL    CIRCULATION.  337 

be  everywhere  intermittent ;  and  it  would  be  delivered  from  an  orifice 
situated  at  any  point,  in  perfectly  interrupted  jets.  But  the  arteries 
are  yielding  and  elastic ;  and  this  elasticity  moderates  the  force  of  the 
separate  arterial  pulsations,  and  partially  fuses  them  with  each  other. 
The  effect  of  this  is  to  produce,  in  the  larger  and  medium-sized  arteries, 
a  movement  of  the  blood  which  is  increased  in  rapidity  and  volume  at 
each  cardiac  impulse,  and  diminished  in  the  interval  of  relaxation. 

Equalization  of  the  Blood-current  in  the  peripheral  parts  of  the 
Arterial  System. — It  has  already  been  shown  that  the  distensible  and 
elastic  properties  of  the  arterial  walls  have  the  effect  of  making  the  flow 
of  blood  more  continuous  than  it  would  be  if  subjected  only  to  the 
intermitting  action  of  the  heart.  A  part  of  the  force  of  each  cardiac 
pulsation  is  absorbed  for  the  time  in  the  distension  of  the  artery ;  and 
this  force  is  again  returned  in  the  form  of  an  impulse  to  the  blood  at 
the  following  interval,  by  the  elastic  reaction  of  the  vessel.  The  farther 
from  the  heart  the  blood  recedes,  the  greater  becomes  the  influence  of 
the  intervening  arteries ;  and  thus  the  remittent  or  pulsating  character 
of  the  arterial  current,  which  is  strongly  pronounced  in  the  vicinity  of 
the  heart,  becomes  gradually  diminished  during  its  passage  through  the 
vessels,  until  in  the  smaller  arteries,  like  the  labials,  it  is  hardly  percep- 
tible to  the  unaided  eye. 

The  physical  influence  of  an  elastic  medium,  in  equalizing  the  force 
of  an  interrupted  current,  may  be  shown  by  forcing  water  from  a 
syringe  alternately  through  two  tubes,  one  of  India  rubber,  the  other  of 
glass  or  metal.  Whatever  be  the  length  of  the  inelastic  tube,  the  water 
thrown  into  one  extremity  will  be  delivered  from  the  other  in  distinct 
jets,  corresponding  with  the  strokes  of  the  piston :  but  if  the  metallic 
tube  be  replaced  by  one  of  India  rubber  of  sufficient  length,  the  elas- 
ticity of  this  substance  merges  the  separate  impulses  into  each  other, 
and  the  water  is  discharged  from  the  farther  extremity  in  a  continuous 
stream. 

The  elasticity  of  the  arteries  never  entirely  equalizes  the  force  of  the 
separate  pulsations,  since  a  pulsating  character  can  be  seen  in  the  flow 
of  the  blood  through  even  the  smallest  arteries,  if  examined  under  the 
microscope  ;  but  this  pulsating  character  diminishes  from  the  heart  out- 
ward, and  the  current  becomes  much  more  continuous  in  the  smaller 
vessels  than  in  the  larger  arteries  or  in  those  of  medium  size. 

The  Arterial  Pressure. — The  arterial  circulation,  as  shown  by  the 
above  facts,  is  not  an  entirely  simple  phenomenon,  but  is  the  combined 
result  of  two  different  physical  forces.  It  is  due,  first,  to  the  intermit- 
ting action  of  the  heart,  by  which  the  blood  is  driven  in  successive  im- 
pulses from  within  outward  ;  and,  secondly,  to  the  elasticity  of  the  entire 
arterial  system,  by  which  it  is  subjected  to  a  continuous  pressure. 

If  an}-  one  of  the  larger  or  medium  sized  arteries  be  divided,  in  the 
living  animal,  and  a  glass  tube  of  the  same  diameter  securely  fixed  in 
its  open  orifice  and  held  in  the  vertical  position,  the  blood  will  at  once 
rise  in  the  tube  to  a  height  of  five  and  a  half  or  six  feet,  and  will  con- 


338  THE    CIRCULATION. 

tinue  to  oscillate  at  or  about  this  level.  The  height  of  the  column  of 
fluid,  thus  supported  outside  the  body,  indicates  the  degree  of  pressure 
to  which  the  blood  is  subjected  in  the  interior  of  the  vessels.  This 
pressure,  due  to  the  reaction  of  the  entire  arterial  system,  is  known  as 
the  arterial  pressure. 

The  arterial  pressure  is  best  measured  by  connecting  the  open  arteiy, 
by  a  flexible  tube,  with  a  small  reservoir  of  mercury,  provided  with  a 
narrow  upright  glass  tube,  open  at  its  upper  extremity.  When  the 
mercury  in  the  receiver  is  exposed  to  the  pressure  of  the  arterial  blood, 
it  rises  in  the  upright  tube  to  a  corresponding  height. 

This  pressure  averages,  in  the  dog  and  other  animals  of  similar  size, 
150  millimetres  of  mercury. 

When  such  an  instrument  is  connected  with  the  carotid  artery,  the 
level  of  the  mercury  in  the  upright  tube,  while  indicating  on  the  whole 
an  average  pressure,  exhibits  two  series  of  oscillations ;  showing  that 
the  degree  of  the  blood-pressure  is  constantly  changing,  owing  to  two 
different  causes.  One  of  these  oscillations  is  synchronous  with  the  move- 
ments of  respiration.  At  every  inspiration,  the  level  of  the  mercury 
falls  somewhat,  with  every  expiration  it  rises.  As  the  movement  of  in- 
spiration consists  in  an  expansion  of  the  cavity  of  the  chest,  its  effect  is 
to  diminish  the  support  afforded  the  heart  and  great  bloodvessels,  and  of 
course  to  lower  in  a  similar  degree  the  tension  of  the  whole  arterial 
system.  At  the  moment  of  expiration,  on  the  other  hand,  the  thoracic 
parietes  return  to  their  former  position,  and  the  pressure  upon  the  heart 
and  the  arteries  in  the  chest  is  re-established.  These  changes  are  indi- 
cated by  corresponding  slow  fluctuations  in  the  arterial  pressure  and  in 
the  height  of  the  mercurial  column.  The  oscillations  of  the  mercury 
due  to  respiration,  however,  are  not  at  all  uniform,  but  vary  according 
to  the  condition  of  the  respiratory  movements.  When  respiration  is 
active  and  somewhat  labored,  the  oscillations  may  reach  the  extent  of 
30  millimetres ;  when  it  is  very  quiet,  as  in  an  animal  deeply  etherized, 
they  may  diminish  so  far  as  to  be  nearly  or  quite  imperceptible. 

The  other  series  of  oscillations  is  a  more  constant  one  and  is  clue  to 
the  cardiac  pulsations.  It  consists  of  comparatively  rapid  undulations 
of  the  mercurial  column,  simultaneous  with  the  movements  of  the  heart. 
At  every  contraction  of  the  ventricle,  the  mercury  rises  from  12  to  15 
millimetres,  and  at  every  relaxation  it  falls  to  its  previous  level.  Thus 
the  instrument  becomes  a  measure,  not  only  for  the  constant  pressure 
of  the  arteries,  but  also  for  the  intermitting  pressure  of  the  heart ;  and 
on  that  account  it  has  received  the  name  of  the  cardiometer.  It  is  seen, 
accordingly,  that  each  contraction  of  the  heart  is  superior  in  force  to 
the  resistance  of  the  arteries  by  nearly  one-tenth ;  and  the  arterial  system 
is,  therefore,  kept  filled  by  successive  cardiac  pulsations,  and  the  arterial 
tension  maintained,  notwithstanding  that  the  blood  is  constantly  being 
discharged  from  the  arteries  into  the  capillary  circulation. 

Velocity  of  the  Arterial  Current. — The  rapidity  with  which  the  blood 
moves  in  the  arterial  tubes  is  much  greater  than  in  any  other  part  of  the 


THE    ARTERIAL    CIRCULATION. 


339 


vascular  system.  Its  exact  rate  varies  somewhat  according  to  the 
situation  of  the  vessel  and  the  period  of  the  pulsation.  Its  velocity  is 
greatest  in  the  immediate  neighborhood  of  the  heart,  and  diminishes  as 
the  blood  recedes  from  the  centre  of  the  circulation.  The  successive 
division  of  the  aorta  and  its  primary  branches  into  smaller  and  smaller 
ramifications  increases  the  extent  of  surface  of  the  arterial  walls  with 
which  the  blood  comes  in  contact.  The  adhesion  produced  by  this  con- 
tact, as  well  as  the  mechanical  obstacle  arising  from  the  frequent  division 
of  the  vessels  and  the  separation  of  the  streams,  contributes  to  retard 
the  current,  which  accordingly  becomes  perceptibly  slower  in  the  small 
arteries  than  in  those  of  larger  or  medium  size.  In  the  smallest  arte- 
ries, as  examined  by  the  microscope  in  the  transparent  tissues,  the  par- 
tial adhesion  of  the  blood  to  the  vascular  wall,  and  the  greater  rapidity 
of  its  flow  in  the  axis  of  the  vessel  are  readily  perceptible.  The  con- 
sistency of  the  circulating  fluid,  however,  and  the  smoothness  of  the 
internal  surface  of  the  arteries,  are  such  that  this  obstacle  to  the  move- 
ment of  the  blood  has  only  a  very  partial  influence  in  retarding  its  flow; 
and  even  in  the  smallest  arteries  it  is  so  rapid,  when  seen  under  the 
microscope,  that  the  shape  of  the  separate  blood-globules  cannot  be  dis- 
tinguished, but  only  a  mingled  current  shootin'g  forward  with  increased 
velocity  at  each  cardiac  pulsation. 

The  average  rapidity  of  the  blood  stream  in  the  larger  arteries,  in 
dogs,  horses,  and  calves,  was  determined  by  Yolkmann,  as  30  centi- 
metres per  second.  The  most  exact  experiments  on  this  point  are 
those  of  Chauveau.1  He  experimented  by  introducing  into  the  carotid 
artery  of  the  horse  a  brass 
tube  with  thin  walls,  about  five 
centimetres  long  and  eight 
or  nine  millimetres  in  diame- 
ter. The  tube  was  introduced 
through  a  longitudinal  incision 
in  the  walls  of  the  exposed 
vessel,  and  secured  in  position 
by  a  ligature  near  each  ex- 
tremity ;  so  that  the  arterial 
current  would  pass,  without 
serious  obstruction,  through 
the  brass  tube  forming,  for  the 
time,  a  part  of  the  arterial 
walls.  In  the  side  of  the  tube 
was  a  small  opening,  three 
millimetres  long  by  one  and 
a  half  millimetre  wide,  closed 
by  an  elastic  membrane  pro- 
perly secured  so  as  to  prevent  the  escape  of  the  blood.  Through  the 
centre  of  the  elastic  membrane  there  was  passed  a  very  light  metallic 

1  Journal  de  la  Physiologic,  Paris,  Octobre,  1860,  p.  695. 


w~^  -v%- A--" 

V 


CHAUVEAU'S  INSTRUMENT,  for  measuring 
the  rapidity  of  the  arterial  current.— a.  Brass  tube, 
introduced  into  the  calibre  of  the  artery,  b.  Index- 
needle  passing  through  the  elastic  membrane  in 
the  side  of  the  brass  tube,  and  moving  by  the  im- 
pulse of  the  blood-current,  c.  Graduated  scale, 
for  measuring  the  extent  of  the  oscillations  of 
the  needle. 


34:0  THE    CIRCULATION. 

needle,  the  inner  extremity  of  which,  somewhat  flattened  in  shape,  pro- 
jected into  the  interior  of  the  vessel,  and  received  the  impulse  of  the 
arterial  blood ;  while  the  outer  portion,  prolonged  into  a  slender  index, 
marked  upon  a  semicircular  graduated  scale  the  oscillations  of  the 
inner  extremity,  and  consequently  the  varying  rapidity  of  the  arterial 
current.  The  actual  velocity,  indicated  by  any  given  oscillation  of  the 
needle,  was  ascertained  beforehand  by  attaching  the  apparatus  to  an 
elastic  tube  and  passing  through  it  a  stream  of  warm  water  of  known 
rapidity. 

Chauveau  found,  by  these  experiments,  that  the  details  of  the  circu- 
latory movement  differ  somewhat  in  the  larger  arteries  near  the  heart 
from  those  in  the  smaller  branches  farther  removed. 

a.  In  the  carotid  artery,  at  the  instant  of  the  systole  of  the  heart,  the 
blood  is  suddenly  put  in  motion  with  a  high  degree  of  rapidity,  amount- 
ing on  the  average  to  a  little  over  fifty  centimetres  per  second. 

At  the  termination  of  the  systole,  and  immediately  before  the  closure 
of  the  aortic  valves,  the  movement  of  the  blood  decreases  considerably, 
and  may  even,  for  the  time,  be  completely  arrested. 

At  the  instant  of  closure  of  the  aortic  valves,  the  circulation  receives 
a  new  impulse,  and  the  blood  again  moves  forward  with  a  velocity  of 
rather  more  than  20  centimetres  per  second. 

Subsequently,  the  rapidity  of  the  current  diminishes  gradually  during 
the  period  of  the  heart's  inaction,  until,  at  the  end  of  this  period  and 
just  before  a  new  systole,  it  is  reduced,  on  the  average,  to  15  centi- 
metres per  second. 

b.  In  the  smaller  arterial  branches,  such  as  the  facial,  the  movement 
of  the  arterial  current  is  more  uniform.     It  is  less  rapid  at  the  moment 
of  the  heart's  systole;  and  on  the  other  hand,  it  is  always  more  active 
during  the  period  of  ventricular  repose. 

The  secondary  impulse,  following  the  closure  of  the  aortic  valves,  is 
much  less  perceptible  than  in  the  larger  arteries,  and  may  even  be  alto- 
gether absent. 

The  Venous  Circulation. 

The  veins  are  composed,  like  the  arteries,  of  three  coats ;  an  inner, 
middle,  and  exterior.  They  differ  from  the  arteries  in  containing  a 
much  smaller  quantity  of  muscular  and  elastic  fibres,  and  a  larger  pro- 
portion of  condensed  connective  tissue.  They  are  consequently  more 
flaccid  and  compressible  than  the  arteries,  and  less  elastic  and  contrac- 
tile. They  are  furthermore  distinguished,  throughout  the  limbs,  neck, 
and  external  portions  of  the  head  and  trunk,  by  being  provided  with 
valves,  arranged  in  the  form  of  festoons,  and  so  placed  as  to  allow  the 
blood  to  pass  readily  from  the  periphery  toward  the  heart,  while  they 
prevent  its  reflux  in  the  opposite  direction. 

Although  the  walls  of  the  veins  are  thinner  and  less  elastic  than  those 
of  the  arteries,  yet  their  capacity  for  resistance  to  pressure  is  equal,  or 
even  superior,  to  that  of  the  arteries.  Milne  Edwards  has  collected  the 


THE    VENOUS    CIRCULATION.  341 

results  of  various  experiments,  which  show  that  the  veins  will  some- 
times resist  a  pressure  which  is  sufficient  to  rupture  the  walls  of  the 
arteries.1  In  one  instance  the  jugular  vein  supported,  without  breaking, 
a  pressure  equal  to  a  column  of  water  148  feet  in  height ;  and  in  another, 
the  iliac  vein  of  a  sheep  resisted  a  pressure  of  more  than  four  atmos- 
pheres. The  portal  vein  was  found  capable  of  resisting  a  pressure  of 
six  atmospheres ;  and  in  one  case,  in  which  the  aorta  of  a  sheep  was 
ruptured  by  a  pressure  of  12  kilogrammes,  the  vena  cava  of  the  same 
animal  supported  a  pressure  equal  to  80  kilogrammes. 

This  property  of  the  veins  is  to  be  attributed  to  the  abundance  of 
white  fibrous  tissue  in  their  composition ;  the  same  tissue  which  forms 
nearly  the  whole  of  the  tendons  and  fasciae,  and  which  is  distinguished 
by  its  density  and  unyielding  nature. 

The  elasticity  of  the  veins,  on  the  other  hand,  is  much  less  than  that 
of  the  arteries.  When  filled  with  blood,  they  enlarge  to  a  certain  size ; 
and  when  cut  across  and  emptied,  their  sides  simply  collapse  and  remain 
in  contact  with  each  other. 

Another  peculiarity  of  the  venous  system  consists  in  its  numerous 
independent  and  communicating  channels. 

In  injected  preparations,  two,  three,  or  more  veins  are  often  to  be 
seen  coming,  together,  from  the  same  region  of  the  body,  and  presenting 
frequent  transverse  communications.  The  deep  veins  accompanying  the 
brachial  artery  inosculate  freely  with  each  other,  and  also  with  the 
superficial  veins  of  the  arm.  In  the  veins  coming  from  the  head,  the 
external  jugulars  communicate  with  the  thyroid  veins,  the  anterior 
jugular,  and  the  brachial  veins.  The  external  and  internal  jugulars 
commuicate  with  each  other,  and  the  two  thyroid  veins  also  form  an 
abundant  plexus  in  front  of  the  trachea. 

Thus  the  blood,  coming  from  the  extremities  toward  the  heart,  flows, 
not  in  a  single  channel,  but  in  several;  and  as  these  channels  communi- 
cate freely  with  each  other,  the  blood  passes  most  abundantly  some- 
times through  one  of  them,  and  sometimes  through  another. 

Movement  of  the  Blood  through  the  Venous  System. — The  flow  of 
blood  through  the  veins  is  less  powerful  and  regular  than  that  through 
the  arteries.  It  depends  on  the  combined  action  of  three  different  physi- 
cal forces. 

I.  The  most  constant  and  important  of  these  forces  is  the  pressure 
of  the  blood  from  the  capillary  circulation.  The  blood  moves  from  the 
arteries  into  and  through  the  capillary  vessels,  under  an  impulse  derived 
originally  from  the  contractions  of  the  heart,  and  converted  by  the  elas- 
ticity of  the  arterial  walls  into  a  more  or  less  steady  and  uniform  pres- 
sure. This  pressure  is  not  entirely  exhausted  in  carrying  the  blood 
through  the  narrow  channels  of  the  capillary  system ;  and  it  accord- 
ingly emerges  from  these  vessels  and  enters  the  commencement  of  the 
veins  with  a  certain  amount  of  force  sufficient  to  fill  the  venous  rootlets 

1  Legons  sur  la  Physiologie.     Paris,  1859,  tome  iv.  p.  301. 


oi2  THE    CIRCULATION. 

and  to  pass  thence  into  the  larger  branches  and  trunks  of  the  venous 
system.  As  the  veins  converge  from  the  periphery  toward  the  centre, 
and  unite  into  branches  of  larger  calibre,  the  resistance  afforded  by 
contact  of  the  circulating  fluid  with  their  inner  surfaces  constantly 
diminishes  from  without  inward;  and  every  contraction  of  the  right 
ventricle,  accompanied  by  the  closure  of  the  tricuspid  valve,  expels  a 
certain  quantity  of  venous  blood,  and  thus  relieves  the  returning  current 
from  the  obstacle  of  its  accumulation.  As  the  pressure  of  the  blood 
from  the  capillaries  continues  uniform,  and  as  the  resistance  to  it  is 
incessantly  neutralized  by  the  action  of  the  right  ventricle,  it  forms 
the  most  simple  and  effective  cause  for  the  movement  of  the  blood 
through  the  venous  channels. 

II.  The  flow  of  the  blood  through  the  veins  is  also  aided  in  great 
measure  by  the  contraction  of  the  voluntary  muscles.  The  veins  which 
convey  the  blood  through  the  limbs,  and  the  parietes  of  the  head  and 
trunk,  lie  among  voluntary  muscles  which  are  more  or  less  constantly 
in  a  state  of  alternate  contraction  and  relaxation.  At  every  contraction 
these  muscles  become  swollen  laterally,  and  thus  compress  the  veins 
situated  between  them.  The  blood,  expelled  from  the  vein  by  this  pres- 
sure, cannot  regurgitate  toward  the  capillaries,  owing  to  the  venous 
valves,  which  shut  back  and  prevent  its  reflux.  It  is  accordingly  forced 
onward  toward  the  heart ;  and  when  the  muscle  relaxes  and  the  vein  is 
liberated  from  pressure,  it  is  again  filled  from  behind,  and  the  circula- 
tion goes  on  as  before. 


Fig.  119.  Fig.  120. 


VEIN  with  valves  open.  VEIN  with  valves  closed;  stream  of  blood 

passing  off  by  a  lateral  channel. 

This  force  is  very  efficient  in  maintaining  the  venous  circulation ; 
since  the  voluntary  muscles  are  more  or  less  active  in  every  position  of 
the  body,  and  the  veins  are  thus  alternately  subjected  to  compression 
and  relaxation.  The  entire  voluntary  muscular  system  acts  in  this  way 
by  communicating  to  the  venous  current  indirect  impulses  of  frequent 


THE    CAPILLARY    CIRCULATION.  343 

repetition,  which,  combined  with  the  action  of  the  valves,  urge  the  blood 
from  the  periphery  toward  the  heart. 

III.  A  third  cause,  which  is  more  or  less  active  in  promoting  the 
movement  of  the  venous  blood,  is  the  force  'of  aspiration  exerted  by 
the  thorax.  When  the  chest  expands  by  the  lifting  of  the  ribs  and  the 
descent  of  the  diaphragm,  this  movement  tends  to  diminish  the  pressure 
upon  its  contents,  and  consequently  to  draw  into  the  thoracic  cavity  any 
fluids  which  can  gain  access  to  it.  The  expanded  cavity  is  principally 
filled  by  the  atmospheric  air,  which  passes  in  through  the  trachea  to  fill 
the  bronchial  tubes  and  the  pulmonary  vesicles.  But  the  blood  in  the 
neighboring  parts  of  the  venous  system  is  solicited  at  the  same  time, 
though  to  a  less  degree,  in  a  similar  direction.  This  force  of  aspiration, 
like  the  respiratory  movements  themselves,  is  gentle  and  uniform  in 
character.  Its  influence  extends  indirectly  throughout  the  venous  sys- 
tem, each  expansion  of  the  chest  causing  an  increased  flow  of  blood  from 
the  extra-  to  the  intra- thoracic  veins,  while  the  former  are  filled  up  from 
behind  as  fast  as  they  are  emptied  in  front. 

Eapidity  of  the  Venous  Circulation — With  regard  to  the  velocity  of 
the  venous  current,  no  direct  results  have  been  obtained  by  experiment. 
Owing  to  the  flaccidity  of  the  veins,  and  the  readiness  with  which  the 
flow  of  blood  through  them  is  disturbed,  it  is  not  possible  to  determine 
this  point,  in  the  same  manner  as  it  has  been  determined  for  the  arteries. 
The  only  calculation  which  has  been  made  in  this  respect  is  based  upon 
a  comparison  of  the  total  capacity  of  the  arterial  and  venous  systems. 
As  the  same  blood  which  passes  outward  through  the  arteries  returns 
inward  through  the  veins,  the  rapidity  of  its  flow  in  each  direction  must 
be  in  inverse  proportion  to  the  capacity  of  the  two  systems.  The  ca- 
pacity of  the  entire  venous  system,  when  distended  by  injection,  is  about 
twice  as  great  as  that  of  the  entire  arterial  system.  During  life,  how- 
ever, the  venous  system  is  at  no  time  so  completely  filled  with  blood  as 
is  the  case  with  the  arteries;  and,  making  allowance  for  this  difference, 
it  may  be  estimated  that  the  entire  quantity  of  venous  blood  is  to  the 
entire  quantity  of  arterial  blood  nearly  as  three  to  two.  The  velocity 
of  the  venous  blood,  as  compared  with  that  of  the  arterial,  is  therefore 
as  two  to  three ;  and  if  we  regard  the  average  rapidity  of  the  arterial 
current,  according  to  Yolkmann's  experiments,  as  30  centimetres  per 
second,  this  would  give  the  movement  of  blood  in  the  large  veins  as 
about  20  centimetres  per  second.  This  calculation,  however,  is  alto- 
gether an  approximative  one ;  since  the  venous  circulation  varies, 
according  to  many  different  circumstances,  in  different  parts  of  the 
body.  'It  may  nevertheless  be  considered  as  expressing  with  sufficient 
accuracy  the  general  relative  velocity  of  the  arterial  and  venous  currents 
in  corresponding  parts  of  their  course. 

The  Capillary  Circulation, 

The  capillary  bloodvessels  are  minute  inosculating  tubes,  which  per- 
meate the  vascular  organs  in  various  directions,  and  bring  the  blood  into 


344 


THE    CIRCULATION. 


Fig.  121. 


indirect  contact  with  the  substance  of  the  tissues.  They  are  continuous 
with  the  terminal  ramifications  of  the  arteries  on  the  one  hand,  and  with 
the  commencing  rootlets  of  the  veins  on  the  other.  They  vary  some- 
what in  size  in  the  different  organs  and  tissues,  their  average  diameter 
in  the  human  subject  being  about  10  mmm.,  or  T^  of  a  millimetre.  The 
largest  capillaries,  according  to  Kolliker,  in  the  glands  and  the  osseous 
tissue,  may  reach  the  diameter  of  15  mmm. ;  while  the  smallest,  in  the 
muscles,  the  nerves,  and  the  retina,  are  4.5  mmm.,  that  is,  almost  exactly 
the  size  of  the  smallest  of  the  red  globules  of  the  blood. 

As  the  arterial  ramifications  approach  the  confines  of  the  capillary 
system  they  diminish  gradually  in  size,  and  lose  first  their  external 
coat  of  connective  tissue.  Their  middle  coat  at  the  same  time  becomes 
reduced  to  a  single  layer  of  fusiform  muscular  fibres,  which  become 
in  turn  less  numerous,  and  lastly  disappear  altogether.  The  vascular 
canal  is  thus  finally  composed  only  of  a  single  tunic  continuous  with 
the  internal  coat  of  the  arterial  ramifications. 

The  capillary  bloodvessel,  examined  in  its  recent  condition,  as  ex- 
tracted from  any  soft  vascular  tissue,  appears  to  consist  of  a  simple, 

nearly  homogeneous  tubular  mem- 
brane, provided  with  flattened  oval 
nuclei  placed  at  more  or  less  regular 
distances  from  each  other,  and  pro- 
jecting slightly  into  the  cavity  of  the 
vessel. 

It  has  been  found,  however,  that  if 
a  capillary  bloodvessel  be  treated  with 
a  weak  solution  of  silver  nitrate,  its 
inner  surface  becomes  marked  off  into 
regular  spaces,  each  of  which  includes 
a  nucleus ;  indicating  that  its  appa- 
rently homogeneous  tunic  is  com- 
posed of  flattened  epithelium-like 
cells,  united  with  each  other  at  their 
adjacent  edges  by  an  intervening 
cement.  It  is  this  thin  layer  of  in- 
tervening substance  which  becomes 
darkened  by  the  action  of  the  silver 

nitrate  and  thus  brings  into  view  the  outlines  of  the  cells  forming  the 
vascular  wall. 

The  form  of  the  cells  constituting  the  vascular  membrane  varies  in 
different  regions  and  in  capillaries  of  different  calibre.  According  to 
Kolliker,  in  the  smallest  capillary  bloodvessels,  measuring  from  4.5 
to  7  mmm.  in  diameter,  the  cells  are  narrow,  elongated,  and  fusiform, 
as  in  Fig.  122;  often  curled  from  side  to  side,  so  as  to  form  each  a 
half  cylinder,  two  of  them  joining  at  their  edges  to  complete  the 
capillary  tube,  and  alternating  longitudinally,  the  pointed  extremity  of 
one  cell  being  intercalated  between  those  of  the  two  following  cells.  In 


AKTERY,  with  its  muscular 
tunic  (a)  breaking  up  into  capillaries. 
From  the  pia  mater. 


THE    CAPILLARY    CIRCULATION. 


345 


the  larger  capillaries,  of  8  to  13  mmm.  in  diameter,  where  the  calibre  of 
the  vessel  is  surrounded  by  three  or  four  cells  placed  side  by  side,  they 
are  shorter  and  wider  in  form,  like  those  of  ordinary  pavement  epithe- 
lium. The  arrangement  of  these  microscopic  forms  in  the  wall  of  the 

Fig.  122. 


CAPILLARY  BLOODVESSEL,  from  the  tail  of  the  tadpole;  showing  the  outlines   of 
its  epithelium-like  cells,  rendered  visible  by  the  action  of  silver  nitrate.    (KOlliker.) 

capillary  bloodvessels  has  given  rise  to  the  opinion,  entertained  by  some 
histologists,  that  the  vascular  system  is  to  be  regarded  as  a  series  of 
intercellular  canals,  provided,  in  different  regions,  with  varying  addi- 
tional layers  of  muscular,  elastic,  and  connective  tissue. 

The  capillary  bloodvessels  ure  further  distinguished  from  both  arteries 
and  veins  by  their  frequent  inosculation.  The  arteries  constantly  divide 
and  subdivide,  as  they  pass  from  within  outward,  while  the  veins  as 
constantly  unite  with  each  other,  to  form  larger  and  less  numerous 
branches  and  trunks,  as  they  converge  from  the  periphery  toward  the 
centre ;  and  although  the  arteries  always  present  inosculations  in  certain 
regions,  and  the  veins  more  frequently  still,  this  feature  is,  nevertheless, 
a  secondary  or  incidental  one  in  both  vascular  systems.  The  arteries 
are  essentially  diverging  tubes  to  distribute  the  blood  from  within  out- 
ward ;  the  veins  are  converging  channels  to  collect  and  transport  it  from 
without  inward. 

The  capillaries,  on  the  other  hand,  are  mainly  characterized  by  their 
constant  and  repeated  intercommunication.  They  are  vascular  canals 
which  penetrate  the  solid  organs  and  tissues,  uniting  with  each  other  at 
23 


346 


THE    CIKCULATION. 


Fig.  123. 


CAPILLARY  PLEXUS,  from  the  web  of  the 
frog's  foot. 


short  intervals,  in  such  a  manner  as  to  form  an  interlacing  network  or 
plexus  of  minute  bloodvessels,  known  as  the  capillary  plexus.     The 

vessels  forming  this  plexus  vary 
somewhat  in  size,  abundance, 
and  arrangement  in  different 
parts  of  the  body.  In  every 
vascular  organ  and  tissue  there 
are  certain  spaces  or  islets,  in- 
closed on  all  sides  by  capilla- 
ries, but  into  the  interior  of 
which  these  vessels  do  not  pene- 
trate. Such  islets  or  intervas- 
cular  spaces  must  therefore  ob- 
tain their  nourishment  by  the 
exudation  and  absorption  of  the 
fluid  ingredients  of  the  blood 
through  the  capillary  walls  and 
the  substance  of  the  intervening 
tissue. 

The    special   arrangement  of 

the  capillary  bloodvessels,  and  the  form  and  size  of  the  meshes  of  their 
network,  are,  in  general,  characteristic  of  each  separate  organ  or  tissue. 
In  the  muscles,  the  meshes  are  in  the  form  of  long  parallelograms,  cor- 
responding with  that  of  the  muscular  fibres ;  in  the  mucous  membranes 
of  the  stomach  and  large  intestine,  they  are  hexagonal,  or  irregularly 
circular,  inclosing  the  orifices  of  the  secreting  follicles ;  in  the  papillae 
of  the  tongue  and  skin,  and  in  the  placental  tufts,  the  capillaries  form 
twisted  vascular  loops  ;  in  the  glomeruli  of  the  kidneys,  convoluted 
coils ;  in  the  connective  tissue,  irregularly  shaped  figures,  correspond- 
ing in  direction  with  the  fibrous  bundles  of  the  tissue. 

The  capillary  bloodvessels  are  the  most  abundant,  and  interlaced  in 
the  finest  network,  in  those  organs  to  which  the  blood  is  distributed  for 
other  purposes  than  for  local  nutrition;  as  for  that  of  aeration,  secre- 
tion, or  absorption.  One  of  the  closest  of  all  the  capillary  networks  is 
that  of  the  lungs,  in  which  the  diameter  of  the  spaces  separating  the 
r  bloodvessels,  in  the  walls  of  the  pulmonary  vesicles,  is  sometimes  a  little 
greater  and  sometimes  a  little  less  than  that  of  the  capillaries  them- 
selves. In  the  glandular  tissue  of  the  liver,  the  spaces  separating  the 
adjacent  vessels  are  only  a  little  wider  than  the  capillaries  forming  the 
intra-lobular  network.  In  the  nerves,  the  serous  membranes,  and  the 
tendons,  on  the  other  hand,  the  capillary  vessels  are  less  closely  inter- 
woven ;  and  in  the  adipose  tissue  they  form  wide,  open  meshes,  em- 
bracing the  exterior  of  the  separate  fat  vesicles. 

Movement  of  the  Blood  in  the  Capillary  Vessels. — The  motion  of  the 
blood  in  the  capillaries  may  be  studied  by  examining,  under  the  micro- 
scope, any  transparent  tissue  of  a  sufficient  degree  of  vascularity.  The 
frog  is  the  most  convenient  animal  for  this  purpose,  owing  to  the  readi- 


THE    CAPILLARY    CIRCULATION. 


347 


ness  with  which  the  circulation  may  be  maintained  even  in  the  internal 
organs,  exposed  at  ordinary  temperatures.  In  order  to  secure  immo- 
bility, the  medulla  oblongata  may  first  be  broken  up  by  a  strong  needle 
introduced  through  the  cranium,  or  the  voluntary  muscles  may  be  para- 
lyzed by  the  subcutaneous  injection  of  six  drops  of  a  filtered  watery 
solution  of  woorara,  made  in  the  proportion  of  one  part  to  five  hundred. 
The  whole  body,  with  the  exception  of  the  part  used  for  observation, 
should  be  enveloped  in  a  light  linen  or  cotton  bandage,  kept  moistened 
to  prevent  desiccation  of  the  surface.  The  tongue,  or  the  web  of  one 
foot,  may  be  stretched  over  a  glass  side,  and  placed  under  the  lens  of 
the  instrument.  To  examine  the  pulmonary  circulation,  an  opening 
should  be  made  in  one  side  just  behind  the  anterior  limb,  and  the 
lung  moderately  inflated  through  the  glottis,  until  it  protrudes  through 
the  external  wound.  For  the  mesenteric  circulation,  an  incision  should 
be  made  in  the  left  flank  of  a  male  frog,  a  loop  of  intestine  carefully 
drawn  out  of  the  abdomen,  and  the  mesentery  allowed  to  rest  upon  a 
circular  glass  plate,  12  millimetres  in  diameter,  and  6  millimetres  in 
thickness,  cemented  upon  a  large  glass  plate,  by  which  the  body  of  the 
animal  is  supported.  Under  favorable  circumstances  the  circulation 
will  go  on  in  either  of  these  organs  for  several  hours. 

When  the  circulation  is  examined  in  this  manner,  the  smaller  arte- 
ries, the  capillary  vessels,  and  the  minute  veins  are  often  -visible  under 
the  microscope  in  the  same 
region.  The  blood  can  be 
seen  entering  the  field  by 
the  smaller  arteries,  shooting 
through  them  with  great  ra- 
pidity in  successive  impulses, 
and  flowing  off  by  the  veins 
at  a  somewhat  slower  rate. 
In  the  capillaries,  the  circula- 
tion is  considerably  less  rapid 
than  in  either  the  arteries  or 
the  veins.  It  is  also  perfectly 
steady  and  uninterrupted  in 
its  flow.  The  blood  moves 
through  its  vascular  channels 
in  a  uniform  current,  without 
their  exhibiting  any  appear- 
ance of  contraction  or  dilata- 
tion. Another  marked  peculiarity  of  the  capillary  circulation  is  that 
it  has  no  definite  direction.  Its  numerous  streams  pass  indifferently 
above  and  below  each  other,  at  right  angles  to  each  other's  course,  or 
even  in  opposite  directions ;  so  that  the  blood,  while  in  the  capillaries, 
circulates  everywhere  among  the  tissues,  in  such  a  manner  as  to  be 
distributed  to  all  parts  of  their  substance. 

The  motion  of  the  red  and  white  globules  is  also  peculiar,  and  shows 


CAPILLARY  CIRCULATION  in  web  of  frog's  foot. 


THE    CIRCULATION. 

distinctly  the  difference  in  their  physical  properties.  In  the  larger  ves- 
sels the  red  globules  are  carried  along  in  close  column,  in  the  central 
part  of  the  stream;  while  near  the  edges  of  the  vessel  there  is  a  trans- 
parent space  occupied  only  by  clear  plasma,  in  which  no  red  globules 
are  to  be  seen.  In  the  smaller  vessels  the  globules  pass  two  by  two,  or 
follow  each  other  in  single  file.  The  flexibility  and  semi-fluid  consist- 
ency of  the  red  globules  are  very  apparent  from  the  readiness  with 
which  they  become  folded  up,  bent  or  twisted,  and  with  which  they 
glide  through  minute  branches  of  communication,  smaller  in  diameter 
than  themselves.  The  white  globules,  on  the  other  hand,  move  more 
slowly  through  the  vessels.  They  drag  along  the  external  portions  of 
the  current,  and  are  sometimes  temporarily  arrested,  adhering  for  a  few 
seconds  to  the  internal  surface  of  the  vessel.  Whenever  the  current  is 
obstructed  or  retarded,  the  white  globules  accumulate  in  the  affected 
portion,  and  become  more  numerous  there  in  proportion  to  the  red. 

It  is  during  the  capillary  circulation  that  the  blood  serves  for  the 
nutrition  of  the  vascular  organs.  Its  fluid  portions  transude  through 
the  walls  of  the  vessels,  and  are  absorbed  by  the  tissues  in  the  propor- 
tions requisite  for  their  nourishment,  or  for  the  products  of  secretion  ; 
while  its  albuminous  ingredients  are  also  transformed  into  new  materials, 
characteristic  of  the  different  tissues  and  fluids.  In  this  way  are  pro- 
duced the  myosine  of  the  muscles,  the  collagen  of  the  bones,  tendons, 
and  ligaments,  the  ptyaline  of  the  saliva,  and  the  pepsine  of  the  gastric 
juice  ;  and  in  the  lungs,  the  exchange  of  oxygen  and  carbonic  acid  takes 
place  in  the  capillary  vessels.  The  blood  in  the  capillary  circulation 
thus  furnishes,  directly  or  indirectly,  the  materials  of  nutrition  for  the 
entire  body. 

Physical  Cause  of  the  Capillary  Circulation. — The  physical  condi- 
tions which  influence  the  movement  of  the  blood  in  the  capillaries  are 
somewhat  different  from  those  of  the  arterial  and  venous  circulations. 
By  the  successive  division  of  the  arteries  from  the  heart  outward,  the 
movement  of  pulsation  is  to  a  great  extent  equalized  in  the  smaller 
arterial  branches.  But  as  these  vessels  reach  the  confines  of  the  capillary 
system,  they  suddenly  break  up  into  a  terminal  ramification  of  still 
smaller  and  more  numerous  vessels,  and  so  lose  themselves  at  last  in 
the  capillary  network.  By  this  final  increase  of  the  vascular  surface, 
the  equalization  of  the  heart's  action  is  completed.  There  is  no  longer 
any  pulsating  character  in  the  force  which  acts  upon  the  circulating 
fluid ;  and  the  blood  moves  through  the  capillary  vessels  under  a  con- 
tinuous and  uniform  pressure. 

This  pressure  is  sufficient  to  cause  the  blood  to  pass  with  considerable 
rapidity  through  the  capillary  plexus,  into  the  commencement  of  the 
veins.  This  fact  was  first  demonstrated  by  Sharpey,1  who  employed  an 
injecting  syringe  with  a  double  nozzle,  one  extremity  of  which  was  con- 

1  Todd  and  Bowman,  Physiological  Anatomy  and  Physiology  of  Man,  vol.  ii. 
p.  350. 


THE    CAPILLARY    CIRCULATION.  349 

nectcd  with  a  mercurial  gauge,  while  the  other  was  inserted  into  the 
artery  of  a  recently  killed  animal.  When  the  syringe,  filled  with  defi- 
brinated  blood,  was  fixed  in  this  position,  the  defibrinated  blood  would 
press  with  equal  force  upon  the  mercury  in  the  gauge  and  upon  the  fluid 
in  the  bloodvessels  ;  and  thus  the  height  of  the  mercurial  column  indi- 
cated the  amount  of  pressure  required  to  force  the  defibrinated  blood 
through  the  capillaries  of  the  animal,  and  to  make  it  return  by  the  cor- 
responding vein.  In  this  way  Prof.  Sharpey  found  that,  when  the  free 
end  of  the  injecting  tube  was  attached  to  the  mesenteric  artery  of  the 
dog,  a  pressure  of  90  millimetres  of  mercury  caused  the  blood  to  pass 
through  the  capillaries  of  the  intestine  and  of  the  liver ;  and  that  under 
a  pressure  of  130  millimetres,  it  flowed  in  a  full  stream  from  the  divided 
extremity  of  the  vena  cava. 

We  have  obtained  similar  results  by  experimenting  upon  the  vessels 
of  the  lower  extremity.  A  full  grown,  healthy  dog  was  killed,  and  one 
of  the  lower  extremities  immediately  injected  with  defibrinated  blood, 
by  the  femoral  artery,  in  order  to  prevent  coagulation  in  the  smaller 
vessels.  A  syringe  with  a  double  flexible  nozzle  was  then  filled  with 
defibrinated  blood,  and  one  extremity  of  its  injecting  tube  attached  to 
the  femoral  artery,  the  other  to  the  mouthpiece  of  a  cardiometer.  By 
making  the  injection,  it  was  then  found  that  the  defibrinated  blood  was 
returned  from  the  femoral  vein  in  a  continuous  stream  under  a  pressure 
of  120  millimetres,  and  that  it  was  discharged  very  freely  under  a  pres- 
sure of  130  millimetres. 

Since  the  arterial  pressure  upon  the  blood  during  life  is  equal  to  150 
millimetres  of  mercury,  it  is  evident  that  this  pressure  is  sufficient  to 
propel  the  blood  through  the  capillary  circulation. 

Furthermore,  the  blood  is  not  altogether  relieved  from  the  influence 
of  elasticity,  after  leaving  the  arteries.  For  the  capillaries  themselves 
have  a  certain  degree  of  elasticity,  and  are  surrounded,  in  addition,  by 
the  tissues  of  the  organs  in  which  they  are  distributed  ;  many  of  which, 
such  as  the  lungs,  spleen,  skin,  lobulated  glands,  and  mucous  membranes, 
contain  elastic  fibres  more  or  less  abundantly  disseminated  through  their 
substance.  The  effect  of  this  physical  property,  in  the  vessels  and  the 
neighboring  parts,  may  be  exhibited  in  artificial  injections  of  one  of  the 
lower  limbs  through  the  femoral  artery,  or  of  the  liver  through  the 
portal  vein.  If,  while  the  parts  are  distended  by  the  fluid  passing 
through  their  vessels,  the  injecting  force  be  suddenly  arrested,  the  move- 
ment of  the  current  does  not  at  once  cease,  but  the  fluid  of  injection 
continues  to  escape  for  several  seconds  from  the  femoral  or  hepatic  vein, 
owing  to  the  continuous  pressure  exerted  from  behind.  The  elasticity 
of  the  surrounding  tissues,  therefore,  supplements,  that  of  the  minute 
bloodvessels,  and  aids  in  producing  a  uniform  movement  of  the  capillary 
circulation. 

Velocity  of  the  Blood  in  the  Capillary  Vessels. — The  motion  of  the 
blood  in  the  capillary  vessels  is  much  less  rapid  than  in  either  the 
arteries  or  the  veins.  It  may  be  measured,  with  a  tolerable  approach 


350  THE    CIRCULATION. 

to  accuracy,  during  the  microscopic  examination  of  transparent  and 
vascular  tissues.  The  results  obtained  in  this  way  by  different  observers 
(Valentin,  Weber,  and  Volkrnann),  show  that  the  rate  of  movement  of 
the  blood  through  the  capillaries  is  rather  less  than  one  millimetre  per 
second ;  or  about  5  centimetres  per  minute.  Since  the  rapidity  of  the 
current  must  be  in  inverse  ratio  to  the  entire  calibre  of  the  vessels 
through  which  it  moves,  it  appears  that  the  united  calibre  of  all  the 
capillaries  must  be  not  less  than  300  times  greater  than  that  of  the 
arteries.  It  does  not  follow  from  this,  however,  that  the  whole  quantity 
of  blood  contained  in  the  capillaries  at  any  one  time  is  so  much  greater 
than  that  in  the  arteries  ;  since,  although  the  united  calibre  of  the  capil- 
laries is  large,  their  length  is  very  small.  The  effect  of  the  anatomical 
structure  of  the  capillary  system  is  to  disseminate  a  comparatively  small 
quantity  of  blood  over  a  very  large  space,  so  that  the  physiological 
reactions  necessary  to  nutrition  take  place  with  promptitude  and  energy. 
Although  the  rate  of  movement  of  the  blood  in  these  vessels,  accordingly, 
is  a  slow  one,  yet  as  the  distance  to  be  passed  over  between  the  arteries 
and  veins  is  very  small,  the  blood  requires  but  a  short  time  to  traverse 
the  capillary  system,  and  to  commence  its  returning  passage  by  the  veins. 

General  Rapidity  of  the  Circulation. 

The  rapidity  with  which  the  blood  passes  through  the  entire  round 
of  the  circulation  has  been  demonstrated  by  Hering,  Poisseuille,  Mat- 
teucci,  and  Vierordt  in  the  following  manner :  A  solution  of  potassium 
ferrocyanide  was  injected  into  the  right  jugular  vein  of  a  horse,  at  the 
same  time  that  a  ligature  was  placed  upon  the  corresponding  vein  on 
the  left  side,  and  an  opening  made  in  it  above  the  ligature.  The  blood 
flowing  from  the  left  jugular  vein  was  then  received  in  separate  vessels, 
which  were  changed  every  five  seconds,  and  the  contents  afterward  ex- 
amined. It  was  thus  found  that  the  blood  drawn  from  the  first  to  the 
twentieth  second  contained  no  traces  of  the  ferrocyanide ;  but  that  which 
escaped  from  the  vein  at  the  end  of  from  twenty  to  twenty-five  seconds, 
showed  unmistakable  evidence  of  the  presence  of  the  foreign  salt.  The 
potassium  ferrocyanide  must,  therefore,  during  this  time,  have  passed 
from  the  point  of  injection  to  the  right  side  of  the  heart,  thence  to  the 
lungs  and  through  the  pulmonary  circulation,  to  the  left  side  of  the 
heart  by  the  pulmonary  veins,  outward  by  the  arteries  to  the  capillary 
circulation  of  the  head  and  neck,  and  must  have  again  commenced  its 
downward  passage  to  the  heart  by  the  opposite  jugular  vein. 

By  extending  these  observations,  it  was  found  that  the  duration  of 
the  circulatory  movement  varies  to  some  extent  in  different  species  of 
animals ;  being,  as  a  general  rule  longer  in  those  of  larger  size.  The 
main  result,  as  given  by  Milne  Edwards,1  is  as  follows: 

1  Leqons  sur  la  Physiologic.     Paris,  1859,  tome  iv.  p.  364. 


LOCAL    VARIATIONS.  351 

DURATION  OF  THE  CIRCULATORY  MOVEMENT. 

In  the  Horse 28  seconds. 

"      Dog 15 

"       Goat 13       " 

"      Rabbit 7       " 

These  results  are  corroborated  by  subsequent  investigations.  In  ex- 
perimenting upon  the  dog,  by  injecting  a  solution  of  potassium  ferrocy- 
anide  into  the  jugular  vein,  and  immediately  drawing  blood  from  the 
corresponding  vein  on  the  opposite  side,  we  have  found  that  the  short 
interval  of  time  requisite  for  closing  the  first  vein  by  ligature  after 
terminating  the  injection,  and  opening  the  second  in  such  a  manner  as 
to  obtain  a  specimen  of  blood  for  examination,  is  sufficient  to  allow 
of  the  passage  of  the  ferrocyanide  through  the  entire  round  of  the  cir- 
culation. If  we  regard  the  duration  of  this  movement  in  the  human 
subject  as  intermediate  between  that  in  the  dog  and  the  horse,  making 
allowance  for  the  difference  in  size,  this  would  give  the  time  required 
by  the  blood  to  make  the  circuit  of  the  veins,  arteries,  and  capillaries, 
in  man,  as  not  far  from  20  seconds. 

Local  Variations  in  the  Capillary  Circulation. 

An  important  class  of  phenomena  connected  with  this  part  of  the 
subject  consists  of  the  local  variations  in  the  capillary  circulation. 
These  variations  are  often  very  marked,  and  show  themselves  in  many 
different  parts  of  the  body.  The  pallor  or  suffusion  of  the  face  under 
mental  emotion,  the  congestion  of  the  mucous  membranes  during  diges- 
tion, and  the  local  and  denned  redness  of  the  skin  produced  by  any 
irritating  application,  are  all  instances  of  this  sort.  These  changes  are 
due  to  the  contraction  or  dilatation  of  the  smaller  arterial  branches 
which  supply  the  part  with  blood,  under  the  influence  of  nervous  action. 
The  middle  coat  of  these  vessels  is  composed  mainly  of  organic  or 
unstriped  muscular  fibres,  arranged  in  a  transversely  circular  direction, 
which  by  their  contraction  diminish  and  by  their  relaxation  enlarge 
the  calibre  of  the  arterial  tube.  They  regulate,  accordingly,  by  this 
means,  the  quantity  of  blood  passing  to  the  capillary  system.  When 
contracted,  they  resist  more  strongly  the  impulsive  force  of  the  arterial 
current,  and  admit  the  blood  in  smaller  quantity.  When  dilated,  they 
allow  a  freer  access  to  the  capillaries  and  the  blood  passes  in  greater 
abundance. 

These  changes  are  most  distinctly  manifested  in  the'  periodical  con- 
gestion of  the  glandular  organs.  All  the  glands  and  mucous  membranes 
connected  with  the  digestive  apparatus  enter  into  a  state  of  unusual 
vascular  excitement  at  the  time  of  secretion  and  digestion.  This  can 
readily  be  seen,  in  the  living  animal,  in  the  pancreas,  and  in  the  mucous 
membranes  of  the  stomach  and  small  intestine ;  the  tissues  of  these 
parts  being  visibly  redder  and  more  turgid  during  digestion  and  absorp- 
tion than  in  the  fasting  condition. 

A  similar  variation  of  the  circulation  has  been  particularly  studied 


352  THE    CIRCULATION. 

by  Bernard1  in  the  submaxillary  gland  of  the  dog.  During  the  ordinary 
condition  of  glandular  repose  he  found  that  it  required  sixty-five  seconds 
to  obtain  five  cubic  centimetres  of  blood  from  the  submaxillary  vein ; 
but,  when  the  gland  was  excited  to  functional  activity,  the  same  quan- 
tity of  blood  was  discharged  by  the  vein  in  fifteen  seconds.  Thus  the 
volume  of  blood  passing  through  the  organ  in  a  given  time  was  more 
than  four  times  as  great  while  the  gland  was  in  a  state  of  active  secre- 
tion, as  in  a  condition  of  repose. 

The  increased  flow  of  blood,  in  a  secreting  gland,  is  accompanied  also 
by  an  important  change  in  its  appearance.  During  repose,  the  blood, 
which  enters  the  submaxillary  gland  from  the  arteries  bright  red,  is 
changed  in  its  tissue  from  arterial  to  venous,  and  passes  out  by  the 
veins  of  a  dark  color.  But  when  the  secretion  of  the  gland  is  excited, 
either  by  galvanization  of  its  nerve  or  by  introducing  vinegar  into  the 
mouth  of  the  animal,  the  blood  is  not  only  discharged  in  larger  quantity, 
but  passes  out  red  by  the  veins,  so  as  hardly  to  be  distinguished  in 
color  from  arterial  blood.  When  the  secretion  of  the  gland  is  suspended, 
the  blood  in  its  vein  again  becomes  dark-colored  as  before.  There  is 
little  doubt  that  the  same  is  true  of  most  of  the  secreting  glands,  and 
that  the  blood  circulating  in  their  capillaries  is  changed  from  red  to  blue 
only  during  the  period  of  functional  repose ;  while  at  the  time  of  active 
secretion  it  not  only  passes  through  the  vessels  in  greater  abundance, 
but  also  retains  its  ruddy  color  in  the  veins. 

This  -is  because,  during  the  period  of  glandular  repose,  the  blood  per- 
forms in  its  tissues  the  usual  functions  of  nutrition.  It  therefore  under- 
goes the  ordinary  changes  and  becomes  altered  in  color  from  arterial  to 
venous.  But  the  period  of  active  secretion  is  a  period  of  congestion, 
during  which  the  blood  passes  in  larger  quantity,  while  its  watery  and 
saline  ingredients  exude  into  the  secretory  ducts,  bringing  with  them 
the  materials  accumulated  in  the  interval  of  repose.  There  is  nothing 
in  this  process  to  exhaust  the  oxygen  of  the  blood  or  to  change  its 
color  from  arterial  to  venous,  and  it  therefore  passes  into  the  veins 
comparatively  unaltered. 

A  similar  ruddy  color  of  venous  blood  is  to  be  seen  in  the  renal  veins, 
where  it  is  often  nearly  identical  with  that  of  arterial  blood.  The  dif- 
ference in  hue  between  the  renal  veins  and  the  neighboring  muscular 
veins  or  the  vena  cava,  when  exposed  by  opening  the  abdomen  of  the 
living  animal,  is  very  marked,  provided  the  kidneys  be  at  the  time  in  a 
state  of  functional  activity.  The  greater  part  of  the  blood  traversing 
these  organs  is  changed  only  by  the  elimination  of  its  urea  and  the 
remaining  ingredients  of  the  urine,  which  exude  into  the  excretory 
tubules.  The  process  of  active  local  nutrition  is  here  altogether  sub- 
servient to  the  discharge  of  organic  materials  already  existing  in  the 
blood;  -and  the  loss  of  oxygen  and  alteration  in  color  of  the  circulating 
fluid  are  thus  comparatively  insignificant. 

1  Leqons  sur  les  Liquides  de  TOrganisme.     Paris,  1859,  tome  ii.  p.  272. 


LOCAL    VARIATIONS. 


353 


Fig.  125. 


On  the  other  hand,  the  venous  blood  coming  from  the  muscular  tissue 
is  very  dark  colored,  especially  if  the  muscles  be  in  a  state  of  active 
contraction.  As  the  muscles  form  so 
large  a  part  of  the  entire  mass  of  the 
body,  their  condition  has  a  prepondera- 
ting influence  upon  the  color  of  the 
venous  blood  in  general.  The  greater 
the  activity  of  the  muscular  system,  the 
darker  is  the  color  of  the  blood  return- 
ing from  the  trunk  and  extremities. 
When  the  muscles  are  in  a  state  of  re- 
pose or  paralysis,  on  the  contrary,  the 
change  is  less  marked  ;  and  in  the  com- 
plete relaxation  produced  by  abundant 
hemorrhage  or  by  complete  etherization, 
the  blood  in  the  veins  often  approxi- 
mates in  color  to  that  in  the  arteries. 

Finally,  in  the  lungs  the  reverse  pro- 
cess takes  place.  In  these  organs  the 
blood  is  supplied  with  a  fresh  quantity 
of  oxygen,  to  replace  that  which  has 
been  consumed  elsewhere ;  and  accord- 
ingly it  changes  its  color  from  dark 
purple  to  bright  red  as  it  passes  through 
the  pulmonary  capillaries. 

Both  the  physical  and  chemical  phe- 
nomena, therefore,  of  the  circulation 
vary  at  different  times  and  in  different 
organs.  The  actions  which  go  on 
throughout  the  body,  are  varied  in  cha- 
racter, and  produce  a  similar  difference 
in  the  phenomena  of  the  circulation. 
The  venous  blood,  consequently,  has  a 
different  composition  as  it  returns  from 
different  organs.  In  the  parotid  gland 
it  yields  the  ingredients  of  the  saliva ; 
in  the  kidneys  those  of  the  urine.  In 
the  intestine  it  absorbs  the  nutritious 
elements  of  the  digested  food ;  and  in 
the  liver  it  gives  up  substances  destined 
to  produce  the  bile,  while  it  absorbs 
glucose  from  the  hepatic  tissue.  In  the 
lungs  it  changes  from  blue  to  red,  and 
in  the  capillaries  of  the  general  system, 
from  red  to  blue ;  and  its  temperature,  also,  varies  in  different  veins, 
according  to  the  peculiar  chemical  and  nutritive  changes  going  on  in  the 
organs  from  which  they  originate. 


DIAGRAM  OF  THK  CIRCULA- 
TION.—1.  Heart.  2.  Lungs.  3.  Head 
and  upper  extremities.  4  Spleen.  6. 
Intestine.  6.  Kidney.  7.  Lower  ex- 
tremities. 8.  Liver. 


CHAPTEE    XVI. 

THE    LYMPHATIC    SYSTEM. 

IN  addition  to  the  connected  series  of  canals  by  which  the  blood 
passes  in  a  continuous  round  through  the  arteries,  capillaries,  and  veins, 
there  is  also  a  system  of  vessels,  leading  only  from  the  periphery  toward 
the  centre,  and  discharging  into  the  great  veins  near  the  heart  the  fluids 
which  have  been  absorbed  in  the  solid  tissues  of  the  body.  The  fluid 
contained  in  these  vessels  is  nearly  or  quite  colorless,  especially  in  thin 
layers,  and  from  its  transparent  and  watery  appearance  is  called  the 
"  lymph,"  and  the  vessels  themselves  constitute  what  is  known  as  the 
lymphatic  system. 

As  the  blood  circulates  through  the  capillaries  under  the  influence  of 
the  arterial  pressure,  certain  of  its  ingredients  transude  through  the  vas- 
cular walls  and  penetrate  the  interstices  of  the  anatomical  elements  of 
the  tissues.  An  increased  pressure  upon  the  blood,  either  from  arterial 
congestion  or  from  obstruction  to  the  venous  current,  will  increase  the 
amount  of  transudation,  producing  an  cedematous  condition  of  the  part, 
which  is  first  perceptible  in  the  loose  connective  tissue,  but  which  may 
afterward  involve  the  more  compact  substance  of  the  organs.  In  the 
normal  state  of  the  circulation,  this  interstitial  fluid,  which  is  the  real 
source  of  nutrition  for  the  solid  parts,  does  not,  however,  stagnate  in 
contact  with  them,  but  is  renewed  by  a  continual  change.  As  fresh  sup- 
plies need  to  be  drawn  from  the  circulating  blood,  the  older  portions  are 
removed  by  absorption  and  returned  to  the  centre  of  the  circulation  by 
the  lymphatic  vessels.  Thus  these  vessels  may  be  considered  as  com- 
plementary in  their  function  to  the  veins.  The  blood,  containing  the  red 
globules,  requires  to  be  rapidly  and  abundantly  returned  to  the  lungs  by 
the  veins,  in  order  to  regain  the  oxygen  necessary  for  its  continued  vital- 
ity ;  while  the  lymphatics  collect  more  gradually  the  fluids  which  have 
served  for  the  slower  process  of  nutrition  and  growth. 

Anatomical  Structure  and  Arrangement  of  the  Lymphatic  System. 
In  structure  the  lymphatics  do  not  essentially  differ  from  the  blood- 
vessels, their  principal  peculiarity  being  that  their  walls  are  more  delicate 
and  transparent.     This  circumstance,  together  with  the  colorless  nature 
of  their  contents,  renders  them  less  easily  recognizable  by  dissection. 
Those  of  larger  and  medium   size  consist  of  three  coats,  similar,  in 
general  characters,  to  the  corresponding  tunics  of  the  bloodvessels. 
According  to  the  observations  of  Kolliker,  the  external  coat  alone  is 
distinguished  from  that  of  the  veins  by  the  possession  of  smooth  mus- 
(354) 


STRUCTURE    OF    LYMPHATIC    SYSTEM.  355 

cular  fibres  which  are  arranged  in  a  longitudinal  and  oblique  direction ; 
a  character  which  is  to  be  seen  in  lymphatics  of  0.2  millimetre  in  diame- 
ter and  upward.  Like  the  veins,  they  are  provided  with  numerous 
valves,  opening  toward  the  heart  and  closing  toward  the  periphery,  the 
vessel  often  presenting  a  well-marked  dilatation  just  within  the  situation 
of  the  valves.  The  smallest  lymphatics  consist  of  only  a  single  coat, 
composed  of  flattened,  epithelium-like,  nucleated  cells,  which  may  be 
brought  into  view,  like  those  of  the  capillary  bloodvessels,  by  the 
staining  action  of  a  silver  nitrate  solution. 

Origin  and  Course  of  the  Lymphatic  Vessels. — So  far  as  the  origin 
of  the  lymphatics  has  been  demonstrated  by  injections,  these  vessels 
commence  in  the  substance  of  the  tissues  by  plexuses.  They  are  more 
abundant  in  organs  which  are  fully  supplied  with  bloodvessels,  and  are 
absent  in  tissues  where  bloodvessels  do  not  exist,  such  as  those  of  the 
cornea,  the  vitreous  body,  and  the  epithelial  coverings  of  the  skin  and 
mucous  membranes.  According  to  Yon  Recklinghausen,  the  meshes 
of  the  lymphatic  plexus,  as  a  general  rule,  are  intercalated  between 
those  of  the  capillary  bloodvessels;  so  that  the  point  of  junction  of  two 
or  more  lymphatics  is  always  in  the  middle  of  the  space  surrounded  by 
the  adjacent  bloodvessels.  Thus  the  lymphatic  capillary  is  situated  at 
the  greatest  distance  possible  from  the  nearest  capillary  bloodvessels; 
and  in  the  trans udation  of  fluids  from  one  to  the  other,  the  interven- 
ing substance  of  the  tissue  will  always  be  completely  traversed  by 
the  nutritious  ingredients  of  the  blood.  In  membranous  expansions 
presenting  a  free  surface,  as  in  the  skin  and  mucous  membranes,  the 
plexus  of  capillary  bloodvessels  is  invariably  nearer  the  surface,  while 
the  lymphatics  occupy  a  deeper  plane  beneath  it.  Even  in  the  villi  of 
the  small  intestine,  the  network  of  bloodvessels  is  situated  immediately 
under  the  epithelial  layer,  and  surrounds  the  lacteal  vessel  which  is 
placed  in  the  central  part  of  the  villus. 

Beside  the  lymphatic  capillaries  proper,  certain  irregularly  shaped 
spaces  or  canals,  containing  only  a  colorless  or  serous  fluid,  have  been 
found  in  organs  consisting  of  condensed  connective  tissue,  like  the  cen- 
tral tendon  of  the  diaphragm  and  muscular  fasciae.  They  have  been 
demonstrated  mainly  by  the  process  of  treating  the  tissues  with  a  solu- 
tion of  silver  nitrate,  which  stains  the  solid  portions  of  a  dark  color, 
but  leaves  the  capillary  vessels  and  the  serous  canals  uncolored.  These 
interstitial  spaces  or  serous  canaliculi  have  been  regarded  by  some  ob- 
servers (Recklinghausen)  as  directly  continuous  with  the  lymphatic 
capillaries,  and  as  constituting  the  immediate  sources  of  supply  for  the 
lymph ;  but  this  connection  is  not  universally  admitted.  The  serous 
canaliculi  are  distinguished  from  the  lymphatic  capillaries  by  their 
much  smaller  size,  and  by  the  fact  that  they  do  not  possess,  like  the 
latter,  a  lining  of  epithelial  cells. 

From  their  plexuses  of  origin  the  lymphatic  vessels  pass  inward 
toward  the  great  channels  and  cavities  of  the  body,  uniting  into  larger 
branches  and  trunks,  and  following  generally  the  course  of  the  prin- 


356  THE    LYMPHATIC    SYSTEM. 

cipal  bloodvessels  and  nerves.  Those  of  the  lower  extremities  enter 
the  cavity  of  the  abdomen,  and  join  with  the  lymphatics  of  the  abdo- 
minal organs  to  form  the  commencement  of  the  thoracic  duct,  which 
ascends  through  the  cavity  of  the  chest,  receiving  branches  from  the 
thoracic  organs  to  the  root  of  the  neck,  where  it  is  joined  by  lymphatics 
from  the  left  side  of  the  head  and  the  left  upper  extremity,  and  ter- 
minates in  the  left  subclavian  vein,  at  the  point  of  its  junction  with  the 
left  internal  jugular.  The  lymphatics  coming  from  the  right  side  of 
the  head  and  neck,  the  right  upper  extremity,  and  a  portion  of  the 
thoracic  organs,  form  a  trunk  of  smaller  size,  the  right  lymphatic  duct, 
which  terminates  in  the  right  subclavian  vein  at  its  junction  with  the 
right  internal  jugular.  Thus  the  lymph,  collected  from  the  vascular 
tissues  of  the  entire  body,  is  mingled  with  the  venous  blood  a  short 
distance  before  its  arrival  at  the  right  side  of  the  heart. 

The  Great  Serous  Cavities  of  the  Body  are  Lymphatic  Lacunae. — 
It  is  well  known  that  in  the  amphibious  reptiles  there  are  irregularly- 
shaped  spaces  or  lacunae,  forming  a  part  of  the  lymphatic  system  and 
interposed  between  adjacent  organs  in  various  parts  of  the  body.  In 
the  mammalia  the  peritoneal  and  pleural  cavities,  and  probably  all  the 
principal  serous  sacs,  are  also  in  direct  communication  with  the  lym- 
phatic vessels.  This  was  first  shown  by  Recklinghausen1  for  the  peri- 
toneal cavity  of  the  rabbit,  which  communicates  by  microscopic  orifices 
with  the  lymphatic  vessels  in  the  central  tendon  of  the  diaphragm. 
These  communications  were  demonstrated  in  two  ways :  First,  on  in- 
jecting into  the  peritoneal  cavity  of  the  animal  milk,  or  a  watery  fluid 
holding  in  suspension  minute  granules  of  coloring  matter,  the  lymphatic 
vessels  of  the  central  tendon  of  the  diaphragm  were  afterward  found  to 
be  filled  with  the  white  or  colored  injection.  Secondly,  the  central  tendon 
of  the  diaphragm  being  carefully  removed  from  the  recently  killed  animal, 
and  a  drop  of  milk  placed  upon  its  peritoneal  surface,  the  milk  globules 
could  be  directly  observed  under  the  microscope,  running  in  converging 
currents  to  certain  points  on  the  surface  of  the  tendon  and  there  pene- 
trating into  its  lymphatic  vessels.  The  cavity  of  the  pleura  has  also 
been  found  by  similar  means  to  communicate  with  the  lymphatic  vessels 
in  its  neighborhood.  The  serous  cavities  accordingly  are  either  exten- 
sive lacunae,  forming  in  some  regions  the  origin  of  the  lymphatic  vessels, 
or  else  they  are  wide  but  shallow  expansions  of  the  cavity  of  the  lym- 
phatics, situated  at  various  points  in  their  course. 

The  Lymphatic  Glands. — During  the  passage  of  the  lymphatic  vessels 
from  the  periphery  toward  the  centre,  they  are  repeatedly  interrupted  by 
ovoid,  glandular-like  bodies,  of  a  pale  reddish  color  and  somewhat  firm 
consistency,  varying  in  size  from  about  two  to  twenty  millimetres  in 
their  long  diameter.  They  do  not  exist  in  fish  and  reptiles,  but  are 
always  present  in  birds  and  mammalia.  As  a  rule,  several  lymphatic 
vessels  reach  these  bodies,  coming  in  a  direction  from  the  periphery ;  and 

1  Strieker's  Manual  of  Histology,  Buck's  Edition.     New  York,  1872,  p.  221. 


STRUCTUKE    OF    LYMPHATIC    SYSTEM. 


357 


several  others  leave  them  at  another  portion  of  their  surface,  passing 
onward  toward  the  centre  of  the  circulation.  The  former  are  called  the 
u  afferent,"  the  latter  the  "  efferent"  lymphatic  vessels.  Owing  to  the 
general  gland ular-like  aspect  which  they  present  to  the  eye,  these  bodies 
are  known  as  lymphatic  "  glands,"  although  they  possess  no  proper  ex- 
cretory duct,  and  whatever  new  materials  are  formed  in  their  interior 
must  be  carried  away  either  by  the  veins  or  by  the  efferent  lymphatic 
vessels. 

The  lymphatic  glands  are  situated  upon  the  course  of  the  lymphatic 
vessels  on  the  inside  of  the  limbs  at  the  flexures  of  the  joints,  in  the 
axilla  and  the  groin,  in  the  thoracic  and  abdominal  cavities,  along  the 
sides  of  the  spinal  column,  in  the  mesentery,  and  in  the  sides  and  ante- 
rior part  of  the  neck. 

Fig.  126. 


LYMPHATIC  VESSELS  AHD  GLANDS  OF  THE  HEAD,  NECK,  AND  THORAX.— 1. 
Thoracic  duct,  at  the  point  of  its  emergence  from  the  chest.  2.  The  same  duct,  at  its  junction 
with  the  left  subclavian  vein.  (Mascagni.) 

As  regards  the  structure  of  the  lymphatic  glands  they  consist,  First, 
of  an  external  fibrous  envelope,  which  sends  from  its  internal  surface 
prolongations  in  the  form  of  septa  and  branching  bands  into  the  deeper 
parts  of  the  gland,  so  that  the  interior  of  the  organ  is  divided  into  a 


358 


THE    LYMPHATIC    SYSTEM. 


multitude  of  smaller  spaces  by  the  inosculations  of  this  fibrous  frame- 
work. The  bands  constituting  this  framework  are  called  the  "  trabeculse." 
Secondly,  in  the  interstices  between  the  trabeculse  there  is  situated  the 
pulpy  substance  of  the  gland.  In  the  more  external  or  cortical  part  of 
the  gland,  the  interspaces  have  a  rounded  or  sac-like  form,  which  gives 
to  this  portion  of  the  organ  a  granular  aspect,  while  this  appearance  is 
wanting  in  the  deeper  or  medullary  portion ;  but  in  both  situations  the 
glandular  pulp  has  essentially  the  same  microscopic  texture.  Thirdly, 
the  bloodvessels  of  the  gland  penetrate  it  from  the  outside,  usually  at  a 
depressed  spot  called  the  "hilum,"  and,  after  reaching  the  interior,  break 
up  into  a  rich  plexus  of  capillaries.  These  bloodvessels  and  their  capil- 
lary plexus  follow  distinct  routes  in  the  gland,  in  the  middle  of  the 
spaces  between  the  trabeculse.  The  capillary  bloodvessels  are  sur- 
rounded and  held  in  position  by  very  fine  branching  fibres  attached  to 
their  external  surface;  and  in  the  meshes  of  these  fibres,  as  well  as 
between  the  bloodvessels,  there  are  imbedded  a  great  number  of  rounded, 
granular,  nucleated  cells,  about  9  mmm.  in  diameter,  similar  to  the  white 
globules  of  the  blood  and  of  the  lymph,  and  which  in  this  situation 
are  known  as  "lymph  globules."  The  presence  of  these  granular  cells, 
fixed  between  and  immediately  around  the  capillary  bloodvessels,  gives 
to  the  parts  occupied  by  them  a  well-marked  opaque  appearance  by 
transmitted  light ;  and  there  are  thus  formed,  in  a  thin  section  of  the 
gland,  elongated,  opaque  tracts  or  cords,  separated  by  intervening  trans- 
parent spaces,  and  communicating  with  each  other  at  frequent  intervals. 


Fig.  127. 


Fig.  128. 


THIN  SECTION  OP  A  LYMPHATIC  GLAND 
FROM  THE  Ox.— o.  Medullary  cords,  b.  Lymph 
paths,  c.  Trabeculae.  (Kolliker.) 


LONGITUDINAL  SECTION  through 
the  hilum  of  a  mesenteric  gland  from 
the  ox,  showing  the  commencement  of 
the  efferent  lymphatic  vessels  injected 
from  a  puncture  of  the  glandular  sub- 
stance.— a.  Plexus  of  efferent  vessels. 
b.  Lymph  paths,  c.  Medullary  cords. 
d.  Trabeculae.  (K6lliker.) 


These  opaque  and  vascular  tracts  are  called  the  medullary  cords  of  the 
lymphatic  gland.  They  are  the  only  vascular  parts  of  the  organ ;  as 
the  capillary  bloodvessels  never  pass  beyond  them  into  the  intervening 
transparent  spaces.  The  transparent  spaces,  situated  between  the 


TRANSUDATION    THROUGH    ANIMAL    TISSUES.          359 

medullary  cords  and  immediately  surrounding  the  trabeculae,  constitute 
the  lymph-paths,  or  the  channels  by  which  the  lymph  traverses  the  glan- 
dular substance  from  the  afferent  to  the  efferent  vessels.  The  afferent 
lymphatic  vessels,  according  to  the  united  testimony  of  more  recent 
observers,  after  ramifying  upon  the  outer  surface  of  the  gland,  penetrate 
its  fibrous  envelope  and  become  continuous  with  the  transparent  por- 
tions of  the  glandular  substance.  This  has  been  shown  by  injections  of 
the  lymphatic  gland  from  the  afferent  vessels ;  and  Kolliker  has  also 
demonstrated  a  similar  connection  of  the  same  channels  with  the  efferent 
vessels,  by  injecting  these  vessels  from  the  substance  of  the  gland. 

The  lymph-paths  present  a  transparent  appearance  in  thin  sections  of 
the  gland  for  the  reason  that  the  granular  lymph-cells  which  they  con- 
tain are  easily  detached  and  removed  by  manipulation,  while  those  of 
the  medullary  cords  are  more  firmly  fixed  in  the  fibrous  mesh-work  and 
do  not  readily  yield  to  a  displacing  force.  It  has  been  found  b/Kolliker 
that  a  watery  or  serous  fluid,  injected  through  the  substance  of  the  gland 
under  very  moderate  pressure,  will  also  displace  these  cells  and  leave 
the  spaces  which  they  occupied  nearly  clear.  For  these  reasons  it  is 
regarded  as  certain  that  the  lighter  spaces  in  the  lymphatic  glands  are, 
as  their  name  indicates,  the  channels  by  which  the  lymph  passes  from 
the  afferent  to  the  efferent  vessels,  and  that  the  lymph-cells  are  detached 
by  this  current  from  the  place  of  their  growth  and  carried  onward 
through  the  rest  of  the  lymphatic  system. 

Translation  and  Absorption  fcy  the  Animal  Tissues. 

During  the  passage  of  the  blood  through  the  capillary  bloodvessels 
a  variety  of  actions  take  place  by  which  some  of  its  ingredients  are 
given  up  to  the  tissues  by  transudation  and  are  at  the  same  time  replaced 
by  others  derived  by  absorption  from  the  adjacent  parts.  The  lym- 
phatic system  of  vessels,  furthermore,  is  entirely  filled  by  the  absorption 
of  materials  taken  up  from  the  surrounding  tissues ;  and  the  composi- 
tion of  the  fluid  which  they  contain  depends  upon  the  property,  belong- 
ing to  animal  membranes,  of  transmitting  or  absorbing  certain  fluid 
substances  in  a  peculiar  way.  This  property  is  exhibited  experiment- 
ally in  the  following  manner. 

If  a  fresh  animal  membrane  be  firmly  attached  over  the  mouth  of  a 
cylindrical  glass  tube,  filled  with  pure  water  and  immersed  in  solutions 
of  various  substances,  in  such  a  manner  that  the  membrane  forms  a 
continuous  diaphragm,  having  the  water  on  one  side  and  the  solution 
on  the  other,  it  is  found  that  different  substances  penetrate  the  mem- 
brane and  pass  through  it  to  the  water  with  very  different  degrees 
of  rapidity.  As  a  general  rule  crystallizable  substances,  such  as 
mineral  salts,  glucose,  urea,  pass  with  facility ;  while  the  non-crystal- 
lizable  organic  matters,  such  as  albumen,  starch,  gum,  pass  with  com- 
parative difficulty  There  are  certain  exceptions,  however,  to  this  rule. 
Thus  albumen,  under  ordinary  circumstances,  transudes  slowly  or  not 
at  all  through  animal  membranes ;  while  albuminose,  which  is  also  non- 


360  THE    LYMPHATIC    SYSTEM. 

crystallizable,  passes  very  rapidly  and  abundantly.  The  distinction, 
furthermore,  between  the  two  classes  of  substances  is  not  a  complete 
one,  since  they  may  nearly  all  be  made  to  transude  in  some  degree  by 
increasing  the  pressure  of  the  column  of  fluid  upon  the  corresponding 
side  of  the  membrane ;  but  the  difference  between  them  is  often  very 
great  in  this  respect.  According  to  the  observations  of  Liebig,1  the 
requisite  pressure  for  different  liquids,  in  passing  through  the  same 
membrane  in  a  given  time,  is  as  follows : 

COMPARATIVE  PRESSURE  HEQUIRED  TO  CAUSE  TRANSUDATION  THROUGH 
OX-BLADDER. 

Kind  of  liquid.  Height  of  the  mercurial  column. 

Water .         .         324  millimetres. 

Solution  of  salt 514 

Oil 920          " 

Aldbhol 1298          " 

Owing  to  their  varying  degree  of  transmissibity  through  membranes 
this  property  has  even  been  employed  for  the  purpose  of  separating 
different  substances  from  each  other,  when  mingled  together  in  the 
liquid  form.  This  process  is  termed  Dialysis.  Thus,  if  a  solution 
containing  both  gum  and  sugar  be  placed  in  contact  with  one  side  of 
the  membranous  diaphragm,  with  pure  water  on  the  other,  the  sugar 
alone  will  pass  through,  while  the  gum  will  be  left  behind.  If  a  mix- 
ture of  albumen  and  sodium  chloride  be  placed  under  the  same  con- 
ditions, the  salt  will  transude  in  a  pure  form  leaving  the  albumen 
by  itself;  both  substances  in  this  way  being  purified  from  each  other 
through  the  action  of  the  membrane.  By  the  same  process  it  has  been 
found  possible  to  extricate  poisonous  c^stallizable  matters,  such  as 
strychnine  or  arsenious  acid,  from  their  admixture  with  albuminous 
substances  in  a  state  of  sufficient  purity  to  allow  of  their  detection  by 
chemical  tests.  The  tissues  of  an  animal  membrane,  accordingly,  may 
in  this  way  exercise  a  kind  of  elective  affinity  for  various  substances, 
and  produce  a  special  composition  in  fluids  which  have  transuded 
through  them. 

Endosmosis  and  Exosmosis. — Beside  the  elimination  of  chemical 
ingredients  above  described,  the  phenomena  of  trans udation  often  give 
rise  to  a  change  in  volume  of  the  fluid  on  either  side  of  the  membranous 
septum.  When  an  animal  membrane  is  interposed  between  two  different 
liquids  which  are  imbibed  and  transmitted  by  it  with  different  degrees 
of  facility,  that  which  passes  most  readily  will  accumulate  in  larger 
quantity  on  the  opposite  side  of  the  membrane. 

If  we  take,  for  example,  a  solution  of  salt  and  an  equal  volume  of 
distilled  water,  and  inclose  them  in  a  glass  tube  with  a  fresh  animal 
membrane  stretched  between,  the  two  liquids  being  in  contact  with 
opposite  sides  of  the  membrane,  after  a  time  they  will  have  become 

1  Cited  in  Longet,  Trait§  de  Physiologie.     Paris,  1861,  tome  i.  p.  384. 


TRANSUDATION    THROUGH    ANIMAL    TISSUES.          361 

mingled,  to  a  certain  extent,  with  each  other.  A  part  of  the  salt  will 
have  passed  into  the  distilled  water,  giving  it  a  saline  taste ;  and  a  part 
of  the  water  will  have  passed  into  the  saline  solution,  making  it  more 
dilute  than  before.  If  the  quantities  of  the  two  liquids,  which  have 
become  so  transferred,  be  measured,  it  will  be  found  that  a  comparatively 
large  quantity  of  water  has  passed  into  the  saline  solution,  and  a  com- 
paratively small  quantity  of  the  saline  solution  has  passed  out  into  the 
water.  That  is,  the  water  passes  inward  to  the  salt  more  rapidly  than 
the  salt  passes  outward  to  the  water.  The  consequence  is,  that  the 
saline  solution  is  increased  in  volume,  while  the  water  is  diminished. 
The  more  abundant  passage  of  the  water,  through  the  membrane  to  the 
salt,  is  called  endosmosis ;  and  the  more  scanty  passage  of  the  salt  out- 
ward to  the  water  is  called  exosmosis. 

The  mode  usually  adopted  for  measuring  the  rapidity  of  endosmosis 
is  to  take  a  glass  vessel,  shaped  somewhat  like  an  inverted  funnel,  wide 
at  the  bottom  and  narrow  at  the  top.  The  bottom  of  the  vessel  is 
closed  by  a  thin  animal  membrane,  stretched  tightly  over  its  edge  and 
secured  by  a  ligature.  From  the  top  of  the  vessel  there  rises  a  narrow 
glass  tube,  open  at  its  upper  extremity.  When  the  instrument  is  thus 
prepared,  it  is  filled  with  a  saline  or  saccharine  solution  and  placed  in  a 
vessel  of  distilled  water;  so  that  the  membrane,  stretched  across  its 
mouth,  shall  be  in  contact  with  pure  water  on  one  side  and  with  the 
interior  solution  on  the  other.  The  water  then  passes  in  through  the 
membrane,  by  endosmosis,  faster  than  the  ingredients  of  the  solution 
pass  out.  An  accumulation  consequently  takes  place  inside  the  vessel, 
and  the  level  of  the  fluid  rises  in  the  upright  tube.  The  height  to  which 
the  fluid  thus  rises  in  a  given  time  is  a  measure  of  the  intensity  of  the 
endosmosis,  and  of  its  excess  over  exosmosis.  By  varying  the  consti- 
tution of  the  two  liquids,  and  the  arrangement  of  the  membrane,  the 
variations  in  endosmotic  action  under  different  conditions  may  be 
readily  ascertained.  Such  an  instrument  is  called  an  endosmometer. 

Physical  Conditions  influencing  Endosmosis. — The  conditions  which 
regulate  the  intensity  and  extent  of  endosmosis  have  been  investigated 
by  Dutrochet,  Graham,  Yierordt,  Matteucci,  and  Cima.  The  first  of 
these  conditions  is  the  freshness  of  the  animal  membrane.  A  mem- 
brane that  has  been  dried  and  moistened  again,  or  one  that  has  begun 
to  putrefy,  will  not  produce  its  full  effect.  It  is  also  found  that  if  the 
membrane  be  allowed  to  remain  and  macerate  in  the  fluids,  after  the 
column  has  risen  to  a  certain  height  in  the  upright  tube,  it  begins  to 
descend  again  when  putrefaction  commences,  and  the  two  liquids  finally 
sink  to  the  same  level. 

The  next  condition  is  the  extent  of  contact  between  the  membrane 
and  the  two  liquids.  The  greater  the  extent  of  contact,  the  more  rapid 
is  endosmosis.  An  endosmometer  with  a  wide  mouth  will  produce 
more  effect  than  with  a  narrow  one,  though  the  volume  of  liquid  may 
be  the  same  in  both  instances.  The  action  takes  place  in  the  substance 
of  the  membrane,  and  is  proportional  to  its  extent  of  surface. 
24 


362  THE    LYMPHATIC    SYSTEM. 

The  nature  of  the  membrane  employed,  and  even  its  position  in  re- 
gard to  the  two  liquids,  also  influence  the  result.  Different  serous  and 
mucous  membranes  act  with  different  degrees  of  force.  The  effect  pro- 
duced is  not  the  same  with  the  integument  of  different  animals,  nor  with 
membranous  tissues  taken  from  different  parts  of  the  body  of  the  same 
animal.  This  depends  upon  the  fact  that  the  power  of  absorption  for 
a  given  liquid  is  different  in  different  tissues.  Chevreuil  investigated 
this  point  by  taking  definite  quantities  of  certain  animal  substances,  and 
immersing  them  in  various  liquids  for  twenty-four  hours,  at  the  end  of 
which  time  the  substance  was  removed  and  weighed.  Its  increase  in 
weight  showed  the  quantity  of  liquid  which  it  had  absorbed.  The  fol- 
lowing table1  shows  the  result  of  these  experiments : 

COMPARATIVE  POWER  OF  ABSORPTION  IN  DIFFERENT  TISSUES. 

100  Parts  of  Water.  Saline  Solution.             Oil. 

Cartilage,                         1  f  231  parts.  125  parts. 

Tendon,  178      "  114     «            8.6  parts. 

Elastic  ligament,              I  absorb  in  I  148      "  30     "            7.2      " 

Cornea,                              f  24  hours,  j  461      "  370     "            9.1     " 

Cartilaginous  ligament,  319      "  3.2     " 

Dried  fibrine,  [301      "  151     " 

The  influence  of  the  position  of  the  membrane  depends  upon  a  similar 
difference  in  the  absorbing  power  of  its  two  surfaces.  With  some 
fluids,  endosmosis  is  more  rapid  when  the  membrane  has  its  mucous 
surface  in  contact  with  the  dense  solution,  and  its  dissected  surface  in 
contact  with  the  water.  With  other  substances,  the  more  favorable 
position  is  the  reverse.  Matteucci  found  that,  in  using  the  mucous 
membrane  of  the  ox-bladder,  with  water  and  a  solution  of  sugar,  if  the 
mucous  surface  of  the  membrane  were  in  contact  with  the  saccharine 
solution,  the  liquid  rose  in  the  endosmometer  between  80  and  113  milli- 
metres in  two  hours.  But  if  the  same  surface  were  turned  toward 
the  water,  the  rise  of  the  column  of  fluid  was  only  63  or  12  millimetres 
in  the  same  time. 

Another  important  circumstance  is  the  constitution  of  the  two  liquids 
and  their  relation  to  each  other.  As  a  general  thing,  if  the  liquids 
employed  be  water  and  a  saline  solution,  endosmosis  is  more  active,  the 
more  concentrated  is  the  solution  in  the  endosmometer ;  that  is,  a  larger 
quantity  of  water  will  pass  inward  toward  a  dense  solution  than  toward 
one  which  is  dilute.  But  the  force  of  endosmosis  varies  with  different 
liquids,  though  they  may  be  of  the  same  density.  Dutrochet  measured 
the  force  with  which  water  passes  through  the  mucous  membrane  of  the 
ox-bladder,  into  different  solutions  of  the  same  density,  with  the  follow- 
ing result  :3 

1  In  Longet,  Trait6  de  Physiologie.     Paris,  1861,  tome  i.  p.  383. 

2  In   Matteucci,   On    the  Physical   Phenomena   of  Living  Beings.     Pereira's 
translation.     Philadelphia,  1848,  p.  48. 


TRANSUDATION    THROUGH    ANIMAL    TISSUES.          363 

COMPARATIVE  INTENSITY  OF  ENDOSMOSIS  OF  WATER  TOWARD  DIFFERENT  LIQUIDS,  AS 
MEASURED  BY  THE  RISE  OF  THE  COLUMN  IN  THE  ExDOSMOMETER. 
Endosmosis  of  water  toward  Divisions  of  the  Endosmometer  tube. 

Solution  of  gelatine     ......        3 

"          gum 5 

"          sugar        .         .                 .         .         .       ]1 
"         albumen 12 

The  primary  cause  of  this  variation  in  the  phenomena  of  endosmosis 
is  the  different  absorptive  power  possessed  by  an  animal  membrane  or 
tissue  for  different  liquids.  This  is  partly  shown  by  the  experiments 
of  Chevreuil,  in  which  oily  matters  were  usually  absorbed  less  readily 
than  either  water  or  saline  solutions.  Nearly  all  animal  membranes 
also  absorb  water  more  rapidly  than  a  solution  of  salt.  If  a  membrane, 
partly  dried,  be  placed  in  a  saturated  solution  of  sodium  chloride,  it 
will  absorb  the  water  in  so  much  larger  proportion  than  the  salt  that  a 
part  of  the  salt  will  be  left  behind  and  deposited  in  a  crystalline  form 
on  the  surface  of  the  membrane. 

When  an  animal  membrane,  accordingly,  is  placed  in  contact  with 
two  different  liquids,  it  absorbs  one  of  them  more  abundantly  than 
the  other ;  and  if  that  which  is  absorbed  in  the  greatest  quantity  is  also 
readily  diffused  into  the  liquid  on  the  opposite  side,  a  rapid  endosmosis 
will  take  place  in  that  direction,  and  a  slow  exosmosis  in  the  other. 
Consequent!}',  the  least  absorbable  fluid  increases  in  volume  by  the  con- 
stant admixture  of  that  which  is  taken  up  more  rapidly.  There  are 
even  some  cases  in  which  endosmosis  takes  place  without  being  accom- 
panied by  exosmosis.  This  occurs  when  water  and  albumen  are  em- 
ployed as  the  two  liquids.  For  while  water  readily  passes  inward 
through  the  animal  membrane,  the  albumen  does  not  pass  out.  If  an 
opening  be  made  in  the  large  end  of  a  fowl's  egg,  so  as  to  expose  the 
shell-membrane,  and  the  whole  be  then  immersed  in  a  goblet  of  water, 
endosmosis  will  take  place  freely  from  the  water  to  the  albumen,  so  as 
to  distend  the  shell-membrane  and  make  it  protrude,  like  a  hernia,  from 
the  opening  in  the  shell.  But  the  albumen  does  not  pass  outward 
through  the  membrane,  and  the  water  in  the  goblet  remains  pure. 
After  a  time  the  pressure  from  within,  due  to  the  accumulation  of  fluid, 
becomes  so  great  as  to  burst  the  shell-membrane,  after  which  the  two 
fluids  mix  uniformly  with  each  other. 

But  a  substance  like  albumen,  which  will  not  pass  out  by  exosmosis 
toward  pure  water,  may  traverse  a  membrane  which  is  in  contact  with 
a  solution  of  salt.  This  has  been  shown  to  be  the  case  with  the  shell- 
membrane  of  the  fowl's  egg,  which,  if  immersed  in  a  watery  solution 
containing  from  3  to  4  per  cent,  of  sodium  chloride,  will  allow  the  escape 
of  a  small  proportion  of  albumen.  Furthermore,  if  a  mixed  solution  of 
albumen  and  salt  be  placed  in  a  dialysing  apparatus,  the  salt  alone  will 
at  first  pass  outward  leaving  the  albumen ;  but  after  the  exterior  liquid 
has  become  perceptibly  saline,  the  albumen  also  begins  to  pass  in  appre- 
ciable quantity. 


UULU 


864  THE    LYMPHATIC    SYSTEM. 

For  the  same  membrane  and  different  solutions  of  the  same  substance, 
the  direction  and  intensity  of  transudation  depend  upon  the  strength  of 
the  solutions.  With  endosmometers  containing  solutions  of  sugar  or 
salt,  and  immersed  in  pure  water,  as  shown  by  Dutrochet,  the  stronger 
the  solution  the  more  rapid  is  the  endosmosis  from  without ;  and  if  two 
solutions  of  salt  be  employed,  with  a  membranous  septum  between  them, 
endosmosis  takes  place  from  the  weaker  solution  to  the  stronger,  and  is 
proportional  to  the  difference  in  their  densities.  Density,  however,  is 
not  always  the  condition  which  determines  the  direction  of  the  current. 
For  although  with  saline  or  saccharine  solutions  the  direction  of  endos- 
mosis is  from  the  lighter  to  the  denser  liquid,  with  alcohol  and  water  it 
takes  place  from  the  water  to  the  alcohol ;  that  is,  from  the  denser  to  the 
lighter  liquid.  It  is  evident  from  these  facts  that  the  process  of  endos- 
mosis does  not  depend  principally  upon  the  attraction  of  the  two  liquids 
for  each  other,  but  upon  the  attraction  of  the  animal  membrane  for  the 
two  liquids.  The  membrane  is  not  a  passive  filter  through  which  the 
liquids  mingle,  but  is  the  active  agent  which  determines  their  transu- 
dation. The  membrane  has  the  power  of  absorbing  liquids,  and  of 
taking  them  up  into  its  own  substance.  This  property,  belonging  to 
the  membrane,  depends  upon  the  organic  ingredients  of  which  it  is  com- 
posed ;  and,  with  different  animal  substances,  the  rate  of  absorption  is 
different.  The  tissue  of  cartilage,  for  example,  as  shown  by  the  experi- 
ments of  Chevreuil,  will  absorb  more  water,  weight  for  weight,  than  that 
of  the  tendons;  and  the  tissue  of  the  cornea  will  absorb  nearly  twice  as 
much  as  that  of  cartilage. 

The  continuance  of  endosmosis  is  much  favored  by  renewal  of  the 
two  liquids.  Since  the  accumulation  of  fluid  on  one  side  of  the  mem- 
brane depends  on  the  difference  in  composition  of  the  liquids  employed 
and  the  consequent  difference  in  their  rate  of  absorption,  when  endos- 
mosis has  been  for  some  time  going  on,  and  the  two  liquids  have 
approximated  each  other  in  composition,  the  activity  of  endosmosis 
will  be  diminished  in  proportion.  As  the  salt  or  sugar  passes  out- 
ward to  the  water  and  the  water  inward  to  the  solution  in  the  endos- 
mometer,  the  external  liquid  acquires  a  saline  or  saccharine  ingredient, 
and  the  interior  solution  becomes  more  dilute ;  and  when  the  two  liquids 
have  thus  arrived  at  the  same  or  nearly  the  same  composition,  endos- 
mosis must  cease.  But  if  the  exterior  liquid  be  constantly  replaced  by 
a  current  of  pure  water,  and  the  interior  solution  maintained  at  its 
original  strength  by  the  addition  of  new  ingredients,  the  process  of 
transudation  will  go  on  with  undiminished  activity  until. the  membrane 
has  lost  its  absorbent  power.  The  effect  of  a  constantly  renewed  cur- 
rent in  aiding  endosmosis  may  be  readily  shown  by  filling  the  cleansed 
intestine  of  a  rabbit  with  water  from  a  reservoir  and  then  placing  it  in 
a  shallow  glass  vessel  containing  a  dilute  solution  of  hydrochloric  acid. 
If  the  water  be  allowed  to  flow  through  the  intestine  under  pressure 
from  the  reservoir,  that  which  is  discharged  from  its  open  extremity 
will  in  a  few  seconds  show  the  presence  of  hydrochloric  acid  by  its 


TRANSUDATION    THROUGH    ANIMAL    TISSUES.          365 

reaction  with  litmus.  The  acid  in  this  case  passes  through  the  wall  of 
the  intestine  against  the  pressure  of  the  current,  which  is  of  course 
directed  from  within  outward. 

Endosmosis  is  also  regulated,  to  a  great  degree,  by  temperature. 
As  a  rule  it  is  more  active  when  the  temperature  is  moderately 
elevated.  Dutrochet  found  that  an  endosmometer,  containing  a  solu- 
tion of  gum,  absorbed  only  one  volume  of  water  at  a  temperature  of 
0°,  but  absorbed  three  volumes  at  about  34°.  Variations  of  tempera- 
ture will  sometimes  even  change  the  direction  of  the  endosmosis  alto- 
gether, particularly  with  dilute  solutions  of  hydrochloric  acid.  In  the 
experiments  of  Dutrochet,  when  the  endosmometer  was  filled  with  dilute 
hydrochloric  acid  and  placed  in  distilled  water  at  the  temperature  of 
10°,  endosmosis  took  place  from  the  acid  to  the  water,  if  the  density  of 
the  acid  solution  were  less  than  1.020 ;  but  from  the  water  to  the  acid, 
if  its  density  were  greater  than  this.  On  the  other  hand,  at  the  tem- 
perature of  22°,  the  current  was  from  within  outward  when  the  density 
of  the  said  solution  was  below  1.003,  and  from  without  inward  when  it 
was  above  that  point. 

Absorption  and  Transudation  in  the  Tissues  of  the  Living  Body. — 
In  the  experiments  above  detailed,  performed  with  membranes  and  tis- 
sues taken  from  the  dead  body,  by  which  the  phenomena  of  endosmosis 
and  exosmosis  were  first  studied,  the  phenomena  represent  imperfectly 
those  which  take  place  in  the  living  organism.  The  property,  belong- 
ing to  an  animal  membrane,  of  determining  the  absorption  or  transu- 
dation  of  various  liquids,  depends  upon  its  organic  constitution  and  is 
exercised  in  the  greatest  intensity  during  life.  In  the  living  body,  all 
the  conditions  requisite  for  the  acts  of  endosmosis  and  exosmosis  are 
present  in  a  higher  degree  than  is  possible  in  any  artificial  experiment. 
The  membranes  and  tissues  are  all  perfectly  fresh,  and  unaltered  by 
either  desiccation  or  putrescence;  the  extent  of  absorbing  surface  is 
indefinitely  multiplied  by  the  repeated  ramification  of  the  capillary 
bloodvessels  or  the  glandular  tubes;  the  internal  temperature  of  the 
body  is  maintained  at  a  point  most  favorable  for  the  activity  of  endos- 
mosis ;  and  finally  the  continuous  movement  of  the  blood  and  the  lymph, 
in  theii  respective  vessels,  supplies  the  ingredients  for  a  constant  renewal 
of  the  process  and  at  the  same  time  removes  the  accumulation  of  the 
transuded  material. 

In  the  living  body,  accordingly,  the  transudation  of  fluids  is  accom- 
plished with  great  rapidity.  It  has  been  shown  by  Gosselin,  that  if  a 
watery  solution  of  potassium  iodide  be  dropped  upon  the  cornea  of  a 
living  rabbit,  the  iodine  passes  into  the  cornea,  aqueous  humor,  iris, 
lens,  sclerotic  and  vitreous  body,  in  the  course  of  eleven  minutes  ;  and 
that  it  will  penetrate  through  the  cornea  into  the  aqueous  humor  in 
three  minutes,  and  into  the  substance  of  the  cornea  in  a  minute  and  a 
half.  In  these  experiments  it  is  evident  that  the  iodine  actually  passes 
into  the  deeper  portions  of  the  eye  by  simple  endosmosis,  and  is  not 


366  THE    LYMPHATIC    SYSTEM. 

transported  by  the  bloodvessels ;  since  no  trace  of  it  is  to  be  found  in 
the  tissues  of  the  opposite  eye,  examined  at  the  same  time. 

The  same  observer  has  shown  that  the  active  principle  of  belladonna 
penetrates  the  tissues  of  the  eyeball  in  a  similar  manner.  He  applied  a 
solution  of  atropine  sulphate*  to  both  eyes  of  two  rabbits.  Half  an  hour 
afterward,  the  pupils  were  dilated.  Three-quarters  of  an  hour  later,  the 
aqueous  humor  was  collected  by  puncturing  the  cornea  with  a  trocar ; 
and  this  fluid,  dropped  upon  the  eye  of  a  cat,  produced  dilatation  and 
immobility  of  the  pupil  in  half  an  hour.  These  facts  show  that  the 
aqueous-  humor  of  the  affected  eye  actually  contains  atropine,  which  it 
absorbs  from  without  through  the  cornea,  and  which  thus  acts  directly 
upon  the  muscular  fibres  of  the  iris. 

But  in  all  vascular  organs,  the  processes  of  endosmosis  and  exosmosis 
are  still  further  accelerated  by  two  important  conditions,  namely,  first, 
the  movement  of  the  blood  circulating  in  the  vessels,  and  secondly,  the 
minute  dissemination  and  distribution  of  these  vessels  through  the 
tissues. 

If  a  solution  of  the  extract  of  nux  vomica  be  injected  into  the  subcu- 
taneous connective  tissue  of  the  hind  leg  of  two  rabbits,  in  one  of  which 
the  bloodvessels  of  the  limb  have  been  left  free,  while  in  the  other  they 
have  been  previously  tied,  so  as  to  stop  the  circulation  of  blood  in  the 
part,  in  the  first  rabbit  the  poison  will  be  absorbed  and  will  produce 
convulsions  and  death  in  the  course  of  a  few  minutes  ;  but  in  the  second 
animal,  owing  to  the  stoppage  of  the  local  circulation,  absorption  will 
be  retarded,  and  the  poison  will  find  its  way  into  the  general  circulation 
so  slowly,  that  its  specific  effects  will  show  themselves  only  at  a  late 
period,  or  even  may  not  be  produced  at  all. 

The  processes  of  exosmosis  and  endosmosis,  therefore,  in  the  living 
body,  are  regulated  by  the  same  or  similar  conditions  as  in  artificial 
experiments ;  but  they  take  place  with  greater  rapidity,  owing  to  the 
movement  of  the  circulating  blood,  and  the  extent  of  contact  existing 
between  the  bloodvessels  and  adjacent  tissues.  Although  the  arterial 
blood  is  everywhere  the  same  in  composition,  yet  its  different  ingredients 
are  imbibed  in  varying  quantities  by  the  different  tissues.  And  the 
proportion  of  each  ingredient  is  determined,  in  each  separate  tissue,  by 
its  special  absorbing  or  endosmotic  power. 

Albumen,  under  ordinary  conditions,  is  not  endosmotic ;  that  is,  it 
will  not  pass  by  transudation  through  an  animal  membrane.  For  this 
reason,  the  albumen  of  the  blood,  in  the  natural  state  of  the  circulation, 
is  not  exuded  from  the  secreting  surfaces,  but  is  retained  within  the 
vascular  system.  But  the  degree  of  pressure  to  which  a  fluid  is  sub- 
jected has  an  influence  in  determining  its  endosmotic  action.  If  the 
pressure  upon  the  blood  in  the  capillary  vessels  be  increased,  by  ob- 
struction to  the  venous  current  and  backward  congestion  of  the  capil- 
laries, then  not  only  the  saline  and  watery  parts  of  the  blood  pass  out 
in  larger  quantities,  but  the  albumen  itself  may  transude  and  infiltrate 
the  neighboring  parts.  In  this  way  albumen  may  make  its  appearance 


THE    LYMPH    AND    CHYLE.  367 

in  the  urine,  in  consequence  of  obstruction  to  the  renal  circulation;  and 
local  oedema  or  general  anasarca  may  follow  upon  venous  congestion  in 
particular  regions,  or  upon  general  disturbance  of  the  circulation. 

The  Lymph  and  Chyle, 

The  tymph  is  the  fluid  which,  having  been  absorbed  from  the  various 
tissues  and  organs  of  the  body,  is  carried  through  the  system  of  lym- 
phatic vessels  towards  the  centre  of  the  circulation  and  is  finally  dis- 
charged, by  the  thoracic  and  right  lymphatic  ducts,  into  the  great  veins 
near  the  heart.  As  the  chyle  is  simply  the  fluid  of  the  mesenteric  lym- 
phatics, which  assumes  an  opaque  white  color  during  digestion  owing 
to  the  absorption  of  fat,  it  is  properly  studied  at  the  same  time  with 
the  lymph  in  general.  The  lymph  has  been  obtained,  for  the  purpose 
of  examination,  from  the  living  animal,  by  introducing  a  silver  canula  of 
proper  size  into  the  thoracic  duct  at  the  root  of  the  neck,  or  into  large 
lymphatic  trunks  in  other  parts  of  the  body.  It  was  obtained  by  Rees 
from  the  lacteals  of  the  mesentery  and  from  the  lymphatics  of  the  leg 
in  the  ass,  by  Colin  from  the  lacteals  and  thoracic  duct  of  the  ox,  and 
from  the  lymphatics  of  the  neck  in  the  horse.  We  have  obtained  it 
from  the  thoracic  duct  both  of  the  dog  and  the  goat. 

Physical  Characters  and  Composition  of  the  Lymph. — The  lymph, 
thus  obtained  from  the  thoracic  duct  in  the  intervals  of  digestion,  is  an 
opalescent  or  nearly  transparent,  alkaline  fluid,  usually  of  a  light  amber 
color,  and  having  a  specific  gravity  of  1022.  Its  analysis  shows  a  close 
resemblance  in  composition  with  the  plasma  of  the  blood.  It  contains 
water,  fibrine,  albumen,  fatty  matters,  and  the  usual  saline  substances 
of  the  animal  fluids.  It  is,  however,  decidedly  poorer  in  albuminous 
ingredients  than  the  blood.  The  following  is  an  analysis  by  Lassaigne,1 
of  the  fluid  obtained  from  the  thoracic  duct  of  the  cow: 

COMPOSITION  OF  THE  LYMPH. 

Water 964.0 

Fibrine 0.9 

Albumen 28.0 

Fat 0.4 

Sodiijm  chloride 5.0 

Sodium  carbonate  \ 

Sodium  phosphate  > 1.2 

Sodium  sulphate     ) 

Lime  phosphate     .........'  0.5 

1000.0 

Owing  to  the  fibrine  contained  as  an  ingredient  in  the  lymph,  this  fluid 
coagulates,  like  blood,  within  a  few  moments  after  its  removal  from  the 
lymphatic  vessels  in  the  living  animal,  forming  a  gelatinous  mass  which 

1  In  Colin,  Physiologic  comparee  des  Aiiimaux  domestiques.  Paris,  1856, 
tome  ii.  p.  111. 


368  THE    LYMPHATIC    SYSTEM. 

is  more  or  less  colorless  and  transparent,  or  whitish  and  opaque,  accord- 
ing to  the  proportion  of  fatty  matter  present  in  the  specimen.  After 
coagulation,  it  separates  into  a  liquid  serum  and  a  solid  clot,  precisely 
as  in  the  case  of  blood. 

It  thus  appears  that  both  fibrine  and  albumen  are  either  formed  in  the 
interior  of  the  lymphatic  system,  or  transude  to  a  certain  extent  from 
the  bloodvessels,  even  in  the  ordinary  condition  of  the  circulation.  If 
so,  this  transudation  takes  place  in  so  small  quantity  that  the  albumi- 
nous matters  are  all  taken  up  by  the  lymphatic  vessels,  and  do  not 
appear  in  the  excreted  fluids. 

When  lymph  is  drawn  from  the  thoracic  duct  and  allowed  to  coagu- 
late, the  clot  after  a  few  moments  almost  invariably  assumes  a  decided 
pink  color,  and  on  microscopic  examination  is  found  to  contain  a  very 
few  red  blood-globules.  The  presence  of  these  globules  is  attributed  by 
some  competent  authorities  (Kolliker,  Robin)  to  the  accidental  rupture 
of  capillary  bloodvessels  and  consequent  introduction  of  their  contents 
into  the  lymphatic  system ;  but  their  occurrence  is  so  constant  that  it 
must  be  doubted  whether  they  have  altogether  an  accidental  origin. 
The  pinkish  color  of  the  lymph  under  these  circumstances  is  never  per- 
ceptible when  it  is  first  drawn  from  the  vessels,  but  only  after  it  has 
been  for  a  short  time  exposed  to  the  air. 

An  important  peculiarity  in  regard  to  the  fluid  of  the  lymphatic 
system,  especially  in  the  carnivorous  animals,  is  that  it  varies,  both  in 
appearance  and  constitution,  at  different  times.  In  the  ruminating  and 
graminivorous  animals,  as  the  sheep,  ox,  goat,  and  horse,  it  is  either 
opalescent  with  a  slight  amber  tinge,  or  nearly  transparent  and  color- 
less. In  the  carnivorous  animals,  as  the  dog  and  cat,  it  is  also  opaline 
and  amber  colored  in  the  intervals  of  digestion,  but  soon  after  feeding 
becomes  of  a  dense,  opaque,  milky  white,  and  continues  to  present  that 
appearance  until  digestion  and  absorption  are  complete.  It  then  regains 
its  original  aspect,  and  remains  opaline  until  digestion  is  again  in  pro- 
gress. 

The  results  of  analysis  show  that  this  variation  in  the  appearance  of 
the  fluid  of  the  thoracic  duct  during  digestion,  like  that  of  the  blood,  is 
due  to  the  absorption  of  fatty  matters  from  the  intestine.  Although 
the  chyle  is  richer  than  lymph  in  nearly  all  its  solid  ingredients,  the 
principal  difference  between  the  two  consists  in  the  proportion  of  fat, 
which  is  nearly  absent  from  the  transparent  or  opaline  lymph,  but  very 
abundant  in  the  white  and  opaque  chyle.  This  is  shown  in  the  following 
analysis  by  Dr.  Rees,1  of  lymph  and  chyle  from  the  ass. 

1  In  Colin,  Physiologic  compare  des  Animaux  domestique.  Paris,  1856  tome 
ii.  p.  18. 


THE    LYMPH    AND    CHYLE.  369 

COMPARATIVE  ANALYSIS  OF  LYMPH  AND  CHYLE. 

Lymph.  Chyle. 

Water 965.36  902.37 

Albumen 12.00  35.16 

Fibrine 1.20  3.70 

Spirit  extract 2.40  3.32 

Water  extract 13.19  12.33 

Fat .      traces  36.01 

Saline  matter  .......        5.85  7.11 

1000.00         1000.00 

When  a  canula,  accordingly,  is  introduced  into  the  thoracic  duct  at 
various  periods  after  feeding,  the  fluid  discharged  varies  considerably, 
both  in  appearance  and  quantity.  In  the  dog,  the  fluid  of  the  thoracic 
duct  is  never  quite  transparent,  but  retains  a  marked  opaline  tinge  even 
so  late  as  eighteen  hours  after  feeding  upon  lean  meat,  and  at  least  three 
days  and  a  half  after  the  introduction  of  fat  food.  Soon  after  feeding,  it 
becomes  whitish  and  opaque,  and  so  remains  while  digestion  and  absorp- 
tion are  in  progress.  After  the  termination  of  this  process  it  resumes 
its  former  appearance,  becoming  light  colored  and  opalescent  in  the  car- 
nivorous animals,  and  nearly  colorless  and  transparent  in  the  herbivora. 

The  Lymph  Globules. — The  lymph,  whatever  may  be  its  other  ingre- 
dients, contains  nearly  always  a  greater  or  less  abundance  of  rounded, 
transparent,  or  finely  granular  nucleated  cells,  similar  to  the  white  glo- 
bules of  the  blood,  which  are  known  as  the  "  lymph-globules."  They 
vary  in  size  from  about  6  to  12  mmm.  in  diameter.  By  treatment  with 
dilute  acetic  acid  they  become  pale  and  transparent;  while  partial  desic- 
cation, or  the  contact  of  a  concentrated  saline  or  saccharine  solution, 
gives  them  a  shrivelled  appearance  with  an  irregular  outline.  Accord- 
ing to  the  observations  of  Kolliker,  the  lymph-globules  vary  much,  both 
in  number  and  in  size,  according  to  the  part  of  the  lymphatic  system 
from  which  the  fluid  is  taken.  In  the  smallest  lymphatic  vessels  of  the 
mesentery  capable  of  examination,  they  may  even  be  altogether  absent, 
the  lymph  consisting  of  a  perfectly  homogeneous  fluid,  not  holding 
any  anatomical  forms  in  suspension ;  and  in  the  lymphatics  where  they 
first  begin  to  show  themselves,  they  are  few  in  number  and  of  less  than 
the  average  size.  After  the  lymph,  however,  has  traversed  one  or  two 
ranges  of  lymphatic  glands,  the  globules  are  larger  and  more  numerous, 
manj^  of  them  in  the  larger  lymphatic  trunks  attaining  the  size  of  12 
mmm.  in  diameter.  From  this  circumstance,  as  well  as  from  the  micro- 
scopic texture  of  the  glands  themselves,  it  is  concluded  that  the  lymph- 
globules  originate,  in  great  part,  in  the  interior  of  the  lymphatic  glands, 
and  that  they  are  brought  thence  by  the  current  which  traverses  the 
lymph-paths  in  the  substance  of  these  organs. 

Movement  of  the  Fluids  in  the  Lymphatic  System. — The  movement 
of  the  lymph  in  the  lymphatic  vessels  diners  from  that  of  the  blood,  in 
the  important  particular  that  its  course  is  always  in  one  direction, 


370  THE    LYMPHATIC    SYSTEM. 

namely,  from  the  periphery  toward  the  centre.  The  fluids  taken  up  by 
the  lymphatic  capillaries  are  collected  into  the  larger  branches  and 
trunks,  and  by  them  conducted  from  without  inward  toward  the  heart. 

The  physical  cause  of  the  continuous  movement  of  the  lymph  is  pri- 
marily the  force  of  endosmosis  acting  at  the  confines  of  the  lymphatic 
system.  As  the  volume  of  fluid  accumulates  in  an  endosmometer,  in 
such  a  manner  as  to  rise  perceptibty  in  the  upright  tube,  so  the  lymph 
accumulates  by  the  force  of  absorption  in  the  lymphatic  capillaries,  and 
thence  fills  the  larger  vessels  of  the  system.  It  is  evident  that  the 
pressure  of  fluids  in  a  particular  direction,  due  to  the  force  of  endos- 
mosis, may  be  very  considerable,  since  it  is  sometimes  sufficient,  as 
already  shown,  to  burst  the  shell-membrane  of  a  fowl's  egg  when  placed 
in  contact  with  water.  As  this  pressure,  in  the  lymphatic  system,  is 
always  directed  from  without  inward,  and  as  the  main  lymphatic  trunks 
finally  terminate  in  the  veins,  the  result  is  a  uniform  movement  of  the 
lymph,  from  the  peripheral  parts  of  the  various  organs  and  tissues 
toward  the  centre  of  the  circulation. 

The  movement  of  the  lymph  is  also  aided  by  several  secondary  causes. 
As  these  vessels  are  provided  with  valves,  even  more  abundantly  than 
the  veins,  the  alternate  contraction  and  relaxation  of  the  voluntary 
muscles  in  the  limbs  and  trunk  must  facilitate  considerably  the  passage 
of  their  fluids  in  an  inward  direction.  The  action  of  the  heart  and  arte- 
ries also  contributes  indirectly  to  this  result.  As  the  thoracic  duct 
passes  upward  through  the  chest,  it  crosses  the  median  line  obliquely 
from  right  to  left,  passing  between  the  spinal  column  and  the  aorta ;  so 
that  at  each  pulsation  of  the  aorta  it  is  compressed,  and  its  contents 
urged  toward  its  upper  extremity.  This  effect  is  often  very  visible  when 
a  canula  is  inserted,  in  the  living  animal,  into  the  thoracic  duct  at  the 
root  of  the  neck.  Under  these  circumstances  we  have  frequently  seen 
the  lymph  projected  from  the  extremity  of  the  canula  in  a  distinct  jet 
at  each  cardiac  pulsation,  owing  to  the  momentary  pressure  from  the 
distended  aorta. 

Lastly,  the  thoracic  movements  of  respiration  take  part  in  maintain- 
ing the  flow  of  lymph.  At  each  inspiration  the  resistance  in  the  inte- 
rior of  the  chest  is  diminished,  and  the  lymph  passes  more  readily  from 
below  into  the  thoracic  duct;  at  each  expiration  the  duct  is  subjected 
to  compression,  and  is  thus  emptied  of  its  fluids  in  a  direction  toward 
its  junction  with  the  veins.  The  influence  of  the  respiratory  move- 
ments, in  a  reversed  form,  may  often  be  seen  in  animals  poisoned  by 
woorara,  where  artificial  respiration  is  kept  up  through  the  trachea. 
If,  in  such  an  animal,  a  canula  be  inserted  into  the  thoracic  duct  at  the 
root  of  the  neck,  the  flow  of  tymph  from  its  open  extremity  is  percep- 
tibly increased  at  each  forcible  insufflation  of  the  lung,  since  this  pro- 
duces more  or  less  pressure  upon  the  thoracic  duct  in  the  cavity  of  the 
chest. 

Of  these  different  physical  causes  of  the  lymph-current,  the  first  alone, 
namely,  the  endosmotic  action,  is  entirely  uniform  and  continuous.  The 


THE  LYMPH  AND  CHYLE.  371 

others  are  all  intermittent  in  their  action,  and  depend  for  their  effi- 
ciency upon  the  existence  of  valves  in  the  lymphatic  vessels.  In  a 
set  of  vessels  provided  with  such  valves,  opening  forward  and  shutting 
backward,  any  force  which  alternately  compresses  and  releases  them 
will  necessarily  cause  the  fluids  which  they  contain  to  move  in  a  definite 
direction.  The  mechanical  forces  above  enumerated  are  more  or  less 
constantly  active,  and  in  point  of  fact  exercise  a  considerable  influence 
in  producing  an  incessant  transportation  of  the  lymph  from  the  peri- 
phery to  the  centre. 

Total  Daily  Quantity  of  the  Lymph  and  Chyle. — The  quantity  of 
fluids  discharged  from  the  thoracic  duct  within  a  given  time  varies 
according  to  the  condition  of  abstinence  or  digestion.  In  the  fasting 
condition  it  is  comparatively  moderate,  but  becomes  more  abundant 
soon  after  the  commencement  of  digestion,  to  diminish  again  during 
the  later  stages  of  the  process.  We  have  found,  at  various  periods  after 
feeding,  in  the  dog,  the  following  quantities  discharged  per  hour,  for 
every  thousand  parts  of  the  bodily  weight  of  the  animal : 

•    HOURLY  QUANTITIES  OF  LYMPH  AND  CHYLE  IN  THE  DOG, 
PER  THOUSAND  PARTS  OF  BODILY  WEIGHT. 

3|  hours  after  feeding 2.45 

7 2.20 

13  .......  0.99 

18  1.15 

18£      "  ......  1.99 

It  would  thus  appear  that  the  hourly  quantity  of  these  fluids,  after  di- 
minishing during  the  latter  stages  of  digestion,  increases  again  somewhat 
about  the  eighteenth  hour,  though  still  considerably  less  abundant  than 
while  digestion  is  in  active  progress.  It  is  probable  that  this  increase 
at  the  two  periods  indicated  is  owing  to  two  different  causes.  The  fluid 
obtained  in  greatest  abundance  in  the  dog,  in  from  3  to  1  hours  after 
feeding,  is  quite  white  and  opaque,  and  its  increase  in  quantity  is  evi- 
dently due  to  the  admixture  of  chyle  absorbed  from  the  intestine.  That 
obtained  so  late  as  the  eighteenth  hour  is  simply  opaline,  or  more  nearly 
transparent,  and  is  composed  of  lymph  alone.  The  absorption  of  chyle, 
therefore,  takes  place,  of  course,  while  digestion  is  in  progress ;  but  the 
most  abundant  production  of  lymph  occurs  some  hours  later,  after  the 
materials  of  nutrition  have  reached  and  permeated  the  tissues  themselves. 

The  entire  daily  quantity  of  lymph  and  chyle  is  found,  by  direct 
observation,  \o  be  much  larger  than  would  be  anticipated.  In  two 
experiments  upon  the  horse,  extending  over  a  period  of  twelve  hours 
each,  Colin1  obtained  from  the  thoracic  duct  in  this  animal,  on  the 
average,  893  grammes  of  fluid  per  hour,  which  would  amount  to  rather 
more  than  20  kilogrammes  per  day.  In  the  ruminating  animals,  accord- 
ing to  the  same  observer,  the  quantity  is  still  greater.  In  an  ordinary 

1  Physiologies  comparee  des  Animaux  domestiques.    Paris,  1856,  tome  ii.  p.  106. 


372  THE    LYMPHATIC    SYSTEM. 

sized  cow,  the  smallest  quantity  obtained,  in  an  experiment  extending 
over  a  period  of  twelve  hours,  was  625  grammes  in  fifteen  minutes ;  that 
is,  2500  grammes  per  hour,  or  60  kilogrammes  per  day.  In  another 
experiment  with  a  young  bull  weighing  185  kilogrammes,  he  actually 
withdrew  from  the  thoracic  duct  in  the  course  of  twenty-four  hours,  15 
kilogrammes  of  lymph  and  chyle,  representing  a  little  more  than  8  per 
cent,  of  the  entire  bodily  weight  of  the  animal. 

We  have  obtained  similar  results  from  experiments  upon  the  dog  and 
goat.  In  a  young  kid  weighing  6.36  kilogrammes,  we  have  obtained 
from  the  thoracic  duct  122.5  grammes  of  lymph  in  three  hours  and  a 
half.  This  quantity  represents  35  grammes  per  hour,  and,  if  continued 
throughout  the  day,  would  amount  to  640  grammes,  or  fully  10  per 
cent,  of  the  entire  bodily  weight.  In  the  dog  the  fluids  discharged  from 
the  thoracic  duct  are  less  abundant.  The  average  of  all  the  results 
obtained  by  us,  in  this  animal,  at  different  periods  after  feeding,  gives 
very  nearly  four  and  a  half  per  cent,  of  the  bodily  weight,  as  the  total 
daily  quantity  of  lymph  and  chyle.  This  is  substantially  the  same 
result  as  that  obtained  by  Colin  in  the  horse ;  and  for  a  man  weigh- 
ing 65  kilogrammes,  it  would  be  equivalent  to  about  3000  grammes 
of  lymph  and  chyle  per  day.  But  this  quantity  represents  both  the 
products  of  tymphatic  transudation  and  those  of  intestinal  absorption 
taken  together.  An  estimate  of  the  total  amount  of  the  lymph  alone 
must  be  based  upon  the  quantity  of  fluids  passing  through  the  thoracic 
duct  in  the  intervals  of  digestion,  when  no  chyle  is  being  taken  up  from 
the  alimentary  canal.  In  the  dog,  as  shown  by  the  experiments  quoted 
above,  the  average  quantity  obtained,  from  the  thirteenth  to  the  eigh- 
teenth or  nineteenth  hour  after  feeding,  when  intestinal  absorption  had 
come  to  an  end,  was  about  1.30  per  thousand  parts  of  the  bodily  weight ; 
or,  for  the  whole  twenty-four  hours,  a  little  over  3  per  cent,  of  the  bodily 
weight.  For  a  man  of  medium  size,  this  would  give  not  far  from  2000 
grammes  as  the  average  daily  quantity  of  lymph  alone. 

Internal  Renovation  of  the  Animal  Fluids. — By  the  combined  actions 
of  secretion,  transudation,  and  reabsorption,  a  continual  interchange  or 
renovation  of  the  animal  fluids  takes  place  in  the  living  body,  which  is 
dependent  for  its  materials  upon  the  circulation  of  the  blood,  and  which 
may  be  considered  as  a  kind  of  secondary  circulation  through  the  sub- 
stance of  the  tissues.  For  all  the  digestive  fluids,  as  well  as  the  bile 
discharged  into  the  intestine,  are  reabsorbed  in  the  natural  process  of 
digestion  and  again  enter  the  current  of  the  circulation.  These  fluids, 
therefore,  pass  and  repass  through  the  mucous  membrane  of  the  alimen- 
tary canal  and  adjacent  glands,  becoming  more  or  less  altered  in  con- 
stitution at  each  passage,  but  still  serving  to  renovate  alternately  the 
constitution  of  the  blood  and  the  ingredients  of  the  digestive  secretions. 
The  elements  of  the  blood  itself  also  transude  in  part  from  the  capillary 
vessels,  and  are  again  taken  up  from  the  tissues  by  the  lymphatics, 
to  be  finally  restored  to  the  venous  blood,  in  the  immediate  neighbor- 
hood of  the  heart. 


THE    LYMPH    AND    CHYLE.  373 

The  daily  quantity  of  all  the  fluids  thus  transuded  and  reabsorbed 
will  serve  to  indicate  the  activity  of  endosmosis  and  exosmosis  in  the 
living  body.  In  the  following  table,  the  quantities  are  all  estimated, 
from  preceding  data,  for  a  man  of  medium  size. 

TOTAL  QUANTITY  OF  FLUIDS  TRANSUDED  AND  REABSORBED 
DURING  TWENTY-FOUR  HOURS. 

Saliva 1300  grammes. 

Gastric  juice 3000 

Pancreatic  juice 800        " 

Bile 1000 

Lymph 2000 

8100 

Not  less  than  8000  grammes  therefore  of  the  animal  fluids,  a  quan- 
tity equal  to  that  of  the  entire  blood  and  amounting  to  more  than  12 
per  cent,  of  the  weight  of  the  whole  body,  transude  through  the  internal 
membranes  and  are  restored  to  the  blood  by  reabsorption,  in  the  course 
of  a  single  day.  It  is  by  this  process  that  the  natural  constitution  of 
the  parts,  though  constantly  changing,  is  still  maintained  in  its  normal 
condition,  through  the  movement  of  the  circulating  fluids  and  the 
renovation  of  their  materials. 


CHAPTEE    XVII. 

THE  URINE. 

THE  urine  is  distinguished  from  all  the  other  animal  fluids  by  the  fact 
that  it  represents  only  the  products  of  the  waste  or  physiological  disinte- 
gration of  the  body.  The  living  body,  while  in  the  active  performance 
of  its  functions,  is  the  seat  of  various  manifestations  of  force,  such  as 
animal  heat,  sensibility,  and  motion,  which  are  the  indications  of  its 
vitality.  These  manifestations  of  force,  in  the  living  organism,  as  well  as 
elsewhere,  are  only  produced  at  the  expense  of  its  materials,  and  by  their 
change  of  state  or  metamorphosis  in  the  internal  process  of  nutrition. 
It  is  accordingly  an  essential  condition  of  the  existence  and  activity  of 
the  animal  body  that  it  should  go  through  with  an  incessant  transfor- 
mation and  renewal  of  its  component  parts.  Every  living  being  absorbs 
more  or  less  constantly  certain  nutritive  materials  from  without,  which 
are  modified  by  assimilation  and  converted  into  the  natural  ingredients 
of  its  tissues.  At  the  same  time  with  this  continuous  process  of  growth 
and  supply,  there  goes  on  an  equally  continuous  change,  by  which  the 
elements  of  the  organized  frame  pass  over  into  new  forms  of  combi- 
nation, destined  to  be  expelled  from  the  body  as  the  products  of  its 
disintegration. 

Certain  substances,  therefore,  are  constantly  making  their  appearance 
in  the  animal  tissues  and  fluids,  which  were  not  introduced  with  the  food, 
but  which  have  been  produced  in  their  interior  b}r  the  process  of  con- 
tinued metamorphosis.  These  substances  result  from  the  new  combina- 
tions taking  place  in  the  organized  frame.  They  are  the  forms  under 
which  those  materials  present  themselves  which  have  once  made  part 
of  the  animal  tissues,  but  which  have  become  altered  by  the  incessant 
changes  characteristic  of  living  beings,  and  which  are  consequently  no 
longer  capable  of  exhibiting  vital  properties,  or  of  aiding  in  the  per- 
formance of  the  vital  functions.  The  process  of  the  elimination  and 
removal  of  these  materials  is  called  excretion,  and  the  materials  them- 
selves are  known  as  the  excrementitious  substances. 

These  substances  have  peculiar  characters  by  which  they  are  distin- 
guished from  other  ingredients  of  the  living  body.  They  are  crystal- 
lizable  and  for  the  most  part  soluble  in  water,  at  least  in  the  form  under 
which  they  appear  in  the  excreted  fluids.  They  are  formed  in  the  blood 
or  in  the  substance  of  the  tissues  from  which  they  are  absorbed  by 
the  blood,  and  are  conveyed  by  the  circulating  fluid  to  the  excretory 
organs  through  which  they  are  discharged.  If  their  elimination  from  the 
body  be  in  any  way  arrested  or  impeded,  their  accumulation  in  the 
system  produces  a  disturbance  of  the  vital  functions,  which  is  more  or 
(SU) 


THE    URINE.  375 

less  severe  according  to  their  special  character  and  the  rapidity  of  their 
production.  This  poisonous  influence  is  especially  manifested  in  its 
action  upon  the  nervous  system,  causing  an  abnormal  irritability,  de- 
rangement of  the  special  senses,  delirium,  insensibility,  coma,  and  death. 
These  effects  are  more  particularly  marked  in  the  case  of  urea  after 
suppression  of  the  urine ;  a  complete  stoppage  of  the  elimination  of  this 
substance  in  the  human  subject  usually  producing  a  fatal  result  in  three 
or  four  days. 

The  excrementitious  matters,  however,  are  not  to  be  considered  as 
poisonous,  or  even  deleterious,  in  the  quantities  in  which  they  normally 
occur  in  the  animal  solids  and  fluids.  On  the  contrary,  they  are  the 
natural  products  of  the  functional  activity  of  the  animal  system,  and 
are,  therefore,  as  essential  to  the  continued  manifestation  of  life  as  the 
nutritious  materials  supplied  by  the  food.  It  is  only  when  the  regular 
course  of  their  elimination  is  retarded  that  they  interfere  with  the  due 
performance  of  the  functions,  by  deranging  the  natural  constitution  of 
the  tissues. 

A  variety  of  excrementitious  substances  are  produced  in  the  body, 
some  of  which  are  probably  eliminated,  in  small  proportion,  with  the 
perspiration  or  with  the  feces.  The  carbonic  acid,  exhaled  in  large 
quantity  from  the  lungs,  is  to  be  regarded  as  belonging  to  this  class, 
since  it  is  produced  in  the  substance  of  the  tissues  and  constantly 
discharged  by  respiration.  But  the  most  important  substances, 
usually  included  under  the  head  of  excrementitious  matters,  are  distin- 
guished by  the  fact  that  they  contain  nitrogen  as  one  of  their  ultimate 
elements,  and  that  they  otherwise  exhibit  a  remarkable  analogy  with 
each  other  in  their  chemical  composition.  They  accordingly  form  a 
natural  group  of  organic  substances,  resembling  each  other  in  their 
origin,  their  constitution,  and  their  physiological  destination.  They  are 
furthermore  associated  together  by  the  circumstance  that  they  are  all 
eliminated  from  the  body  by  the  urine,  of  which  they  form  the  essential 
and  characteristic  ingredients. 

The  urine  is  therefore  the  only  animal  fluid  which  is  solely  an  excre- 
tion. It  is  a  solution  of  the  nitrogenous  excrementitious  matters  of  the 
animal  frame ;  and  by  its  abundance  and  composition  it  indicates  the 
activity  of  the  healthy  metamorphosis  of  the  organic  tissues  and  fluids. 
Beside  its  nitrogenous  ingredients,  it  contains  also  most  of  the  mineral 
salts  which  are  discharged  from  the  body ;  and  by  the  water  which  holds 
these  solid  matters  in  solution  it  forms  the  channel  for  a  large  propor- 
tion of  the  fluids  passing  daily  through  the  system.  Furthermore,  acci- 
dental or  abnormal  ingredients,  introduced  into  the  blood,  almost 
invariably  find  their  way  out  of  the  system  by  the  kidneys,  and  thus 
appear  as  temporary  ingredients  of  the  urine.  The  constitution  and 
physiological  variations  of  this  fluid  during  health,  and  its  alteration 
in  disease,  are  regulated  by  the  corresponding  changes  of  nutrition  or 
activity  in  the  body  at  large.  The  urine  is  therefore  one  of  the  most 
essential  products  of  the  animal  system,  and  its  formation  is  second 
in  importance  only  to  the  function  of  respiration. 


376  THE    URINE. 

Physical  Properties  of  the  Urine. 

The  urine  is  a  clear,  amber-colored  fluid,  of  a  watery  consistency,  and 
with  a  distinctly  acid  reaction.  As  a  general  rule,  its  transparency  is  so 
nearly  perfect  that  no  appearance  of  turbidity  is  perceptible  by  ordinary 
diffused  daylight.  It  contains,  however,  a  very  small  quantity  of 
mucus  from  the  urinary  bladder,  which  may  be  rendered  visible  as  a 
faint  opalescence  when  a  sunbeam  is  made  to  pass  through  it  in  a  lateral 
direction.  If  the  urine  be  allowed  to  remain  at  rest  for  a  few  hours  in 
a  cylindrical  glass  vessel,  the  mucus  gradually  subsides,  forming  a  very 
light  cloudy  mass  at  the  bottom  and  leaving  the  supernatant  fluid  en- 
tirely clear.  The  ingredients  of  the  urine  itself  are  all  therefore  in  a 
state  of  complete  solution.  While  still  warm  and  fresh,  the  urine  has  a 
peculiar  but  not  offensive  odor,  which  disappears  on  cooling  and  may 
be  then  restored  by  gentle  heating.  The  average  specific  gravity  of 
healthy  urine,  in  the  adult,  is  from  1020  to  1025  ;  and  its  daily  quantity 
is  about  1200  cubic  centimetres. 

Variations  of  the  Urine  in  Quantity,  Acidity,  and  Specific  Gravity. 
— The  urine  does  not  present  uniformly  the  same  characters,  but  varies 
normally  from  hour  to  hour,  in  each  individual,  at  different  periods  of 
the  day.  It  is  usually  discharged  from  the  bladder  five  or  six  times  in 
the  twenty-four  hours,  and  each  specimen  shows  more  or  less  variation 
in  its  physical  properties.  This  variation  depends  upon  the  changing 
conditions  of  the  body,  as  to  rest,  exercise,  food,  drink,  sleeping,  and 
waking.  In  the  same  person,  leading  a  uniform  mode  of  life  from  day 
to  day,  the  diurnal  variations  of  the  urine  follow  each  other  with  great 
regularity ;  although  in  different  persons,  whose  habits  are  different,  they 
may  not  be  altogether  the  same.  Asa  general  rule,  the  urine  which 
collects  in  the  bladder  during  the  night  and  is  first  discharged  in  the 
morning  is  strongly  colored,  of  high  specific  gravity,  and  has  a  very 
distinct  acid  reaction.  That  passed  during  the  forenoon,  on  the  other 
hand,  is  pale  and  of  comparatively  low  specific  gravity ;  often  falling 
so  low  as  1018  or  even  1015.  At  the  same  time,  its  acidity  diminishes 
or  even  disappears  altogether  ;  so  that  at  this  time  in  the  day  the  urine 
is  frequently  neutral  or  slightly  alkaline.  Toward  noon,  its  density  and 
depth  of  color  increase,  and  its  acidity  returns.  All  these  properties 
become  more  strongly  marked  during  the  afternoon  and  evening ;  and 
toward  night  the  urine  is  again  deeply  colored  and  strongly  acid,  and 
has  a  specific  gravity  of  1028  or  1030. 

The  following  instances  will  serve  to  show  the  general  characters  of 
this  variation  : 

OBSERVATION  FIRST.     March  20th. 

Urine  of  1st  discharge,  acid,        sp.  gr.  1025. 

"       2d  '•          alkaline,      "       1015. 

3d          "         neutral,       "       1018. 

"       4th         "          acid,  "       1018. 

"       5th         "         acid,  "       1027 


PHYSICAL    PROPERTIES    OF    THE    URINE.  377 

OBSERVATION  SECOND.     March  2lst. 
Urine  of  1st  discharge,  acid,         sp.  §T.  1029. 

-  2d          "          neutral,       <;       1022. 

-  3d          "          neutral,       "       1025. 
••       4th         -          acid,  "       1027. 
"       5th         "         acid,  "       1030. 

These  variations  do  not  always  follow  a  perfectly  regular  course,  since 
they  are  liable  to  temporary  modification  from  accidental  causes  during 
the  day ;  but  their  general  tendency  corresponds  with  that  given  above. 

The  acidity  of  the  urine  is  also  liable  to  vary  from  temporary  causes, 
owing  to  the  introduction  of  organic  substances  with  the  food  which 
give  rise  to  alkalescence  in  the  animal  fluids.  The  salts  of  the  organic 
acids,  such  as  the  lactates,  acetates,  malates,  and  tartrates,  when  taken 
into  the  stomach  and  absorbed  by  the  circulation,  are  replaced  by 
carbonates  of  the  same  bases,  and  appear  under  that  form  in  the  urine. 
When  these  salts,  or  the  fruits  and  vegetables  which  contain  them,  are 
taken  in  large  quantit}^  the  urine  becomes  alkaline  from  the  presence 
of  the  carbonates.  The  use  of  summer  fruits,  therefore,  though  they 
may  have  an  acidulous  taste,  is  followed  by  alkalescence  of  the  urine. 
The  effect  thus  produced  may  be  manifested  in  a  very  short  time; 
according  to  the  observations  of  Lehmann,  the  urine  sometimes  becom- 
ing alkaline  within  a  quarter  of  an  hour  after  taking  a  little  over  15 
grammes  of  sodium  acetate. 

It  is  evident,  therefore,  that  when  the  specific  gravity  or  the  acidity 
of  the  urine  is  to  be  tested,  either  in  health  or  disease,  it  will  not  be 
sufficient  to  rely  upon  the  examination  of  a  single  specimen.  The  nor- 
mal variations  in  specific  gravity  during  the  day  do  not  usually  exceed 
the  limits  of  1015  as  a  minimum  and  1030  as  a  maximum;  but  either 
of  these  would  be  unnatural  if  continued  during  the  whole  twenty-four 
hours.  All  the  different  specimens  'of  urine  passed  during  the  day 
should  therefore  be  collected  and  examined  together.  The  average 
specific  gravity  thus  obtained  will  represent  the  normal  daily  density 
of  the  excretion. 

The  daily  volume  of  the  urine  is  also  to  be  taken  into  account.  The 
total  amount  of  solids  discharged  by  the  urine  in  health  is  from  50  to 
60  grammes  per  day ;  and  this  quantity  of  solid  material  is  dissolved  in 
about  1200  cubic  centimetres  of  water.  This  gives  an  average  daily 
quantity  and  an  average  specific  gravity  of  the  urine,  as  the  measure  of 
the  excretory  process  during  twenty-four  hours. 

Both  the  quantity  of  the  urine  and  its  mean  specific  gravity  are 
liable  to  vary  somewhat  in  different  individuals,  or  even  in  the  same 
individual  from  day  to  day.  Ordinarily,  the  water  of  the  urine  is  more 
than  sufficient  to  hold  all  the  solid  matters  in  solution ;  and  its  propor- 
tion may  therefore  be  diminished  by  temporary  causes  without  the 
production  of  turbidity  or  the  formation  of  a  deposit.  Under  such  cir- 
cumstances, the  urine  merely  becomes  deeper  in  color,  and  of  higher 
25 


378  THE    UEINE. 

specific  gravity.  If  a  smaller  quantity  of  water  than  usual  be  taken 
into  the  system  with  the  drink,  or  if  the  exhalation  from  the  lungs  and 
skin,  or  the  intestinal  discharges,  be  increased,  a  smaller  quantity  of 
water  will  necessarily  pass  off  by  the  kidneys ;  and  the  urine  will  be 
diminished  in  quantity,  while  its  specific  gravity  is  increased.  The 
urine  is  sometimes  reduced  in  this  way  to  500  or  600  cubic  centimetres 
per  day,  its  specific  gravity  rising  at  the  same  time  to  1030.  On  the 
other  hand,  if  the  fluid  ingesta  be  unusually  abundant,  or  if  the  per- 
spiration be  diminished,  the  surplus  quantity  of  water  will  pass  off  by 
the  kidneys  ;  so  that  the  amount  of  urine  in  twenty- four  hours  may  be 
increased  to  1350  or  1400  cubic  centimetres,  and  its  mean  specific 
gravity  reduced  at  the  same  time  to  1020  or  even  1017.  Under  such 
conditions,  the  total  amount  of  solid  matter  discharged  remains  about 
the  same.  These  changes  depend  simply  upon  the  fluctuating  quantity 
of  water,  which  may  pass  off  by  the  kidneys  in  larger  or  smaller  quan- 
tity, according  to  circumstances.  In  purely  normal  or  physiological 
variations  of  this  nature,  the  entire  quantity  of  the  urine  and  its  mean 
specific  gravity  vary  always  in  an  inverse  direction  with  regard  to  each 
other ;  the  former  increasing  while  the  latter  diminishes,  and  vice  versa. 
If,  however,  it  be  found  that  both  the  quantity  and  specific  gravity  of 
the  urine  are  increased  or  diminished  at  the  same  time,  or  if  either  one 
be  increased  or  diminished  while  the  other  remains  stationary,  such  an 
alteration  will  show  an  actual  change  in  the  total  amount  of  solid  ingre- 
dients, and  consequently  an  unnatural  and  pathological  condition. 

Ingredients  of  the  Urine. 

The  chemical  composition  of  the  urine,  as  derived  from  the  most 
recent  and  numerous  analyses,  is  as  follows: 


Nitrogenous 

organic 
substances. 


Mineral  salts. 


COMPOSITION  OF  THE  UKINE. 

Water 950.00 

Urea 26.20 

Creatinine 0.87 

Sodium  and  potassium  urates     .        .         .  1.45 

Sodium  and  potassium  hippurates      .         .  0.70 

Sodium  biphosphate  .....  0.40 

Sodium  and  potassium  phosphates     .         .  3.35 

Lime  and  magnesium  phosphates       .         .  0.83 

Sodium  and  potassium  chlorides         .         .  12.55 

Sodium  and  potassium  sulphates        .         .  3.30 

Mucus  and  coloring  matter        .        .        .  0.35 

1000.00 

The  constitution  of  the  urine  is  not  invariable,  but  changes  more  or 
less  at  different  periods  of  the  day,  according  to  the  rapidity  of  excre- 
tion of  its  different  ingredients.  The  foregoing  list,  however,  repre- 
sents, in  an  approximate  manner,  its  average  composition  for  the  entire 
twenty-four  hours. 


INGREDIENTS    OF    THE    URINE.  379 

Urea. — This  is  the  most  important  constituent  of  the  urine,  both  in 
regard  to  character  and  amount,  forming  more  than  one-half  the  entire 
quantity  of  its  solid  ingredients,  and  over  80  per  cent,  of  all  those  of  an 
organic  nature.  The  most  important  fact  known  with  regard  to  the 
origin  of  urea  is,  that  it  is  not  formed  in  the  kidneys,  but  pre-exists  in 
the  blood  in  small  proportion,  and  is  drained  away  from  the  circulat- 
ing fluid  during  its  passage  through  the  renal  vessels.  This  was  first 
shown  by  the  experiments  of  Prevost  and  Dumas,1  who,  after  extir- 
pating the  kidneys,  or  tying  the  renal  arteries  in  the  living  animal, 
found  the  quantity  of  urea  in  the  blood  increased  in  marked  proportion, 
owing  to  the  arrest  of  its  elimination  by  the  kidneys.  It  has  also  been 
found  in  the  blood  of  the  human  subject  in  cases  of  renal  disease, 
sometimes  in  so  large  a  proportion  as  1.5  parts  per  thousand,2  or  nearly 
ten  times  its  normal  quantity.  It  has  not  been  found,  however,  in  suf- 
ficient quantity  in  any  of  the  solid  tissues  to  indicate  the  immediate 
source  of  its  production.  It  is  either  formed  in  the  blood  itself,  by 
transformation  of  some  previous  nitrogenous  combination,  or  it  is  ab- 
sorbed by  the  blood  too  rapidly  to  be  detected  as  an  ingredient  of  the 
solid  tissues. 

Urea  is  obtained  most  readily  from  the  urine  by  first  converting  it 
into  the  form  of  a  nitrate.  For  this  purpose  the  fresh  urine  is  evapo- 
rated over  the  water-bath  until  it  is  reduced  to  one-quarter  of  its  original 
volume.  It  is  then  filtered,  and  the  filtered  fluid  mixed  with  an  equal 
quantity  of  nitric  acid,  which  produces  nitrate  of  urea.  This  salt,  being 
less  soluble  than  urea,  rapidly  separates  in  the  form  of  abundant  crys- 
talline scales.  The  c^stalline  deposit  is  separated  from  the  mother 
liquor,  mixed  with  water,  and  decomposed  by  the  addition  of  barium 
carbonate,  which  sets  free  the  urea,  with  the  formation  of  barium  nitrate. 
This  process  is  continued  so  long  as  carbonic  acid  is  given  off;-  after 
which  the  whole  is  evaporated  to  dryness,  and  the  dry  residue  extracted 
with  absolute  alcohol,  which  dissolves  out  the  urea.  The  alcoholic  solu- 
tion is  then  filtered  and  evaporated  until  the  urea  separates  in  a  crys- 
talline form.3 

The  quantity  of  urea  in  a  given  volume  of  urine  is  readily  ascertained 
by  decomposing  it,  according  to  Davy's  method,  with  a  solution  of  so- 
dium hypochlorite.  A  long  and  narrow  graduated  glass  tube,  open  at 
one  extremity,  and  capable  of  holding  about  50  cubic  centimetres  of 
fluid,  is  filled  to  a  little  more  than  one-third  its  capacity  with  mercury, 
upon  which  are  poured  3  or  4  cubic  centimetres  of  the  urine  to  be  ex- 

1  Prevost  and  Dumas,  Annales  de  Chimie  et  de  Physique,  1823,  tome  xxiii. 
p.  90 ;  Segalas,  Journal  de   Physiologie,  tome  ii.  p.  354 ;  Mitscherlich,  Tiede- 
mann.  and   Gmelin,   Poggendorf's   Annalen,  band   xxxi.  p.  303 ;    Cl.  Bernard, 
Liquides  de  1'Organisme.     Paris,  1859,  tome  ii.,  Deuxieme  Legon. 

2  In  Milne  Edwards,  Legons  sur  la  Physiologie.     Paris,  1857,  tome  i.  p.  298. 

3  Hoppe-Seyler,  Handbuch  der  Physiologisch-  und   Pathologisch-Chemischen 
Analyse.     Berlin,  1870,  p.  120. 


380  THE    UKINE. 

amined.  The  remainder  of  the  tube  is  then  filled  with  the  sodium 
hypochlorite  solution,  the  mouth  of  the  tube  closed,  the  fluids  well 
mixed,  and  the  tube  then  inverted  in  a  shallow  glass  dish  filled  with  a 
saturated  solution  of  sodium  chloride.  The  mixture  of  urine  and  hypo- 
chlorite solution  remains  in  the  tube ;  and  as  the  urea  is  decomposed, 
its  nitrogen  is  given  off  in  the  gaseous  form  and  collects  in  the  upper 
closed  end  of  the  tube,  where  its  volume  may  be  read  off  on  the  scale, 
after  the  action  has  ceased.  Every  cubic  centimetre  of  nitrogen,  thus 
disengaged,  represents  2.5  milligrammes  of  urea. 

The  conditions  influencing  the  quantity  of  urea  produced  and  dis- 
charged in  the  healthy  subject  during  twenty-four  hours,  are  the  size 
and  general  development  of  the  body,  the  nature  of  the  food,  and  the 
state  of  rest  or  activity.  Like  other  products  of  the  living  organism, 
its  quantity  is  in  proportion  to  the  entire  mass  of  the  body.  As  a 
general  rule,  its  daily  quantity,  in  man,  is  0.5  per  thousand  parts  of  the 
entire  bodily  weight ;  and  for  a  man  of  medium  size  it  amounts  to  about 
35  grammes  per  day.  As  it  is  a  nitrogenous  substance,  resulting  from 
the  final  consumption  of  the  albuminous  elements  of  the  system,  its 
proportion  is  greater  under  a  diet  of  animal  food,  which  is  comparatively 
rich  in  albuminous  matters,  than  under  one  of  vegetable  food,  in  which 
these  substances  are  less  abundant.  Its  daily  quantity  falls  to  a 
minimum  when  the  diet  is  exclusively  confined  to  non-nitrogenous  arti- 
cles of  food,  namely,  starch,  sugar,  and  fat.  It  is  still,  however,  pro- 
duced and  excreted  under  an  exclusively  non-nitrogenous  diet,  and  even 
when  no  food  whatever  is  taken,  so  long  as  the  animal  functions  con- 
tinue to  be  performed. 

The  results  obtained  by  nearly  all  experimenters  led  to  the  conclu- 
sion that  the  quantity  of  urea  excreted  is  especially  increased  by  mus- 
cular exertion ,  until  a  doubt  was  thrown  upon  this  point  by  Tick  and 
Wislicenus  in  1866.  These  observers  ascended  a  mountain  on  foot, 
the  ascent  occupying  a  little  over  eight  hours ;  during  which  time,  and 
for  seventeen  hours  beforehand,  they  confined  themselves  to  a  diet  of 
non-nitrogenous  food.  They  found  the  amount  of  urea  discharged  per 
hour  to  be  less,  while  engaged  in  ascending  the  mountain,  than  it  was 
before ;  but  it  increased  during  the  following  night,  after  a  meal  of 
animal  food. 

Subsequent  observers  have  obtained  various  results.  Dr.  Parkes,  in  a 
series  of  very  careful  and  extended  observations,1  found  that  the  dis- 
charge of  urea  was  increased  not  during,  but  after,  a  period  of  muscular 
work.  This  was  shown  even  in  a  man  confined  for  five  days  to  a  non- 
nitrogenous  diet,  in  whom  the  discharge  of  urea  was  not  increased  on 
the  day  of  unusual  muscular  effort,  but  on  the  following  day  was  a  little 
more  than  doubled. 

The  observations  of  Prof.  A.  Flint,  Jr.,  on  the  excretion  of  urea  in 
the  case  of  the  pedestrian  Weston,  have  the  important  advantage  of  ex- 

1  Proceedings  of  the  Royal  Society  of  London,  vol.  xvi.  p.  48,  and  March  2, 
1871. 


INGKEDiENTS    OF    THE    UEINE. 


381 


tending  over  comparatively  long  periods,  both  of  exercise  and  rest,  the 
diet  at  the  same  time  remaining  unchanged  in  its  general  characters. 

The  pedestrian  was  under  observation  for  fifteen  days ;  namely,  five 
days  previous  to  the  walk,  five  days  during  its  continuance,  and  five 
days  immediately  afterward.  For  the  period  preceding  the  walk,  the 
average  exercise  was  about  eight  miles  per  day ;  during  the  walk  it  was 
nearly  sixty-four  miles  per  day,  and  for  the  period  subsequent  to  the 
walk,  it  was  a  little  over  two  miles  per  day.  The  results  obtained 
during  the  three  peri9ds  showed,  accordingly,  the  normal  amount  of 
urea  excreted  by  the  pedestrian  under  ordinary  conditions,  the  amount 
discharged  during  an  unusual  and  nearly  continuous  muscular  exertion, 
and  the  subsequent  effects  of  the  exertion  on  the  general  condition  of 
the  system. 

The  nitrogenous  ingredients  of  the  food,  during  all  three  periods, 
were  also  recorded,  so  that  the  influence  of  the  food  itself  on  the  amount 
of  urea  may  be  estimated  at  the  same  time  with  that  of  the  muscular 
exertion. 

The  following  table  gives  the  main  result  of  these  experiments,  so 
far  as  they  are  connected  with  the  present  subject : 


Daily  Quantity  of 

First  Period. 
Five  days 
before  the  walk. 

Second  Period. 
Five  days 
during  the  walk. 

Third  Period. 
Five  days 
after  the  walk. 

Urea        
Nitrogen  in  food 
Nitrogen  in  urea     . 
Total  nitrogen  in  urea  and  feces 
Nitrogen  in  urea  and  feces  per 
100  parts  of  nitrogen  in  food 

628.24  grains. 
339.46      " 
293.18      " 
315.09      " 

95.53 

722.16  grains. 
234.76      " 
337.01      " 
361.52      " 

174.81 

726.79  grains. 
440.93      " 
339.17      " 
373.15      " 

91.93 

It  is  evident,  therefore,  that  during  the  time  of  unusual  muscular 
exertion  the  daily  quantity  of  urea  was  increased  by  nearly  fifteen  per 
cent,  over  that  of  the  previous  ordinary  condition,  the  nitrogenous  ele- 
ments of  the  food  being  at  the  same  time  considerably  diminished  ;  and 
that,  during  the  period  of  exertion,  the  total  quantity  of  nitrogen  dis- 
charged by  the  urea  and  feces  combined  was  nearly  seventy-five  per 
cent,  greater  than  that  introduced  with  the  food,  while  in  both  the  pre- 
vious and  subsequent  periods  it  was  from  about  four  and  a  half  to  eight 
per  cent.  less.  During  the  period  of  exertion  there  was  a  loss  of  nearly 
three  and  a  half  pounds  of  bodily  weight,  and  an  increase  of  similar 
amount  during  the  subsequent  period  of  rest.  The  author  fairly  explains 
the  above  loss  of  weight  by  the  disintegration  of  muscular  tissue;  and 
the  subsequent  increase,  by  a  retention  of  nitrogenous  constituents  in 
the  body,  to  repair  the  waste  thus  produced. 

"During  the  five  days  of  the  walk,1  Mr.  Weston  consumed  in  all 
1173.80  grains  of  nitrogen  in  his  food.  During  the  same  period  he 


New  York  Medical  Journal,  June,  1871,  p.  669. 


382  THE    URINE. 

eliminated  1807.60  grains  of  nitrogen,  in  the  urine  and  feces.  This 
leaves  633.80  grains  of  nitrogen,  over  and  above  the  nitrogen  of  the  food, 
which  must  be  attributed  to  the  waste  of  his  tissues,  and  probably 
almost  exclusively  to  the  waste  of  his  muscular  tissue.  According  to 
the  best  authorities,  lean  meat  uncooked,  or  muscular  tissue,  contains  3 
per  cent,  of  nitrogen.  The  loss  of  633.80  grains  of  nitrogen  would  then 
represent  a  loss  of  21,121.00  grains,  or  3.018  Ibs.  of  muscular  tissue. 
The  actual  loss  of  weight  was  3.450  Ibs.  This  allows  about  0.43  Ib.  of 
loss  unaccounted  for,  which  might  be  fat  or  water." 

Creatinine. — This  substance  is  perhaps  next  in  physiological  import- 
ance to  the  urea,  considering  its  analogy  in  chemical  composition,  but 
is  produced  in  much  smaller  quantity ;  its  total  amount  usually  not  ex- 
ceeding 1  gramme  per  day.  It  has  not  been  found  in  any  of  the  solid 
tissues ;  but  it  is  probably  derived  by  transformation  of  the  creatine  of 
the  muscles,  since  it  may  be  artificially  produced  from  the  latter  by  the 
action  of  heat  and  dilute  sulphuric  acid.  It  is  undoubtedly,  like  urea, 
a  product  of  the  metamorphosis  of  the  albuminous  ingredients  of  the 
body,  from  which  it  derives  its  nitrogenous  element.  But  little  is  known 
with  regard  to  the  conditions  which  increase  or  dimmish  its  production. 

Sodium  and  Potassium  Urates. — The  urates  are  due  to  a  combination 
of  the  alkaline  base  with  a  nitrogenous  mineral  acid,  belonging  to  the 
same  physiological  class  of  excrernentitious  matters  as  urea  and  creati- 
nine.  This  substance  is  known  to  be,  like  urea,  increased  in  quantity 
by  a  nitrogenous,  and  decreased  by  a  non-nitrogenous  diet ;  but  its  rela- 
tions to  muscular  exercise  and  other  temporary  conditions  are  not  fully 
known.  The  urates  are  readily  soluble  in  water,  and  are  usually  excreted 
to  the  amount  of  about  1.75  gramme  per  day.  The  hippurates  have,  in 
general,  similar  chemical  and  physiological  relations  to  those  of  the 
urates,  excepting  that  they  are  more  abundant  under  the  use  of  a  vege- 
table diet,  and  disappear  altogether  when  the  food  is  exclusively  of  an 
animal  nature.  In  the  human  subject  under  an  ordinary  mixed  diet, 
they  amount  to  about  one-half  the  quantity  of  the  urates. 

The  preceding  ingredients  of  the  urine  are  all  associated  in  a  single 
physiological  group,  forming  its  nitrogenous  excrementitious  substances. 
Beside  them,  it  also  contains  a  variety  of  inorganic  or  mineral  constitu- 
ents, derived  from  the  waste  of  the  animal  tissues  and  fluids. 

Acid  Sodium  Phosphate,  or  sodium  biphosphate. — This  is  the  ingre- 
dient which  gives  to  the  urine  its  acid  reaction  to  test-paper.  It  is 
regarded  as  derived  from  the  ordinary  sodium  phosphate  of  the  blood 
(Xa.2H  P04)  by  the  action  of  the  uric  acid  produced  in  the  system,  which 
unites  with  a  part  of  its  sodium,  forming  sodium  urate,  and  leaving  an 
acid  sodium  phosphate  (NaHQPOJ.  The  uric  acid  produced  from  the 
decomposition  of  animal  substances,  although  it  does  not  itself  appear 
in  a  free  form,  is,  therefore,  indirectly  the  cause  of  the  acid  reaction  of 
the  urine ;  and  this  reaction  will  vary  in  intensity  with  the  amount  of 
uric  acid  discharged. 


INGREDIENTS    OF    THE    URINE.  383 

The  Alkaline  Phosphates,  or  ordinary  phosphates  of  sodium  and 
potassium. — These  are  the  soluble  phosphates,  which  exist  in  the  blood 
as  well  as  in  the  urine,  and  which,  in  solution,  have  a  mild  alkaline  re- 
action. Owing  to  their  ready  solubility,  they  never  appear  as  a  precipi- 
tate, nor  disturb  in  any  way  the  transparency  of  the  urine.  It  is  under 
the  form  of  these  salts  that  most  of  the  phosphoric  acid  in  combination 
is  discharged  with  the  urine.  According  to  Yogel,  the  excretion  of 
phosphoric  acid  by  this  channel  is  increased  by  the  use  of  food  contain- 
ing soluble  phosphates  or  substances  capable  of  yielding  phosphoric 
acid  by  the  changes  which  they  undergo  in  the  system.  It  is  accord- 
ingly more  abundant  under  a  diet  of  animal  food,  less  so  under  a  vege- 
table regimen.  Its  discharge,  however,  does  not  depend  exclusively 
upon  the  ingredients  of  the  daily  food,  since  it  continues,  although  in 
diminished  quantity,  after  long-continued  abstinence  from  all  food.  Its 
immediate  origin  is,  therefore,  wholly  or  partly  from  the  constituents 
of  the  body  itself.  The  observations  of  Wood,1  as  well  as  those  of 
Yogel  and  others,  show  also  that  there  is  a  diurnal  variation  of  con- 
siderable regularity  in  the  normal  excretion  of  the  salts  of  phosphoric 
acid.  Its  hourly  quantity  is  at  a  minimum  during  the  forenoon,  in- 
creases in  the  latter  part  of  the  day  after  the  principal  meal,  and  reaches 
a  maximum  in  the  evening  or  during  the  night,  to  diminish  again  on  the 
morning  of  the  following  day.  It  is  under  the  form  of  phosphates  that 
the  phosphorus  contained  in  certain  organic  substances  (lecithine)  is 
finally  discharged  from  the  system.  The  average  quantity  of  the  alka- 
line phosphates  discharged  during  health  under  an  ordinary  diet  is  a  little 
over  four  grammes  per  day. 

The  Earthy  Phosphates,  or  the  phosphates  of  lime  and  magnesium. — 
The  earthy  phosphates  are  usually  present  in  the  urine  in  much  smaller 
quantity  than  the  preceding.  They  are  held  in  solution  only  by  the  acid 
reaction  of  the  urine,  and  when  this  is  absent  or  very  much  diminished 
they  are  thrown  down  as  a  light  precipitate,  consequently,  the  neutral 
or  faintly  alkaline  urine  passed  in  the  forenoon  is  often  slightly  turbid 
with  a  deposit  of  the  earthy  phosphates,  without,  however,  indicating 
any  abnormal  increase  in  their  amount.  According  to  the  extensive 
and  careful  observations  of  Wood,  the  alkaline  and  earthy  phosphates 
differ  from  each  other  in  the  conditions  which  influence  their  excretion. 
"While  the  alkaline  phosphates  of  the  urine  are  increased  in  amount 
during  continued  mental  application,  the  earthy  phosphates  are  dimin- 
ished, and  the  total  quantity  of  both  kinds  is  not  materially  altered. 
The  earthy  phosphates,  on  the  other  hand,  are  increased  by  abstinence 
from  mental  labor.  Their  average  daily  quantity  under  ordinary  condi- 
tions is  about  one  gramme,  or  rather  less  than  one-quarter  that  of  the 
earthy  phosphates. 

1  On  the  Influence  of  Mental  Activity  on  the  Excretion  of  Phosphoric  Acid  by 
the  Kidneys.  Proceedings  of  the  Connecticut  Medical  Society,  1869. 


THE    URINE. 

Sodium  and  Potassium  Chlorides. — The  sodium  chloride,  which  repre- 
sents nearly  the  whole  of  these  two  salts,  is  also  by  far  the  most  abundant 
mineral  ingredient  in  the  urine,  forming  over  one-half  of  its  inorganic 
constituents.  It  is  derived  in  great  measure  from  the  sodium  chlo- 
ride taken  with  the  food,  and  is  increased  or  diminished  in  quantity 
with  the  variation  in  the  amount  of  common  salt  in  the  diet.  Various 
circumstances,  however,  influence  its  excretion  at  different  periods  of  the 
day.  Its  hourly  discharge  is  habitually  least  "during  the  night,  increases 
in  the  forenoon  and  is  greatest  during  the  latter  part  of  the  day.  Ac- 
cording to  Vogel,1  both  mental  and  bodily  exertion  perceptibly  increase 
its  excretion ;  and  even  water,  when  taken  in  unusual  abundance,  by  in- 
creasing the  activity  of  the  kidneys,  causes  also  a  temporary  augmen- 
tation in  the  discharge  of  sodium  chloride,  which  is  subsequently  followed 
by  a  corresponding  diminution.  The  average  amount  of  the  chlorides 
discharged  with  the  urine  is  about  fifteen  grammes  per  day. 

Sodium  and  Potassium  Sulphates. — The  sulphates  present  in  the 
urine  are  derived  partly  from  those  which  have  been  introduced,  under 
their  own  form,  as  ingredients  of  the  food  ;  and  observation  has  shown 
that  their  quantity  is  increased  by  the  medicinal  administration  of  sul- 
phuric acid  or  of  sodium  sulphate.  The  administration  of  sulphur  or 
the  sulphurets  produces  a  similar  effect.  The  albuminous  matters  of 
the  system,  furthermore,  which  contain  sulphur  as  one  of  their  con- 
stituent elements,  give  rise,  by  their  changes  in  the  oxidizing  process  of 
nutrition  and  excretion,  to  sulphuric  acid  and  the  sulphates ;  since  the 
whole  of  their  carbon,  hydrogen,  and  nitrogen  is  finally  discharged 
under  the  form  of  water,  carbonic  acid,  and  urea,  while  the  small 
quantity  of  sulphur  remaining  appears  as  sulphuric  acid  in  the  sul- 
phates. Consequently  the  excretion  of  sulphates,  as  shown  by  Vogel, 
is  increased  by  an  abundant  diet  of  animal  food,  and  diminished  under 
a  vegetable  regimen.  The  sulphates  are  freely  soluble  and  never  appear 
as  a  spontaneous  precipitate  in  the  urine.  Their  average  quantity  is 
about  3.96  grammes  per  day. 

Reactions  of  the  Urine  to  Chemical  Tests. 

The  reactions  of  the  urine  to  a  variety  of  ordinary  tests  form  a  ready 
criterion  for  ascertaining  its  normal  or  abnormal  constitution.  The 
more  exact  quantitative  determination  of  its  ingredients  requires  the 
attention  and  skill  of  the  professional  chemist;  but  many  of  its  im- 
portant characters  may  be  recognized  by  the  use  of  simple  means. 

The  Application  of  Heat. — If  transparent  healthy  urine,  of  a  dis- 
tinctly acid  reaction,  be  heated  in  a  test-tube  over  a  spirit  lamp  to  the 
boiling  point,  no  change  in  its  appearance  is  produced.  If  its  acidity 
be  very  slightly  pronounced,  on  the  other  hand,  it  becomes  turbid  on 
boiling,  from  a  precipitation  of  its  earthy  phosphates.  This  is  because 
the  earthy  phosphates  are  less  soluble  in  a  hot  than  in  a  cold  liquid; 

1  Analyse  des  Hams.     Wiesbaden,  1872,  p.  350. 


KEACTIONS    OF    UKINE    TO    CHEMICAL    TESTS. 


385 


and  the  faintly  acid  reaction  of  the  urine,  which  was  enough  to  hold 
them  in  solution  at  ordinary  temperatures,  is  no  longer  sufficient  after 
the  application'  of  heat,  and  the  phosphates  are  accordingly  thrown 
down  as  a  deposit.  The  precipitation  from  this  cause  is  never  very 
abundant,  and  it  is  instantly  cleared  up  again  by  the  addition  of  a  drop 
of  nitric  acid,  which  restores  the  normal  acidity  of  the  urine.  The  tur- 
bidity thus  produced  by  boiling,  from  the  precipitation  of  the  earthy 
phosphates,  is  not,  therefore,  usually  due  to  an  increased  quantity  of 
these  salts  in  the  urine,  but  simply  to  a  deficiency  of  its  acid  reaction. 

Diseased  urine  may  also  become  turbid  on  boiling,  from  the  coagula- 
tion of  albumen.  This  is  readily  distinguished  from  a  precipitation  of 
the  earthy  phosphates  by  two  facts — namely,  first,  that  it  may  take 
place  in  urine  which  is  distinctly  acid ;  and  second,  that  the  addition  of 
nitric  acid,  which  redissolves  the  phosphatic  precipitate,  only  increases 
the  turbidity  which  is  due  to  albumen. 

Acids. — The  addition  of  the  mineral  acids  to  healthy  urine  produces 
no  immediate  visible  effect,  beyond  increasing  its  acidity  and  slightly 
modifying  its  color.  They,  however,  decompose  its  urates  ;  and  the  uric 
acid  thus  set  free  is  slowly  deposited  in  the  crystalline  form.  If  nitric 
or  hydrochloric  acid  be  added  to  fresh  filtered  urine,  in  the  proportion 
of  about  2  per  cent,  by  volume,  and  the  mixture  be  allowed  to  remain 
at  rest  for  twenty-four  or  forty-eight  hours,  the  sides  and  bottom  of  the 
vessel  become  covered  with  a  thinly  scattered  deposit  of  uric  acid 
crystals.  These  crystals  have 
usually  the  form  of  transparent 
rhomboidal  plates,  or  oval 
laminaj  with  pointed  extremi- 
ties, and  are  generally  tinged  of 
a  yellowish  hue  by  the  coloring 
matter  of  the  urine.  They  are 
frequently  arranged  in  radiated 
clusters,  or  small  spheroidal 
masses,  presenting  the  appear- 
ance of  minute  calculous  con- 
cretions, which  vary  much  in 
size  and  regularity,  according 
to  the  time  occupied  in  their 
formation. 

The  deposit  of  uric  acid  crys- 
tals,  thus   formed   in    healthy 
urine  from  the  addition  of  a 
mineral  acid,  is  always  scanty  in  amount,  and  only  becomes  visible  as 
a  crystalline  precipitate  after  several  hours. 

In  rare  cases,  when  the  urine  is  loaded  with  an  unusual  proportion 
of  the  urates,  a  few  drops  of  nitric  acid  will  produce  at  once  a  per- 
ceptible turbidity,  from  the  precipitation  of  abundant  microscopic  crys- 


CRYSTALS  OF  URIC  ACID;  deposited  from 
urine,  after  the  addition  of  nitric  acid.    " 


386  THE    URINE. 

tals  of  uric  acid.  This  deposit  may  be  distinguished  from  albumen  by 
the  appearance  of  the  crystals  under  the  microscope,  and  also  by  the 
fact  that,  unlike  albumen,  it  is  not  produced  by  the  application  of  a 
boiling  temperature. 

When  the  urine  is  scanty  and  concentrated,  owing  to  temporary  causes, 
with  a  specific  gravity  of  1030  to  1035,  but  without  any  abnormal  in- 
gredient, if  it  be  mixed  with  one-half  its  volume  of  nitric  acid  and 
exposed  to  a  low  temperature,  a  crystallization  of  nitrate  of  urea  will 
often  take  place  in  the  course  of  half  an  hour  or  an  hour.  This  is 
clue  simply  to  the  diminished  proportion  of  water,  which  is  still  suffi- 
cient to  hold 'the  urea  in  solution,  but  allows  a  separation  of  nitrate  of 
urea  when  this  salt  is  formed  by  the  addition  of  nitric  acid.  It  never 
takes  place  when  the  urine  has  its  normal  specific  gravity  of  1020  to 
1025. 

Alkalies. — The  addition  of  a  free  alkali  or  an  alkaline  carbonate  to 
normal  urine  diminishes  its  acid  reaction,  and,  as  soon  as  the  point  of 
saturation  has  been  reached,  produces  a  turbidity,  owing  to  the  pre- 
cipitation of  the  earthy  phosphates.  These  are  the  only  ingredients  of 
the  urine  which  are  thrown  down  by  the  addition  of  an  alkali,  and  a 
free  acid  immediately  restores  its  transparency. 

Mineral  Salts. — Solutions  of  barium  chloride,  barium  nitrate,  or  the 
tribasic  lead  acetate,  when  added  to  healthy  urine,  decompose  its  sul- 
phates, and  produce  a  dense  precipitate  of  the  corresponding  metallic 
salts.  Solutions  of  silver  nitrate  produce  a  precipitate  with  the  sodium 
and  potassium  chlorides,  forming  silver  chloride  which  is  insoluble.  The 
tribasic  lead  acetate  and  silver  nitrate  also  throw  down  mucus  and 
coloring  matters. 

Abnormal  Ingredients  of  the  Urine. 

The  abnormal  ingredients  which  appear  in  the  urine  are  either:  1st. 
Foreign  substances  accidentally  present  in  the  blood,  which  are  elimi- 
nated by  the  kidneys,  such  as  glucose,  biliary  matters,  and  medicinal 
substances;  or  2d.  The  albuminous  constituents  of  the  blood,  which  are 
discharged  with  the  urine  owing  to  a  disturbance  of  the  renal  circulation. 

Glucose. — The  presence  of  glucose  in  the  urine  is  characteristic  of 
diabetes  mellitus.  In  this  disease  the  urine  is  generally  increased  in 
quantity  and  at  the  same  time  of  unusually  high  specific  gravity,  namely, 
from  1035  to  1050.  It  is  of  a  light,  clear,  amber  or  straw  color,  and 
remarkably  transparent ;  so  that  it  has  the  appearance  of  being  dilute, 
although  it  is  in  reality  denser  than  usual,  owing  to  the  presence  of 
glucose  in  solution.  The  glucose  is  detected  by  the  application  of  Trom- 
mer's  or  Fehling's  test,  or  by  that  of  fermentation.  For  the  latter  pur- 
pose a  little  yeast  should  be  mixed  with  15  or  20  times  its  volume  of 
water,  and  the  mixture  allowed  to  remain  at  rest  in  a  cylindrical  upright 
glass  vessel  until  the  yeast  globules  have  subsided  in  a  dense  homo- 
geneous layer  at  the  bottom.  The  supernatant  fluid,  containing  the 


ABNORMAL    INGREDIENTS    OF    THE    URINE. 


387 


Fig.  130. 


soluble  impurities  of  the  yeast,  is  poured  off,  and  a  small  quantity  of 
the  moist  yeast-deposit  at  the  bottom  is  added  to  the  urine  under  exami- 
nation. The  mixture  is  then  placed 
in  a  ferment-apparatus  and  kept  at  a 
temperature  of  about  25°  (77°  F.),  for 
forty-eight  hours,  when  the  gaseous 
products  of  fermentation  will  have 
been  completely  disengaged.  The 
most  convenient  form  of  apparatus  is 
a  test-tube  of  known  capacity  (Fig. 
-130,  a,  6),  supported  by  a  foot  and 
provided  with  an  India-rubber  stopper, 
through  which  passes  a  narrow  glass 
tube  (c),  open  at  both  ends ;  its  inner 
portion  reaching  to  the  bottom  of  the 
test-tube,  where  it  is  bent  upward,  to 
prevent  the  escape  of  gas,  its  outer 
portion  being  bent  downward,  to  allow 
the  liquid  expelled  to  drop  freely  from 
its  orifice.  The  test-tube  may  be 
graduated  in  cubic  centimetres  from 
above  downward.  The  apparatus 
being  filled  with  saccharine  urine, 
when  fermentation  begins  the  disen- 
gaged gas  rises  in  bubbles  to  the 
upper  part  of  the  test-tube  and  col- 
lects there,  while  the  urine  is  forced 
out  through  the  bent  glass  tube. 
Every  cubic  centimetre  of  carbonic 
acid  produced  corresponds  to  0.26 

milligrammes  of  sugar  decomposed.  A  similar  apparatus,  containing 
the  same  quantity  of  healthy  urine  and  yeast,  should  be  kept  at  the 
same  temperature  for  an  equal  time,  as  a  comparative  test;  since  a  small 
quantity  of  carbonic  acid  might  be  disengaged  from  the  yeast  itself, 
owing  to  its  imperfect  purification.  The  difference  between  the  two 
cases  is  that  in  the  yeast  alone  the  disengagement  of  gas  soon  ceases ; 
while  in  a  saccharine  solution  the  yeast-cells  multiply  indefinitely,  and 
carbonic  acid  continues  to  be  produced  until  most  of  the  sugar  has  been 
decomposed.  This  method  does  not  give  the  precise  quantity  of  the 
glucose  contained  in  any  single  specimen,  since  some  of  the  urine 
escapes  before  its  fermentation  is  fully  completed ;  but  it  is  at  the  same 
time  the  surest  indication  of  the  existence  of  sugar,  and  a  ready  means 
of  determining  approximatively  whether  it  be  scanty  or  abundant  in 
amount. 

The  simplest  method  of  ascertaining  the  quantity  of  glucose  in  a 
given  specimen  of  urine  with  sufficient  accuracy  for  all  clinical  pur- 


FERMENT-APPARATUS,  contain- 
ing saccharine  urine  in  fermentation. — a. 
Upper  part  of  the  test-tube  containing 
carbonic  acid.  6.  Lower  part  of  the  test- 
tube  containing  the  fermenting  liquid,  c. 
Bent  glass  tube,  to  allow  the  escape  of 
liquid,  d.  Liquid  which  has  been  forced 
out  from  the  test-tube  by  the  accumula- 
tion of  gas. 


388  THE    URINE. 

poses  is  that  of  Dr.  Roberts,1  which  depends  upon  the  loss  of  specific 
gravity  occasioned  by  the  decomposition  of  the  glucose  in  fermentation. 
A  portion  of  the  urine  is  taken  and  its  specific  gravity  ascertained  at 
the  temperature  of  25°  (77°  F.).  A  little  yeast  is  then  added  and  the 
mixture  kept  at  the  same  temperature  until  fermentation  has  ceased ; 
when  the  specific  gravity  is  again  taken.  The  diminution  in  density 
caused  by  the  conversion  of  the  glucose  into  alcohol  and  carbonic  acid 
is  such  that  the  loss  of  one  degree  in  specific  gravity  indicates  the  dis- 
appearance of  2.191  milligrammes  of  glucose  for  every  cubic  centimetre 
of  urine. 

The  glucose  can  be  obtained  directly  from  diabetic  urine,  according  to 
the  method  of  Hoppe-Seyler,  by  evaporating  the  urine  over  the  water- 
bath  to  the  consistency  of  a  syrup,  and  allowing  it  to  remain  at  rest  for 
some  days  or  weeks  until  completely  crystallized.  The  crystalline  mass 
is  triturated  and  washed  with  a  small  quantity  of  cold  alcohol,  to  re- 
move tire- urea.  The  residue  is  then  extracted  with  boiling  alcohol,  and 
the  alcoholic  solution  filtered  while  still  hot,  after  which  the  glucose  is 
deposited  in  a  crystalline  form. 

The  glucose  of  diabetic  urine  is  not  formed  in  the  kidneys,  but  pre- 
exists in  the  blood,  from  which  it  is  eliminated  in  the  renal  circulation. 
If  a  solution  of  sugar  be  introduced  in  sufficient  quantity  directly  into 
the  bloodvessels  of  the  rabbit,  or  injected  into  the  subcutaneous  con- 
nective tissue  so  as  to  be  absorbed  thence  by  the  blood,  it  is  soon 
discharged  by  the  kidneys.  It  has  been  shown  by  Bernard,2  that  the 
time  within  which  sugar  appears  in  the  urine  under  these  circum- 
stances varies  with  the  quantity  injected  and  the  rapidity  of  its  absorp- 
tion. If  a  solution  of  one  gramme  of  glucose  in  25  cubic  centimetres  of 
water  be  injected  under  the  skin  of  a  rabbit  weighing  a  little  over  one 
kilogramme,  it  is  entirely  destroyed  in  the  circulation,  and  does  not  pass 
out  with  the  urine.  A  dose  of  1.5  gramme,  however,  injected  in  the 
same  way,  appears  in  the  urine  at  the  end  of  two  hours,  2  grammes  in 
an  hour  and  a  half,  2.5  grammes  in  an  hour,  and  12.5  grammes  in  fifteen 
minutes.  Whenever,  accordingly,  glucose  accumulates  in  the  circula- 
tion beyond  a  certain  quantity  in  proportion  to  the  whole  mass  of  the 
blood,  it  is  eliminated  as  a  foreign  substance,  and  appears  as  an  in- 
gredient of  the  urine. 

Biliary  Matters. — In  some  cases  of  jaundice,  the  coloring  matter  of 
the  bile  passes  into  the  urine  in  sufficient  abundance  to  give  to  the  fluid 
a  deep  yellow  or  yellowish-brown  tinge,  so  that  it  may  even  stain  linen 
or  cotton  fabrics,  with  which  it  comes  in  contact,  of  a  similar  color. 
The  saline  biliary  substances,  namely,  sodium  glycocholate  and  tauro- 
cholate,  according  to  Lehmann,  have  also  been  detected  in  the  urine. 
In  these  instances,  the  biliary  matters  are  reabsorbed  from  the  hepatic 
ducts  and  conveyed  by  the  blood  to  the  kidneys. 

1  Urinary  and  Renal  Diseases.     Philadelphia  edition,  1872,  p.  198. 

2  Leqons  de  Physiologic  Expe>imentale.     Glycog6nie.     Paris,  1855,  p.  216. 


ABNORMAL    INGREDIENTS    OF    THE    URINE.  389 

Potassium  ferrocyanide,  when  introduced  into  the  circulation,  ap- 
pears with  great  readiness  in  the  urine ;  and,  according  to  the  observa- 
tions of  Bernard,  may  begin  to  be  eliminated  within  twenty  minutes 
after  being  injected  into  the  duct  of  the  submaxillary  gland. 

Iodine,  in  all  its  combinations,  passes  out  by  the  same  channel. 
After  the  administration,  in  the  healthy  human  subject,  of  192  milli- 
grammes of  iodine,  in  the  form  of  syrup  of  the  iodide  of  iron,  we  have 
found  it  to  be  present  in  the  urine  at  the  end  of  thirty  minutes,  and  that  it 
continued  to  be  discharged  for  nearly  twenty-four  hours.  In  the  case  of 
two  patients  who  had  been  taking  potassium  iodide,  one  of  them  for  six 
weeks,  the  other  for  two  months,  the  urine  still  contained  iodine  at  the 
end  of  three  days  after  the  suspension  of  the  medicine ;  but  at  the  end 
of  three  days  and  a  half  it  was  no  longer  present.  Even  when  iodine, 
however,  is  taken  in  a  free  form,  as  in  that  of  alcoholic  solution,  it 
always  passes  out  by  the  urine  in  combination.  It  cannot  be  detected, 
accordingly,  by  the  simple  admixture  of  starch  with  the  urine,  but  must 
be  set  free  by  the  addition  of  a  drop  or  two  of  nitric  acid,  after  which  it 
produces  its  characteristic  blue  color  by  union  with  the  starch.  The 
same  thing  is  true  of  the  other  animal  fluids,  such  as  the  saliva  and  the 
perspiration,  by  which  iodine  is  also  eliminated  after  its  introduction 
into  the  system. 

Quinine,  when  taken  as  a  remedy,  has  been  detected  in  the  urine. 
Ether  passes  out  of  the  circulation  in  the  same  way,  and  its  odor  may 
sometimes  be  very  perceptible  in  the  urine,  after  having  been  inhaled 
for  the  purpose  of  producing  anaesthesia.  The  peculiar  odors  developed 
in  the  urine  after  the  use  of  Asparagus,  and  certain  other  vegetable  sub- 
stances, are  produced  by  a  transformation  of  their  ingredients  while 
passing  through  the  animal  system. 

Albumen. — Under  ordinary  conditions  the  albumen  of  the  blood  does 
not  pass  out  in  any  proportion  from  the  renal  vessels  ;  but  whenever  the 
pressure  in  these  vessels  is  increased  beyond  a  certain  point,  owing  to 
congestion,  compression  of  the  renal  veins  by  abdominal  tumors,  preg- 
nancy, or  altered  nutrition  of  the  kidneys  in  Bright's  disease,  the 
albuminous  ingredients  of  the  blood  transude  through  the  capillaries 
and  make  their  appearance  in  the  urine. 

Albuminous  urine  is  usually  rather  pale,  and  often  somewhat  opales- 
cent from  the  admixture  of  exfoliated  epithelium  cells  or  of  fibrinous 
casts  from  the  uriniferous  tubules  of  the  kidney.  When  this  is  the  case, 
it  should  be  rendered  transparent  by  filtration  before  applying  the  tests, 
since  the  turbidity  already  existing  might  mask  the  reaction,  if  the 
albumen  were  present  in  small  proportion. 

If  the  urine  have  an  acid  reaction,  the  application  of  heat  produces  a 
turbidity  which  is  more  marked  in  proportion  to  the  quantity  of  albu- 
men which  it  contains  In  extreme  cases  the  fluid  may  solidify,  like 
the  serum  of  blood,  before  reaching  the  boiling  point ;  but  the  albumen 
is  more  frequently  thrown  down  in  loose  whitish  flakes.  When  the 


390  THE    URINE. 

turbidity  produced  by  boiling  is  moderate  in  amount,  it  may  resemble 
that  due  to  the  precipitation  of  the  earthy  phosphates.  It  can,  how- 
ever, be  distinguished  by  the  addition  of  a  drop  of  free  acid,  which  at 
once  redissolves  the  earthy  phosphates,  while  it  does  not  affect  a  tur- 
bidity caused  by  albumen.  An  albuminous  precipitate,  on  the  contrary, 
however  abundant,  is  redissolved  by  the  addition  of  a  caustic  alkali. 

If  the  urine  be  alkaline  in  reaction,  boiling  may  not  throw  down  the 
albumen  present,  this  substance  being  soluble  in  an  alkali.  Urine, 
accordingly,  which  is  suspected  of  being  albuminous,  should  be  first 
rendered  distinctly  acid  in  reaction,  if  necessary,  by  the  addition  of  a 
small  quantity  of  acetic  acid. 

Nitric  acid,  added  to  albuminous  urine,  produces  a  turbidity  by 
coagulation  of  the  albumen.  Alcohol,  added  to  the  urine  in  equal 
volume,  will  have  the  same  effect ;  and  a  solution  of  potassium  ferrocy- 
anide,  acidulated  with  acetic  acid,  will  also  produce  coagulation.  All 
the  above  tests,  if  applied  in  succession,  will  leave  no  doubt  as  to  the 
presence  or  absence  of  albumen. 

Deposits  in  the  Urine. 

The  deposits  which  appear  spontaneously  in  the  urine  consist  either : 
1st,  of  some  of  its  normal  ingredients,  thrown  down  in  consequence 
of  a  disturbance  in  its  relative  composition;  or  2d,  of  exudations 
from  the  mucous  membrane  of  the  urinary  passages,  owing  to  a  dis- 
eased condition  of  the  parts.  Those  belonging  to  the  first  class  are  the 
earthy  phosphates  and  the  urates.  The  most  common  of  those  belong- 
ing to  the  second  are  blood,  mucus,  and  pus. 

Deposits  of  the  Earthy  Phosphates, — These  deposits  are  always  of  a 
white  color,  and  are  seldom  abundant.  When  the  urine  is  first  passed, 
the  phosphates  are  disseminated  through  its  mass  in  the  form  of  a  light 
cloudiness,  which  settles  slowly  to  the  bottom  of  the  vessel.  The 
urine  is  alkaline  or  neutral  in  reaction,  and  is  usually  of  less  than  the 
average  specific  gravity.  The  precipitate  is  amorphous,  presenting  no 
crystalline  forms  under  the  microscope.  It  is  at  once  redissolved  on 
the  addition  of  an  acid,  and  presents  all  the  chemical  reactions  which 
have  been  described  as  belonging  to  the  earthy  phosphates.  The  alka- 
line reaction  of  the  urine,  which  gives  rise  to  the  appearance  of  this 
deposit,  may  be  due  to  a  temporary  diminution  in  the  quantity  of  uric 
acid  produced  in  the  system,  or  to  an  unusual  formation  of  alkaline 
carbonates  from  the  use  of  fruits  or  vegetables  containing  salts  of  the 
vegetable  acids. 

Deposits  of  the  Urates. — The  urates  appear  as  a  deposit  when  the 
formation  of  uric  acid  in  the  system  is  unusually  abundant  in  propor- 
tion to  the  entire  quantity  of  the  urine,  so  that  a  portion  of  the  urates 
are  no  longer  held  in  solution.  The  urine  is  nearly  always  concentrated, 
highly  colored,  above  the  average  specific  gravity,  and  of  a  strongly 
acid  reaction.  The  deposit  is  sometimes  nearly  white,  but  usually  it  is 
of  a  light  pink  or  even  red  color,  according  to  the  degree  of  concentra- 


DEPOSITS    IN    THE    URINE. 


391 


tion  of  the  urine  from  which  it  is  deposited.  If  the  urine  be  allowed  to 
settle  in  a  white  earthen  or  porcelain  vessel,  and  then  carefully  poured 
off,  the  more  deeply  colored  deposits  are  left  as  a  brick-red  stain  upon 
the  inner  surface  of  the  vessel,  forming  what  is  known  as  the  "  brick- 
dust"  sediment. 

Deposits  of  the  urates  are  easily  recognized  by  two  special  characters, 
namely :  First,  they  never  appear  while  the  urine  is  still  warm,  but  only 
after  it  has  cooled ;  the  urine,  when  first  passed,  being  always  perfectly 
clear,  and  becoming  turbid  on  repose,  more  or  less  rapidly  according  to 
the  rate  of  cooling.  Secondly,  the  urine,  after  cooling,  however  turbid, 
if  heated  in  a  test-tube,  becomes  clear  again,  usually  before  reaching 
the  boiling  point.  Both  these  characters  depend  upon  the  solubility 
of  the  urates  at  high  temperatures. 

In  rare  cases,  when  a  specimen  of  urine  is  turbid  with  the  urates  and 
also  contains  albumen,  a  double  effect  may  be  produced  by  the  applica- 
tion of  heat.  When  such  a  specimen  is  first  heated,  it  is  cleared  up, 
owing  to  the  solution  of  the  urates ;  but,  on  approaching  the  boiling 
point,  it  again  becomes  turbid  from  precipitation  of  the  albumen. 

The  urates  are  also  soluble  in  the  caustic  alkalies,  so  that  the  ad- 
dition of  a  few  drops  of  a  solution  of  sodium  or  potassium  hydrate 
redissolves  the  precipitate.  The  addition  of  a  free  acid  decomposes  it, 
with  the  formation  of  a  soluble  salt,  and  the  separation  of  uric  acid  which 
afterward  crystallizes,  as  when  thrown  down  in  the  same  manner 
from  normal  urine.  But  the  volume  of  the  uric  acid  thus  produced  is 
so  much  smaller  than  that  of  the  urates  previously  disseminated  through 
the  urine,  that  the  immediate  apparent  effect  is  that  of  simple  solution 
of  the  precipitate.  A  deposit 
of  the  urates  is  accordingly  the 
only  one  liable  to  occur  in  the 
urine,  which  is  cleared  up  by 
the  addition  of  both  alkalies 
and  acids. 

Deposits  of  the  urates,  when 
first  thrown  down,  are  pulver- 
ulent in  form,  presenting  un- 
der the  microscope  only  the 
appearance  of  a  collection  of 
minute  granules.  After  a  day 
or  two  they  sometimes  crystal- 
lize in  the  form  of  bundles  or 
globular  masses  of  radiating 
needles,  often  with  straight  or 
curved  projections,  extending 
from  the  outer  surface.  If 
a  few  drops  of  free  acid  be 
added  to  this  deposit  while  under  the  microscope,  the  crystalline  masses 
of  sodium  urate  may  be  seen  to  grow  transparent,  and  slowly  dissolve 


CRYSTALLINE  MASSES  OF  SODITTM  URATE, 
from  a  urinary  deposit. 


392  THE    URINE. 

from  without  inward,  while  rhomboidal  tabular  crystals  of  uric  acid 
make  their  appearance  in  the  adjacent  fluid. 

Crystals  of  uric  acid  sometimes  appear  spontaneously  in  a  deposit 
of  the  urates  within  a  few  hours  after  its  formation,  owing  to  the  de- 
velopment of  a  free  acid  in  the  urine ;  and  they  are  sometimes  formed 
within  the  urinary  passages,  so  as  to  be  present  when  the  urine  is  first 
passed.  Owing  to  their  density  and  angularity  they  are  the  cause  of 
much  irritation  to  the  mucous  membrane  of  the  bladder  and  urethra, 
and  are  known  as  the  "gravel"  of  the  urine.  In  a  mingled  precipitate 
of  the  urates  and  uric  acid,  the  urates  form  an  abundant  light,  pulver- 
ulent, pinkish  turbidity  ;  while  the  uric  acid  is  a  comparatively  scanty, 
dense,  deeply  colored,  crystalline  deposit,  which  sinks  rapidly  and  accu- 
mulates at  the  bottom  of  the  vessel,  the  urates  being  more  slowly  depos- 
ited above  it. 

Blood. — Urine  containing  blood  is  more  or  less  tinged  throughout  its 
mass  with  a  dull  reddish  color  which  is  easily  distinguished  from  that 
due  to  a  concentration  of  the  normal  color  of  the  urine  itself.  After 
one  or  two  hours  of  repose  in  a  cylindrical  glass  vessel,  the  blood- 
globules  are  slowly  deposited ;  and  when,  as  frequently  happens,  they 
are  entangled  in  minute  filamentous  coagula,  these  form  a  strongl}- 
colored  red  layer  at  the  bottom  of  the  vessel.  The  nature  of  the  deposit 
is  recognized  by  two  well-marked  characters,  namely :  1st.  The  blood- 
globules  are  easily  distinguished  by  microscopic  examination,  their 
natural  form  not  being  entirely  lost  even  after  they  have  remained  in 
the  urine  for  several  hours ;  and  2d.  The  supernatant  fluid,  when  de- 
canted from  the  deposit,  is  found  to  contain  albumen. 

Mucus. — The  slight  quantity  of  vesical  mucus  which  is  normally  con- 
tained in  the  urine  is  at  first  uniformly  disseminated  throughout  its  mass, 
and  even  after  being  left  in  repose  is  insufficient  to  produce  any  well 
marked  or  consistent  deposit.  The  light  cloudy  opalescence,  which  it 
forms  at  the  bottom  of  the  vessel,  is  visible  only  on  close  inspection,  and 
is  readily  disseminated  again  by  the  least  agitation.  But  in  cases  of 
inflammation  of  the  urinary  bladder,  the  mucus  discharged  is  much 
increased  in  quantity  and  altered  in  quality.  It  then  appears  as  a  con- 
sistent mass,  which  does  not  mix  uniformly  with  the  rest  of  the  urine, 
but  subsides  to  the  bottom  as  a  semifluid  deposit.  Mucus  by  itself 
is  transparent  and  colorless,  but  it  frequently  contains  a  certain 
number  of  epithelium  cells  exfoliated  from  the  inner  surface  of  the 
bladder;  and  when  crystalline  or  pulverulent  deposits  begin  to  take 
place  in  the  urine,  they  occur  first  in  contact  with  the  mucus,  so  that 
its  surface  is  often  sprinkled  with  a  thin  layer  of  the  urates  or  phos- 
phates, which  give  it  a  partly  opaque  appearance.  It  is  distinguished 
by  its  viscid  and  semifluid  consistency.  It  is  not  affected  by  heat,  but 
is  coagulated  and  shrivelled  by  the  action  of  alcohol  and  of  nitric  or 
acetic  acid.  Urine  containing  mucus  is  especially  liable  to  rapid  de- 
composition, and  often  has,  soon  after  being  discharged,  a  peculiarly 
offensive  odor  from  this  cause. 


DECOMPOSITION    OF    THE    URINE.  393 

Pus. — When  pus  is  contained  in  the  urine  it  subsides  on  standing, 
and  forms  at  the  bottom  a  dense,  homogeneous-looking,  creamy-white 
layer.  It  is  perfectly  fluid  in  consistency  and  may  be  easily  dissemi- 
nated by  agitation.  Microscopic  examination  shows  it  to  be  composed 
exclusively  of  colorless,  granular,  nucleated  "  pus-globules,"  identical 
in  appearance  with  the  white  globules  of  the  blood,  but  distinguishable 
from  those  belonging  to  a  deposit  of  blood  by  their  much  greater 
abundance  and  by  the  absence  of  red  globules.  If  the  supernatant  fluid 
be  poured  off,  and  a  few  drops  of  a  solution  of  caustic  alkali  added  to 
the  purulent  deposit,  it  loses  its  white  color  and  opacity,  owing  to  the 
solution  of  its  granular  cells,  and  swells  up  into  a  transparent,  colorless 
substance  of  gelatinous  consistency,  which  can  no  longer  be  poured 
out  of  the  vessel  in  drops,  but  slides  out  in  a  single  semi-solid  mass. 
This  character  alone  will  serve  to  distinguish  a  deposit  of  pus  from 
any  other  liable  to  occur  in  the  urine.  The  supernatant  fluid,  when 
carefully  filtered,  is  found  to  contain  a  small  quantity  of  albumen,  the 
interstitial  fluid  of  pus  being  itself  albuminous. 

Decomposition  of  the  Urine. 

After  its  discharge  from  the  body,  the  urine  undergoes  spontaneous 
changes,  by  wrhich  its  ingredients  are  altered  and  finally  disappear.  This 
process  of  spontaneous  decomposition  is  closely  dependent  upon  the 
small  quantity  of  mucus  contained  in  the  urine,  since  it  is  very  much 
retarded  if  the  mucus  be  separated  by  immediate  filtration,  and  is  hast- 
ened in  a  corresponding  degree  when  the  mucus  is  abnormally  abundant. 
It  is  characterized  by  two  different  stages,  which  are  distinguished  from 
each  other  by  the  successive  development  of  an  acid  and  an  alkaline 
reaction.  They  are  known  accordingly  as  the  acid  and  the  alkaline 
fermentations. 

Acid  Fermentation  of  the  Urine. — This  process,  which  is  the  first  to 
show  itself  in  the  urine,  takes  place  for  the  most  part  within  the  first 
twelve,  twenty-four,  or  forty-eight  hours  after  the  discharge  of  the  urine, 
according  to  the  elevation  of  the  surrounding  temperature.  It  consists 
in  the  production  of  a  free  acid,  usually  lactic  acid,  from  some  of  the 
undetermined  organic  ingredients  of  the  excretion.  The  urine  when 
fresh  contains  no  free  acid  substance,  its  reaction  to  test-paper  being 
due  to  the  presence  of  its  sodium  biphosphate.  But  lactic  acid  has, 
notwithstanding,  been  so  often  found  in  nearly  fresh  urine  as  to  be 
sometimes  regarded  as  one  of  its  normal  constituents.  Observation  has 
shown,  however,  that  urine,  although  entirely  free  from  lactic  acid  when 
first  passed,  may  present  distinct  traces  of  this  substance  after  some 
hours  of  exposure  to  the  air.  Its  production  in  this  way,  although  not 
constant,  appears  to  be  sufficiently  frequent  to  be  regarded  as  a  normal 
process. 

During  the  period  of  the  acid  fermentation,  there  is  reason  to  believe 
that  oxalic  acid  is  also  sometimes  produced  in  a  similar  manner.  It  is 
26 


394 


THE    URINE. 


Fig.  132. 


certain  that  a  deposit  of  lime  oxalate  is  frequently  present  in  perfectly 
normal  urine  after  a  day  or  two  of  exposure  to  the  atmosphere,  and  may 
be  observed,  under  these  circumstances,  without  the  existence  of  any 
morbid  symptom.  Whenever  oxalic  acid  is  formed  in  the  urine  it  must 
unite  with  the  lime  in  preference  to  any  other  of  the  bases  present,  and 
is  consequently  deposited  under  the  form  of  lime  oxalate ;  a  salt  which 
is  quite  insoluble  both  in  water  and  in  the  urine,  even  when  heated  to 
the  boiling  point.  In  these  cases,  the  lime  oxalate  crystals  gradually 
appear  in  the  light  cloud  of  mucus  collected  at  the  bottom  of  the  vessel, 

while  the  supernatant  fluid  re- 
main s  clear.  They  are  of  minute 
size,  for  the  most  part  just 
visible  to  the  naked  eye,  rather 
scanty  in  amount,  transparent, 
and  colorless.  They  have  the 
form  of  regular  octohedra,  or 
double  quadrangular  pyramids, 
united  base  to  base.  They  make 
their  appearance  usually  about 
the  commencement  of  the  sec- 
ond day,  the  urine  at  the  same 
time  continuing  clear  and  re- 
taining its  acid  reaction.  They 
frequently  appear  as  a  deposit 
when  no  substance  containing 
oxalic  acid  or  oxalates  has  been 
taken  with  the  food.  The  pre- 
cise source  from  which  the  oxalic  acid,  under  these  circumstances,  is 
derived  has  not  been  fully  determined,  but  it  is  most  probably  produced 
from  a  metamorphosis  of  a  small  portion  of  the  uric  acid  of  the  urine. 
If  uric  acid  be  boiled  in  two  parts  of  water  with  lead  peroxide,  it  is  de- 
composed, with  the  production,  among  other  substances,  of  urea  and 
oxalic  acid  ;  and  it  is  supposed  that  some  similar  change  may  take  place 
in  the  urine,  causing  the  appearance  of  a  minute  quantity  of  oxalic  acid, 
which  decomposes  a  portion  of  the  lime  salts  and  thus  appears  as  a 
crystalline  deposit  of  lime  oxalate. 

Alkaline  Fermentation  of  the  Urine. — At  the  end  of  a  few  days  the 
changes  above  described  come  to  an  end,  and  are  Succeeded  by  a  different 
process,  which  consists  essentially  in  the  decomposition  of  the  urea  of 
the  urine  and  its  transformation  into  ammonium  carbonate.  This 
change,  which  may  be  produced  artificially  in  a  watery  solution  of  urea 
by  continued  boiling,  takes  place  in  the  urine  slowly  at  low  tempera- 
tures, more  rapidly  during  warm  weather.  The  elements  of  two 
molecules  of  water  unite  with  those  of  the  urea  undergoing  decomposi- 
tion, to  produce  ammonium  carbonate,  as  follows  : 

Urea.  Ammonium  carbonate. 

CH4N20  +  H40,  =  (NH4).C03. 


CRYSTALS  OF  IJIME  OXALATE,  deposited 
from  healthy  urine,  during  the  acid  fermentation. 


DECOMPOSITION    OF    THE    URINE.  395 

The  first  portions  of  the  ammoniacal  salt  thus  produced  neutralize  a 
corresponding  quantity  of  the  sodium  biphosphate,  so  that  the  acid 
reaction  of  the  urine  diminishes  in  intensity.  This  reaction  gradually 
becomes  weaker,  as  the  fermentation  proceeds,  until  it  at  last  disappears 
altogether  and  the  urine  becomes  neutral.  The  production  of  ammonium 
carbonate  still  continuing,  the  reaction  of  the  fluid  then  becomes  alkaline, 
and  its  alkalescence  grows  more  pronounced  with  the  constant  accumu- 
lation of  the  ammoniacal  salt. 

The  time  at  which  the  alkaline  reaction  of  the  urine  becomes  estab- 
lished varies  with  its  original  degree  of  acidity  and  with  the  rapidity  of 
its  decomposition.  Urine  which  is  neutral  when  first  passed,  as  often 
happens  with  that  discharged  during  the  earlier  part  of  the  day,  will  of 
course  become  alkaline  more  readily  than  that  which  has  at ,  first  a 
strongly  acid  reaction.  In  the  summer,  urine  will  become  alkaline,  if 
freely  exposed,  on  the  third,  fourth,  or  fifth  day ;  while  in  the  winter,  a 
specimen  kept  in  a  cool  place  may  still  be  neutral  at  the  end  of  fifteen 
days.  In  cases  of  paralysis  of  the  bladder  accompanied  with  cystitis, 
where  the  vesical  mucus  is  increased  in  quantity  and  altered  in  quality, 
and  the  urine  is  retained  in  the  bladder  for  ten  or  twelve  hours  at  the 
temperature  of  the  bod}r,  it  may  change  so  rapidly  as  to  be  distinctly 
alkaline  and  ammoniacal  at  the  time  of  its  discharge.  In  these  cases  it 
is  acid  when  first  secreted  by  the  kidneys,  and  becomes  alkaline  while 
retained  in  the  interior  of  the  bladder. 

The  first  effect  of  the  alkaline  condition  of  the  urine,  thus  produced, 
is  the  precipitation  of  the  earthy  phosphates.  This  precipitate  slowly 
settles  upon  the  sides  and  bottom  of  the  vessel,  or  is  partly  entangled 
with  certain  animal  matters  which  rise  to  the  surface  and  form  a  thin, 
opaline  scum  upon  the  urine.  There  are  no  crystals  to  be  seen  at  this 
time,  but  the  deposit  is  entirely  amorphous  and  granular. 

The  next  change  consists  in  the  production  of  a  new  salt,  the 
ammonio-magnesian  phosphate,  by  the  combination  of  the  ammonia 
formed  from  the  urea  with  the  magnesium  phosphate  already  present  in 
the  urine.  The  change  may  be  represented  as  follows : 

Magnesium  phosphate.  Ammonia.        Ammonio-magnesian  phosphate. 

MgHP04         +         NH3          =          MgNH4PO, 

The  crystals  of  this  salt  are  very  elegant  and  characteristic.  They 
show  themselves  throughout  all  parts  of  the  mixture,  growing  gradually 
in  the  mucus  at  the  bottom,  adhering  to  the  sides  of  the  glass,  and 
scattered  abundantly  over  the  film  which  collects  upon  the  surface.  By 
their  refractive  power  they  give  to  this  film  a  peculiar  glistening  and 
iridescent  appearance,  which  is  nearly  always  visible  at  the  end  of  six 
or  seven  days.  The  crystals  are  perfectly  colorless  and  transparent,  and 
have  the  form  of  triangular  prisms,  generally  with  bevelled  extremities. 
Their  edges  and  angles  are  frequently  replaced  by  secondary  facets. 
They  are  insoluble  in  alkalies,  but  are  easily  dissolved  by  acids,  even 
in  very  dilute  form.  At  first  they  are  of  minute  size,  but  gradually 


396 


THE    URINE. 


CRYSTALS  OP  AMMO>- IO-MAGNESIA  w 
PHOSPHATE,  deposited  from  healthy  uriue, 
during  the  alkaline  fermentation. 


133-  increase,  so  that  after  seven  or 

eight   days    they  may   become 
visible  to  the  naked  eye. 

As  the  decomposition  of  the 
urine  continues,  the  ammonium 
carbonate  which  is  produced, 
after  saturating  all  the  other 
ingredients  with  which  it  is  ca- 
pable of  entering  into  combina- 
tion, begins  to  be  given  off  in  a 
free  form.  The  urine  then  ac- 
quires an  ammoniacalodor;  and 
a  piece  of  moistened  test-paper, 
held  a  little  above  the  surface, 
will  have  its  color  turned  by 
the  alkaline  gas  escaping  from 
the  fluid.  This  is  the  source 
of  the  ammoniacal  vapor  given 

off  wherever  urine  is  allowed  to  remain  and  decompose.     It  continues 

until  all  the  urea  has  been  decomposed. 

Renovation  of  the  Body  in  the  Nutritive  Process. 

As  the  materials  of  nutrition  are  constantly  introduced  with  the  food, 
while,  on  the  other  hand,  the  products  of  excretion  are  removed  from 
the  body  and  discharged  externally  by  the  breath,  the  perspiration,  the 
urine,  and  the  feces,  an  incessant  renewal  takes  place  in  the  ingredients 
of  which  the  animal  system  is  composed.  During  the  early  periods  of 
growth  and  development,  the  quantity  of  material  introduced  is  greater 
than  that  discharged,  and  the  body  consequently  increases  in  weight 
and  size.  In  wasting  diseases  and  in  advanced  age,  the  loss  of  sub- 
stance by  excretion  exceeds  the  gain  by  nutrition,  and  the  weight  of 
the  body  is  therefore  diminished.  But  during  health,  in  adult  life,  the 
two  processes  are  equal;  and,  with  certain  temporary  fluctuations 
which  counterbalance  each  other,  the  weight  of  the  body  remains  the 
same. 

The  total  quantity  of  material,  introduced  and  discharged  within  a 
given  time,  forms,  accordingly,  a  measure  of  the  rapidity  with  which  the 
internal  changes  of  nutrition  and  metamorphosis  go  on  in  the  animal 
system.  It  is  not  possible  to  indicate  this  quantity  in  either  case  with 
absolute  accuracy;  but  the  observations  which  have  been  made  in  this 
direction  are  sufficiently  definite  to  show,  in  a  general  way,  the  average 
results  of  the  two  corresponding  actions  of  waste  and  supply.  The 
following  table  gives,  approximately,  the  daily  quantity  of  material 
absorbed  and  discharged  in  a  healthy  adult,  the  weight  of  the  body 
remaining  sensibly  unaltered : 


RENOVATION    OF    THE    BODY.  397 

Absorbed  during  24  hours.  Discharged  during  24  hours. 

Water        .        .         .  2250  grammes.  Carbonic  acid     .  .       750  grammes. 

Oxygen      .         .         .  700        "  Aqueous  vapor .  .       500         " 

Albuminous  matter   .  130        "  Perspiration       .  .       850        " 

Starch  and  sugar        .       300        "  Water  of  the  urine  .     1200        " 

Fat     ....       100        "  Urea  and  salts  70         " 

Salts  20  Feces         .        .  .130 

3500  grammes.  3500  grammes. 

Rather  more  than  5  per  cent.,  therefore,  of  the  entire  bodily  weight  is 
absorbed  and  discharged  daily  by  the  healthy  adult  human  subject; 
and,  for  a  man  having  the  average  weight  of  65  kilogrammes,  a  quantity 
of  material,  equal  to  the  weight  of  the  whole  body,  thus  passes  through 
the  system  in  the  course  of  twenty  days. 


SECTION  II. 
THE  NERVOUS  SYSTEM. 


CHAPTER   I. 

GENERAL  STRUCTURE  AND   FUNCTIONS  OF  THE 
NERVOUS  SYSTEM. 

THE  nervous  system  is  an  apparatus  of  intercommunicating  fibres  and 
cells,  disseminated  throughout  the  body,  and  standing  in  anatomical 
connection  with  the  various  organs  of  the  animal  system.  It  has  pro- 
perties which  are  different  from  those  of  the  other  organized  tissues, 
and  the  effect  of  its  operation  is  to  bring  the  active  phenomena  of  vari- 
ous parts  of  the  body  into  a  definite  relation  with  each  other,  and  with 
those  of  the  outside  world.  It  is  therefore  a  medium  of  communica- 
tion, by  which  the  different  animal  functions  are  associated  together  in 
harmonious  action,  and  are  stimulated  or  modified  according  to  the 
demands  of  the  system  itself  or  the  varying  influence  of  external  condi- 
tions. 

Each  organ  and  tissue  of  the  body  possesses,  independently  of  the 
nervous  system,  certain  characteristic  properties  or  modes  of  activity, 
which  may  be  called  into  operation  by  any  appropriate  stimulus  or 
exciting  cause.  If  the  heart  of  a  frog,  after  its  removal  from  the  body, 
be  touched  with  the  point  of  a  steel  needle,  it  contracts  and  repeats 
very  nearly  the  movement  of  an  ordinary  pulsation.  If  the  leg  of  the 
same  animal  be  separated  from  the  thigh,  the  integument  removed,  and 
the  poles  of  a  galvanic  batter}^  applied  to  its  exposed  surface,  a  mus- 
cular contraction  takes  place  at  the  moment  the  electric  circuit  is  com- 
pleted. The  application  of  heat,  friction,  or  an  irritating  liquid  to  a 
particular  part  of  the  integument  brings  on  a  local  redness  which  again 
subsides  after  the  removal  of  the  exciting  cause  ;  and  a  solution  of 
belladonna  dropped  upon  the  cornea,  when  absorbed  by  the  tissues  and 
brought  in  contact  with  the  iris,  produces  a  change  in  the  condition  of 
its  fibres  and  a  dilatation  of  the  pupil.  In  these  instances,  the  organ 
which  performs  the  vital  act  is  excited  by  the  direct  application  of  a 
stimulus  to  its  own  tissues. 

But  this  is  not  the  mode  in  which  the  natural  functions  of  the  animal 
system  are  excited  during  life.  The  physiological  stimulus  which  calls 

(  399  ) 


400  GENERAL    STRUCTURE    AND    FUNCTIONS 

into  action  the  organs  of  the  living  body  is  not  direct  but  indirect  in  its 
operation.  In  the  healthy  and  uninjured  condition  of  the  frame,  the 
muscles  are  never  made  to  contract  by  an  external  stimulus  applied 
immediately  to  their  own  fibres,  but  by  one  which  first  operates  upon 
some  other  organ,  adjacent  or  remote.  The  various  secreting  glands 
have  their  functional  activity  increased  or  diminished  by  causes  which 
are  directly  applied  not  to  themselves  but  to  other  parts  of  the  body ; 
as  where  a  flow  of  saliva  from  the  parotid  is  produced  by  food  intro- 
duced into  the  cavity  of  the  mouth,  or  where  the  discharge  of  perspira- 
tion by  the  skin  is  modified  by  the  influence  of  mental  conditions.  As 
a  rule,  therefore,  in  the  natural  state  of  the  system,  the  various  organs 
situated  in  different  parts  of  the  body  are  connected  with  each  other  by 
a  mutual  sympathy  which  regulates  their  physiological  action.  This 
connection  is  established  through  the  medium  of  the  nervous  system. 

The  function  of  the  nervous  system  is  therefore  to  associate  the 
different  parts  of  the  body  in  such  a  manner,  that  stimulus  applied  to 
one  organ  may  excite  the  activity  of  another. 

The  instances  of  this  mode  of  action  are  as  numerous  as  the  different 
vital  phenomena.  The  stimulus  of  light  falling  upon  the  retina  pro- 
duces contraction  of  the  pupil.  The  introduction  of  food  into  the 
stomach  causes  the  gall-bladder  to  empty  itself  into  the  duodenum. 
The  contact  of  alimentary  substances  with  the  mucous  membrane  of 
the  intestine,  excites  the  peristaltic  action  of  its  muscular  coat.  The 
presence  of  a  growing  foetus  in  the  uterus  is  accompanied  by  an  increased 
growth  of  the  mammary  glands.  Every  organ  is  subservient,  in  the 
manifestation  of  its  functional  activity,  to  influences  from  other  parts,  of 
a  structure  different  from  its  own. 

General  Structure  of  the  Nervous  System, 

The  nervous  system  consists  of  two  kinds  of  nervous  tissue,  differing 
from  each  other  in  appearance,  structure,  and  physiological  endowments. 
One  of  these  is  the  white  substance,  composed  of  nerve  fibres  alone ;  the 
other  is  the  gray  substance,  which  contains,  in  addition  to  the  nerve 
fibres,  interstitial  matter  and  nerve  cells.  The  white  substance  is  found 
in  the  trunks  and  branches  of  the  nerves,  on  the  surface  of  the  spinal 
cord,  and  in  the  internal  parts  of  the  brain.  The  gray  substance  forms 
the  external  layer  or  convolutions  of  the  brain,  as  well  as  various  de- 
posits about  its  base  and  central  parts,  the  central  portion  of  the  spinal 
cord,  and  a  large  number  of  small  detached  masses  in  different  parts  of 
the  body.  These  two  kinds  of  nervous  tissue  are  so  different  in  their 
properties  and  function  as  to  require  for  each  a  separate  description. 

Nerve  Fibres. 

The  nerve  fibres  are  cylindrical  filaments,  arranged  in  bundles  or 
tracts,  in  which  they  run,  for  the  most  part,  in  a  direction  parallel  to 
each  other.  Their  diameter  varies  considerably,  even  in  the  same 


OF    THE    NERVOUS    SYSTEM. 


401 


Fig.  134. 


locality  ;  some  of  the  fibres  in  a  single  bundle  being  10,  15  or  18  micro- 
millimetres  in  diameter,  while  others  are  not  more  than  2.5  mmm.  Their 
average  size  also  varies  in  different  parts  of  the  nervous  system.  The 
larger  fibres  are  found  in  the  peripheral  trunks  and  branches  of  the 
nerves,  where  they  have  an  average  diameter  of  12.5  mmm. ;  in  the 
white  substance  of  the  brain  and  spinal  cord  their  average  diameter  is 
5  mmm.,  and  in  the  gray  substance  it  is  reduced  to  2  mmm.  Two  por- 
tions of  the  nervous  system,  both  of  which  contain  nerve  fibres,  are 
often  distinguished  from  each  other  by  the  relative  numbers  of  their 
larger  and  smaller  fibres.  Thus  in  the  cutaneous  nerves  of  man,  accord- 
ing to  Bidder,  Yolkmann,  and  Kolliker,  the  larger  and  smaller  fibres  are 
present  in  about  equal  quantity,  while  in  the  muscular  nerves  the  larger 
fibres  are  three  times  as  abundant  as  the  smaller.  In  the  nerves  of  bony 
tissue  the  proportion  of  small  fibres  is  double  that  of  the  large  ones, 
and  in  the  gray  substance  of  the  cerebral  hemispheres  there  are  none 
larger  than  6  or  7  mmm.  in  diameter.  The  nerve  fibres  belonging  to  the 
same  bundle  or  tract  may  even  become  increased  or  diminished  in  diameter 
in  different  parts  of  their  course ;  as  Kolliker  has  shown  that  the  fibres 
of  the  posterior  roots  of  the  spinal  nerves,  in  passing  through  the  cord 
from  the  exterior  to  the  gray 
substance,  are  reduced  in  their 
average  diameter  from  10  to  5 
mmm. ;  and  those  of  the  white 
substance,  of  the  cerebral  hemi- 
spheres, on  entering  the  gray 
matter  of  the  convolutions,  are 
reduced  from  5  mmm.  to  2 
mmm.  in  diameter. 

The  structure  of  the  nerve- 
fibre,  in  its  most  complete 
form,  presents  three  distinct 
elements,  namely  :  an  external 
tubular  sheath,  an  intermediate 
medullary  layer,  and  a  central 
axis  cylinder. 

The   Tubular  Sheath The 

exterior  of  the  nerve  fibre  is 
composed  of  a  colorless,  trans- 
parent tubular  membrane, 
which  closely  invests  the  re- 
maining portions  and  is  seen 
with  some  difficulty  in  the 
natural  condition  of  the  fibre,  owing  to  its  extreme  thinness  and 
delicacy.  It  may  often,  however,  be  distinguished  at  certain  points 
where  the  nervous  fibre  is  accidentally  compressed  or  indented,  as  at  c, 
Fig.  134;  or  it  may  be  brought  into  view  for  considerable  distances 
according  to  the  method  of  Kolliker,  by  treating  the  fibres  with  a  cold 


NBRVB  FIBRES  from  the  Sciatic  Nerve.— At 
a,  the  torn  extremity  of  a  nerve  fibre  with  the  axis 
cylinder  (b)  protruding  from  it.  At  c,  the  medul- 
lary layer  is  nearly  separated  by  accidental  com- 
pression, but  the  axis  cylinder  passes  across  the 
injured  portion.  The  outline  of  the  tubular  mem- 
brane is  also  seen  at  c  on  the  outside  of  the  remain- 
ing portions  of  the  fibre. 


402 


GENERAL    STRUCTURE    AND    FUNCTIONS 


solution  of  sodium  hydrate,  and  afterward  boiling  them  for  an  instant 
in  the  same  fluid.  This  extracts  the  greater  part  of  their  contents,  and 
leaves  the  tubular  sheath  in  the  form  of  an  empty  cylindrical  canal.  Jn 
its  general  chemical  relations,  the  tubular  sheath  is  similar  to  the  sar- 
colemma  of  muscular  fibre,  its  principal  physical  properties  being  its 
cohesion  and  elasticity.  Its  physiological  function  is  undoubtedly  that 
of  a  protecting  envelope,  by  which  the  internal  portions  are  maintained 
in  place  and  preserved  from  mechanical  injury. 

The  Medullary  Layer. — Immediately  within  the  tubular  sheath  is  a 
layer  of  transparent,  highly  refractive,  nearly  fluid  material,  of  oleagi- 
nous consistency,  termed  the  medullary  layer,  or  medulla,  which  gives 
to  the  nerve  fibres,  and  the  tracts  composed  of  them,  a  white  and 
shining  aspect.  This  substance  is  readily  altered  by  a  diminution  of 
temperature,  or  by  the  contact  of  unnatural  fluids,  even  by  exposure  to 
the  air  or  the  imbibition  of  water,  or  by  the  ordinary  manipulations 
required  in  preparing  it  for  microscopic  examination.  Under  these  in- 
fluences it  undergoes  a  sort  of  coagulation,  being  increased  in  density 
and  in  refractive  power,  so  that  both  its  external  and  internal  limits  are 
indicated  by  a  dark  and  strongly  marked  outline.  This  gives  to  the 
nerve  fibre  the  very  characteristic  appearance  of  a  cylinder  with  a 
double  contour,  presenting  two  distinct  parallel  outlines  at  each  edge ; 
an  appearance  by  which  it  may  be  easily  distinguished  from  any  other 
anatomical  element.  As  the  coagulation  of  the  medullary  layer  goes 
on,  its  outlines  become  more  or  less  irregular,  and  after  a  certain  time 
it  involves  the  whole  of  the  fibre  in  a  more  or  less  confused  mass  of 
irregularly  refracting  substance.  The  fibres  containing  a  medullary 
layer,  and  exhibiting  the  characteristic  double  contour  due  to  its  pre- 
sence, are  called  "  medullated  nerve  fibres." 

In  the  smaller  variety  of  nerve  fibres  from  the  substance  of  the  brain 

and  spinal  cord,  the  external 
tubular  sheath  is  wanting,  or 
at  least  cannot  be  demon- 
strated ;  and  such  fibres,  owing 
to  their  want  of  support  and 
their  soft  consistency,  are  read- 
ily distorted  by  accidental  pres- 
sure, or  by  the  contact  of  rea- 
gents. They  become  swollen 
or  varicose  at  many  points; 
and  the  medullary  substance 
is  forced  out  or  exudes  from 
their  torn  extremities  in  irre- 
gularly globular,  fusiform,  or 
filamentous  masses,  which  show 
on  their  exterior  the  double 

NERVE  FIBRES,  from  the  white  substance  of      contour    due    to     a    Superficial 
the  brain.— a,  a,  a  Portions  of  the  myeline,  pressed  „„  ,          ,      , 

out,  and  floating  in  irregularly  rounded  drops.  Coagulation.      1  hese    detached 


Fig.  135. 


OF    THE    NERVOUS    SYSTEM.  403 

portions,  which  are  everywhere  visible  in  ordinary  microscopic  prepa- 
rations of  the  brain  substance,  are  termed  "  myeline  drops,"  and  owe 
their  peculiar  appearance  to  the  nature  of  the  ingredients  which  form 
the  medullary  layer  of  the  nerve  fibre.  The  medullary  layer  is  com- 
posed of  a  substance  termed  myeline,  which  is  not,  however,  a  distinct 
proximate  principle,  but  is  itself  a  mixture  of  various  different  mate- 
rials. It  consists  mainly  of  cerebrine,  a  nitrogenous  matter  found  only 
in  the  nervous  centres,  together  with  a  large  proportion  of  cholesterine 
and  fat.  There  is  also  a  certain  proportion  of  lecithine,  a  nitrogenous 
and  phosphorized  matter,  which  is  also  found  in  the  gray  substance. 
The  mixture  of  these  ingredients  gives  to  the  myeline  its  peculiar  con- 
sistency and  reaction. 

In  regard  to  its  physiological  function,  the  medullary  layer  of  the 
nerve  fibre  is  generally  considered  as  an  isolating  substance,  like  the 
gutta-percha  envelope  of  a  submarine  telegraph  wire,  so  arranged  as  to 
confine  the  transmission  of  nerve  force  within  proper  limits,  and  prevent 
its  diffusion  to  neighboring  parts.  We  have  no  absolute  proof  that 
such  is  its  true  character,  but  there  are  some  facts  which  lend  a  certain 
probability  to  this  view.  The  medullary  layer  exists  throughout  the 
main  portion  of  a  large  majority  of  the  nerve  fibres,  where  they  trans- 
port the  nervous  stimulus  uninterruptedly  from  one  point  to  another ; 
but  they  are  destitute  of  it  both  at  their  origins  and  terminations, 
where  they  come  in  contact  with  the  elements  of  the  gray  matter,  or  are 
connected  with  the  peripheral  organs  of  sensation  and  motion.  What- 
ever may  be  its  exact  function,  therefore,  the  medulla  evidently  plays  a 
secondary,  and  not  a  principal  part,  in  the  physiological  action  of  the 
nerve  fibre. 

The  Axis  Cylinder — The  central  part  of  the  nerve  fibre  consists  of  a 
pale,  homogeneous,  or  finely  granular  cord,  of  a  cylindrical  or  slightly 
flattened  form,  occupying  the  position  of  the  longitudinal  axis  of  the 
fibre.  From  these  characters  it  has  received  the  name  of  the  "  axis 
cylinder."  It  differs  from  the  medullary  layer,  by  which  it  is  enveloped, 
in  consistency ;  for  while  the  latter  is  nearly  fluid  in  its  natural  condi- 
tion, the  axis  cylinder  is  solid,  and,  though  very  delicate,  possesses  a 
certain  degree  of  elasticity.  By  some  observers  (Schultze,  Gerlach)  the 
axis  cylinder  is  regarded  as  composed  of  many  excessively  minute  fibril- 
Ise,  united  into  a  uniform  bundle;  by  others  of  equal  authority  (K61- 
liker)  the  indications  of  such  a  fibrillated  constitution  of  this  part  of  the 
nerve  fibre  are  considered  as  uncertain. 

The  axis  cylinder  is  composed  of  an  albuminous  substance  which  is 
insoluble  in  water,  alcohol,  and  ether ;  becomes  pale  and  swollen  by  the 
action  of  concentrated  acetic  acid ;  and  is  readily  dissolved  by  a  boiling 
solution  of  sodium  hydrate.  It  is  stained  red  by  treatment  with  a  solu- 
tion of  carmine,  while  the  enveloping  medullary  layer  remains  un- 
colored;  and  by  this  means  a  visible  distinction  may  be  made  between 
the  two.  The  application  of  a  solution  of  gold  chloride,  and  subsequent 
exposure  to  light,  stains  the  axis  cylinder  of  a  dark  purple,  nearly 


GENERAL    STRUCTURE    AND    FUNCTIONS 

black  color;  and  by  this  mode  of  preparation  nervous  fibres  of  extreme 
delicacy  have  been  traced  among  surrounding  tissues,  where  they  would 
otherwise  escape  observation. 

In  its  physiological  properties,  the  axis  cylinder  is  undoubtedly  the 
most  essential  element  of  the  nerve  fibre,  since  it  is  the  only  one  univer- 
sally present,  and  always  extending  throughout  the  whole  length  of  a 
fibre  from  its  origin  to  its  termination.  Its  albuminous  nature  also 
distinguishes  it  from  other  parts  of  the  nerve  fibre,  and  indicates  the 
relative  importance  of  its  function.  It  is  probably  through  the  axis 
cylinder  that  the  passage  of  the  nerve  current  takes  place,  and  in  its 
substance  that  the  principal  changes  accompanying  this  action  are 
effected. 

Non-Medullated  Nerve  Fibres. — Beside  the  nerve  fibres  constituted, 
as  above,  by  an  axis  cylinder,  surrounded  by  a  medullary  layer,  with  or 
without  an  external  tubular  membrane,  there  are  others  which  consist 
of  the  axis  cylinder  destitute  of  any  medullary  layer,  and  which  conse- 
quently do  not  exhibit  the  appearance  of  a  double  contour.  These  are 
called  "  non-medullated  nerve  fibres."  They  are  found,  in  man,  only  in 
certain  parts  of  the  sympathetic  nerves,  in  the  terminal  nervous  expan- 
sions of  the  muscles  and  organs  of  sense,  and  in  the  nervous  centres  in 
the  immediate  vicinity  of  the  cells  of  the  gray  substance.  In  the  sym- 
pathetic nerves,  they  are,  for  the  most  part,  mingled  with  a  considerable 
proportion  of  inedullated  fibres,  though  some  of  the  sympathetic  branches 
distributed  to  the  intestine  and  the  spleen,  according  to  Schultze,  are 
composed  of  non-medullated  fibres  exclusively.  The  branches  of  the 
olfactory  nerve,  distributed  to  the  nasal  mucous  membrane,  also  consist 
altogether  of  fibres  of  this  kind.  Such  nervous  branches  have  not  the 
white,  opaque  aspect  belonging  to  other  nerves,  but  are  grayish-looking 
and  semi-transparent  in  appearance ;  a  peculiarity  which  is  evidently  due 
to  the  absence  of  the  myeline  or  medullary  layer. 

The  same  nerve  fibre  may  be  inedullated  for  the  greater  part  of  its 
course,  and  become  destitute  of  medulla  at  its  termination,  as  is  the  rule 
with  the  cerebro-spinal  nerves  generally ;  or  fibres  may  originate  in  the 
gray  substance  as  non-medullated  axis  cylinders,  and  become  invested, 
after  a  short  distance,  with  a  distinct  medullary  layer.  The  non-medul- 
lated nerve  fibres  are  not,  therefore,  regarded  as  essentially  different 
from  the  others,  but  only  as  presenting  a  less  complicated  form  of  struc- 
ture. 

Course  and  Mutual  Relation  of  the  Nerve  Fibres. — In  the  white  sub- 
stance of  the  brain  and  spinal  cord,  the  nerve-fibres  form  continuous 
tracts,  of  larger  or  smaller  size,  lying  in  contact  with  each  other,  and 
not  mingled  with  any  considerable  proportion  of  other  tissue.  But  on 
passing  out  of  the  bony  cavities  toward  the  exterior,  they  become  col- 
lected into  small  bundles,  each  of  which  is  invested  with  a  thin  pro- 
longation of  connective  tissue,  derived  from  the  dura  mater  and 
periosteum ;  these  bundles  are  associated  into  larger  ones  which  are 
held  together  by  a  denser  layer  of  the  same  connective  tissue ;  and 


OF    THE    NERVOUS    SYSTEM. 


405 


finally  the  whole  are  united  into  a  single  compound  mass  by  its  exterior 
investment,  which  is  known  as  the  u  neurilemma."  Such  a  complete 
bundle  is  called  a  nerve,  and  the  nerve  fibres  of  which  it  is  composed 
are  usually  all  distributed,  after  a  longer  or  shorter  transit,  to  associated 
organs,  or  to  adjacent  regions  of  the  body. 

The  nerve  fibres  themselves  are  not  known  to  divide,  branch,  or  inoscu- 
late with  each  other  in  any  part  of  their  course  through  the  main  trunks 
and  branches  of  the  nerves.  So  far  as  observation  goes,  each  nerve 
fibre  is  continuous  and  independent,  from  its  origin  in  the  nervous 
centres  to  within  a  microscopic  distance  of  its  peripheral  termination. 
When  a  nerve  therefore  divides  during  its  course  into  several  branches, 
or  when  the  branches  of  adjacent  nerves  inosculate  with  each  other 
to  form  a  plexus,  like  the  cervical,  brachial,  or  lumbar  plexuses,  this  is 
only  because  certain  ultimate  nerve  fibres,  or  bundles  of  fibres,  leave 
those  with  which  they  were  previously  associated,  and  pursue  a  different 


Fig.  136. 


Fig.  137. 


DIVISION  OF  A  NKRVOUS  BRANCH 
(a),  into  its  ultimate  fibres,  6,  c,  d,  e. 


Inosculation  of  NERVES. 


direction.  A  nerve  which  originates,  for  example,  from  the  spinal  cord 
and  runs  down  the  upper  extremity,  to  be  finally  distributed  to  the  in- 
tegument and  muscles  of  the  hand,  contains  at  its  point  of  origin  all  the 
filaments  into  which  it  is  afterward  divided,  and  which  are  merely  sepa- 
rated at  successive  points  from  the  main  bundle.  Jn  case  of  the  inoscu- 


406  GENERAL    STRUCTURE    AND    FUNCTIONS 

lation  of  two  nerves,  the  communication  between  them  is  effected  by 
some  of  the  fibres  belonging  to  the  first  passing  over  from  it  to  join  the 
second,  while  some  of  those  belonging  to  the  second  may  also  cross  and 
join  the  first ;  the  individual  fibres  in  each  instance  remaining  distinct, 
and  retaining  their  identit}r  throughout.  In  whatever  way,  therefore, 
the  nerve  fibres  are  associated  in  the  various  trunks  and  branches  of 
the  nerves,  they  may  still  act  independently  and  preserve  their  specific 
functions  in  every  part  of  their  course. 

Peripheral  Termination  of  the  Nerve  Fibres. — Near  the  termination 
of  the  nerve  fibres  in  the  tissues  to  which  they  are  distributed,  they 
present  certain  important  modifications  both  in  structure  and  arrange- 
ment. 

First,  the  smaller  nervous  branches,  or  bundles  of  nerve  fibres,  after 
penetrating  the  substance  of  the  tissues,  suddenly  divide  and  subdivide 
with  unusual  rapidity ;  and  these  subdivisions,  uniting  with  each  other 
by  inosculation,  form  abundant  plexuses,  from  which  are  given  off  the 
individual  fibres  supplying  the  anatomical  elements  of  the  tissues.  In 
the  skin  there  are  two  such  nervous  plexuses,  a  deeper  and  a  more 
superficial,  of  which  the  latter  is  the  more  closely  set  and  composed  of 
more  slender  bundles,  containing  only  one  or  two  fibres  each.  As  a 
general  rule,  also,  in  other  tissues,  the  last  or  terminal  plexus  is  the 
finest,  and  incloses  between  its  meshes  the  narrowest  interspaces.  The 
nerve  fibres,  on  reaching  the  situation  of  the  terminal  plexus,  are  also 
considerably  reduced  in  size,  being  diminished  both  in  the  skin  and  the 
muscles  from  10  or  15  mmm.  to  4  or  5  mmm.  in  diameter.  According 
to  Kolliker  it  is  sometimes  possible  to  observe  this  diminution  in  the 
size  of  a  single  nerve  fibre  in  different  parts  of  its  course  through  the 
muscular  tissue. 

Secondly,  both  in  the  terminal  plexus  and  the  branches  given  off  from 
them,  the  nerve  fibres  themselves  undergo  division;  so  that  a  single 
fibre  in  this  situation  may  give  rise  to  two  or  more  branches,  each  branch 
retaining  all  the  original  anatomical  characters  of  a  nerve  fibre.  There 
is  usually  a  marked  constriction  at  the  point  where  the  nerve  fibre 
divides ;  but  this  is  followed  by  a  corresponding  enlargement,  so  that 
the  secondary  fibres  soon  become  nearly  or  quite  equal  in  diameter  to 
that  from  which  they  were  derived.  A  nerve  fibre  may  accordingly  pass 
undivided,  so  far  as  we  know,  throughout  its  course  in  the  roots,  trunks, 
and  principal  branches  and  ramifications  of  the  nerve,  and  may  then, 
shortly  before  its  termination,  break  up  into  a  number  of  separate  but 
closely  adjacent  secondary  fibres.  It  has  been  estimated  by  Reichert, 
that,  in  the  subcutaneous  muscle  of  the  frog,  ten  primitive  nerve  fibres 
may  give  rise  by  their  division,  to  about  300  terminal  extremities. 

Thirdly,  the  nerve  fibre,  when  near  its  peripheral  termination,  be- 
comes altered  in  structure.  This  alteration  consists  in  a  disappearance 
of  the  medullary  layer,  by  which  the  fibre  loses  its  double  contour;  and 
by  a  similar  disappearance  or  a  separation  of  the  tubular  sheath.  The 
nerve  fibre,  thus  altered,  is  reduced,  in  its  constituent  parts,  to  the  axis 


OF    THE    NERVOUS    SYSTEM.  407 

cylinder  alone;  that  is,  all  the  secondary  elements  of  its  structure  are 
lost,  and  there  remains  only  the  essential  conducting  filament  of  the 

Fig.  138. 


DIVISION  o*  WERVE  FIBRES,  in  a  small  branch  from  the  subcutaneous  muscle  of  a 

frog.    (Kolliker.) 

axis  cylinder.  Lastly  the  nerve  fibre,  at  the  point  of  its  final  termina- 
tion, is  frequently  brought  into  relation  with  cell-like  bodies,  which  are 
sometimes  regarded  as  analogous  in  character  to  the  nerve  cells  of  the 
gray  substance  in  the  nervous  centres. 

The  ultimate  termination  of  the  nerve  fibres  in  the  skin  has  been  most 
distinctly  seen  in  the  so-called  "  Pacinian  bodies"  and  the  "  tactile  cor- 
puscles." The  Pacinian  bodies  are  ovoid-shaped  masses  from  1  to  4.5 
millimetres  in  length,  found  in  the  subcutaneous  connective  tissue  of  the 
hands  and  feet,  and  various  other  parts  of  the  body,  consisting  of  a 
series  of  concentric  laminae  of  connective  tissue,  with  a  central  cavity, 
inclosing  a  transparent,  colorless,  fluid  or  semifluid  material.  A  single 
ultimate  nerve  fibre  penetrates  the  Pacinian  body  at  one  extremity,  and 
passes  into  its  central  cavity.  At  the  point  of  entrance,  the  external 
tubular  sheath  leaves  the  nerve  fibre  and  becomes  continuous  with  the 
connective  tissue  laminae  of  the  Pacinian  body.  The  medullary  layer 
also  disappears,  and  the  nerve  fibre,  thus  reduced  to  its  axis  cylinder, 
runs  longitudinally  through  the  greater  part  of  the  central  cavity  and 
terminates,  toward  its  farther  end,  in  either  one  or  several  slightly 
rounded  extremities.  The  "tactile  corpuscles,"  found  in  the  sensitive 
papillae  of  the  skin  of  the  hands  and  feet,  are  similar  in  form  to  the 
Pacinian  bodies,  but  of  much  smaller  size ;  having  an  average  length, 


408 


GENERAL    STRUCTURE    AND    FUNCTIONS 


in  man,  of  about  100  mmm.  They  consist  each  of  a  central,  trans- 
parent, gelatinous  mass,  surrounded  by  an  envelope  of  connective 
tissue,  which  is  marked  by  many  tranverse  elongated  nuclei.  Each 
corpuscle  receives  one  or  two  nerve  fibres  which  run  upward,  in  either 
a  straight  or  spiral  course,  and,  after  losing  their  medullary  layer,  in 
some  instances  reach  the  central  gelatinous  nucleus,  though  for  the 
most  part  their  terminations  are  not  distinctly  visible. 

The  simplest  form  of  tactile  corpuscle  is  that  known  as  the  "terminal 
bulbs"  of  the  sensitive  nerves,  in  the  conjunctiva,  the  lips,  the  papillae 
of  the  tongue,  and  the  soft  palate.  They  are  round  or  elongated  ovoid 
bodies,  consisting  of  a  closed  sac  of  connective  tissue,  sometimes  marked 
with  transverse  nuclei,  and  containing  a  homogeneous  or  finely  granular 
substance.  Into  this  body  is  received  the  ultimate  branch  of  a  nerve 


Fig.  139. 


Fig.  140. 


TERMINAL  BULB  of  a  sensi- 
tive nerve;  from  the  conjunctiva 
of  the  calf.  (Frey.) 


TACTILE  CORPUSCLES,  from  the  edge  of  the 
tongue  of  the  sparrow.— 1,  2.  3.  IWedullated  nerve 
fibres  supplying  four  tactile  corpuscles.  One 
fibre  divides  into  two  branches;  and  one  of  them 
is  traced  to  near  the  extremity  of  the  correspond- 
ing corpuscle,  where  it  ends  in  a  cell-like  expan- 
sion. (Ihlder.) 


fibre,  which  is  reduced  to  its  axis  cylinder  and  terminates  in  the  inte- 
rior by  a  free  extremity.  In  some  regions,  as,  for  example,  the  lips  in 
the  human  subject,  and  the  tongue  in  birds,  are  to  be  seen  structures 
which  are  intermediate  in  form  between  the  terminal  bulbs  and  the 
tactile  corpuscles. 

In  the  muscles,  as  a  rule,  each  muscular  fibre  has,  connected  with  it, 
at  least  one  nerve  fibre,  and  sometimes  more  than  one.     The  ultimate 


OF    THE    NERVOUS    SYSTEM.  409 

nerve  fibre,  given  off  as  a  branch  from  the  terminal  Fig.  141. 

plexus,  approaches  the  muscular  fibre,  usually  at 
a  right  angle,  and  penetrates  its  exterior;  the 
tubular  sheath  of  the  nerve  fibre  becoming  con- 
tinuous with  the  sarcolemma.  At  the  same  time 
its  medullary  layer  ceases  abruptly,  and  the  axis 
cylinder  spreads  out  into  a  thin  oval  expansion 
of  granular  matter  interspersed  with  nuclei,  called 
the  "  terminal  plate,"  and  lying  in  immediate  con- 
tact with  the  contractile  substance  of  the  muscular  TERMINATION  OF  A 

fibre.     Some  variations  in  the  form  and  disposi-     NERVE  FIBRE  in  mus- 
cular fibre,  from  the  fowl, 
tion  of  the  axis  cylinder  in  the  terminal  plate  are     (ROUget.) 

to  be  seen  in  the  muscles  of  amphibia ;  but  the 

above  represents  its  essential  characters  in  the  muscles  of  birds  and 

mammalians. 

Physiological  Properties  of  the  Nerve  Fibres. — The  nerve  fibres  are 
organs  of  communication.  They  serve  as  connecting  filaments  between 
the  nervous  centres  on  the  one  hand  and  the  peripheral  organs  of  sensa- 
tion and  motion  on  the  other.  For  this  purpose  they  are  endowed  with 
a  power  of  irritability  by  which,  when  excited  at  one  or  the  other 
extremity,  they  transmit  the  nervous  impulse  throughout  their  entire 
length,  and  produce  a  corresponding  effect  at  their  opposite  termination. 
Thus  the  nerve  fibres  distributed  to  the  skin,  when  excited  at  their 
peripheral  extremities,  produce  in  the  brain  a  sensation  corresponding 
to  the  external  impression.  On  the  other  hand,  those  which  are  distri- 
buted to  the  muscles,  when  excited  at  their  origin  by  the  impulse  of  the 
will,  produce  a  contraction  in  the  muscular  fibres  at  their  periphery. 
This  physiological  action  produces  no  visible  change  in  the  nerve  fibre 
itself.  Its  effects  are  manifest  only  at  the  extremities  of  the  nerve,  in 
the  organs  where  it  terminates.  Nevertheless,  it  is  evident  that  the 
nerve  fibre  serves  to  communicate  in  some  way  an  action  from  one  of 
its  extremities  to  the  other ;  since,  if  it  be  divided  in  any  part  of  its 
course,  the  communication  at  once  ceases,  and  sensation  can  no  longer 
be  perceived  from  impressions  made  upon  the  skin,  nor  voluntary  con- 
traction excited  in  the  muscles. 

Owing  to  the  different  effects  thus  produced,  at  their  central  and  peri- 
pheral extremities,  the  nerve  fibres  and  the  nerves  composed  of  them 
have  been  distinguished  by  different  names.  Those  which  transmit  the 
stimulus  of  sensation,  from  the  periphery  to  the  nervous  centres,  are 
called  sensitive  nerves  or  nerve  fibres  ;  those  which  transmit  the  stimulus 
of  motion,  from  the  nervous  centre  outward  to  the  muscles,  are  called 
motor  nerves  or  nerve  fibres.  As  a  general  rule,  both  sensitive  and 
motor  nerve  fibres  are  associated  together  in  the  same  nervous  bundle, 
and  separate  from  each  other  only  when  near  their  final  distribution  in 
the  skin  or  mucous  membranes  on  the  one  hand,  and  in  the  muscles  on 
the  other.  But  in  some  situations,  near  the  origin  of  the  nerves  as  well 
as  near  their  termination,  the  sensitive  and  motor  fibres  run  in  distinct 
27 


410  GENERAL    STRUCTURE    AND    FUNCTIONS 

bundles ;  as  for  example  in  the  sensitive  and  motor  roots  of  the  fifth 
pair  of  cranial  nerves,  and  in  the  anterior  and  posterior  roots  of  the 
spinal  nerves  generally.  The  fibres  belonging  to  the  facial  nerve  are 
all  motor  fibres,  making  this  exclusively  a  motor  nerve.  The  three 
branches  of  the  fifth  pair,  on  the  other  hand,  which  are  distributed  to 
the  integument  and  mucous  membranes  of  the  face,  are  composed  exclu- 
sively of  sensitive  fibres  ;  while  the  branch  of  the  same  nerve  distributed 
to  the  muscles  of  mastication  is  made  up  principally  or  entirely  of  motor 
fibres. 

No  essential  distinction  has  been  discovered  in  the  anatomical  char- 
acters of  sensitive  and  motor  nerve  fibres.  In  nerves  and  nervous 
branches  which  perform  a  motor  function,  the  nerve  fibres,  as  a  rule,  are 
of  comparatively  large  size,  averaging  15  mmm.  in  diameter ;  while  in 
those  performing  a  sensitive  function  they  are  smaller,  averaging  not 
more  than  10  mmm.  in  diameter,  and  many  of  them  being  considerably 
less.  But  this  difference  is  only  one  of  proportion  in  numbers  between 
the  larger  and  smaller  fibres  ;  since  both  large  and  small  fibres  are  found 
in  both  motor  and  sensitive  nerves.  Even  in  the  motor  nerves,  the 
large  fibres  become  reduced  to  the  size  of  the  smaller  ones  before  their 
termination  in  the  muscular  tissue;  and  the  nerve  fibres  generally  are 
diminished  or  increased  in  diameter  on  passing  into  or  out  of  the  gray 
substance  of  the  nervous  centres.  No  absolute  distinction  therefore  can 
be  made  between  sensitive  and  motor  nerve  fibres  as  regards  their  size ; 
and  in  regard  to  the  essential  details  of  their  structure,  namely,  the 
tubular  sheath,  the  medullary  layer,  and  the  cylinder  axis,  they  are  to 
all  appearance  completely  identical. 

Effect  of  Division  upon  the  Nerve  Fibres. — The  immediate  effect  of 
dividing  or  seriously  injuring  the  nerve  fibres  is  a  suspension  of  their 
physiological  function.  The  physical  communication  being  cut  off  be- 
tween their  extremities,  the  sensitive  fibres  can  no  longer  transmit  an 
impression  from  the  skin  to  the  nervous  centre,  and  the  motor  fibres 
can  no  longer  convey  the  stimulus  of  voluntary  motion  from  the  nervous 
centre  to  the  muscles.  In  addition  to  this  result,  when  the  divided 
nerve  fibre  is  permanently  separated  from  its  central  connections,  there 
also  follows  a  change  in  its  texture,  which  is  propagated  mainly  in 
one  direction,  and  which  consists  in  an  atrophy  or  degeneration  of 
the  nervous  substance.  The  most  distinct  effects  of  this  degeneration 
of  a  divided  nerve  fibre  are  to  be  seen  in  its  medullary  layer.  According 
to  the  observations  of  Yulpian  and  Philippeaux,  the  alteration  in  struc- 
ture, which  takes  place  from  the  point  of  division  toward  the  periphery, 
begins  to  be  perceptible  in  mammalians,  by  microscopic  examination,  at 
the  end  of  five  days.  The  transparency  of  the  fibre  is  first  diminished, 
its  contents  having  a  more  or  less  cloudy  appearance.  At  the  end  of 
eight  or  ten  days,  the  double  contour  of  the  fibre  has  become  irregular 
and  at  various  points  partially  or  completely  interrupted ;  and  the  sub- 
stance of  the  medullary  layer  is  broken  up  into  separate  masses  of 
varying  size,  presenting  the  appearance  of  a  coagulation  and  dislocation. 


OF    THE    NERVOUS    SYSTEM.  411 

As  the  process  goes  on,  the  continuity  of  the  medullary  layer  is  entirely 
destroyed,  and  this  substance  is  reduced  to  the  condition  of  isolated 
oily-looking  drops,  scattered  through  the  interior  of  the  tubular  sheath, 
which  become  gradually  transformed  into  a  diffused  mixture  of  minute 
granules.  Finally,  the  granules  themselves  disappear,  and  the  tubular 
sheath,  partially  emptied  by  the  atrophy  of  the  medullary  layer,  becomes 
collapsed  and  wrinkled.  The  nerve  which  has  suffered  these  changes 
has  lost  its  white  glistening  color,  and  has  assumed  a  grayish  hue.  The 
axis  cylinder  either  does  not  participate  in  the  above  alterations,  or  its 
changes  are  not  so  manifest  to  the  eye ;  since,  according  to  some  ob- 
servers, it  remains  visible  after  the  medullary  layer  has  disappeared. 

According  to  various  observers  (Waller,  Krause,  Yulpian),  the  de- 
generation of  divided  nerve  fibres,  both  in  the  sensitive  and  motor 
nerves,  may  be  propagated  throughout  their  peripheral  extremities, 
extending  even  to  the  sensitive  papillae  of  the  tongue  and  the  tactile 
corpuscles  of  the  skin.  Yulpian1  has  found  that  in  dogs,  six  weeks 
after  the  division  of  the  sciatic  nerve,  no  nerve  fibres  could  be  dis- 
covered in  the  muscles  of  the  foot  which  had  not  undergone  the  same 
alteration. 

The  rapidity  with  which  degeneration  takes  place  in  the  fibres  of  a 
divided  nerve  varies  with  the  species  and  age  of  the  animal  to  which  it 
belongs.  The  change  is  less  rapid  in  the  cold-blooded,  more  so  in  the 
warm-blooded  animals.  In  those  of  the  same  species,  it  goes  on  more 
quickly  in  the  young,  more  slowly  in  animals  which  are  fully  grown. 
According  to  Yulpian,  in  young  dogs,  as  a  general  rule,  the  disappear- 
ance of  the  medullary  layer  is  complete  at  the  end  of  six  weeks  or  two 
months  from  the  date  of  the  injury. 

The  degeneration  of  the  peripheral  portions  of  divided  nerves  has 
often  been  utilized  in  order  to  determine  the  source  of  particular  bun- 
dles of  nerve  fibres.  If  a  nerve,  for  example,  receives  roots  or  commu- 
nicating branches  from  two  different  sources,  and  afterward  supplies 
by  its  ramifications  several  organs,  it  may  be  ascertained  whether  the 
fibres  coming  from  one  source  are  or  are  not  distributed  to  a  particular 
organ.  For  this  purpose  the  root  or  communicating  branch  in  question 
is  divided ;  and  when  the  subsequent  process  of  degeneration  is  com- 
plete, the  atrophied  nerve  fibres  derived  from  this  source  may  be  fol- 
lowed by  microscopic  examination  throughout  their  course,  and  recog- 
nized in  the  organ  to  which  they  are  distributed. 

Union  and  Regeneration  of  divided  Nerves — The  loss  of  function 
in  a  divided  nerve  is  not  permanent ;  but,  if  the  neighboring  parts  be 
healthy  and  no  other  injury  have  been  inflicted,  the  nerve  fibres  may 
reunite,  and  their  power  of  communication  be  restored.  When  the 
division  has  been  a  simple  one,  the  two  extremities  of  the  divided  nerve 
remaining  in  contact  or  in  close  proximity  with  each  other,  their  union 
takes  place  with  comparative  readiness ;  but  even  when  a  considerable 

1  Leqons  sur  la  Physiologie  du  Systdme  Nerveux.     Paris,  1866,  p.  243. 


412  GENERAL    STRUCTURE    AND    FUNCTIONS 

portion  of  the  nerve  has  been  cut  out,  there  may  be  a  reproduction  of 
the  lost  parts,  and  the  nerve  may  finally  regain  its  natural  continuity. 
The  fibres  of  new  formation,  thus  produced,  are  at  first  of  small  diameter 
and  of  grayish  aspect.  They  gradually  increase  in  size,  become  pro- 
vided with  a  medullary  layer,  and  at  last  present  all  the  anatomical 
characters  of  the  healthy  nerve  fibre.  Schiff,  Yulpian,  and  Philippeaux 
have  found  that  it  is  possible  for  the  continuity  of  a  nerve  to  be  re- 
established, after  the  excision  of  portions  of  its  trunk  equal  to  five  or 
even  six  centimetres  in  length.  According  to  Yulpian,  in  very  young 
animals,  a  loss  of  nerve  substance  from  one  to  two  centimetres  in  length 
may  be  restored  at  the  end  of  six  weeks ;  and  the  same  observer  has 
seen,  in  young  rats,  a  portion  of  the  sciatic  nerve,  six  millimetres  long, 
reproduced  in  the  course  of  seventeen  days. 

At  the  same  time,  the  degenerated  portion  of  the  nerve,  situated 
beyond  the  point  of  its  division,  becomes  restored.  There  is  a  reproduc- 
tion of  the  medullary  layer,  which  had  become  atrophied  by  the  de- 
generative process,  and  the  entire  nerve  again  exhibits  its  normal 
anatomical  character.  The  time  required,  for  the  complete  regeneration 
of  the  peripheral  portion  of  a  divided  nerve,  is  in  general  from  three  to 
twelve  months,  according  to  the  age  and  species  of  the  animal  upon 
which  the  experiment  is  performed. 

The  complete  regeneration  of  a  divided  or  exsected  nerve  is  indicated 
by  the  restoration  of  its  normal  function.  If  it  be  a  sensitive  nerve,  the 
power  of  sensation,  which  was  at  first  lost,  returns  in  that  portion  of 
the  integument  to  which  its  fibres  are  distributed ;  if  it  be  a  motor 
nerve,  the  power  of  voluntary  motion  is  regained  in  the  corresponding 
muscles.  The  observations  of  Yulpian  have  shown  that,  after  the  ex- 
cision of  the  central  extremity  of  the  hypoglossal  nerve  in  dogs,  its 
peripheral  portion  may  become  capable  of  exciting  contraction  in  the 
muscles  of  the  tongue  at  the  end  of  four  months  j1  and  according  to 
those  of  Schiff  upon  young  dogs  and  cats,  sensibility  may  reappear  in 
the  tongue  and  lip  in  fourteen  days  after  the  excision  of  portions  of  the 
lingual  and  infra-orbital  nerves,  from  two  to  two  and  a  half  centimetres 
in  length. 

In  the  human  subject,  at  least  in  adult  life,  the  restoration  of  divided 
nerves  is  much  less  rapid ;  and,  according  to  L'Etievant2  and  Weil- 
Mitchell,3  often  either  does  not  take  place  at  all,  when  the  injured  nerves 
are  of  considerable  size,  or  does  so  very  imperfectly. 

The  smaller  nervous  branches  supplying  the  skin  are  frequently 
divided  by  accidental  incisions,  causing  a  local  anaesthesia,  or  loss  of 
tactile  sensibility  in  the  immediate  neighborhood.  This  anaesthesia 
persists  usually  for  weeks,  or  even  months,  after  the  healing  of  the 
wound ;  but  it  almost  invariably  disappears  at  last,  and  the  skin  re- 

1  Le<jons  sur  la  Physiologie  du  SystSme  Nerveux.     Paris,  1866,  p.  272. 

2  Trait6  des  Sections  Nerveuses.     Paris,  1873. 

3  Injuries  of  Nerves,  and  their  Consequences.     Philadelphia,  1874,  p.  84. 


OF    THE    NERVOUS    SYSTEM. 


413 


covers  its  normal  sensibility.  Restoration  may  also  undoubtedly  take 
place  in  nerves  of  larger  size,  as  in  the  case  reported  by  L'EtieVant,1 
where  the  median  nerve  was  divided  in  a  man  twenty-six  years  of  age, 
at  the  upper  third  of  the  arm.  The  power  of  motion  and  sensibility, 
dependent  on  the  fibres  of  this  nerve,  remained  abolished  for  ten 
months,  but  began  to  reappear  in  fourteen  months,  and  were  almost 
completely  restored  at  the  end  of  a  year  and  a  half. 

Nerve  Cells, 

The  nerve  cells,  which  form  the  characteristic  anatomical  element  of 
the  gray  substance,  are  rounded  or  irregularly  shaped  bodies,  consisting 
of  a  soft,  semi-transparent,  finely  granular,  albuminous  matter,  and  con- 
taining a  rather  large,  distinctly  marked  nucleus  and  nucleolus.  Some- 
times they  also  contain  a  certain  quantity  of  brown,  yellowish,  or 
blackish  pigment  grains,  which  are  especially  abundant  in  the  imme- 
diate neighborhood  of  the  nucleus.  The  nerve  cells  vary  in  size  in  dif- 
ferent parts  of  the  gray  substance.  The  smaller  ones,  from  10  to  20 
mmm.  in  diameter,  are  found  in  the  ganglia  of  the  sympathetic  system, 
the  convolutions  of  the  cerebral  hemispheres,  and  in  the  posterior  horns 
of  gray  matter  in  the  spinal  cord.  The  larger,  averaging  from  40  to  60 
mmm.,  are  in  the  convolutions  of  the  cerebellum,  and  in  the  medulla 
oblongata  ;  the  largest  of  all,  as  a  general  rule,  being  met  with  in  the 
anterior  horns  of  gray  mat- 
ter of  the  spinal  cord,  where 
they  reach  the  diameter  of 
130  or  135  mmm.,  or  seven- 
teen times  the  size  of  the  red 
globules  of  the  blood. 

The  most  marked  anato- 
mical features  of  the  nerve 
cells  are  their  prolonga- 
tions. These  are  narrow 
processes  or  extensions  of 
the  cell  substance,  and  con- 
sisting apparently  of  the 
same  material.  In  the  gan- 
glia of  the  sympathetic  sys- 
tem, and  in  those  situated 
upon  the  roots  of  the  spinal 
and  cranial  nerves  in  man, 
the  nerve  cells  have  for  the 
most  part  a  rounded  form, 
and  only  one  or  two  pro- 
longations. Throughout  the 
gray  substance  of  the  braiu 


Fig.  142. 


**"  ™ 


°'  "" 


Trait6  des  Sections  Nerveuses,  p.  54. 


414  GENERAL    STRUCTURE    AND    FUNCTIONS 

and  spinal  cord,  on  the  contrary,  they  present  three,  four,  five,  or  even 
eight  prolongations,  running  in  different  directions  and  giving  to  the 
cell  a  peculiar  radiated  appearance.  The  prolongations  after  a  certain 
distance  become  branched,  the  branches  thus  formed  again  dividing 
and  subdividing,  growing  at  the  same  time  smaller  in  size,  until  they 
terminate  in  a  more  or  less  abundant  tuft  or  ramification  of  exceedingly 
slender  filaments.  According  to  Gerlach,  the  terminal  fibres  of  this 
ramification  constitute  a  plexus  of  fine  nervous  threads,  penetrating 
the  interstitial  substance  of  the  gray  matter.  It  is  not,  however,  known 
with  certainty  whether  these  fibres  terminate  by  free  extremities,  or 
whether  they  form  a  network  of  communication  between  different  nerve 
cells. 

Connection  between  the  Nerve  Cells  and  Nerve  Fibres. — In  all  cases 
the  nerve  fibres  are  connected,  at  their  central  origin,  with  masses  of 
gray  substance,  into  which  they  penetrate  and  in  which  they  are  inti- 
mately mingled  with  the  nerve  cells.  In  some  instances,  a  direct  con- 
tinuity can  be  seen  between  the  nerve  fibres  and  certain  prolongations 
of  the  nerve  cells ;  in  others,  such  a  direct  anatomical  connection  is  only 
rendered  more  or  less  probable  by  the  similarity  in  direction  between 
the  nerve  fibres  and  the  processes  of  the  nerve  cells,  and  by  their  resem- 
blance in  physical  constitution. 

In  the  ganglia  of  the  sympathetic  system  and  in  those  of  the  roots  of 
the  spinal  and  cranial  nerves,  the  nerve  cells  of  a  rounded  form  give 
off,  as  a  rule,  in  man  and  the  mammalians,  only  a  single,  pale,  undivided 
process,  which  at  first  presents  the  appearance  of  an  axis  cylinder  of 
small  diameter,  but  which  subsequently  increases  in  size  and  becomes 
provided  with  a  medullary  layer,  assuming  at  the  same  time  the  distinct 
double  contour,  characteristic  of  a  fully  formed  nerve  fibre.  These  cells, 
sending  out  a  single  nerve  process  in  one  direction,  are  called  "  unipolar" 
nerve  cells.  In  the  ganglia  of  the  spinal  nerve  roots,  and  in  the  Gasse- 
rian  ganglion  of  fishes,  nerve  cells  are  found  which  send  off  two  such 
processes  in  opposite  directions  ;  the  medullary  layer  of  the  nerve  fibre 
ceasing  on  each  side  just  before  its  union  with  the  body  of  the  cell. 
Such  cells,  with  two  opposite  nerve  processes,  are  called  "bipolar"  nerve 
cells.  These  connections  have  been  recognized  by  all  observers,  and 
there  is  no  doubt  as  to  their  existence. 

In  the  gray  substance  of  the  brain  and  spinal  cord,  the  nerve  cells,  as 
above  described,  are  "  multipolar,"  or  send  out  a  number  of  prolonga- 
tions, in  different  directions,  which  divide  and  ramify  without  making 
any  certain  anatomical  connection  with  other  parts.  Beside  these 
branching  prolongations,  however,  according  to  the  observations  of 
Deiters,  confirmed  by  Schultze,  Gerlach,  and  Kolliker,  the  multipolar 
nerve  cell  also  sends  out  a  single  prolongation  which  is  different  from 
the  others,  in  that  it  does  not  branch  but  continues  on  its  course  for  a 
considerable  distance,  presenting  the  usual  physical  aspect  of  a  naked 
axis  cylinder.  This  simple  unbranched  process  is  called  the  "axis 
cylinder  process,"  to  distinguish  it  from  the  remaining  ramified  pro- 


OF    THE    NERVOUS    SYSTEM.  415 

longations.  Cells  of  this  description,  provided  both  with  ramified  pro- 
longations and  with  a  single  unbranched  axis  cylinder  process,  are 
found  abundantly  in  the  spinal  cord,  the  medulla  oblongata,  the  cerebel- 
lum, the  corpora  striata,  and  the  optic  thalami.  The  axis  cylinder  pro- 
cess, in  the  spinal  cord,  passes  into  the  bundles  of  medullated  nerve 
fibres  forming  the  roots  of  the  nerves  and  the  columns  of  the  cord ;  and 
in  the  convolutions  of  the  cerebellum  and  the  cerebral  ganglia,  the  nerve 
fibres  which  penetrate  the  gray  substance  lose  their  medullary  layer 
and  become  reduced  to  the  condition  of  a  naked  axis  cylinder,  similar  in 
appearance  to  the  prolongations  of  the  nerve  cells.  For  these  reasons 
it  is  considered  probable  that  the  nerve  fibres  are  connected  by  con- 
tinuity of  substance  with  the  axis  cylinder  process  of  the  nerve  cells. 
But,  according  to  the  most  careful  observers,1  this  connection  is  more  or 
less  hypothetical,  and  is  not  positively  shown  by  direct  observation.  It 
is  evident  that  there  is  a  physiological  communication  between  the  nerve 
fibres  and  the  nerve  cells-;  but  it  is  possible  that  such  a  communication 
may  take  place  by  other  methods  than  an  immediate  continuity  of  their 
substance. 

Finally,  it  is  certain  that  there  are  nerve  cells  in  the  gray  matter 
which  are  not  directly  connected  with  nerve  fibres.  According  to  the 
observations  of  Gerlach,  there  is  a  tract  throughout  the  dorsal  portion 
of  the  spinal  cord,  near  the  central  part  of  its  gray  substance,  where  all 
the  nerve  cells  are  provided  with  branching  prolongations,  but  do  not 
possess  any  undivided  process  resembling  a  cylinder  axis.  It  is  not 
known  whether  such  cells  exist  also  in  other  portions  of  the  nervous 
system. 

Physiological  Properties  of  the  Nerve  Cells. — The  nerve  cells,  and 
the  gray  substance  of  which  they  form  a  part,  act  as  centres,  in  which 
the  nervous  impressions  are  received  through  the  sensitive  nerve  fibres 
from  the  periphery,  and  from  which  a  stimulus  is  sent  out  through  the 
motor  fibres  to  the  muscles.  Every  collection  of  gray  substance  is 
therefore  called  a  "nervous  centre."  While  the  nerve  fibres  accordingly 
are  organs  of  transmission  onty,  the  gray  substance  and  its  nerve  cells 
constitute  an  apparatus  in  which  the  nervous  influence  is  modified  in 
character,  and  changed  from  one  form  to  another.  Their  function  is 
to  receive  impressions  conveyed  to  them  by  the  nerve  fibres,  and  to 
convert  these  impressions  into  impulses  which  are  transmitted  to  dis- 
tant organs.  The  nature  of  the  process  by  which  this  change  is  effected, 
and  the  action  which  goes  on  in  the  nerve  cells  during  its  accomplish- 
ment, are  entirely  unknown  to  us ;  but  it  is  evidently  essential  to  the 
physiological  operation  of  the  nervous  system,  since  neither  sensation 
nor  movement  is  ever  excited,  in  the  natural  condition,  through  the 
nerve  fibres,  unless  they  are  in  communication  with  the  gray  substance 
of  a  nervous  centre. 

1  Kolliker,  Elements  d'Histologie  Humaine,  5me  Edition.  Paris,  1868,  pp.  361, 
363,  365,  399. 


416          GENERAL    STRUCTURE    AND    FUNCTIONS,   ETC. 

Reflex  Action  of  the  Nervous  System. — The  nervous  system  thus 
stands  as  a  medium  of  communication  between  different  parts  of  the 
living  body,  so  that  a  stimulus  applied  to  one  organ  may  excite  the 
activity  of  another.  This  communication  between  adjacent  or  distant 
parts  is  never  direct,  but  always  a  circuitous  one.  It  passes  invariably 
through  an  intermediate  nervous  centre,  which  receives  the  impression 
conveyed  to  it  by  nerve  fibres  from  one  organ,  and  reacts  by  sending 
out  a  stimulus  which  calls  into  activity  the  other.  This  is  called 
the  "reflex  action"  of  the  nervous  system,  because  the  stimulus  is  first 
sent  inward  to  the  nervous  centre  and  then  returned  or  reflected  in  the 
opposite  direction.  In  this  process,  the  intermediate  act  between  the 
inward  and  outward  passage  of  the  nervous  stimulus  is  accomplished  in 
the  gray  substance  of  the  nervous  centres. 


CHAPTEE  II. 

NERVOUS    IRRITABILITY   AND   ITS   MODE   OF 
ACTION. 

THE  property  possessed  by  nerves  of  being  called  into  excitement  by 
an  appropriate  stimulus  is  termed  their  "  irritability."  This  property 
is  not  confined  to  the  elements  of  the  nervous  system,  but  exists  also  in 
other  tissues  and  organs.  Each  organ  or  anatomical  element,  when 
subjected  to  the  application  of  a  stimulus  adapted  to  its  physiological 
character,  reacts  in  a  way  peculiar  to  itself  and  produces  a  visible  result 
of  a  definite  kind.  Thus  a  glandular  organ,  when  excited,  exhibits  the 
phenomena  of  secretion ;  a  muscle  or  a  muscular  fibre,  those  of  contrac- 
tion. The  visible  result  of  glandular  activity  is  the  accumulation  and 
discharge  of  the  secreted  fluids,  that  of  muscular  contraction  is  a  change 
of  form  in  the  muscle,  and  a  movement  of  the  parts  to  which  it  is  at- 
tached. The  irritability  of  a  nerve  or  a  nerve  fibre,  on  the  other  hand,  is 
not  manifested  by  any  perceptible  change  in  its  own  substance,  but  by 
the  phenomena  of  sensation  or  motion  in  the  organs  to  which  it  is 
distributed. 

Irritability  of  Sensitive  Fibres. 

The  irritability  of  the  sensitive  nerve  fibres  is  most  directly  mani- 
fested during  life  by  the  production  of  sensation.  This  sensation, 
however,  does  not  exist  in  the  nerve  itself,  but  in  the  nervous  centre 
where  its  fibres  terminate.  The  proof  of  this  is  that  if  the  communica- 
tion between  any  part  of  a  sensitive  nerve  and  the  brain  be  cut  off  by 
division  of  the  nerve  fibres,  no  stimulus  subsequently  applied  to  the 
separated  trunk  or  branches  of  the  nerve  will  produce  any  perceptible 
sensation.  If,  however,  the  connection  between  the  nerve  and  the 
nervous  centre  be  retained,  while  that  with  the  external  integument  be 
cut  off,  stimulants  of  various  kinds  applied  to  the  nerve  itself  will  pro- 
duce a  sensation  which  is  more  or  less  acute  according  to  the  stimulus 
employed.  Pinching  or  pricking  the  nerve,  variations  of  temperature, 
or  the  passage  of  an  electric  current,  will  all  have  the  effect  of  bringing 
into  action  the  nervous  irritability,  and  thus  producing  the  effect  of  a 
sensation. 

In  order  to  accomplish  this  result,  however,  two  conditions  are  essen- 
tial. First,  the  nerve  must  be,  as  above  mentioned,  in  communication 
with  the  nervous  centre  where  the  sensation  is  to  be  perceived ;  and 
secondly,  the  nerve  fibres  themselves  must  retain  their  power  of 
irritability.  The  irritability  of  a  sensitive  nerve  may  be  so  deadened 

(417) 


418  NERVOUS    IRRITABILITY 

by  the  compression  of  a  bandage  or  the  application  of  cold,  that  no 
stimulus  applied  to  the  part  will  produced  any  perceptible  effect.  Ac- 
cording to  the  observations  of  Weir  Mitchell,1  the  application  of  extreme 
cold,  in  man,  to  the  region  of  the  ulnar  nerve  at  the  elbow  produces, 
when  the  chilling  process  has  reached  a  certain  stage,  complete  loss  of 
sensibility  in  the  parts  to  which  the  nerve  is  distributed.  The  irrita- 
bility of  sensitive  nerve  fibres  may  also  be  temporarily  suspended  by 
mechanical  injuries  in  their  immediate  neighborhood,  not  involving  the 
fibres  themselves.  Thus  a  division  of  certain  parts  of  the  white  sub- 
stance in  the  brain  or  spinal  cord,  is  known  to  produce  a  loss  of  sensi- 
bility in  particular  regions  of  the  body,  which  may  disappear  after  a 
short  time,  notwithstanding  that  the  wounded  fibres  remain  ununited  ;2 
and  according  to  the  observations  of  L'Etievant,3  section  of  one  branch 
of  a  sensitive  nerve,  beside  the  persistent  anaesthesia  of  the  divided 
fibres,  may  also  cause  a  temporary  loss  of  sensibility  in  neighboring 
fibres,  derived  by  anastomosis  from  other  branches. 

The  irritability  of  sensitive  nerve  fibres  may  also  be  abnormally 
increased  by  vascular  congestion,  or  local  injuries.  The  application  of 
cold,  or  shutting  off  the  supply  of  blood  by  the  ligature  of  arteries, 
may  produce  in  the  nerve,  before  it  reaches  the  stage  of  insensibility,  a 
condition  of  unnatural  excitement  which  is  indicated  by  pain,  in  the 
parts  corresponding  to  its  distribution. 

During  life  the  irritability  of  sensitive  nerves  is  manifested  by  the 
evidences  of  conscious  sensation.  After  death,  as  in  a  decapitated 
animal,  it  may  also  be  shown  to  exist,  for  a  certain  time,  by  the  reflex 
actions  taking  place  in  the  spinal  cord  or  in  other  parts  of  the  nervous 
system. 

Irritability  of  Motor  Fibres. 

The  motor  nerves  are  especially  convenient  for  studying  the  action 
of  nervous  irritability,  because  their  excitement  has  for  its  result  a 
visible  muscular  contraction ;  and  this  may  take  place,  even  when  the 
nerve  and  its  muscle  have  been  separated  from  the  rest  of  the  body. 
To  produce  this  result,  however,  as  in  the  case  of  the  sensitive  nerves, 
two  conditions  are  requisite,  namely;  first,  the  nerve  fibre  must  pre- 
serve its  normal  irritability ;  and  secondly,  the  muscular  tissue  must 
also  be  capable  of  responding  to  a  stimulus  by  the  contraction  of  its 
fibres.  The  laws  regulating  these  two  sets  of  phenomena  may  therefore 
be  studied  in  connection  with  each  other. 

Mode  of  exhibiting  Muscular  Irritability. — This  is  best  shown  in  the 
cold-blooded  animals,  since  in  them  it  continues  active  for  a  longer  time 
than  in  the  birds  and  mammalians.  A  frog's  leg  is  separated  from  the 
body  of  the  animal,  the  skin  removed,  and  the  poles  of  a  galvano-electric 

1  Injuries  of  Nerves  and  their  Consequences.     Philadelphia,  1872,  p.  59. 

2  Veyssiere,  Recherches  sur  PHemianaesthe'sie.     Paris,  1874,  p.  78. 
8  Traite  des  Sections  Nerveuses.     Paris,  1873,  pp.  171,  192. 


AND    ITS    MODE    OF    ACTION. 


419 


apparatus  (Fig.  143,  a,  6)  applied  to  the  surface  of  Fig.  143. 

the   denuded   muscles.     A   contraction   takes  place 

each  time  the  circuit  is  completed,  when  the  elec- 

tric discharge  passes  through  the  limb.     In  this  case, 

the  stimulus  is  applied  directly  to  the  muscles,  and 

shows  that  their  irritability,  or   power  of  contrac- 

tion under  the  influence  of  an  exciting  cause,  does 

not    depend    upon    their    remaining    in    connection 

with  the  nerves  or  nervous  centres.     A  single  mus- 

cular fibre,  in  fact,  separated  from  all  neighboring 

parts,  may  sometimes  be  seen  to  contract  under  the 

microscope  for  a  certain  time  after  its  removal  from 

the  muscular  tissue.     The  muscles  will  also  respond 

by  contraction  to  various  other  kinds  of  mechanical 

or   chemical   stimulus,  such    as   pinching,  pricking, 

cauterizing,  the  contact  of  hot  or  cold   bodies,  or      FROG'S  LEG,  with 

the  application  of  various  acid,  alkaline,  or  saline    vanic  battery  applied 

solutions.     The  most  efficient  and  manageable  stimu-    to   the  muscles  at 

lus,  however,  is  the  electric  discharge. 

Mode  of  exhibiting  Nervous  Irritability.  —  In  order  to  exhibit  the 
irritability  of  the  motor  nerve  fibres,  a  frog's  leg  is  prepared,  as  in  the 
preceding  experiment,  except  that  the  sciatic  nerve  is  cut  off  at  its 
point  of  emergence  from  the  spinal  canal,  and  dissected  from  the  adja- 
cent tissues,  so  that  a  considerable  portion  of  it  is  left  exposed,  but 
retaining  its  connection  with  the  separated  limb 
(Fig.  144).  If  the  two  poles  of  a  galvanic  battery 
be  now  placed  in  contact  with  different  points  (a,  6) 
of  the  exposed  nerve,  and  a  current  allowed  to  pass 
between  them,  at  the  moment  of  its  passage  a  con- 
traction takes  place  in  the  muscles  below.  It  will 
be  seen  that  this  experiment  is  altogether  different 
from  the  one  represented  in  Fig.  143.  In  that  case 
the  electric  discharge  passes  through  the  muscles 
themselves,  and  acts  upon  them  by  direct  stimulus. 
Here  the  current  passes  only  from  a  to  b  through 
the  tissues  of  the  nerve,  and  acts  directly  upon  the 
nerve  alone;  while  the  nerve,  acting  upon  the 
muscles  by  its  own  special  agency,  causes  in  this 
way  a  muscular  contraction.  So  long,  therefore, 
as  the  muscles  are  in  a  healthy  condition,  their  con- 
traction, under  the  influence  of  a  stimulus  applied 
to  the  nerve,  demonstrates  the  irritability  of  the 
latter,  and  may  be  used  as  a  convenient  measure  of 
its  intensity. 

The  irritability  of  a  motor  nerve  continues  after 
death.     The   knowledge  of  this    fact   follows  from     the  "cittto 
what  has  been  said  with  regard  to  experimenting     attached 
upon  the  frog's  leg,  prepared  as  above.     The  irrita- 


Fig.  144. 


b,  Poles 


420  NERVOUS    IRRITABILITY 

bility  of  the  nerve,  like  that  of  the  muscles,  depends  directly  upon  its 
anatomical  structure  and  constitution;  and  so  long  as  these  remain 
unimpaired,  the  nerve  will  retain  its  vital  properties,  though  respira- 
tion and  circulation  may  have  ceased.  For  the  same  reason,  nervous 
irritability  lasts  longer  after  death  in  the  cold-blooded  than  in  the 
warm-blooded  animals.  Yarious  artificial  irritants  may  be  employed 
to  call  it  into  activity.  Pinching  or  pricking  the  exposed  nerve  with 
steel  instruments,  the  application  of  caustic  liquids,  and  the  passage  of 
galvanic  discharges,  all  have  this  effect.  The  galvanic  current,  how- 
ever, is  the  best  means  to  employ  for  this  purpose,  since  it  is  more 
delicate  in  its  operation  than  the  others,  and  will  continue  to  succeed 
for  a  longer  time. 

The  nerve  is  so  sensitive  to  the  galvanic  current  that  it  will  respond 
to  it  when  insensible  to  all  other  kinds  of  stimulus.  A  frog's  leg 
freshly  prepared,  as  above,  with  the  nerve  attached,  will  react  so  readity 
when  a  discharge  is  passed  through  the  nerve,  that  it  forms  an  ex- 
tremely delicate  instrument  for  detecting  the  presence  of  electric  cur- 
rents of  low  intensity,  and  has  been  sometimes  used  for  this  purpose 
under  the  name  of  the  "  galvanoscopic  frog."  It  is  only  necessary  to 
introduce  the  nerve  as  part  of  the  electric  circuit ;  and  if  even  a  very 
feeble  current  be  present,  it  is  at  once  betrayed  by  a  muscular  con- 
traction. 

Nervous  irritability,  like  that  of  the  muscles,  is  exhausted  by  repeated 
excitement.  If  a  frog's  leg,  prepared  in  the  manner  above  described, 
with  the  sciatic  nerve  attached,  be  allowed  to  remain  at  rest  in  a  damp 
and  cool  place,  where  its  tissue  will  not  become  altered  by  desiccation, 
the  nerve  will  remain  irritable  for  many  hours ;  but  if  it  be  excited, 
soon  after  its  separation  from  the  body,  by  repeated  shocks,  it  begins 
to  react  with  diminished  energy,  and  becomes  gradually  less  irritable, 
until  at  last  it  ceases  to  exhibit  any  further  excitability.  If  it  be  now 
allowed  to  remain  for  a  time  at  rest,  its  irritability  will  be  partially 
restored ;  and  muscular  contraction  will  again  ensue  on  the  application 
of  a  stimulus  to  the  nerve.  Exhausted  a  second  time,  and  a  second 
time  allowed  to  repose,  it  will  again  recover  itself;  and  this  may  be 
repeated  several  times  in  succession.  At  each  repetition,  however,  the 
recovery  of  nervous  irritability  is  less  complete,  until  it  finally  disap- 
pears altogether,  and  can  no  longer  be  recalled.  The  irritability  of  the 
muscles  may  be  exhausted,  in  a  similar  way,  by  repeated  excitement. 

Yarious  circumstances  tend  to  diminish  or  suspend  the  irritabilit}^  of 
the  motor  nerve  fibres.  As  in  the  case  of  the  sensitive  fibres,  compres- 
sion, cold,  or  other  similar  agencies  will  depress  the  power  of  the 
muscular  nerves,  so  that  they  can  no  longer  excite  a  contraction  when 
subjected  to  the  galvanic  current.  Severe  and  sudden  mechanical  in- 
juries often  have  the  same  effect ;  as  where  general  muscular  relaxation, 
or  diminished  power  of  voluntary  motion,  is  produced  by  any  extensive 
contusion  or  laceration  of  one  of  the  limbs.  Such  an  injury  produces  a 
general  disturbance  or  shock^  which  affects  the  entire  nervous  system, 


AND    ITS    MODE    OF    ACTION.  421 

and  destroys  or  suspends  its  irritability.  The  effects  of  a  nervous 
shock  of  this  kind  may  frequently  be  seen  in  man  after  railroad  acci- 
dents, where  the  patient,  though  extensively  injured,  may  remain  for 
some  hours  in  a  state  of  unusual  muscular  debility,  and  at  the  same  time 
without  the  sensation  of  pain.  It  is  only  after  reaction  has  taken  place, 
and  nervous  irritability  has  been  restored  by  repose,  that  the  powers  of 
sensation  and  voluntary  motion  are  re-established. 

It  is  often  found,  on  preparing  the  frog's  leg  for  experiment  as  above, 
that  immediately  after  the  limb  has  been  separated  from  the  body  and 
the  integument  removed,  the  nerve  is  destitute  of  irritability.  Its 
vitality  has  been  suspended  by  the  violence  inflicted  in  the  preparatory 
operation.  In  a  few  moments,  if  kept  under  favorable  conditions,  it 
recovers  from  the  shock,  and  regains  its  natural  irritability. 

Different  Action  of  the  Direct  and  Inverse  Currents. — The  action 
of  the  galvanic  current  upon  the  nerves,  as  first  shown  by  Matteucci,  is 
in  many  respects  peculiar.  If  the  current  be  made  to  traverse  the  nerve 
in  the  natural  direction  of  its  fibres,  namely,  from  its  origin  toward  its 
distribution,  as  from  a  to  b  (Fig.  144),  it  is  called  the  direct  current. 
If  it  be  made  to  pass  in  the  contrary  direction,  as  from  b  to  a,  it  is  called 
the  inverse  current.  When  the  nerve  is  fresh  and  exceedingly  irritable, 
or  when  the  galvanic  current  is  of  sufficient  intensity,  a  muscular  con- 
traction takes  place  at  both  the  commencement  and  termination  of  the 
current,  whether  it  be  direct  or  inverse.  But  when  the  activity  of  the 
nerve  has  become  somewhat  diminished,  or  when  the  current  emploj^ed 
is  of  feeble  intensity,  contraction  takes  place  only  at  the  commencement 
of  the  direct  and  at  the  termination  of  the  inverse  current.  This  may 
readily  be  shown  by  preparing  the  two  legs  of  the  same  frog  in  such  a 
manner  that  they  remain  connected  with  each  other  by  the  sciatic  nerves 

Pi?.  145. 


and  that  portion  of  the  spinal  column  from  which  these  nerves  take  their 
origin.  The  two  legs,  so  prepared,  are  placed  each  in  a  vessel  of  water, 
with  the  nervous  connection  hanging  between.  (Fig.  145.)  If  the  posi- 
tive pole,  a,  of  the  battery  be  now  placed  in  the  vessel  which  holds  leg 


422  NERVOUS    IRRITABILITY 

No.  1,  and  the  negative  pole,  6,  in  that  containing  log  No.  2,  it  will  be 
seen  that  the  galvanic  current  will  traverse  the  two  legs  in  opposite 
directions.  In  No.  1,  it  will  pass  in  a  direction  contrary  to  the  course 
of  its  nervous  fibres,  that  is,  it  will  be  for  this  leg  an  inverse  current ; 
while  in  No.  2  it  will  pass  in  the  same  direction  with  that  of  the  nervous 
fibres,  that  is,  it  will  be  for  this  leg  a  direct  current.  It  will  now  be 
found  that  at  the  moment  when  the  circuit  is  completed,  a  contraction 
takes  place  in  No.  2  by  the  direct  current,  while  No.  1  remains  at  rest ; 
but  at  the  time  the  circuit  is  broken,  a  contraction  is  produced  in  No.  1 
by  the  inverse  current,  while  no  movement  takes  place  in  No.  2.  A  suc- 
cession of  alternate  contractions  may  thus  be  produced  in  the  two  legs 
by  repeatedly  closing  and  opening  the  circuit.  If  the  position  of  the 
poles,  a,  6,  be  reversed,  the  effects  of  the  current  will  be  changed  in  a 
corresponding  manner. 

After  a  nerve  has  become  exhausted  by  the  direct  current,  it  is  still 
sensitive  to  the  inverse ;  and  after  exhaustion  by  the  inverse,  it  is  still 
sensitive  to  the  direct.  It  was  even  found  by  Matteucci  that  after  a 
nerve  has  been  exhausted  for  the  time  by  the  direct  current,  the  return 
of  its  irritability  is  hastened  by  the  subsequent  passage  of  the  inverse 
current ;  so  that  it  will  become  again  sensitive  to  the  direct  current 
sooner  than  if  allowed  to  remain  at  rest.  Nothing,  accordingly,  is  so 
exciting  to  a  nerve  as  the  passage  of  direct  and  inverse  currents,  alter- 
nating with  each  other  in  rapid  succession.  Such  a  mode  of  applying 
the  electric  stimulus  is  that  afforded  by  the  Faradic  apparatus,  in  which 
momentary  currents  of  induced  electricity  are  made  to  traverse  the  cir- 
cuit in  two  opposite  directions  in  rapid  alternation. 

The  irritability  of  motor  nerves  is  distinct  from  that  of  the  muscles. 
This  is  shown  by  the  fact  that  the  two  properties  may  be  destroyed 
or  suspended  independently  of  each  other.  When  the  frog's  leg  has 
been  prepared  and  separated  from  the  body,  with  the  sciatic  nerve  at- 
tached, the  muscles  contract,  as  shown  above,  whenever  the  nerve  is 
irritated.  The  irritability  of  the  nerve,  therefore,  is  manifested  in  this 
instance  only  through  that  of  the  muscle,  and  that  of  the  muscle  is 
called  into  action  only  through  that  of  the  nerve.  But  the  action  of 
woorara  has  the  power,  as  first  pointed  out  by  Bernard,1  of  destroying 
the  irritability  of  the  nerve  without  affecting  that  of  the  muscles.  If  a 
frog  be  poisoned  by  this  substance,  and  the  leg  prepared  as  above,  the 
poles  of  a  galvanic  battery  applied  to  the  nerve  will  produce  no  effect. 
But  if  the  galvanic  discharge  be  passed  directly  through  the  muscles, 
contraction  takes  place.  The  muscular  irritability  has  survived  that 
of  the  nerves,  and  must  therefore  be  regarded  as  essentially  distinct 
from  it. 

There  are,  therefore,  two  kinds  of  paralysis :  first,  a  muscular  par- 
alysis, in  which  the  muscular  fibres  themselves  are  directly  affected ; 

1  Le<jons  sur  la  Physiologic  du  Systfeme  nerveux.     Paris,  1858,  tome  i.  p.  199. 


AND    ITS    MODE    OF    ACTION.  423 

and  secondly,  a  nervous  paralysis,  in  which  the  affection  is  confined  to 
the  nerve  fibres,  the  muscles  retaining  their  natural  properties,  and  being 
still  capable  of  contraction  under  the  influence  of  direct  stimulus. 

Identity  of  Action  in  the  Sensitive  and  Motor  Nerve  Fibres. 

The  results  which  are  produced  by  the  physiological  action  of  the 
nerve  fibres  differ  from  each  other  in  the  two  classes  to  which  they 
belong.  The  stimulation  or  excitement  of  the  sensitive  fibres  produces 
a  sensation,  or  a  sensitive  impression  in  the  nervous  centre  ;  that  of  the 
motor  fibres  causes  contraction  of  the  muscles  to  which  they  are  distrib- 
uted. Moreover,  if  a  sensitive  nerve  or  nerve  fibre  be  divided,  stimulus 
applied  to  its  central  or  attached  extremity  still  excites  a  sensation,, 
while  the  application  of  the  same  stimulus  to  its  separated  or  peripheral 
portion  produces  no  apparent  result.  On  the  other  hand,  if  a  motor 
nerve  be  divided,  irritation  of  its  attached  extremity,  which  is  still  in 
connection  with  the  nervous  centre,  is  without  effect ;  but  irritation  of 
its  peripheral  portion  causes  a  muscular  contraction  as  before.  In  other 
words,  the  nervous  force,  in  a  sensitive  nerve,  appears  to  move  always 
in  a  centripetal  direction,  that  is  from  without  inward ;  in  a  motor  nerve, 
on  the  other  hand,  in  a  centrifugal  direction,  or  from  within  outward. 
In  the  natural  condition  of  the  parts,  also,  the  excitement  of  a  sensitive 
nerve  never  produces  directly  any  other  effect  than  sensation ;  that  of  a 
motor  nerve  only  gives  rise  to  the  phenomena  of  movement. 

These  facts  easily  suggest  the  idea  that  the  two  kinds  of  nerve  fibres 
may  be  distinct  in  their  properties  and  modes  of  action ;  that  the  sensi- 
tive fibres  may  be  capable  of  acting  only  in  a  centripetal  direction  and 
of  exciting  the  phenomena  of  sensibility ;  and  that  the  motor  fibres 
can  only  act  from  within  outward  and  transmit  a  special  kind  of  nerve 
force,  adapted  to  excite  muscular  contraction. 

It  is  evident,  however,  that  the  reasons  given  above  are  not  sufficient 
to  indicate  a  difference  in  the  activity  of  the  nerves  themselves,  but  only 
in  the  sensible  results  of  its  operation.  In  neither  case  is  there  any 
perceptible  effect  produced  in  the  nerve,  but  only  in  the  organ  with 
which  it  is  in  connection.  When  a  sensitive  nerve  is  excited,  the  sensa- 
tion is  perceived  in  the  nervous  centre  ;  when  a  motor  nerve  is  called 
into  activity,  the  contraction  is  performed  by  the  muscular  fibres  at  its 
periphery.  It  is  possible  that  the  condition  of  the  nerve  fibres,  when  in 
a  state  of  excitement,  may  be  the  same  in  each  instance,  and  that  the  dif- 
ference in  the  effect  produced  may  be  due  to  the  different  physiological 
properties  of  the  organs  in  which  they  terminate ;  just  as  the  conducting 
wire  of  a  galvanic  battery  may  be  made  to  ring  a  bell  or  move  an  index, 
according  to  the  mechanism  with  which  its  poles  are  connected.  There 
are  certain  facts  which  can  hardly  bear  any  other  interpretation  than 
this,  and  which  lead  to  the  conclusion  that  the  physiological  action  in 
the  nerve  fibres  themselves  is  not  essentially  different  in  different  kinds 
of  nerves. 


42-i  NERVOUS    IRRITABILITY 

1.  The  stimulus  applied  to  a  nerve,  whether  sensitive  or  motor,  pro- 
duces the  same  effect  throughout  its  entire  length. 

In  the  natural  condition  of  the  parts,  the  impressions  made  upon  the 
external  integument,  when  they  give  rise  to  sensation,  are  transmitted 
by  the  sensitive  nerve  through  its  whole  course  to  the  nervous  centre. 
There  it  is  perceived  as  a  sensation;  and  the  sensation  thus  produced  is 
referred  by  the  individual,  not  to  the  brain  or  to  any  part  of  the  nerve, 
but  to  the  integument  where  the  nerve  originated.  If  an  irritation  be 
applied  to  the  nerve  in  the  middle  of  its  course,  the  sensation  is  still 
perceived  as  if  it  came  from  the  same  portion  of  the  integument  and  had 
travelled  through  the  same  distance  as  before.  It  is  well  known  that 
after  amputation  of  a  limb  in  the  human  subject,  if  the  severed  extremity 
of  one  of  the  nerves  happen  to  be  compressed  or  otherwise  irritated  by 
the  tissues  of  the  cicatrix,  or  if  it  be  the  seat  of  inflammatory  action, 
many  different  sensations  of  pain,  movement,  heat,  or  cold,  are  excited, 
which  are  always  referred  by  the  individual  to  the  amputated  portion 
of  the  limb ;  and  patients  often  assert  that  they  can  feel  the  separated 
parts  as  distinctly  as  if  they  were  still  attached  to  the  body.  The  im- 
pression conveyed  through  the  remaining  portion  of  the  nerve  is  the 
same  as  if  the  whole  of  it  were  still  in  existence. 

The  action  of  the  motor  nerves  is  of  a  similar  kind.  A  voluntary 
stimulus,  which  originates  in  the  brain,  passes  through  the  entire  length 
of  a  motor  nerve  to  reach  the  muscles  and  excite  their  contraction. 
But  if  the  nerve  be  divided  at  any  intermediate  point,  and  a  galvanic 
stimulus  applied  to  the  peripheral  portion,  a  contraction  follows  in  the 
same  muscles  as  before.  In  each  case,  the  physiological  effect  is  pro- 
duced at  the  extremity  of  the  nerve  fibres ;  and  it  seems  to  make  no 
essential  difference  in  its  character  from  how  great  a  distance  it  has 
been  transmitted. 

So  far  as  yet  known,  therefore,  the  nerve  fibre,  whether  sensitive  or 
motor,  when  its  irritability  is  excited,  may  be  thrown  at  once  into  a 
condition  of  activity  throughout  its  entire  length;  the  whole  nerve 
assuming  a  state  of  polarity,  analogous  to  that  of  a  magnetized  bar,  in 
which  the  visible  phenomena  of  attraction  or  repulsion  are  manifested 
only  at  its  extremities,  although  the  whole  substance  of  the  bar  partici- 
pates in  its  magnetic  molecular  action.  When  the  exciting  stimulus,  as 
in  the  sensitive  nerves,  is  naturally  applied  at  the  peripheral  extremity, 
it  must  necessarily  be  communicated  from  without  inward ;  and  when 
it  commences  at  the  inner  extremity,  as  in  a  motor  nerve,  it  must  move 
in  a  direction  from  within  outward.  But  nothing  thus  far  shows  that 
it  may  not  be  capable  of  moving  in  either  of  these  two  directions  in  the 
same  nervous  fibre.  The  following  experiments  show  that  this  is  in 
reality  the  case,  so  far  as  regards  the  sensitive  nerves. 

2.  Sensitive  impressions  may  pass,  in  the  fibres  of  a  sensitive  nerve, 
either  from  without  inward  or  from  within  outward. 

This  of  course  never  takes  place  in  the  natural  condition  of  the  parts ; 
but  its  possibility  has  been  demonstrated,  in  the  experiments  of  Paul 


AND    ITS    MODE    OF    ACTION.  425 

Bert,1  by  dividing  a  sensitive  nerve  and  then  reversing  its  position, 
so  that  its  peripheral  extremity  is  brought  into  connection  with  the 
nerve  centres.  The  end  of  the  tail,  in  a  young  rat,  was  deprived  of  its 
integument  for  a  length  of  five  centimetres,  and  the  denuded  portion 
inserted  beneath  the  integument  of  the  back  of  the  same  animal.  At 
the  end  of  eight  days,  when  the  ingrafted  portion  had  become  adherent 
to  the  subcutaneous  tissues,  and  had  contracted  sufficient  vascular  con- 
nection for  its  support,  the  tail  was  amputated  at  its  base,  and  thence- 
forward remained  attached  to  the  body  of  the  animal  only  by  what  was 
previously  its  peripheral  extremity.  In  three  months  the  signs  of  sensi- 
bility again  began  to  be  manifested  when  the  end  of  the  tail,  thus  re- 
versed, was  subjected  to  compression ;  and  at  the  end  of  six  months  its 
sensibility  was  re-established  to  an  unmistakable  degree.  The  nerves 
of  the  tail,  which  before  the  operation  transmitted  sensitive  impressions 
from  its  point  toward  its  base,  afterward  transmitted  the  same  impres- 
sions from  its  base  toward  its  point. 

There  is  no  evidence,  therefore,  that  nerve  fibres  are  endowed  with  two 
different  modes  of  action,  one  for  sensation,  the  other  for  motion.  In 
each  case  the  condition  of  the  nerve  itself  may  be  of  the  same  nature. 
But,  being  thrown  into  a  state  of  excitement  throughout  its  entire  length, 
it  communicates  a  stimulus  to  the  organ  with  which  it  is  connected.  If 
this  organ  be  a  perceptive  nervous  centre,  the  effect  produced  is  a  sen- 
sation ;  if  a  muscle,  it  results  in  contraction  and  movement.  These  acts 
cannot  be  interchanged  with  each  other,  because  the  muscle  cannot  feel 
and  the  nervous  centre  is  incapable  of  contraction ;  but  they  are  both 
indirect  effects  of  the  nervous  influence,  and  do  not  necessarily  depend 
upon  any  difference  in  its  nature. 

Rapidity  of  Transmission  of  the  Nerve  Force, 

It  is  a  matter  of  conscious  experience  that  the  operations  of  the  nerv- 
ous system  require  a  certain  time  for  their  accomplishment.  The  action 
both  of  the  senses  and  of  the  will  is  exceedingly  rapid,  but  still  is  not 
absolutely  instantaneous.  Between  the  mental  decision  to  perform  a 
voluntary  movement  and  its  actual  execution,  there  is  a  short  but  real 
interval  of  time,  during  which  the  nervous  mechanism  is  called  into 
activity.  A  certain  period  also  intervenes  between  the  contact  of  a 
foreign  body  with  the  skin,  and  our  complete  perception  of  its  existence 
and  qualities.  There  is  even  more  or  less  difference  between  individuals 
in  the  length  of  time  required  for  the  performance  of  nervous  action ; 
the  quickness  of  the  senses  and  the  promptitude  of  the  will  frequently 
varying  to  a  perceptible  degree.  In  the  case  of  a  voluntary  movement, 
the  period  consumed  in  its  entire  accomplishment  may  be  occupied 
by  three  different  processes,  namety :  1.  The  act  of  volition,  taking 
place  in  the  brain  ;  2.  The  transmission  of  the  motor  impulse,  through 
the  spinal  cord  and  nerves,  to  their  peripheral  terminations ;  and  3.  The 

1  La  Vitalit6  propre  des  Tissues  animaux.     Paris,  1866,  p.  12. 

28 


426  NERVOUS    IRRITABILITY 

excitement  of  the  muscular  fibres  to  a  state  of  contraction.  In  the  case 
of  a  sensation,  there  are  also  three  analogous  successive  acts,  namely : 
1.  The  reception  of  the  impression  by  the  sensitive  membrane;  2.  Trans- 
mission of  the  stimulus  through  the  nerve  fibres  inward;  and  3.  Its  per- 
ception in  the  brain  as  a  conscious  sensation.  It  is  an  important  phy- 
siological problem  to  determine  the  degree  of  rapidity  with  which  the 
transmission  of  stimulus  takes  place  through  the  nerve  fibres  in  either 
direction ;  and  it  has  recently  become  a  matter  of  practical  interest  in 
relation  to  pathology. 

Methods  of  determining  the  Rate  of  Transmission  of  the  Nerve  Force. 
— The  measurement  of  the  rate  of  transmission  of  the  nerve  force  was 
first  accomplished  by  Helmholtz,1  and  has  since  been  carried  out  by  a 
number  of  different  observers  with  essentially  similar  results.  The 
principle  adopted  is  in  all  cases  the  same.  Muscular  contraction  is 
excited  by  a  stimulus  which  passes  through  two  nerves  of  different 
length,  or  through  two  different  lengths  of  the  same  nerve ;  the  delay 
in  contraction,  when  the  stimulus  passes  through  the  greater  of  these 
two  distances,  gives  the  time  required  for  its  transmission  by  the  inter- 
vening nerve  fibres. 

These  experiments  were  first  performed  upon  nerves  rnd  muscles 
freshly  separated  from  the  body  in  the  cold-blooded  animals.  The  gas- 
trocneinius  muscle  of  a  frog  is  prepared,  with  a  portion  of  the  sciatic 
nerve  attached.  A  galvanic  battery  with  an  induction  apparatus  is  also 
provided,  so  that  the  closure  of  the  circuit  of  the  battery  will  produce 
an  instantaneous  electric  current  in  the  induction  coil.  By  this  means 
the  stimulus  of  the  induced  current  is  first  applied  to  the  muscle  itself, 
and  the  time  noted  which  intervenes  between  the  closure  of  the  circuit 
and  the  muscular  contraction.  This  represents  the  period  required  for 
the  excitement  of  the  muscular  fibres  themselves,  and  was  found  in  the 
experiments  of  Helmholtz  to  be  about  T^  of  a  second.  If  the  stimulus 
be  now  applied  to  the  nerve  in  immediate  proximity  to  the  muscle,  the 
above  interval  is  not  perceptibly  altered.  But  if  it  be  applied  to  the 
nerve  at  a  point  one,  two,  or  three  centimetres  distant,  a  decided  retarda- 
tion is  manifested  in  the  muscular  contraction ;  and  this  retardation 
becomes  greater  as  the  length  of  the  nerve,  between  the  muscle  and  the 
point  of  stimulation,  is  increased. 

The  intervals  of  time  in  these  experiments  have  been  measured  by 
various  contrivances,  the  most  successful  of  which  depend  upon  the  use 
of  an  automatic  registering  apparatus,  on  the  principle  of  that  employed 
by  Marey.2  In  this  apparatus,  a  card,  with  its  surface  blackened  by 
smoke,  moves  by  clockwork,  with  uniform  velocity,  in  a  horizontal 
direction.  Upon  this  card  the  extremity  of  a  diapason  or  tuning  fork, 
vibrating  500  times  per  second,  traces  an  undulating  line  (Fig.  146,  a) 
which  records  the  time  occupied  by  the  card  in  moving  from  one  point 

1  Comptes  Eendns  de  1'Academie  des  Sciences.    Paris,  1851.  tome  xxxiii.  p.  262. 

2  Du  Mouvemcnt  duns  les  Fonctioris  de  la  Vie.    Paris,  1868,  p.  422. 


AND    ITS    MODE    OF    ACTION.  427 

to  another.  A  straight  horizontal  line  (b ,  is  also  traced  upon  the  card 
by  the  extremity  of  a  slender  steel  lever,  the  other  end  of  which  forms 
a  part  of  the  galvanic  circuit.  The  closure  of  the  circuit  is  accom- 
plished by  a  movement  which  pushes  aside  this  lever,  and  thus  causes  a 

Fig.  146. 


DIAGRAM  OF  THE  REGISTERING  APPARATUS,  according  to  the  plan  of  Marey. 
a.  Undulating  line  traced  by  the  diapason,  which  marks  the  time  consumed  by  the  card  in 
moving  from  one  point  to  another,  b.  Line  traced  by  the  first  lever,  forming  part  of  the 
galvanic  circuit,  c  Line  traced  by  the  second  lever,  which  is  moved  by  the  contraction  of 
the  muscle,  d.  Deviation  of  the  line  6,  indicating  the  closure  of  the  galvanic  circuit  and  the 
stimulation  of  the  nerve,  e.  Deviation  of  the  line  c,  indicating  the  muscular  contraction. 

deviation  (d )  in  the  line  traced  by  its  extremity.  This  deviation  registers 
upon  the  card  the  instant  of  the  closure  of  the  circuit,  and  consequently 
that  of  the  stimulation  of  the  nerve.  The  muscle  used  for  experiment 
is  fixed  in  position,  with  its  tendon  attached  to  a  second  lever  in  such  a 
way  that  any  muscular  contraction  will  draw  aside  its  free  extremity. 
This  lever  traces  upon  the  card  a  second  straight  horizontal  line  (c) 
parallel  to  the  first ;  and  when  the  muscle  contracts,  the  line  is  devi- 
ated, as  at  (e),  by  the  lateral  movement  of  the  lever. 

Thus  when  the  experiment  has  been  performed,  there  are  left  upon  the 
surface  of  the  card  two  deviations  d  and  e,  one  of  which  represents  the 
stimulation  of  the  nerve,  the  other  the  muscular  contraction;  and  between 
the  two  is  included  a  certain  interval.  The  number  of  undulations  in 
the  diapason-trace  (a),  corresponding  to  this  interval,  gives  the  time 
which  has  elapsed  between  the  stimulation  of  the  nerve  and  the  contrac- 
tion of  the  muscle.  In  the  example  shown  in  Fig.  146,  as  the  interval 
between  the  deviations  includes  13  simple  variations,  of  which  500 
would  represent  one  second,  the  time  occupied  is  0.026  of  a  second. 
By  this  means,  intervals  of  time  of  very  short  duration  may  be  registered 
and  compared  with  accuracy. 

Subsequently  to  the  experiments  upon  separated  nerves  and  muscles 
in  the  lower  animals,  investigations  of  a  similar  kind  were  extended  to 
the  human  subject  during  life.  In  the  experiments  of  Baxt,1  this  was 
done  by  applying  the  electrodes  to  the  surface  of  the  skin  immediately 
over  the  situation  of  the  median  nerve,  and  at  varying  distances  from 
the  muscles  to  which  its  fibres  are  distributed.  The  nerve  was  thus 

1  Monatsbericlit  dor  Eoniglichen  Freussischen  Akademie,  April,  1867,  and 
March,  1870. 


428  NERVOUS    IRRITABILITY 

stimulated  at  the  wrist,  at  the  elbow,  and  at  the  upper  arm  near  the 
lower  extremities  of  the  coraco-brachialis  and  deltoid  muscles ;  the  effect 
of  the  stimulation  being  marked  by  the  swelling  of  the  muscles  at  the 
ball  of  the  thumb.  Here  also  it  was  found  that  the  intervening  time 
between  the  application  of  the  electrodes  and  the  muscular  contraction 
was  greater  when  the  stimulus  was  applied  to  the  nerve  at  the  upper 
arm,  than  when  applied  at  the  wrist ;  this  increased  interval  being  evi- 
dently the  time  required  for  the  transmission  of  the  nervous  impulse 
from  one  point  to  the  other.  The  rate  of  transmission,  as  ascertained 
by  these  experiments,  was  found  to  vary  considerably  according  to  the 
different  conditions  of  cold  and  warmth;  the  transmission  in  the  me- 
dian nerve,  when  subjected  to  cold,  being  sometimes  less  than  one-half 
as  rapid  as  in  the  same  nerve  at  a  higher  temperature. 

Finally,  in  the  experiments  of  Burckhardt,1  the  rate  of  transmission  of 
the  nerve  force,  for  voluntary  motion  and  the  acts  of  conscious  sensa- 
tion in  man,  has  been  investigated  at  considerable  length.  In  these 
experiments,  an  automatic  registering  apparatus  was  employed,  in  which 
the  beginning  and  end  of  the  nervous  transmission  were  marked,  as 
above,  by  corresponding  deviations  of  a  traced  line. 

Hate  of  Transmission  in  the  Motor  Nerves. — The  transmission  of 
the  voluntary  impulse  was  measured  in  Burckhardt's  investigations  as 
follows :  The  galvanic  battery  and  the  registering  apparatus  being  pro- 
perly attached  to  the  person  serving  for  experiment,  the  signal  for  the 
contraction  of  a  particular  muscle  was  given  by  the  sound  of  a  bell 
connected  with  the  battery.  Thus  the  entire  interval  registered  was 
that  between  the  sound  of  the  bell  and  the  muscular  contraction.  A 
part  of  this  time  was  consumed  in  the  double  act  of  hearing  the  sound 
and  producing  the  volitional  impulse.  A  part  was  also  taken  up  in  the 
local  process  of  muscular  contraction,  and  only  the  remainder  was  occu- 
pied in  that  of  nervous  transmission.  But  it  is  evident  that,  if,  in  two 
different  observations,  the  same  signal  were  used  for  the  contraction  of 
two -muscles  supplied  by  different  lengths  of  nerve,  the  process  taking 
place  in  the  brain  and  that  taking  place  in  the  muscle  would  be  alike 
in  both ;  and  any  difference  in  the  time  observed  must  be  due  to  the 
different  distances  of  nerve  fibre  traversed  by  the  voluntary  motor 
impulse.  The  muscles  employed  for  this  purpose  were,  in  the  lower 
limb,  the  extensor  digitorum  communis  brevis,  tibialis  anticus,  and 
semimembranosus,  supplied  by  branches  of  the  sciatic  nerve,  and  the 
quadriceps  extensor  cruris,  supplied  by  the  anterior  crural  nerve;  in 
the  upper  limb,  the  interosseus  externus  primus,  extensor  digitorum 
communis,  flexor  digitorum  and  deltoid,  all  supplied  by  branches  of 
the  brachial  plexus.  The  result  of  all  the  observations  upon  eight 
different  healthy  persons  was,  that  the  mean  velocity  of  transmission 
for  the  voluntary  impulse,  in  the  peripheral  nerves  of  the  upper  and 

1  Die  Physiologische  Diagnostik  der  Nervenkrankheiten.  Leipzig,  187o, 
p.  32. 


AND    ITS    MODE    OF    ACTION.  429 

lower  extremities,  is  a  little  over  2t  metres  per  second.  The  minimum 
velocity  was  20  metres,  and  the  maximum  36  metres ;  but  of  all  the 
observations,  which  were  thirty  in  number,  twenty-three,  or  nearly  four- 
fifths,  gave  results  between  26  and  28  metres. 

In  one  instance  the  rate  of  movement  in  the  same  nerve,  for  the 
voluntary  impulse  and  for  that  excited  by  galvanism,  was  tested  com- 
paratively, and  but  little  difference  was  found  to  exist  in  the  two  cases. 

According  to  Burckhardt,  also,  the  rate  of  transmission  does  not  vary 
essentially  for  weak  or  strong  motor  impulses;  that  for  a  muscular  con- 
traction of  moderate  force  passing  as  rapidly  through  the  nerve  as  that 
for  contractions  of  greater  power. 

Rale  of  Transmission  in  the  Sensitive  Nerves. — The  rate  of  trans- 
mission for  impressions  of  conscious  sensibility  is  determined  by  an 
analogous  method.  An  irritation  or  tactile  impression  is  produced 
upon  the  skin  at  varying  distances  from  the  nervous  centres — as,  for 
instance,  upon  the  foot,  the  thigh,  and  the  loins ;  and  the  instant  at 
which  the  sensation  is  perceived  is  indicated  by  a  movement  of  the 
finger.  As  the  time  required  for  the  act  of  conscious  perception  in 
the  brain  and  for  the  voluntary  movement  of  the  finger  is  the  same 
in  all  cases,  the  difference  between  two  successive  observations  is  owing 
to  the  different  lengths  of  the  nerves  transmitting  the  stimulus. 

In  the  investigations  of  Burckhardt,  which  were  made  upon  thirteen 
different  individuals,  the  mean  rate  of  transmission  for  sensitive  impres- 
sions through  the  peripheral  nerves  was  found  to  be  a  little  less  than 
47  metres  per  second;  that  is,  more  than  one  and  a  half  times  as  rapid 
as  that  for  voluntary  motion.  The  variations  were  from  a  minimum 
of  20  to  a  maximum  of  73  metres;  but  in  nearly  three-fourths  of  all  the 
observations,  the  results  were  confined  within  a  variation  of  from  40  to 
56  metres.  The  rapidity  of  transmission  varied  but  little  with  the  in- 
creased or  diminished  intensity  of  the  impression;  the  difference,  on 
the  average,  being  but  little  over  one  per  cent. 

Eate  of  Transmission  in  the  Spinal  Cord. — The  investigations  of 
Burckhardt  first  indicated  a  difference  between  the  rate  of  transmission 
in  the  spinal  cord  and  that  in  the  peripheral  nerves.  This  rate  was 
determined  for  the  spinal  cord  by  comparing  the  time  consumed  in 
the  passage  of  a  voluntary  impulse  to  the  extremities  of  two  nerves, 
like  the  sciatic  and  the  ulnar,  which  emerge  from  the  spinal  cord  at 
different  points.  In  this  case  the  voluntary  impulse,  after  leaving  the 
brain,  will  traverse  different  lengths  of  the  spinal  cord ;  and  as  its  rate 
of  movement  in  the  peripheral  nerves  is  known,  the  difference  in  the 
time  of  its  entire  passage  may  be  easily  referred  to  its  increased  or 
diminished  rate  of  movement  in  the  spinal  cord.  Thus  a  motor  impulse, 
which  calls  into  action  the  interosseous  muscles  of  the  hand,  passes 
through  the  cervical  portion  of  the  spinal  cord,  and  thence  through  the 
lower  cervical  nerves,  the  brachial  plexus^  and  the  whole  length  of  the 
ulnar  nerve.  An  impulse  which  excites  contraction  in  the  quadriceps 
extensor  cruris  passes  through  both  the  cervical  and  dorsal  portions  of 


430  NERVOUS    IRRITABILITY 

the  spinal  cord,  and  thence  through  the  lumbar  plexus  and  the  anterior 
crural  nerve  to  the  thigh.  Consequently  its  transit  through  the  spinal 
cord  is  about  three  times  as  long  in  the  second  instance  as  in  the  tirst ; 
and  its  amount  of  retardation  will  indicate  the  rate  of  transmission  in 
the  spinal  cord  as  compared  with  that  in  the  nerves. 

By  this  means  it  was  found  that  the  transmission  of  voluntary  motor 
impulses  in  the  spinal  cord  is  considerably  slower  than  in  the  nerves. 
Its  average  rapidity  was  a  little  over  10  metres  per  second ;  the  mini- 
mum being  8,  the  maximum  14  metres.  Thus  the  difference  in  rapidity 
of  transmission  through  the  nerves  and  the  spinal  cord  becomes  very 
manifest. 

TRANSMISSION  OF  VOLUNTARY  MOTOR  IMPULSES. 
Through  the  spinal  cord       .         .         .         .10  metres  per  second. 
"  "       nerves    .         .         .         .     27      " 

A  comparison  of  observations  on  the  two  opposite  sides  of  the  body 
gave  a  difference  in  the  rate  of  transmission,  for  the  right  and  left 
lateral  halves  of  the  spinal  cord,  of  from  1  to  3  metres  per  second, 
always  in  favor  of  the  left  side. 

The  transmission  of  sensitive  impressions  through  the  spinal  cord, 
on  the  other  hand,  was  found  to  be  nearly  as  rapid  as  through  the 
nerves,  the  average  rate  being  a  little  over  42  metres  per  second.  A 
remarkable  difference,  however,  appeared  in  the  transmission  of  simple 
tactile  impressions  and  of  those  which  were  painful  in  character.  The 
former  are  comparatively  rapid,  as  above  stated,  while  painful  impres- 
sions are  communicated  through  the  spinal  cord  at  a  much  slower  rate, 
amounting  on  the  average  to  not  more  than  13  metres  per  second. 
Thus  the  transmission  of  motor  impulses  and  of  tactile  and  painful 
impressions  respectively,  through  the  spinal  cord,  is  as  follows : 

RATE  OF  TRANSMISSION  THROUGH  THE  SPINAL  CORD. 
For  tactile  impressions          .         .         .         .42  metres  per  second. 

"    painful  13      " 

"    motor  impulses        ...  .     10      " 

According  to  these  results  the  passage  of  a  motor  impulse,  from  the 
brain  to  the  muscles  of  the  foot,  would  occupy  0.088  of  a  second ;  of 
which  time  about  one-half  would  be  required  for  transmission  through 
the  spinal  cord,  and  one-half  for  transmission  through  the  fibres  of  the 
sciatic  nerve. 

Rapidity  of  Nervous  Action  in  the  Brain. — In  all  the  experiments 
detailed  above,  an  essential  part  of  the  nervous  operation  consists  in 
the  hearing  of  the  signal  for  a  voluntary  movement  and  in  the  act  of 
volition  which  sets  in  motion  the  voluntary  impulse.  This  process, 
which  takes  place  in  the  brain,  includes  both  the  action  of  the  gray 
substance  of  the  nervous  centres  and  its  transmission  b}r  the  nerve 
fibres  of  the  white  substance  to  the  origin  of  the  spinal  cord.  The  time 
thus  consumed  is  ascertained  by  deducting,  from  the  whole  period 
intervening  between  the  signal  given  and  the  contraction  of  the  muscle, 


AND    ITS    MODE    OF    ACTION.  431 

first,  the  time  requisite  for  the  mechanism  of  muscular  contraction, 
namely,  0.0 1",  and,  secondly,  that  occupied  in  the  transmission  of  the 
impulse  through  the  spinal  cord  and  nerves.  Thus  if  the  entire  period 
be  0.220",  and  the  time  required  for  transmission  through  the  spinal 
cord  and  nerves  be  0.088",  there  remains  0.132",  which  is  occupied  in 
muscular  contraction  and  in  the  acts  of  sensation  and  volition.  Burck- 
hardt's  experiments,  like  those  of  Ilelmholtz,  fix  the  time  required  for 
local  stimulation  of  the  muscle  at  0.01"  ;  and  he  estimates  that  about 
an  equal  interval  is  necessary  for  the  mechanism  of  hearing  in  the 
external,  middle,  and  internal  parts  of  the  ear.  The  whole  process, 
therefore,  of  executing  a  voluntary  movement  in  the  foot,  at  the  signal 
given  by  a  bell,  would  be  divided  in  time  as  follows : 

TIME  OCCUPIED  IN  EXECUTING  A  VOLUNTARY  MOVEMENT  AT  A  GIVEN  SIGNAL. 

Mechanism  of  hearing 0.010" 

Acts  of  perception  and  volition  in  the  brain         .         .         .     0.112" 
Transmission  through  the  spinal  cord  .         .  .         .     0.044" 

Transmission  through  the  sciatic  nerve        ....     0.044" 
Mechanism  of  muscular  contraction      .....     0.010" 


0.220" 

It  appears  that  the  nervous  action  in  the  brain,  which  represents  the 
operation  of  the  gray  substance  of  the  nervous  centres,  requires  a  con- 
siderably longer  time  than  the  transmission  of  a  nervous  impulse  through 
the  nerve  fibres. 

The  physiological  variation  in  rapidity  of  any  or  all  the  nervous 
actions  above  enumerated,  in  different  individuals,  causes  a  difference 
in  the  promptitude  with  which  sensible  phenomena  are  perceived  and 
recorded  by  different  observers.  This  fact  was  first  distinctly  noticed 
in  astronomical  observations,  where  it  was  found  that  the  exact  time 
of  the  passage  of  a  star  across  the  thread  of  a  transit  instrument  was 
differently  recorded  by  different  observers  ;  this  variation  in  some  cases 
amounting  to  as  much  as  one  second.  Subsequent  observations  showed 
that  in  no  case  was  the  time  of  the  transit  recorded  with  absolute 
accuracy ;  but  that  a  certain  delay  always  intervened,  due  to  the  time 
necessarily  occupied  by  the  nervous  mechanism  of  the  observer.  This 
fact  was  established  by  imitating  the  transit  of  a  star  by  means  of  a 
single  luminous  point  moving  in  a  circle  with  uniform  velocity  before 
the  field  of  a  telescope.  By  contrivances  similar  to  those  described 
above,  the  real  instant  of  the  passage  of  this  luminous  point  across  the 
thread  of  the  telescope  field  was  recorded  upon  a  revolving  cylinder, 
and  the  observer  also  marked  its  passage  by  similar  means.  The 
difference  between  the  real  and  the  observed  time  represented  the 
"  personal  error"  of  the  observer.  The  amount  of  this  error,  however, 
although  it  varies  for  different  persons,  is  constant,  or  nearly  so,  for  the 
same  individual ;  and,  when  it  has  been  once  ascertained,  the  results  of 
observation  may  be  so  corrected  as  to  r.pproach  nearly  to  absolute 
precision. 


CHAPTEE  III. 

GENERAL  ARRANGEMENT  OF  THE  VARIOUS 
PARTS  OF  THE  NERVOUS  SYSTEM. 

IN  man  and  the  vertebrate  animals  the  nervous  system  may  be  divided 
into  two  secondary  systems,  or  groups  of  nervous  centres  with  their 
commissural  fibres  and  nerves.  These  are,  first,  the  ganglionic  or  sym- 
pathetic, and  secondly,  the  cerebro-spinal  system. 

Ganglionic  System. — The  ganglionic  or  "sympathetic"  system  oc- 
cupies mainly  the  great  cavities  of  the  body.  It  is  connected  by  its 
nervous  branches  and  ramifications  with  the  internal  organs  concerned 
in  the  functions  of  nutrition,  and  more  especially  with  the  heart  and 
bloodvessels,  which  it  follows  throughout  their  peripheral  distribution. 
Its  especial  anatomical  character  consists  in  its  being  composed  of  numer- 
ous separate  masses  or  collections  of  gray  matter,  of  small  size  and 
rounded  form,  called  "ganglia;"  from  which  circumstance  the  whole 
ganglionic  system  takes  its  name.  These  ganglia,  connected  with  each 
other  by  slender  nervous  filaments,  form  a  double  chain  of  distinct  but 
associated  nervous  centres,  situated  in  front  of  the  spinal  column 
throughout  the  neck  and  thorax ;  while  in  the  abdomen  they  are  at 
certain  points  fused  together  into  larger  and  more  irregularly  shaped 
masses  upon  the  median  line.  There  are  also  scattered  ganglia  about 
the  head,  outside  the  cranial  cavity ;  and  everywhere  the  ganglia  or 
their  nerves  receive  some  fibres  of  communication  from  the  other  divi- 
sion of  the  nervous  system.  The  scattered  arrangement  of  the  sym- 
pathetic ganglia,  and  their  deep  situation  among  the  thoracic  and 
abdominal  organs,  have  hitherto  prevented  a  complete  investigation  of 
their  functions ;  and  it  is  doubtful  how  far  any  one  portion  exercises  a 
central  or  controlling  influence  over  the  remainder. 

Cerebro- Spinal  System. — The  cerebro-spinal  system,  as  its  name  indi- 
cates, is  made  up  of  the  brain  and  spinal  cord  as  the  great  nervous  cen- 
tres, with  the  nerves  which  originate  from  them  and  which  are  distributed 
to  the  voluntary  muscles  and  integument,  the  organs  of  special  sense, 
and  the  commencement  and  termination  of  the  internal  passages  of 
the  body.  It  is  especially  distinguished  by  the  fact  that  its  deposits  of 
gray  substance,  instead  of  being  distributed  in  separate  nodules  as  in 
the  ganglionic  system,  are  collected  into  two  principal  continuous  masses, 
the  brain  and  the  spinal  cord,  occupying  the  cranial  and  spinal  cavities, 
where  they  are  enveloped  and  connected  by  tracts  of  white  substance, 
which  often  conceal  in  an  external  view  the  divisions  between  them. 

The  cerebro-spinal  nervous  system  is  also  distinguished  by  a  nearly 
(  432  ) 


GENERAL    ARRANGEMENT    OF    NERVOUS    SYSTEM.      433 


Fig.  147. 


complete  symmetry  of  arrangement.  The  internal  abdominal  organs 
are  in  great  measure  unsymmetrical,  and  the  corresponding  nerves  and 
nervous  centres  of  the  ganglionic  S3'stem  present  the  same  want  of 
regularity  in  their  locality  and  distribution.  But  while  the  ganglionic 
system  presides  over  the  internal  organs  and 
functions  of  nutrition,  the  cerebro-spinal  sys- 
tem, on  the  other  hand,  is  connected  with  the 
apparatus  of  animal  life,  namely,  the  organs 
of  sensation  and  movement  by  which  the 
living  body  is  brought  into  relation  with  the 
exterior.  As  these  organs,  in  man  and  the 
vertebrate  animals,  are  symmetrically  ar- 
ranged, tlie  cerebro-spinal  nervous  system 
presents  the  same  character.  Both  the  brain 
and  the  spinal  cord  are  composed  of  two, 
right  and  left,  lateral  halves ;  each  one  of 
which  furnishes  the  nerves  of  sensation  and 
motion  to  the  corresponding  sides  of  the 
body. 

Another  striking  peculiarity  of  this  part 
of  the  nervous  system  is  the  mutual  decus- 
sation  of  the  nerve  fibres  belonging  to  its 
two  sides.  Both  the  brain  and  spinal  cord 
have  their  right  and  left  halves  connected 
by  fibres  which  pass  across  the  median  line 
from  one  to  the  other ;  the  different  bundles 
being  often  interwoven  with  eacli  other,  at 
the  point  of  transit,  in  a  somewhat  compli- 
cated manner.  This  peculiarity  extends  to 
the  origins  of  the  nerves,  which  decussate 
with  each  other  internally  ;  so  that  the  nerve 
fibres  emerging  from  the  right  side  of  the 
cerebro-spinal  mass  have  their  origin  from 
the  gray  substance  of  the  left  lateral  half, 
and  those  emerging  from  the  left  side  origi- 
nate from  the  gray  substance  of  the  right 
lateral  half.  The  only  uncertainty  in  this 
respect  is  whether  the  decussation  be  com- 
plete or  partial;  that  is,  whether  all  the 
fibres  of  a  given  nerve  root  be  connected 
with  the  opposite  side  of  the  central  mass,  or 
whether  a  part  of  them  originate  from  the 
same  and  a  part  from  the  opposite  side.  The  decussating  fibres,  in  a 
large  number  of  instances,  are  anatomically  demonstrated.  In  some 
remaining  exceptions  their  course  is  more  or  less  a  matter  of  doubt. 

The  Spinal  Cord  is  a  nearly  cylindrical  nervous  mass,  inclosed  in  the 
cavity  of  the  spinal  canal,  commencing  by  a  slightly  enlarged  extremity 


THE  BRAIN  AND  SPINAL 
CORD,  in  profile. 


434  GENEKAL    ARKANGEMENT    OP 

at  the  brain  above,  and  terminating  below  in  a  conical  point  at  the  level 
of  the  first  lumbar  vertebra.  Its  inner  portions  are  occupied  by  gray 
substance,  which  forms  a  continuous  chain  of  ganglionic  matter,  run- 
ning from  one  extremity  of  the  cord  to  the  other.  Its  outer  portions 
are  composed  of  white  substance,  the  fibres  of  which  run  mainly  in  a 
longitudinal  direction,  connecting  its  different  parts  with  each  other, 
and  forming  a  communication  between  it  and  the  brain. 

The  spinal  nerves  are  given  off  from  the  cord  at  regular  intervals 
and  in  symmetrical  pairs ;  one  pair  for  each  successive  portion  of  the 
^  body,  their  branches  being  distributed  to  the  integument  and  muscles 
of  the  corresponding  regions.  In  fish  and  serpents,  where  locomotion 
is  performed  by  means  of  simple,  alternating,  lateral  movements  of  the 
spinal  column,  the  cord  is  nearly  or  quite  uniform  in  size;  or  tapers 
gradually  from  its  anterior  to  its  posterior  extremity.  But  in  the  other 
vertebrate  classes,  where  the  body  is  provided  with  special  organs  of 
locomotion  as  fore  and  hind  limbs,  or  wings  and  legs,  the  cord  is  in- 
creased in  size  where  the  nerves  of  these  organs  are  given  off;  and  the 
nerves  supplying  the  limbs  are  larger  than  those  which  originate 
from  other  parts  of  the  cord.  In  man,  the  lower  cervical  nerves, 
which  form  the  brachial  plexus  and  supply  the  arms,  and  the  sacral 
nerves  forming  the  sacral  plexus,  which  supplies  the  legs,  are  larger 
than  those  given  off  in  the  upper  cervical,  dorsal,  and  lumbar  regions. 
The  cord  itself,  furthermore,  presents  two  marked  enlargements  cor- 
responding with  the  points  of  origin  of  these  nerves,  namely,  the  cervical 
enlargement,  which  is  the  source  of  the  nerves  for  the  upper  extremity, 
and  the  lumbar  enlargement,  which  gives  off  the  nerves  destined  for  the 
lower  extremity. 

A  transverse  section  of  the  spinal  cord  shows  that  it  is  incompletely 
divided  into  right  and  left  lateral  halves  by  an  anterior  and  posterior 

median   fissure ;    of  which   the 

Fig.  148.  anterior  is  the  wider  and  pene- 

trates for  a  comparatively  short 
distance,  while  the  posterior  is 
narrower  but  extends  inward 
nearly  or  quite  to  the  centre  of 
the  cord.  The  gray  substance 
in  the  interior  of  the  cord  forms 
a  double  crescentic-shaped  mass, 
writh  the  concavities  of  the 
crescents  turned  outward.  As 
TRANSVERSE  SECTION  OP  THE  SPINAL  these  masses  are  found  at  all 

CORD,  showing    its  central   mass  of   gray  sub-  tg    of  the  CQrd    they  haye  in 

Btance,  and  the  roots  of  the  spinal  nerves.— a,  b. 

Spinal  nerves  of  right  and  left  sides,  d.  Origin  of  reality  the  form  of  elongated 
anterior  root.  e.  Origin  of  posterior  root.  c.  ribbons  or  bands  of  gray  sub_ 
Ganglion  of  posterior  root. 

stance,  one  on  each  side,  run- 
ning continuously  throughout  the  length  of  the  cord.  The  two  are 
united  with  each  other  by  a  transverse  band  of  gray  substance,  known 


THE    NEKVOUS    SYSTEM.  435 

as  the  "gray  commissure,"  in  the  centre  of  which  is  a  narrow  longi- 
tudinal canal,  the  "  central  canal,"  but  little  over  0.2  millimetre  in  di- 
ameter, and  lined  internally  with  epithelium. 

The  anterior  and  posterior  portions  of  gray  substance,  in  each  lateral 
half  of  the  cord,  are  called  the  anterior  and  posterior  horns.  Imme- 
diately in  front  of  the  gray  commissure  is  a  transverse  band  of  white 
substance,  the  "  white  commissure"  of  the  cord. 

The  spinal  nerves  originate  from  the  cord  on  each  side  by  two  dis- 
tinct sets  of  fibres,  forming  the  anterior  and  posterior  roots.  The 
anterior  root  (Fig.  148,  d)  passes  out  from  the  surface  of  the  cord  near 
the  extremity  of  the  anterior  horn  of  gray  matter.  The  posterior  root 
(e)  originates  at  a  point  corresponding  with  the  posterior  horn  of  gray 
matter.  Both  roots  are  composed  of  a  considerable  number  of  fibres, 
united  with  each  other  in  parallel  bundles.  The  posterior  root  is  dis- 
tinguished from  the  anterior  by  the  presence  of  a  small  rounded  mass 
of  gray  matter,  or  ganglion,  with  which  it  is  incorporated  and  through 
which  its  fibres  pass.  The  two  roots  unite  with  each  other  soon  after 
leaving  the  cavity  of  the  spinal  canal,  and  mingle  their  fibres  in  a  common 
trunk. 

The  white  substance  of  each  lateral  half  of  the  spinal  cord  is  thus 
divided  into  three  portions  or  "  columns ;"  so  called  because  the  nerve 
fibres  composing  them  run,  for  the  most  part,  parallel  with  each  other, 
in  a  longitudinal  or  vertical  direction.  The  portion  which  is  included 
between  the  anterior  median  fissure  and  the  origin  of  the  anterior  nerve 
roots  is  the  anterior  column  ;  that  between  the  anterior  and  posterior 
nerve  roots  is  the  lateral  column;  while  that  between  the  posterior 
nerve  roots  and  the  posterior  median  fissure  is  the  posterior  column. 
As  the  posterior  median  fissure  penetrates  deeply  into  the  substance  of 
the  cord,  quite  down  to  the  gray  substance,  the  posterior  columns  ap- 
pear entirely  separated  from  each  other  in  a  transverse  section ;  but  the 
anterior  median  fissure  is  more  shallow  and  stops  short  of  the  gray 
matter,  so  that  the  anterior  columns  are  connected  with  each  other  by 
the  white  commissure  above  mentioned. 

The  brain,  or  "encephalon,"  is  that  portion  of  the  cerebro-spinal 
system  contained  in  the  cranial  cavity.  It  forms  a  more  or  less 
rounded  mass  of  nervous  matter,  consisting,  as  in  the  spinal  cord,  of 
right  and  left  lateral  halves  which  remain  connected  with  each  other  by 
their  central  parts.  In  man  and  the  higher  vertebrate  animals,  it  pre- 
sents, above  and  behind,  two  principal  divisions,  namely,  the  cerebrum 
and  cerebellum,  which  are  composed  externally  of  a  convoluted  layer  of 
gray  substance,  these  two  divisions  together  forming  at  least  nineteen- 
twentieths  of  the  whole  encephalon ;  while  beneath  them  is  a  smaller 
portion  composed  externally  of  white  substance,  like  the  spinal  cord,  and 
forming  the  communication  between  the  cord  below  and  the  brain  above. 
This  inferior  portion  is  called  the  "isthmus,"  and  comprehends  the 
medulla  oblongata,  the  tuber  annulare,  and  the  peduncles  of  the  cere- 
brum. Beside,  however,  the  portion  visible  externally,  there  are,  in 


436 


GENERAL    ARRANGEMENT    OF 


Fig.  149. 


each  of  these  divisions,  various  deep-seated  deposits  of  gray  substance, 
which  are  concealed  by  the  overlying  parts. 

The  construction  of  the  brain,  as  a  whole,  may  therefore  be  represented 
by  considering  it  as  a  double  series  of  nervous  centres  or  deposits  of 
gray  substance,  of  varying  size  and  position,  connected  with  each  other 
and  with  the  spinal  cord  by  transverse  and  longitudinal  tracts  of  white 
substance.  The  number  and  relative  importance  of  these  nervous 
centres,  in  different  kinds  of  animals,  depend  upon  the  perfection  of  the 
bodily  organization  in  general,  and  more  especially  upon  the  develop- 
ment of  the  functions  and  capacities  connected  with  particular  parts  of 
the  nervous  system.  In  the  inferior  classes,  as  fish  and  reptiles,  the 
brain  is  more  simple  in  its  anatomical  characters  ;  while  it  becomes  suc- 
cessively more  complicated  in  birds,  quadrupeds,  and  man. 

In  fish  and  reptiles  the  different  nervous  centres  of  the  brain  are  so 
distinctly  separated,  and  of  such  moderate  size,  that  they  are  frequently 
designated  as  "  ganglia."  In  the  brain  of  the  alligator  (Fig.  149)  there 
are  five  pairs  of  these  ganglia,  arranged  one  behind  the  other  in  the 
cavity  of  the  cranium.  The  first  of  these  are  two  rounded  masses  ( a ), 

lying  just  above  and  behind  the  nasal  cavi- 
ties, which  distribute  their  nerves  upon  the 
olfactory  membrane.  These  are  the  olfac- 
tory ganglia.  They  are  connected  with  the 
rest  of  the  brain  by  two  long  and  slender 
commissures,  the  "  olfactory  commissures." 
The  next  pair(3)  are  somewhat  larger  and 
of  a  triangular  shape,  when  viewed  from 
above  downward.  They  are  termed  the 
u  hemispherical  ganglia,"  or  the  hemispheres, 
and  correspond  to  the  "  cerebrum"  in  the 
higher  classes.  Immediately  following  them 
are  two  quadrangular  masses  (3)  which  give 
origin  to  the  optic  nerves,  and  are  therefore 
called  the  optic  ganglia.  They  are  termed 
also  the  "  optic  tubercles ;"  and  in  some  of 
the  higher  animals,  where  they  present  an 
imperfect  division  into  four  nearly  equal 
parts,  they  are  known  as  the  "tubercula 
quadrigemina."  Behind  them  is  a  single  tri- 
angular collection  of  nervous  matter  (4),  the 
cerebellum.  Finally,  the  upper  portion  of  the  cord,  just  behind  and 
beneath  the  cerebellum,  is  seen  to  be  enlarged  and  spread  out  laterally, 
so  as  to  form  a  broad  oblong  mass(5),  the  medulla  oblongata.  It  is 
from  this  latter  portion  of  the  brain  that  the  pneumogastric  or  respira- 
tory nerves  originate,  and  its  ganglia  are  therefore  sometimes  termed 
the  "  pneumogastric"  or  "  respiratory"  ganglia. 

It  will  be  seen  that  the  posterior  columns  of  the  cord,  as  they  diverge 
laterally,  to  form  the  medulla  oblongata,  leave  between  them  an  open 


BRAIN  OF 
1.  Olfactory  ganglia.  2.  Hemi- 
spheres. 3.  Optic  tubercles.  4. 
Cerebellum.  5.  Medulla  oblon- 
gata. 


THE    NERVOUS    SYSTEM. 


437 


Fig.  150. 


BUAIN  OF  PIGEON  — Profile  view.— 
1.  Cerebrum.  2.  Optic  tubercle.  3.  Ce- 
rebellum. 4.  Optic  nerve.  6.  Medulla 
oblongata. 


space,  which  is  continuous  with  the  posterior  median  fissure  of  the 
cord.  This  space  is  known  as  the  "  fourth  ventricle."  It  is  partially 
covered  in  by  the  backward  projection  of  the  cerebellum,  but  in  the 
alligator  is  still  somewhat  open  posteriorly,  presenting  a  kind  of  chasm 
or  gap  between  the  two  lateral  halves  of  the  medulla  oblongata. 

The  successive  ganglia  which  compose  the  brain,  being  arranged  in 
pairs  as  above  described,  are  separated  from  each  other  on  the  two 
sides  by  a  longitudinal  median  fissure,  which  is  continuous  with  the 
posterior  median  fissure  of  the  spinal  cord.  In  the  brain  of  the  alligator 
this  fissure  appears  to  be  interrupted  at  the  cerebellum ;  but  this  is  due 
to  the  incomplete  development  of  the 
lateral  portions  of  this  organ,  as  com- 
pared with  its  middle.  The  same  pe- 
culiarity is  to  be  seen  in  birds  and  in 
most  quadrupeds ;  while  in  man  the 
lateral  portions  of  the  cerebellum  are 
so  highly  developed  as  to  project,  on 
each  side,  above  the  level  of  its  central 
part,  and  the  longitudinal  median  fis- 
sure, accordingly,  appears  complete 
throughout. 

In  birds  the  hemispheres,  or  cere- 
brum, are  of  comparatively  larger  size,  and  partially  or  completely  con- 
ceal the  optic  tubercles  in  a  view  taken  from  above.     The  cerebellum  is 
well  developed  in  this  class,  and  presents  on  its  surface  a  number  of 
transverse    foldings    or   convolutions 
by  which  its  gray  substance  is  con- 
siderably increased  in  quantity.     The 
cerebellum  extends  so  far  backward  as 
to  completely  cover  the  medulla  ob- 
longata and  the  fourth  ventricle. 

In  quadrupeds  the  cerebrum  and 
the  cerebellum  attain  a  still  greater 
size  as  compared  with  the  remain- 
ing parts  of  the  brain.  There  are 
also  two  other  collections  of  gray 
substance  on  each  side,  situated  in  the 
inferior  part  of  the  hemispheres,  ante- 
riorly to  the  tubercula  quadrigemina. 
These  are  the  "corpora  striata"  in 
front,  and  the  "  optic  thalami"  behind. 
These  bodies  are  frequently  designated 
by  the  name  of  the  "  cerebral  gan- 
glia," Since  they  are  collections  of  BRAIN  OF  RABBIT,  viewed  f.-om 
,,  ...  above.— 1.  Olfactory  ganglia.  2.  Hemi- 

gray    matter  Which   OCCUpy   the   lower      spheres  of   the  cerebrum,  turned  aside. 

and  central  parts  of  the  cerebrum,  and     3   CorP°ra  striata.     4   Optic  thaiimi. 

,  5.  Tubercula  quadrigemina.     6.  Cerebei- 

intervene  between  the  tracts  of  white     ium. 


Fig.  151. 


438  GENERAL    ARRANGEMENT    OF 

substance,  coming  up  from  below,  and  those  which  continue  upward  to 
the  convolutions  of  the  hemispheres.  The  cerebellum,  in  the  quadru- 
peds, is  somewhat  enlarged  by  the  increased  development  of  its  lateral 
portions,  and  shows  an  abundance  of  transverse  convolutions.  It  con- 
ceals from  view  the  fourth  ventricle  and  the  greater  part  of  the  medulla 
oblongata. 

In  the  more  highly  developed  quadrupeds,  the  cerebral  hemispheres 
increase  in  size  so  as  to  cover  more  or  less  completely  the  olfactory 
ganglia  in  front  and  the  cerebellum  behind.  Their  surface  also  becomes 
covered  with  numerous  convolutions,  which  are  mainly  longitudinal  or 
curvilinear  in  direction,  instead  of  being  transverse  as  in  the  cere- 
bellum. 

In  Man  the  development  of  the  cerebral  hemispheres  reaches  its 
highest  point,  so  that  they  preponderate  completely  over  all  the  other 
nervous  centres  in  the  cranial  cavity.  In  the  human  brain,  accord- 
ingly, when  viewed  from  above,  there  is  nothing  to  be  seen  but  the 
convex  convoluted  surface  of  the  hemispheres ;  and  even  in  a  posterior 
view  they  conceal  everything  but  a  portion  of  the  cerebellum.  The 
remaining  parts,  which  are  concealed  by  the  cerebrum  and  cerebellum, 
participate,  however,  in  the  structure  of  the  entire  encephalon,  and 
form,  as  in  the  lower  animals,  a  series  of  associated  nervous  centres  and 
connecting  tracts  of  nerve  fibres. 

As  the  spinal  cord  passes  upward  into  the  cranial  cavity,  it  enlarges, 
by  a  kind  of  lateral  expansion,  to  form  the  medulla  oblongata.  This 
portion  of  the  cerebro-spinal  axis  is  distinguished  from  the  cord  below, 
not  only  by  its  external  form,  but  also  by  the  somewhat  different 
arrangement  of  its  gray  and  white  substance.  The  gray  substance, 
which  in  the  cord  presents  on  each  side,  in  front  and  rear,  the  pro- 
jections of  the  anterior  and  posterior  horns,  recedes,  in  the  medulla 
oblongata,  more  and  more  in  a  backward  direction,  and  becomes  accu- 
mulated in  a  nearly  single  mass  at  its  posterior  surface.  At  the  same 
time,  the  masses  of  white  substance  on  each  side  of  the  posterior  median 
fissure,  which  in  the  cord  are  called  the  "  posterior  columns,"  diverge 
from  each  other  at  an  acute  angle,  leaving  between  them  the  space  of 
the  fourth  ventricle,  and  assume  the  name  of  the  resitform  bodies. 
They  become  continuous  with  the  inferior  peduncles  of  the  cerebellum, 
and  send  some  of  their  fibres,  in  a  radiating  direction,  into  the  white 
substance  of  the  cerebellum,  to  terminate  in  the  gray  substance  of  its 
convolutions.  The  floor  of  the  fourth  ventricle,  thus  exposed  by  the 
divergence  of  the  posterior  columns,  is  formed  by  the  graj7  substance 
of  the  medulla  oblongata,  which  is  accordingly  continuous  with  that  of 
the  cord,  although  it  has  a  different  position  and  a  different  form. 

Yiewed  in  front,  the  medulla  oblongata  presents  two  longitudinal 
eminences  of  white  substance,  one  on  each  side  of  the  median  line,  the 
anterior  pyramids,  which  take  the  place  of  the  anterior  columns  of  the 
cord.  At  their  commencement  below,  the  anterior  pyramids  are  narrow, 
but  grow  wider  as  they  ascend.  At  their  lower  portion  they  exhibit  a 


THE    NERVOUS    SYSTEM. 


439- 


remarkable  decuxsation,  easily  seen  by  gently  separating  the  sides  of 
the  anterior  median  fissure,  formed  by  distinct  bundles  of  white  sub- 
stance crossing  the  median  line  obliquely,  from  below  upward  and  from 
side  to  side.  Thus  the  right  anterior  pyramid  is  formed  of  fibres  which 
come  from  the  left  side  of  the  cord,  and  the  left  anterior  pyramid  of 
those  which  come  from  the  right  side  of  the  cord. 

Fig.  152. 


MEDULLA  OBLONGATA  AND  BASE  OF  THB  BRAIN  IN  MAN— Anterior  view.— 
1.  Decussation  of  the  optic  nerves.  2,2.  Middle  lobes  of  the  cerebrum.  3,  3.  (Jrura  cerebri. 
4.  Tuber  annulare.  5,6.  Lateral  lobos  of  the  cerebellum.  6.  Anterior  pyramid.  7.  Olivary 
body.  8.  Eestiform  body.  (Hirschfeld.) 

Immediate!}7'  outside  of  the  pyramids,  in  a  lateral  direction,  are  two 
elongated  oval  masses,  the  olivary  bodies,  whicli  consist  externally  of 
white  substance,  but  internally  contain  each  a  distinct  thin  convoluted 
layer  of  gray  substance,  resembling  in  miniature  the  convolutions  of  the 
cerebrum.  The  olivary  bodies  are,  therefore,  special  deposits  of  gray 
substance  in  the  anterior  portion  of  the  medulla  oblongata,  superadded 
to  the  rest  and  not  continuous  with  that  of  the  spinal  cord. 

At  the  upper  limit  of  the  medulla  oblongata  is  the  tuber  annulare,  so 
called  because  it  forms  a  ring-like  protuberance  at  this  part  of  the  base 
)f  the  brain.  Superficially,  when  viewed  in  front,  it  consists  of  trans- 
verse bundles  of  white  substance,  containing  fibres  passing  over,  in  an 
arched  form,  from  one  side  of  the  cerebellum  to  the  other,  and  decus- 
sating with  each  other  at  the  median  line.  Where  they  cross  the  tuber  annu- 
lare  these  fibres  constitute  the  "  pons  Varolii ;"  at  the  two  sides,  where 
they  pass  backward  to  the  cerebellum,  they  form  the  "  middle  peduncles 
)f  the  cerebellum." 


440 


GENERAL    ARRANGEMENT    OF 


Fig.  153. 


In  its  deeper  parts,  the  tuber  annulare  contains  longitudinal  tracts  of 
white  substance,  passing  upward  from  the  medulla  oblongata  toward 
the  cerebrum.  The  continuation  of  the  anterior  pyramids  in  front,  and 
the  remainder  of  the  longitudinal  bundles  of  the  medulla  oblongata 
behind,  pass  into  and  through  the  substance  of  the  tuber  annulare,  where 
they  are  mingled  with  an  irregular  diffused  deposit  of  gray  substance. 

From  the  upper  border  of  the  tuber  annu- 
lare, the  longitudinal  tracts  of  white  sub- 
stance emerge  in  the  form  of  two  thick, 
obliquely  diverging,  bundles  of  nerve  fibres, 
the  crura  cerebri,  or  peduncles  of  the  brain. 
They  are  joined  posteriorly  by  other  longi- 
tudinal bundles  coming  from  the  cerebellum, 
known  as  the  "anterior  peduncles  of  the 
cerebellum*"  which  are  the  organs  of  com- 
munication between  the  cerebellum  and  the 
cerebrum.  The  fibres  of  the  crura  cerebri, 
thus  constituted,  then  plunge  into  the  sub- 
stance of  the  two  collections  of  gray  matter 
known  as  the  "  cerebral  ganglia,"  namely, 
the  corpora  striata  and  optic  thalami ;  thus 
making  a  connection  between  these  ganglia 
and  the  medulla  oblongata  and  spinal  cord 
below. 

Finally,  from  the  outer  and  upper  por- 
tions of  the  cerebral  ganglia,  the  nerve  fibres 
of  the  white  substance  radiate  in  all  direc- 
tions, following  a  more  or  less  curvilinear 
course  from  within  outward,  until  they  reach 
the  gray  substance  of  the  convolutions  at 
the  surface  of  the  hemispheres.  The  cere- 
bral convolutions  of  the  two  sides  are  also 
united  by  the  transverse  fibres  of  the  cor- 
pus callosum. 

The  entire  brain  may,  therefore,  be  con- 
sidered as  a  symmetrical  series  of  nervous  centres  connected  with  each 
other  and  with  the  spinal  cord  by  longitudinal  tracts  of  white  substance. 
They  occur  in  the  following  order :  1.  The  olfactory  lobes,  of  small  size 
and  concealed  beneath  the  anterior  portion  of  the  brain ;  2.  The  cerebral 
hemispheres,  surrounding  and  covering  the  remaining  parts  by  their 
lateral  and  posterior  extension;  3.  The  corpora  striata,  4.  The  optic 
thalami,  and  5.  The  tubercula  quadrigemina,  occupying  the  central  por- 
tion of  the  base  of  the  cerebrum,  and  resting  upon  6,  the  crura  cerebri; 
Y.  The  tuber  annulare ;  8.  The  cerebellum,  and  9.  The  medulla  oblon- 
gata. Of  the  collections  of  gray  substance  just  enumerated,  the  cere- 
brum and  cerebellum  only  are  convoluted  externally,  the  others  being 


MEDTTLLA  OBLONGATA, 
TUBER  ANNTJLAEK,  AND 
CRURA  CEREBRI.— The  super- 
ficial and  deep  transverse  fibres 
of  the  tuber  annulare  have  been 
cut  away,  showing  the  continua- 
tion of  the  longitudinal  fibres  in 
its  interior.  1.  Decussation  of  the 
optic  nerves.  2.  Crus  cerebri.  3. 
Lateral  portion  of  the  pons  Va- 
rolii.  4.  Anterior  pyramid.  5.  Oli- 
vary body.  (Hirschfeld.) 


either  smooth  and  rounded  or  irregular  in  form. 


THE    NERVOUS    SYSTEM.  441 

It  is  not  to  be  supposed  that  the  nervous  communications  between 
the  successive  deposits  of  gray  matter  are  necessarily  of  so  simple  a 
character  as  those  represented  in  Fig.  154.  This  is  only  a  diagram, 
representing  the  general  fact  of  the  longitudinal  connection  existing 

Fig.  154. 


DIAGRAMATIC  SECTION  OP  HUMAN  BRA i N  ;  showing  the  situation  of  the  nervous 
centres  and  the  longitudinal  tracts  of  white  substance.— 1,  Olfactory  lobe.  2, 2.  Convolutions 
of  the  cerebral  hemispheres.  3.  Corpus  striatum.  4.  Optic  thalamus.  6.  Tubercula  quadri- 
gemina.  6.  Crura  cerebri.  7.  Tuber  annulare.  8.  Cerebellum.  9.  Medulla  oblongata. 

between  the  spinal  cord  and  the  different  parts  of  the  encephalon.  It 
is  by  no  means  certain  that  all  or  any  of  the  fibres  of  the  cord  run  con- 
tinuously through  the  medulla  oblongata,  the  tuber  annulare,  and  the 
cerebral  ganglia,  to  the  gray  matter  of  the  convolutions.  On  the  con- 
trary, careful  examination  of  successive  microscopic  sections  by  the  best 
observers  have  failed  to  show  such  a  direct  continuity.  It  appears  more 
probable  that  the  fibres  coming  from  the  spinal  cord  terminate  in  the 
medulla  oblongata,  and  that  other  fibres  originating  from  the  gray  matter 
of  the  medulla  pass  upward,  partly  to  the  cerebellum  and  partly  to  the 
corpora  striata  and  optic  thalami ;  while  other  fibres  still,  originating 
from  these  ganglia,  diverge  thence  to  form  the  connection  between  them 
and  the  cerebral  convolutions.  According  to  this  view,  the  longitudinal 
tracts  of  white  substance  consist  of  nerve  fibres  which  are  interrupted 
in  their  course  by  the  nerve  cells  of  different  deposits  of  gray  matter, 
so  that  an  impression  or  impulse  conveyed  from  one  to  the  other  is  not 
the  same  throughout  its  course,  but  is  modified  by  the  action  of  the 
nervous  centres  which  successively  receive  and  transmit  it. 

Each  portion  of  the  cerebro-spinal  axis  has  its  right  and  left  halves 
connected  with  each  other  by  transverse  commissures,  and  sends  out 
nerves,  containing  motor  and  sensitive  fibres,  to  corresponding  regions 
of  the  body.  The  spinal  cord  supplies  the  integument  and  muscles  of 
the  neck,  trunk,  and  extremities.  The  medulla  oblongata  sends  out 
motor  and  sensitive  nerves  to  the  muscles  of  the  head  and  face,  and  to 
the  skin  and  mucous  membranes  of  the  same  region;  while  it  also  sup- 
29 


442      GENERAL    ARRANGEMENT    OF    NERVOUS    SYSTEM. 

plies  nerves  of  a  special  character  to  the  mucous  and  muscular  coats  of 
the  pharynx,  oesophagus,  and  stomach,  and  to  those  of  the  organs  of 
respiration  in  the  neck  and  thorax.  From  the  medulla  oblongata  and 
the  inferior  or  central  parts  of  the  brain,  are  also  supplied  the  nerves 
destined  for  the  organs  of  special  sense. 

In  every  region  of  the  cerebro-spinal  system,  the  two  functions  of 
sensibility  and  motion  are  associated  with  each  other  by  means  of  the 
gray  substance  of  the  nervous  centres.  In  the  spinal  cord  the  gray 
substance  is  continuous  and  of  nearly  the  same  configuration  through- 
out. In  the  different  parts  of  the  brain  it  presents  itself  under  the  form 
of  more  or  less  distinct  deposits,  of  varying  form  and  size.  In  either 
of  these  parts  a  reflex  action  may  take  place  independently  of  those 
beyond,  and  calling  into  operation  the  special  functions  of  the  nervous 
centre  involved.  But  a  nervous  action  may  also  pass  through  the  entire 
series,  by  the  longitudinal  connections  of  the  cord,  medulla  oblongata, 
tuber  annulare,  and  cerebral  ganglia,  and  thence  through  the  radiating 
fibres  of  the  white  substance  to  the  cortical  layer  of  the  cerebral  convo- 
lutions. This  layer  may  be  regarded  as  a  sort  of  concave  mirror,  where 
the  impressions  coming  from  without  are  finally  received  and  reflected, 
in  the  form  of  conscious  sensation  and  intelligent  voluntary  acts ;  the 
whole  nervous  mechanism  of  the  cerebro-spinal  system  being  thus  called 
into  operation  at  the  same  time. 


CHAPTEE  IV. 

THE  SPINAL   COED. 

THE  spinal  cord  is  that  part  of  the  cerebro- spinal  system  which  is 
contained  within  the  spinal  canal,  and  which  sends  its  nerves  to  the 
muscles  and  integument  of  the  trunk  and  limbs.  It  consists  externally 
of  white  substance,  forming  longitudinal  tracts  of  nerve  fibres,  the  con- 
tinuations of  which  make  connection  with  those  of  the  brain  above ;  and 
internally  of  gray  substance  arranged  in  two  symmetrical  bands  occupy- 
ing the  central  portions  of  its  right  and  left  lateral  halves.  It  is  so 
constituted,  therefore,  as  to  act  in  a  double  capacity:  First,  as  an  organ 
of  nervous  communication  between  the  brain  and  the  external  parts ; 
and  secondly,  as  an  independent  nervous  centre,  with  endowments  and 
functions  of  its  own. 

Arrangement  of  Gray  and  White  Substance  in  the  Spinal  Cord, 

The  mutual  relations  of  the  gray  and  white  substance  form  the  neces- 
sary basis  for  a  complete  physiological  anatomy  of  this  part  of  the 
nervous  system.  The  connections  of  the  nerve  fibres  with  the  cells  of 
the  gray  substance  and  with  various  parts  of  the  longitudinal  columns, 
as  well  as  those  of  the  different  nerve  cells  with  each  other,  are  the  most 
important  for  this  purpose.  It  has  not  yet  been  possible  to  make  out 
these  connections  with  certainty  for  all  parts  of  the  cord ;  but  much  has 
been  accomplished  in  this  respect  by  the  examination  of  microscopic 
sections  made  in  various  directions,  after  hardening  the  tissues  of  the 
cord  in  alcohol  or  in  weak  solutions  of  chromic  acid  or  potassium  bichro- 
mate, and  by  making  the  fibres  and  cells  more  distinct  by  means  of 
staining  preparations.  With  regard  to  the  relative  proportions,  in  dif- 
ferent parts  of  the  cord,  of  its  two  constituent  elements,  it  is  evident, 
as  shown  by  Kolliker  and  Gerlach,  that  the  gray  substance  is  increased 
in  quantity  at  the  situation  of  the  cervical  and  lumbar  enlargements, 
and  that  the  white  substance,  on  the  other  hand,  diminishes  gradually, 
from  its  upper  to  its  lower  extremity.  This  fact  corresponds  with  the 
known  physiological  relations  of  the  cord  ;  namely,  that  by  its  gray  sub- 
stance it  acts  as  a  nervous  centre  for  the  corresponding  regions  of  the 
body ;  and  also  that  the  fibres  of  its  white  substance  form  communica- 
tions between  the  parts  above  and  the  spinal  nerves  which  are  given 
off  below. 

The  Or  ay  Substance. — The  gray  substance  in  the  spinal  cord,  as 
elsewhere,  consists  of  a  mixture  of  nerve  cells  and  nerve  fibres,  of  which 
the  nerve  cells  are  the  peculiar  and  distinctive  element.  They  are  all 

(443) 


444 


THE    SPINAL    CORD. 


"  multipolar"  cells ;  that  is,  they  send  out  several  prolongations  in  vari- 
ous directions,  transverse,  longitudinal  and  oblique,  most  of  which  are 
abundantly  subdivided  and  terminate  in  minute  ramifications,  while  a 
single  one  frequently  continues  its  course  for  a  long  distance  undivided, 

Fig.  155. 


TRANSVERSE  SECTION  OF  THE  SPINAL  CORD;  lower  cervical  region. — 1.  Anterior 
median  fissure;  immediately  behind  it  are  seen  the  decussating  fibres  of  the  white  commis- 
sure. 2.  Central  canal,  situated  in  the  middle  of  the  gray  commissure.  3.  Posterior  median 
fissure.  4,  4.  Anterior  columns  of  white  substance.  5,  5.  Posterior  columns.  6,  6.  Lateral 
columns.  7,  7.  Anterior  horns  of  gray  substance.  8,  8.  Posterior  horns.  9,  9.  Anterior 
nerve  roots.  10,  10.  Posterior  nerve  roots. 

and  assumes  the  appearance  of  an  axis  cylinder.  They  vary  in  form 
and  size  in  different  parts  of  the  gray  substance.  The  most  remarkable 
of  these  cells  are  situated  in  the  anterior  horns,  where  they  are  dis- 
tinguished by  their  large  size,  being,  according  to  the  measurements  of 
Kolliker,  from  67  to  135  mmm.  in  diameter,  the  largest  known  cells  in 
the  nervous  system.  They  are  arranged  in  two  or  three  more  or  less 
distinct  groups  near  the  extremity  and  outer  portion  of  the  anterior 
horns.  Beside  these  there  are  found  scattered  everywhere  in  the  gray 
substance,  but  more  abundantly  in  the  posterior  horns,  nerve  cells  which 
are  much  smaller  in  size  than  the  preceding,  but  of  similar  form  and 
provided  with  similar  branching  prolongations.  The  anterior  and  pos- 
terior horns  are  not  therefore  absolutely  distinguished  from  each  other 
by  the  character  of  their  nerve  cells,  but  only  by  the  relative  proportions 
of  their  size  and  numbers ;  since  a  few  cells  of  comparatively  large  size 
are  found  in  the  posterior  horns,  and  the  smaller  ones  exist  in  both 
situations. 


GRAY    AND    WHITE    SUBSTANCE.  445 

The  nerve  fibres  of  the  gray  substance  are,  in  general,  of  much 
smaller  diameter  than  those  of  the  white  substance,  but  otherwise  pre- 
sent the  same  anatomical  characters.  Most  of  them  run  in  a  horizontal 
transverse,  antero-posterior,  or  radiating  direction.  They  consist,  first, 
of  fibres  which  have  penetrated  into  the  gray  substance  from  the  ante- 
rior and  posterior  roots  of  the  spinal  nerves;  secondly,  of  fibres  which 
cross  the  median  line  in  the  gray  commissure,  from  one  side  of  the  cord 
to  the  other,  thus  forming  a  commissural  connection  between  the  two 
lateral  halves  of  the  gray  substance ;  and,  thirdly,  of  fibres  which  run 
in  a  great  variety  of  directions  with  regard  to  each  other,  and  of  which 
the  origin  and  terminations  are  unknown. 

The  White  Substance. — The  white  substance  of  the  spinal  cord  con- 
sists of  nerve  fibres,  the  large  majority  of  which  run  in  a  longitudinal 
direction,  forming  tracts  or  "columns,"  designated,  according  to  their 
situation,  by  the  names  of  the  anterior,  lateral,  and  posterior  columns 
of  the  cord.  In  transverse  sections  of  the  cord  which  have  been  prop- 
erly hardened,  the  longitudinal  fibres  are  readily  distinguished  by  their 
presenting  the  circular  outline  of  a  minute  cylinder  cut  across ;  while 
those  which  are  horizontal  or  oblique  are  seen  in  profile  for  a  longer  or 
shorter  distance  in  the  preparation. 

The  anterior,  lateral,  and  posterior  columns  consist  almost  exclu- 
sively of  longitudinal  fibres.  But  at  the  bottom  of  the  anterior  median 
fissure  there  is  a  band  of  white  substance,  the  fibres  of  which  run  hori- 
zontally across  from  the  inner  portions  of  each  anterior  column  to  the 
opposite  side  of  the  cord.  This  is  called  the  white  commissure  of  the 
cord;  but  the  name  is  not  entirely  appropriate,  since  its  fibres  do  not 
form  a  connection  between  exactly  corresponding  parts  on  the  right  and 
left  sides.  According  to  both  Kolliker  and  Gerlach,  the  fibres  which 
pass  across  at  the  median  line  from  the  right  anterior  column  spread 
out  in  the  gray  substance  of  the  left  anterior  horn ;  and  those  coming 
from  the  left  anterior  column  spread  out  in  the  gray  substance  of  the 
right  anterior  horn.  The  transverse  fibres,  accordingly,  of  the  white 
commissure  connect  the  right  and  left  anterior  columns  respectively 
with  the  gray  substance  of  the  opposite  side  of  the  cord. 

Counting  the  transverse  fibres,  therefore,  of  both  the  gray  and  the 
white  commissures,  it  may  be  said  that  there  is  a  direct  bilateral  con- 
nection, by  means  of  communicating  nerve  fibres,  between  the  right 
and  left  halves  throughout  the  length  of  the  cord ;  but  it  is  not  possible 
to  determine,  with  precision,  the  exact  origin  or  termination  of  the  indi- 
vidual fibres  by  which  this  connection  is  made. 

Connection  of  the  Spinal  Nerve-roots  with  the  Spinal  Cord. — The 
fibres  of  the  anterior  roots  of  the  spinal  nerves  are  distinguished  from 
those  of  the  posterior  by  their  relatively  larger  size ;  but  on  penetrating 
into  the  white  substance  of  the  cord,  their  diameter  is  diminished,  and 
they  assume  all  the  characters  of  the  central  nerve  fibres.  They  then 
pass  inward,  in  a  horizontal  or  oblique  and  backward  direction,  and 
reach  the  gray  substance  of  the  anterior  horn. 


446  THE    SPINAL    CORD. 

The  exact  termination  of  the  nerve  fibres  in  the  gray  substance  of  the 
cord  is  a  matter  of  much  importance,  but  which  is  not  yet  fully  eluci- 
dated. The  strong  probability  is  'that  some  of  the  fibres  of  the  anterior 
nerve  roots  are  directly  connected  with  radiating  nerve  cells  in  this 
locality  by  means  of  the  long  axis-cylinder  processes  of  these  cells  ;  but 
the  most  accomplished  and  careful  microscopists  have  found  it  impos- 
sible to  actually  see  this  connection.  Its  probability  rests  upon  the 
facts  that,  first,  the  long  processes  of  the  nerve  cells  in  the  anterior 
horns  closely  resemble,  as  their  name  indicates,  the  axis-cylinder  of  the 
nerve  fibres ;  and,  secondly,  these  processes  are  often  seen,  in  horizontal 
or  antero-posterior  vertical  sections,  to  pass  forward  toward  the  origin 
of  the  anterior  root  fibres,  and  emerge,  in  company  with  them,  from  the 
gray  into  the  white  substance  of  the  cord.1  Beside  these  fibres,  how- 
ever, others,  forming  a  part  of  the  anterior  nerve  roots,  pass  distinctly, 
according  to  Kolliker,  from  the  gray  substance  of  the  anterior  horn  into 
the  white  commissure,  and  thence,  crossingt  the  median  line,  into  the 
anterior  column  of  white  substance  on  the  opposite  side ;  while  others, 
radiating  backward  and  outward,  may  be  seen  to  emerge  from  the  ex- 
ternal border  of  the  gray  substance,  and  to  join  the  longitudinal  fibres 
of  the  lateral  column  on  the  same  side. 

Thus  it  is  certain  that  the  immediate  connection  of  all  the  fibres  of 
the  anterior  nerve  roots  is  with  the  gray  substance  of  the  anterior 
horn  ;  but  some  of  them  pass  subsequently  to  the  anterior  column  of 
the  opposite  side  of  the  cord,  others  to  the  lateral  column  of  the  same 
side. 

The  posterior  roots  are  distinguished  from  the  anterior,  first,  by  the 
generally  smaller  size  of  their  nerve  fibres ;  secondly,  by  the  presence 
of  the  ganglia,  known  as  the  "  spinal  ganglia,"  or  the  ganglia  of  the 
spinal  nerve  roots,  The  gray  substance  of  these  ganglia  contains  nerve 
cells  which  are  distinguished  from  those  of  the  spinal  cord  by  not  pos- 
sessing ramified  prolongations.  They  present,  however,  often  one, 
sometimes  two  or  more,  pale,  unbranched  axis-cylinder  processes,  which 
subsequently  become  continuous  with  medullated  nerve  fibres,  running 
outward  with  the  other  nerve  fibres  toward  the  periphery.  These  ganglia 
therefore  give  origin  to  additional  nerve  fibres,  which  afterward  form 
part  of  the  trunk  of  the  spinal  nerve.  The  fibres  of  the  posterior  nerve 
roots,  on  the  contrary,  coming  from  the  spinal  cord,  according  to  Kolli- 
ker, only  traverse  the  gray  matter  of  the  ganglion,  without  making  any 
anatomical  connection  with  its  substance. 

The  fibres  of  the  posterior  roots,  on  entering  the  spinal  cord,  between 
its  posterior  and  lateral  columns,  pass  into  the  posterior  horns  of  gray 
matter ;  after  which  some  of  them  change  their  direction  and  become 
longitudinal,  still  remaining  in  the  gray  substance,  others  become  trans- 

1  Kolliker,  Elements  d'Histologrie  Humaine.  Paris,  1868,  p.  343.  Gerlach,  in 
Strieker's  Manual  of  Histology,  Buck's  edition.  New  York,  1872,  pp.  636,  637. 


TRANSMISSION    OF    IMPULSES.  447 

verse,  passing  into  both  the  gray  and  white  commissures,  while  others 
lose  themselves  in  the  gray  substance  of  the  posterior  and  even  of  the 
back  part  of  the  anterior  horns. 

The  connection  of  the  anterior  and  posterior  root  fibres  of  the  spinal 
nerves  with  the  cord  is  therefore  not  exactly  the  same ;  but  they  both, 
so  far  as  known,  first  reach  the  gray  matter,  where  a  portion  of  them 
terminate,  or  at  least  escape  further  observation,  while  the  rest  partly 
become  longitudinal  on  the  same  side,  and  partly  cross  over  to  the 
opposite  side  of  the  spinal  cord. 

Transmission  of  Motor  and  Sensitive  Impulses  in  the  Spinal  Cord  and 

Nerves. 

The  experimental  methods  adopted  for  determining  the  functions  of 
different  pnrts  of  the  nervous  system  are  twofold  ;  first,  by  applying  an 
artificial  stimulus  to  the  nerve  or  nervous  tract,  and  observing  the  effect 
which  is  produced ;  secondly,  by  dividing  or  destroying  it,  and  seeing 
what  nervous  function  is  abolished  in  consequence  of  the  operation.  In 
the  peripheral  parts  of  the  nervous  system,  and  in  those  generally  which 
serve  as  simple  organs  of  transmission,  both  these  methods  yield  defi- 
nite and  positive  results.  In  the  central  parts,  they  are  sometimes 
complicated  by  the  peculiar  properties  or  the  mutual  reactions  of  the 
gray  and  white  substance. 

Motor  and  Sensitive  Transmission  in  the  Spinal  Nerves  and  Nerve 
Hoots. — If  the  spinal  canal  of  a  living  animal  be  opened,  and  a  mechanical 
or  galvanic  stimulus  be  applied  to  the  anterior  root  alone  of  a  spinal 
nerve,  the  effect  of  this  irritation  is  a  convulsive  movement  of  the  part 
to  which  the  nerve  is  distributed.  The  muscular  contraction  is  imme- 
diate, involuntary,  and  instantaneous  in  duration  ;  and  is  repeated  with 
mechanical  precision  each  time  the  stimulus  is  applied.  It  is  usually 
unaccompanied  by  any  indication  of  sensibility,  and  is  evidently  a 
direct  result  of  the  excitement  of  the  nerve  fibres  of  the  anterior  root. 
This  root  is  therefore  said  to  be  "  excitable,"  because  its  irritation 
excites  a  movement  in  the  corresponding  parts. 

Furthermore,  if  the  anterior  root  of  a  spinal  nerve,  under  the  same 
circumstances,  be  cut  across,  the  remaining  nervous  connections  being 
left  untouched,  the  result  is  an  immediate  and  total  paralysis  of  volun- 
tary movement  in  the  muscles  to  which  that  nerve  is  distributed.  At 
the  same  time,  the  power  of  sensibility  is  undiminished,  and  the  animal 
is  still  capable  of  feeling  the  contact  of  foreign  bodies,  or  a  galvanic  cur- 
rent applied  to  the  skin,  as  before.  If  the  anterior  roots  of  a  series  of 
spinal  nerves  be  thus  divided,  as,  for  example,  those  of  all  the  lumbar 
and  sacral  nerves  on  one  side,  the  above  effect  will  be  produced  for  an 
entire  corresponding  region  of  the  body,  and  the  whole  posterior  limb 
on  that  side  will  lose  the  power  of  voluntary  motion  while  retaining  its 
sensibility.  This  is  not  clue  to  any  loss  of  the  physiological  properties 
of  either  the  nerve  or  the  muscles,  since  irritation  of  the  nerve  or  nerve 
root,  outside  the  point  of  section,  still  produces  muscular  contraction  as 


4-48  THE    SPINAL    CORD. 

before.  All  these  facts  prove  that  the  path  by  which  impulses  for  vol- 
untary motion  pass,  from  the  brain  and  spinal  cord  to  the  muscles,  is 
exclusively  the  anterior  root  of  the  spinal  nerve. 

On  the  other  hand,  if  the  posterior  root  be  irritated,  by  pinching, 
pricking,  or  galvanism,  a  sensation  is  produced,  more  or  less  acute  ac- 
cording to  the  amount  and  quality  of  the  irritation  applied.  This  sen- 
sation, when  of  a  certain  intensity,  is  accompanied  by  movements.  But 
these  movements  are  general  and  not  necessarily  confined  to  the  part  to 
which  the  nerve  is  distributed;  and  if  the  corresponding  anterior  root 
have  been  previously  divided,  this  part  will  remain  motionless,  while 
muscular  contractions  continue  to  be  produced  elsewhere.  The  move- 
ments which  follow  irritation  of  the  posterior  root,  accordingly,  are 
not  produced  directly  by  its  influence,  but  are  caused  indirectly  by 
the  reaction  of  the  nervous  centres.  The  only  immediate  result  of  irri- 
tation of  a  posterior  nerve  root  is  a  sensation,  and  this  root  is  therefore 
said  to  be  "  sensitive." 

Furthermore,  if  the  posterior  root  be  divided,  the  consequence  is  a 
loss  of  the  power  of  sensation  in  the  corresponding  region  of  the  body. 
Here  also  the  effect  is  simply  to  cut  off  the  medium  of  communica- 
tion between  the  integument  and  the  nervous  centres ;  since  irritation 
of  that  part  of  the  divided  nerve  which  is  still  attached  to  the  spinal 
cord  produces  a  sensation  as  before.  Thus  the  channel  of  communica- 
tion for  sensitive  impressions,  in  this  part  of  the  nervous  system,  is 
exclusively  the  posterior  root  of  the  spinal  nerve. 

But  just  beyond  the  situation  of  the  spinal  ganglia,  the  two  roots 
unite  to  form  the  trunk  of  the  spinal  nerve.  Here,  the  fibres  of  the 
anterior  and  those  of  the  posterior  root  become  intimately  mingled,  and 
inclosed  within  the  neurilemma  in  such  close  juxtaposition  that  they 
can  no  longer  be  separately  irritated  by  artificial  means.  They  pass, 
still  associated  in  this  manner,  into  the  branches  and  subdivisions  of 
the  nerve ;  and  only  finally  separate  from  each  other  at  its  terminal 
ramifications,  where  the  sensitive  fibres  are  distributed  mainly  to  the 
integument  and  the  motor  fibres  to  the  muscles. 

The  trunk  and  branches  of  a  spinal  nerve,  therefore,  outside  the 
spinal  canal,  contain  both  sensitive  and  motor  fibres,  and  it  is  conse- 
quently said  to  be  a  "  mixed"  nerve.  It  is  both  excitable  and  sensitive, 
since  its  artificial  irritation  causes  at  the  same  time  sensation  and  con- 
vulsive movement ;  and  if  it  be  divided,  this  injury  is  followed  by  the 
loss  of  both  sensibility  and  voluntary  motion  in  the  corresponding 
parts.  It  is  also  important  to  remember  that,  in  all  these  instances  of 
section  of  the  trunk,  or  branches,  or  anterior  or  posterior  roots  of  a 
spinal  nerve,  the  consequent  loss  of  sensibility  or  motion  is  permanent 
while  the  injury  lasts  ;  and  the  nervous  functions  are  not  restored  until 
the  divided  nerve  fibres  have  reunited,  and  have  again  acquired  their 
natural  continuity  of  texture.  This  shows  that  the  suspension  of  func- 
tional activity  is  directly  due  to  the  division  of  the  nerve  fibres,  and  is 
not  produced  by  the  sympathetic  action  of  other  parts. 


TRANSMISSION    OF    IMPULSES.  449 

Motor  and  Sensitive  Transmission  in  the  Spinal  Cord. — The  simplest 
fact  determined,  in  this  respect,  both  by  experimental  research  and 
pathological  observation,  is  that  the  spinal  cord  is  the  exclusive  organ 
of  communication  between  the  brain,  on  the  one  hand,  and  the  external 
organs  of  sensation  and  motion,  on  the  other;  since  if  it  be  divided  by 
a  transverse  section,  or  compressed  by  fractured  bone,  or  disorganized 
by  diseased  action  at  any  part  of  its  length,  the  result  is  a  complete 
loss  of  voluntary  motion  and  sensibility  in  the  muscles  and  integument 
below  the  point  of  injury.  The  general  nervous  function,  performed  by 
the  cord  as  a  whole,  is  therefore  easily  and  completely  demonstrated, 
and  is  not  subject  to  any  doubtful  interpretation. 

But  the  precise  path  which  is  followed  by  the  motor  and  sensitive 
impulses  respectively  in  different  parts  of  the  spinal  cord  is  much  less 
easy  of  determination  than  in  the  two  sets  of  nerve  roots.  The  fibres 
of  the  nerve  roots  pass  directly  to  the  gray  matter  in  the  interior  of  the 
cord ;  and  their  subsequent  course  has  not  been  completely  followed  by 
microscopic  examination.  The  white  substance  of  the  cord,  at  least  in 
the  lateral  columns,  is  partly  formed  of  fibres  which  come  from  the 
nerve-roots  ;  but  the  greater  part  of  both  anterior,  lateral,  and  posterior 
columns  may  consist  of  fibres  which  originate  in  the  gray  matter,  and 
thus  form  secondary  tracts  of  communication  between  it  and  the  brain. 
The  close  juxtaposition  and  continuity  of  texture  between  the  gray 
substance  and  the  various  columns  of  white  substance  in  the  spinal 
cord  give  it  a  more  or  less  complicated  structure ;  and  the  investigation 
of  the  functional  endowments  of  its  different  parts  has  yielded  results 
which  are  less  simple  and  uniform  than  in  the  case  of  the  nerves  and 
the  nerve  roots.  The  methods  and  objects  of  the  investigation,  however, 
are  the  same  in  both  instances ;  and  are  intended  to  ascertain  the 
following  points,  namely,  first,  what  parts  of  the  spinal  cord  are  found 
to  be  sensitive  or  excitable  under  the  application  of  an  artificial 
stimulus?  and  secondly,  what  parts  act  as  the  natural  channels  of 
transmission  for  the  two  functions  of  sensation  and  motion?  The 
latter  of  these  questions  is  the  more  important  in  a  purely  physiological 
point  of  view;  but  the  former  is  also  of  consequence  as  a  guide  in 
experimental  research,  and  also  for  the  explanation  of  many  pathological 
phenomena. 

I.  What  parts  of  the  Spinal  Cord  are  sensitive  or  excitable  under  the 
influence  of  artificial  stimulus? 

When  the  spinal  canal  is  opened  in  the  living  animal,  the  first  por- 
tions of  the  cord  which  present  themselves  for  examination  are  the 
posterior  columns.  The  irritation  of  these  columns  by  artificial  stimu- 
lus, according  to  the  united  testimony  of  all  observers,  produces  evident 
signs  of  sensibility  in  the  animal.  It  is  also  found  by  experimenters 
generally  that  this  sensibility  is  most  marked  in  the  immediate  neigh- 
borhood of  the  attachment  of  the  posterior  nerve  roots,  while  at  the 
greatest  distance  from  this  point,  namely,  at  the  inner  edge  of  the  poste- 
rior columns,  on  each  side  of  the  median  line,  their  sensibility  may  be 


450  THE    SPINAL    CORD. 

nearly  absent.  It  is  evident  that  the  sensibility  of  the  posterior  columns 
is  largely  due  to  the  presence  of  fibres  of  the  posterior  nerve  roots, 
which  may  be  included  in  the  irritation,  and  many  of  which  traverse  the 
outer  portion  of  the  posterior  columns  horizontally  in  their  passage 
toward  the  gray  matter.  The  only  discrepancy  on  this  subject  is  in 
regard  to  the  question  whether  the  fibres  of  the  nerve  roots  are  the  only 
sources  of  sensibility  for  the  posterior  columns,  or  whether  the  longitu- 
dinal fibres  of  the  columns  themselves  are  also  sensitive.  According  to 
some  authors  (Yan  Deen,  Brown-Sequard,  Poincare'),  the  posterior 
columns  have  no  sensibility  of  their  own,  but  only  what  is  due  to  that 
of  the  posterior  nerve  roots;  since  if  these  roots  be  torn  out,  irritation 
of  the  posterior  columns  no  longer  produces  any  perceptible  sensation. 
In  the  experiments  of  Schiff  and  Vulpian,  on  the  other  hand,  the  poste- 
rior columns,  after  being  divided  by  a  transverse  section,  and  then 
separated  from  the  adjacent  parts  for  a  distance  of  several  centimetres 
in  front  of  the  point  of  section,  still  indicate  the  existence  of  sensi- 
bility when  subjected  to  irritation.  Irritation  of  the  posterior  columns, 
like  that  of  sensitive  tracts  generally,  produces  also  movements  in  va- 
rious parts ;  but  these  movements  are  reflex  in  character,  and  are  simply 
the  signs  of  an  irritation  communicated  to  the  nervous  centres. 

Sensibility  also  exists,  according  to  Yulpian,  in  that  portion  of  the 
lateral  columns  which  is  contiguous  to  the  outer  edge  of  the  posterior 
columns,  and  to  the  line  of  attachment  of  the  posterior  nerve  roots. 
But  as  the  irritation  is  applied  to  points  farther  forward,  the  signs  of 
sensibility  in  the  lateral  columns  rapidly  diminish,  and  soon  disappear 
altogether.  In  all  these  parts,  of  both  posterior  and  lateral  columns,  the 
sensibility,  as  found  by  all  observers,  is  most  marked,  or  even  exclu- 
sively situated,  in  their  superficial  portions;  and  experimenters  are  also 
generally  agreed  that  the  gray  substance  of  the  cord,  throughout,  is 
destitute  of  sensibility  to  the  application  of  any  ordinary  artificial 
stimulus. 

Whatever  minor  points,  therefore,  may  remain  in  doubt,  the  principal 
fact  is  unquestioned,  namely,  that  the  posterior  parts  of  the  spinal  cord, 
consisting  of  the  posterior  columns  and  the  adjacent  parts  of  the  lateral 
columns,  are  sensitive  to  external  irritation,  especially  at  their  surface; 
and  accordingly  inflammation  of  the  meninges,  or  other  diseased  action 
in  this  locality,  may  be  accompanied  by  painful  irritation  of  the  spinal 
cord.  The  irritation  thus  produced  is  still  more  liable  to  cause  pain,  on 
account  of  the  attachment  at  the  surface  of  the  cord  of  the  posterior 
nerve  roots,  which  are  themselves  acutely  sensitive. 

The  properties  shown  by  the  anterior  columns  on  the  application  of 
artificial  stimulus  are,  on  the  whole,  quite  different  from  those  of  the 
posterior  columns.  There  is  some  difference  in  the  results  obtained  in 
this  respect  by  different  experimenters.  This  difference  mainly  con- 
sists in  the  fact  that,  according  to  the  large  majority  (Magendie,  Longet. 
Bernard,  Brown-Se'quard,  Yulpian,  Flint),  irritation  of  the  anterior 
columns  produces  convulsive  movement  in  the  parts  below ;  while 


TRANSMISSION    OF    IMPULSES.  451 

others  (Calmeil  and  Chauveau)  have  found  these  columns  quite  inexcita- 
ble,  and  incapable  of  causing  muscular  contraction.  But  in  such  in- 
stances experiments  with  a  positive  result  are  much  more  decisive  than 
those  which  are  merely  negative,  since  the  natural  excitability  of  the 
anterior  columns  might  be  temporarily  suspended  by  the  operation  of 
opening  the  spinal  canal,  or  other  incidental  conditions;  but  nothing 
of  this  kind  could  confer  upon  them  a  property  which  they  did  not 
naturally  possess. 

Vulpian  has  shown1  that,  if  in  the  living  animal  the  spinal  cord  be 
divided  transversely,  and  both  posterior  and  lateral  columns,  together 
with  the  anterior  and  posterior  nerve  roots,  separated  from  it  for  a 
distance  of  four  or  five  centimetres  below  the  point  of  section,  leaving 
this  portion  of  the  cord  to  consist  of  the  anterior  columns  and  the 
gray  substance  only,  irritation  of  the  anterior  columns,  thus  isolated, 
will  still  produce  convulsive  movement  in  the  parts  below. 

There  can  be  no  doubt,  accordingly,  of  the  excitability  of  the  anterior 
columns.  This  excitability,  which  produces  simple  convulsive  move- 
ments in  the  parts  below,  is  also  in  most  instances  unaccompanied  by 
pain  or  other  evidences  of  sensibility.  The  absence  of  pain,  in  cases 
where  the  convulsive  action  is  well  marked,  has  been  especially  noticed 
by  Flint,2  and  is  also  mentioned  by  various  other  writers. 

The  sensibility  of  these  parts  which  has  sometimes  been  observed  is 
comparatively  slight  in  degree,  and  is  frequently  altogether  suspended 
or  abolished  by  the  opening  of  the  vertebral  canal  and  the  exposure  of 
the  spinal  cord. 

The  lateral  columns  are  also  excitable  in  their  anterior  portions,  near 
the  attachment  of  the  anterior  nerve  roots ;  while  as  we  approach  their 
posterior  portions,  this  direct  excitability,  according  to  Vulpian,  dimin- 
ishes in  degree,  and  gradually  gives  place  to  the  phenomena  of  sensi- 
bility characteristic  of  the  posterior  parts  of  the  cord. 

The  anterior,  lateral,  and  posterior  columns  of  the  cord  are  not  there- 
fore absolutely  limited  and  distinguished  from  each  other  by  their 
physiological  properties.  The  fibres  of  the  anterior  and  posterior  nerve 
roots  pass  in  horizontally  between  the  longitudinal  fibres  of  the  adjacent 
columns ;  but  both  the  anterior  and  lateral  columns,  on  each  side  of  the 
anterior  nerve  roots,  are  excitable  and  produce  movement  on  being  irri- 
tated, and  both  the  posterior  and  lateral  columns,  near  the  entrance  of 
the  posterior  nerve  roots,  are  endowed  with  sensibility.  Inflamma- 
tory or  other  irritation  of  the  meninges,  over  any  part  of  the  anterior 
aspect  of  the  cord,  may  accordingly  cause  convulsive  movements  in  the 
regions  situated  below  the  diseased  point ;  and  it  is  possible  that  either 
pain  alone  or  convulsions  alone  may  be  the  symptoms  of  inflammatory 
irritation  of  the  posterior  or  anterior  portions  of  the  cord  respectively. 
But  it  is  most  frequently  the  case  that  the  morbid  action  extends  more 

1  Systeme  Nerveux.     Paris,  1866,  p.  360. 

2  Physiology  of  Man  ;  Nervous  System.     New  York,  1872,  p.  276. 


452  THE    SPINAL    COBD. 

or  less  to  both  regions,  and  the  disturbances  of  sensibility  and  motion 
are  both  present  at  the  same  time,  or  at  different  periods  in  the  progress 
of  the  disease. 

II.  What  parts  of  the  Spinal  Cord  are  the  natural  channels  of  trans- 
mission for  sensation  and  movement? 

This  question  cannot  be  settled  by  the  experiments  which  consist  in 
applying  an  artificial  stimulus  to  the  various  parts  of  the  cord.  Such 
experiments  can  only  determine  the  sensibility  or  excitability  of  a 
nervous  tract,  but  not  its  function  as  a  channel  of  transmission.  A 
part  of  the  spinal  cord  might  be  sensitive  to  direct  external  irritation, 
and  yet  the  natural  impulses  of  sensation,  coming  from  the  peripheral 
nerves,  might  follow  a  different  route.  On  the  other  hand,  a  part  might 
be  perfectly  capable  of  transmitting  the  nervous  impulses  of  sensation  or 
of  motion,  received  from  the  corresponding  nerve  fibres,  and  yet  might 
not  itself  be  either  excitable  or  sensitive.  In  the  peripheral  nerves  and 
the  nerve  roots,  the  two  sets  of  properties  coexist.  The  nerve  fibres  of 
the  posterior  roots,  which  transmit  sensation,  are  themselves  sensitive  ; 
and  those  of  the  anterior  nerve  roots,  which  transmit  the  power  of 
motion,  are  also  excitable.  But  although  these  properties  are  connected 
in  the  nerves  and  nerve  roots,  they  are  not  necessarily  so  in  the  nervous 
centres  ;  and  investigation  shows  that  in  the  spinal  cord  they  are  often 
independent  of  each  other. 

The  only  method  of  ascertaining  what  path  is  followed,  in  the  spinal 
cord,  by  the  sensitive  and  motor  impulses  respectively,  is  to  divide  or 
destroy,  in  successive  experiments,  different  portions  of  the  cord,  and  to 
observe  which  of  these  injuries  is  accompanied  by  the  loss  or  preserva- 
tion of  sensation  or  voluntary  movement.  Even  these  experiments  are 
not  always  as  decisive  in  the  spinal  cord  as  in  the  nerves  and  nerve 
roots ;  for  the  reason  that  the  different  parts  of  the  white  and  gray  sub- 
stance influence  each  other,  and  are  sometimes  affected  by  sympathetic 
action.  If  the  division  of  one  of  the  columns  of  the  spinal  cord  be  fol- 
lowed by  a  continuance  of  the  power  of  sensation,  we  know  that  column 
cannot  be  the  natural  channel  for  sensitive  impressions.  But  if,  on  the 
other  hand,  it  be  followed  by  immediate  loss  of  sensibility,  we  cannot  be 
sure,  in  this  case,  that  the  column  in  question  is  really  the  organ  of 
transmission  ;  because  the  loss  of  sensibility  may  be  temporary,  and  due 
to  the  shock  inflicted  upon  neighboring  parts  of  the  cord.  Nothing  is 
more  common,  in  experiments  on  the  nervous  system,  than  to  see  a  par- 
alysis of  sensation  or  motion,  more  or  less  complete,  follow  directly 
upon  the  injury  of  a  particular  part,  and  yet  these  symptoms  disappear 
within  a  few  hours  or  days,  although  the  injury  to  the  nerve  substance 
may  remain  for  a  much  longer  period.  The  immediate  effect,  in  these 
cases  is  not  due  directly  to  the  division  of  the  injured  nerve  fibres,  but 
to  their  sympathetic  reaction  upon  neighboring  parts  of  the  nervous 
centre.  The  most  decisive  experiments,  accordingly,  upon  the  spinal 
cord,  for  determining  the  channels  of  transmission  for  sensation  and 


TRANSMISSION    OF    IMPULSES.  453 

motion,  are  those  in  which  these  functions  have  remained,  notwith- 
standing the  section  of  certain  parts  of  the  cord. 

By  investigating  in  this  way  the  nervous  channels  for  sensation  in 
the  spinal  cord,  the  first  fact  which  is  demonstrated  in  such  a  manner  as 
to  be  generally  accepted,  is  that  after  division  of  the  posterior  columns 
of  white  substance  the  power  of  sensibility  is  undiminished,  and  the 
animal  continues  to  feel  impressions  made  upon  the  integument  of  the 
corresponding  parts.  This  result,  which  was  obtained  by  several  of  the 
older  experimenters,  is  fully  confirmed  by  the  observations  of  Brown- 
Se'quard1  and  Yulpian.2  The  posterior  columns  therefore  are  not  the 
channels  for  ordinary  sensitive  impressions,  notwithstanding  they  have 
themselves  a  certain  degree  of  sensibility.  The  converse  of  this  experi- 
ment, namely,  transverse  division  of  all  parts  of  the  spinal  cord  excepting 
the  posterior  columns,  as  performed  by  the  same  observers,  is  followed 
by  complete  loss  of  the  power  of  sensation. 

On  the  other  hand,  if  both  the  anterior  and  lateral  columns  of  white 
substance  be  divided,  leaving  only  the  posterior  columns  and  the  gray 
substance,  sensibility  is  preserved ;  and  Brown-S^quard  has  varied  the 
mode  of  procedure  by  dividing  both  anterior,  lateral,  and  posterior 
columns  in  the  same  animal  at  different  levels,  one  above  the  other, 
so  that  the  continuity  of  the  cord  as  a  whole  is  preserved,  but  all  the 
longitudinal  tracts  of  white  substance  are  divided,  leaving  only  the  gray 
substance  uninjured.  In  this  case  sensibility  is  preserved,  although 
diminished  in  intensity. 

The  transmission  of  sensitive  impressions,  therefore,  takes  place 
through  the  gray  matter.  This  substance,  which  is  itself  insensible  to 
direct  irritation,  forms  the  medium  of  communication  between  the 
peripheral  fibres  of  the  sensitive  nerves  and  the  brain  above.  It  is  not 
known  whether  this  communication  be  made  by  nerve  fibres  running 
continuously  through  the  gray  substance  in  a  longitudinal  direction,  or 
by  successive  connections  of  the  nerve  cells. 

With  regard  to  the  channels  for  voluntary  motion  in  the  cord,  the 
posterior  columns,  it  is  certain,  take  no  direct  part  in  the  transmission 
of  these  impulses,  since  after  their  complete  section  the  power  of  vol- 
untary motion  remains  unimpaired ;  and  if  all  the  remaining  parts  of 
the  cord  be  divided,  according  to  the  observations  of  Brown-Se'quard, 
leaving  the  posterior  columns  untouched,  voluntary  motion  is  entirely 
lost.  Further  experiments  by  the  same  author  on  the  anterior  and 
lateral  columns  and  the  gray  substance  of  the  anterior  horns  lead  to  the 
conclusion  that,  for  the  transmission  of  the  voluntary  impulses  from 
the  brain  to  the  muscles  of  the  body  and  limbs,  both  the  white  and  gray 
substance  of  the  anterior  half  of  the  cord  must  be  in  a  state  of  integrity; 
since  section  of  either  the  white  substance  alone  or  of  the  gray  sub- 

1  Physiology  and  Pathology  of  the  Central  Nervous  System.     Philadelphia, 
1860,  p.  19. 

2  Systeme  Nerveux.     Paris,  1866,  p.  373. 


454  THE    SPINAL    CORD. 

stance  alone  is  followed  by  almost  complete  paralysis  of  the  parts  below 
the  level  of  the  injury.  In  the  dorsal  region,  injury  of  the  anterior 
columns  produces  a  greater  amount  of  paralysis  than  that  of  the  lateral 
columns;  in  the  cervical  region,  on  the  other  hand,  this  relation  is 
reversed,  the  lateral  columns  taking  a  more  important  part  in  voluntary 
transmission  than  the  anterior. 

It  is  evident,  accordingly,  that  in  the  spinal  cord  the  transmission  of 
sensitive  and  motor  impulses  does  not  take  place  with  the  same  sim- 
plicity as  in  the  nerves  and  nerve-roots.  The  various  nervous  tracts, 
as  well  as  the  white  and  the  gray  substance,  are  associated  in  such  a 
manner  as  to  make  of  the  cord  a  single  organ,  more  or  less  complicated 
in  structure,  which  cannot  be  separated,  so  far  as  our  present  knowledge 
extends,  into  completely  independent  parts. 

Crossed  Action  of  the  Spinal  Cord, 

The  spinal  cord,  as  a  medium  of  nervous  communication  between  the 
brain  and  the  external  parts,  exerts  a  crossed  action.  That  is,  the 
sensitive  impressions  received  by  the  integument  on  one  side  of  the 
body  are  conducted  through  the  cord  to  the  opposite  side  of  the  brain  ; 
and  the  voluntary  motor  impulses  which  originate  on  one  side  of  the 
brain  pass  to  the  nerves  and  muscles  on  the  opposite  side  of  the  body. 
This  is  established  both  by  experiments  upon  animals  and  by  patholo- 
gical observations  in  man ;  since  injury  or  disease  situated  upon  the 
right  side  of  the  brain  is  known  to  cause  paralysis,  both  of  sensation 
and  voluntary  motion,  on  the  left  side  of  the  body,  and  vice  versa. 
These  two  nervous  functions  may  be  paralyzed  either  together  or 
separately,  according  to  the  locality  and  extent  of  the  injury  to  the 
brain  substance ;  but  when  the  paralysis  is  distinctly  confined  to  one 
side  of  the  body,  the  alteration  of  nervous  tissue  upon  which  it  depends 
is  found  after  death  to  be  seated  upon  the  opposite  side  of  the  brain. 

The  crossing  or  decussation  of  the  motor  and  sensitive  tracts,  from 
side  to  side,  takes  place  in  the  following  manner : 

Decussation  of  the  Motor  Tracts. — It  may  be  said,  in  general  terms, 
that  the  transmission  of  voluntary  motor  impulses,  in  the  spinal  cord 
itself,  takes  place  continuously  upon  the  same  side.  That  is,  if  a  trans- 
verse section  of  one  lateral  half  of  the  cord  be  made  at  any  point  in  the 
lumbar,  dorsal,  or  cervical  region,  a  paralysis  of  voluntary  motion  is 
produced  upon  the  same  side  for  all  parts  situated  below  the  level  of 
the  injury.  This  observation,  which  was  first  made  by  Galen,  has  been 
confirmed  by  all  subsequent  experimenters.  But  in  the  cervical  region, 
the  lateral  columns  gradually  preponderate  in  importance,  as  the  organs 
of  transmission  for  voluntary  motion,  over  the  anterior  columns ;  and 
on  approaching  the  level  of  the  medulla  oblongata,  their  fibres  pass  in  « 
direction  forward  and  inward,  until  they  reach  the  inner  and  anterior 
part  of  the  cord.  At  the  medulla  oblongata,  these  fibres  cross  the 
median  line,  as  distinct  bundles  of  considerable  size  passing  obliquely 
upward,  to  form  the  anterior  pyramids  of  the  opposite  side.  This 


CROSSED    ACTION    OF    THE    SPINAL    CORD.  455 

constitutes  the  so-called  "decussation  of  the  anterior  pyramids;"  and 
beyond  this  point  the  longitudinal  fibres  of  the  medulla  oblongata  con- 
tinue their  course  toward  the  peduncles  of  the  brain  and  the  cerebral 
ganglia  above.  Thus  the  crossing  of  the  tracts  for  voluntary  motion  is 
completed  in  the  lower  half  of  the  medulla  oblongata.  Injury  of  one 
lateral  half  of  the  brain  above  this  situation  causes  muscular  paralysis 
on  the  opposite  side  of  the  body ;  injury  of  one  lateral  half  of  the  spinal 
cord  below  it  causes  paralysis  on  the  same  side  of  the  body. 

These  are  the  general  results  obtained  from  both  pathological  observa- 
tion and  physiological  experiment;  and  they  evidently  point  to  the 
medulla  oblongata  as  the  principal  or  exclusive  seat  of  the  bilateral 
decussation  of  the  channels  for  voluntaiy  motion.  At  the  same  time  it 
is  shown,  by  mircroscopic  examination,  that  this  is  not  the  only  spot 
where  an  anatomical  intercharge  of  fibres  takes  place  between  the  two 
lateral  halves  of  the  spinal  cord.  On  the  contrary,  a  decussation  of 
fibres  exists  everywhere,  throughout  the  length  of  the  cord,  from  left  to 
right,  and  vice  versa,  at  the  situation  of  the  "  white  commissure,"  at  the 
bottom  of  the  anterior  median  fissure ;  the  right  anterior  column  con- 
stantly receiving  fibres  from  the  left  side  of  the  cord,  and  the  left  anterior 
column  from  the  right  side  of  the  cord.  This  continuous  decussation  is 
concealed  from  view  externally,  and  is  only  discoverable  by  means  of 
transverse  microscopic  sections ;  while  that  at  the  level  of  the  anterior 
pyramids  is  easily  visible,  owing  to  the  size  of  the  decussating  bundles 
and  their  oblique  direction. 

The  anatomical  distinction  between  the  two  sets  of  decussating  fibres 
may  answer  to  a  corresponding  difference  in  their  physiological  action ; 
and  the  decussation  at  the  white  commissure  may  be  connected  with 
the  reflex  action  of  the  cord,  or  with  the  simultaneous  action  of  its  twro 
opposite  sides.  It  is  certain  that  this  commissure  does  not  take  part  in 
the  transmission  of  voluntary  impulses;  since  in  the  celebrated  experi- 
ment of  Galen,1  "if  the  spinal  cord  be  divided  by  a  longitudinal  section, 
from  above  downward,  in  the  median  line,"  so  as  to  separate  its  two 
lateral  halves  from  each  other,  this  operation  is  not  followed  by  loss 
of  motion  either  on  one  side  or  the  other.  This  result  has  also  been 
obtained  by  Brown-Se'quard2  in  the  lumbar  region,  voluntary  motion 
being  retained  in  both  the  posterior  limbs.  On  the  other  hand,  as 
shown  by  the  same  observer,  a  longitudinal  section  of  the  medulla 
oblongata  alone  in  the  median  line,  so  as  to  divide  the  decussating  fibres 
of  the  anterior  pyramids,  produces  complete  loss  of  voluntary  movement 
in  all  the  limbs  at  once. 

Decussation  of  the  Sensitive  Tracts. — The  sensitive  impressions, 
conveyed  from  the  integument  to  the  nervous  centres,  undergo,  like  the 
motor  impulses,  a  complete  bilateral  decussation  by  the  time  they  arrive 

1  De  Administrationibus  Anatomicis.     Liber  viii.  cap.  vi. 

2  Physiology  and  Pathology  of  the  Central  Nervous  System.     Philadelphia, 
1860,  p.  33. 


456  THE    SPINAL    CORD. 

at  the  upper  part  of  the  medulla  oblongata ;  since  lesions  of  the  brain 
above  this  point  cause  a  diminution  or  loss  of  sensibility  on  the  opposite 
side  of  the  body. 

But  while  the  tracts  for  voluntary  motion  have  a  continuous  or  uni- 
lateral course  in  the  spinal  cord  itself,  and  decussate  only  or  principally 
at  the  level  of  the  anterior  pyramids,  those  for  sensation  in  great 
measure  cross  from  side  to  side  at  successive  points  throughout  the 
length  of  the  spinal  cord.  This  is  shown  by  the  fact  that  a  transverse 
section  of  one  lateral  half  of  the  spinal  cord,  which  paralyzes  motion 
on  the  same  side  with  the  injury,  causes,  on  the  contrary,  a  loss  of  sen- 
sation on  the  opposite  side ;  while  sensibility  remains  upon  that  side  of 
the  body  where  the  section  of  the  cord  has  been  made.  Thus  if  the 
lateral  section  of  one-half  the  spinal  cord  be  made  at  the  lower  end  of 
the  dorsal  region  on  the  right  side,  the  right  hind  leg  is  paralyzed  of 
motion  but  retains  its  sensibility ;  the  left  hind  leg,  at  the  same  time, 
retains  its  power  of  motion  but  loses  its  sensibility.  Furthermore,  the 
sensibility  of  the  parts  is  not  only  retained  on  the  side  of  the  section, 
but  is  even  exaggerated  in  a  very  perceptible  manner ;  so  that  an  im- 
pression upon  the  skin  is  perceived  on  that  side  more  acutely  than  before 
the  section. 

These  results,  which  were  partially  obtained  by  several  of  the  older 
experimenters,  were  first  .distinctly  brought  out  by  Brown-Sequard. 
According  to  his  experiments,  the  phenomena  are  so  complete  as  to  imply 
an  entire  crossing  of  the  sensitive  tracts  in  the  spinal  cord.  Other 
observers  have  found  the  appearances  not  so  decisive ;  Yulpian,  among 
others,  maintaining  that  the  loss  of  sensibility  on  the  opposite  side,  after 
section  of  a  lateral  half  of  the  cord,  is  never  complete  but  only  partial, 
and  that  the  sensitive  impressions  conveyed  through  the  gray  matter 
may  even  continue  to  pass,  after  one  lateral  half  of  the  cord  has  been 
divided  in  the  dorsal,  and  the  other  in  the  cervical  region,  by  two  sec- 
tions placed  at  a  considerable  distance  from  each  other. 

It  is  certain,  however,  that  after  section  of  one  lateral  half  of  the 
cord  the  phenomena  which  indicate  a  crossing  of  the  sensitive  tracts  are 
distinctly  marked.  We  have  repeated  this  experiment,  and  have  found 
that  after  such  a  section,  in  the  dog,  in  the  dorso-lumbar  region,  the 
difference  in  the  effects  produced  upon  sensation  and  motion  on  the  two 
sides  is  very  striking.  Sensibility  is  either  lost  or  very  much  diminished 
upon  the  opposite  side,  while  upon  the  same  side  with  the  section,  where 
there  is  complete  muscular  paralysis,  the  sensibility  remains  and  is  in- 
creased in  intensity.  On  the  opposite  side,  there  is  power  of  motion 
with  diminution  or  loss  of  sensibility  ;  on  the  same  side,  there  is  hyper- 
sesthesia  with  loss  of  voluntary  motion. 

What  is  the  cause  of  the  local  hyperaesthesia,  after  section  of  one 
lateral  half  of  the  spinal  cord?  This  is  an  instance  of  the  indirect 
influence  exerted  upon  the  nervous  centres  by  injury  of  any  part  of 
their  substance.  After  transverse  division  of  one-half  of  the  cord,  not 
only  are  its  motor  and  sensitive  fibres  cut  off,  causing  paralysis  of  motion 


CROSSED    ACTION    OF    THE    SPINAL    CORD.  457 

on  the  same  side  and  paralysis  of  sensibility  on  the  opposite  side,  but 
the  gray  substance  is  irritated  in  the  neighborhood  of  the  section  and 
is  thrown  into  a  state  of  unusual  activity.  The  sensitive  fibres  of  the 
posterior  nerve  roots  on  the  same  side  pass  into  this  gray  substance 
below  the  point  of  section,  and  thence  make  communication  with  the 
opposite  side  of  the  spinal  cord  and  the  brain.  The  irritation  of 
the  gray  matter  thus  causes  an  increase  in  the  intensity  of  the  nervous 
impressions  coming  from  the  side  of  the  injury  and  an  apparent  hyper- 
aesthesia  of  the  integument  on  that  side.  For  this  purpose  it  is  not 
necessary  to  make  a  complete  section  of  all  the  lateral  parts  of  the  cord ; 
since  Brown-Se'quard  has  found  that  division  of  the  posterior  columns 
alone  will  cause  hyperaesthesia,  more  or  less  pronounced ;  and  according 
to  Vulpian,  the  same  effect  may  be  produced  by  simply  pricking  with  a 
pointed  instrument  the  posterior  or  lateral  parts  of  the  cord  on  one  side. 

Another  experiment  is  much  relied  on  by  Brown-Sequard  to  demon- 
strate the  crossing  of  the  sensitive  tracts  in  the  spinal  cord.  According 
to  him,  if  the  spinal  cord  be  divided,  in  the  lumbar  region,  by  a  longi- 
tudinal section  in  the  median  line,  so  as  to  separate  its  two  lateral 
halves  from  each  other  without  further  injury,  the  operation  is  followed 
by  complete  loss  of  sensibility  in  both  hind  legs.  This  result  by  itself 
would  not  be  decisive,  since  such  an  operation  might  readily  cause  a 
temporary  suspension  of  sensibility,  owing  to  the  shock  inflicted  on  the 
spinal  cord  as  a  whole ;  but  it  is  of  much  value  when  taken  in  connec- 
tion with  the  fact  that  after  this  operation,  while  sensibility  is  lost,  the 
power  of  voluntary  movement,  on  the  contrary,  is  retained  in  both  the 
posterior  limbs. 

Finally,  instances  in  the  human  subject,  where  a  lesion  of  one  side 
of  the  spinal  cord  is  accompanied  by  loss  of  voluntary  motion  on  the 
same  side  and  loss  of  sensibility  on  the  opposite  side,  below  the  seat 
of  the  disease,  confirm  the  results  derived  from  experiments  on  animals. 
The  decussation  of  both  motor  and  sensitive  tracts  is  completed  at  the 
medulla  oblongata  ;  but  below  this  point  the  cord  acts  as  a  conductor 
for  motor  impulses  going  to  the  muscles  on  the  same  side  of  the  body, ' 
and  for  sensitive  impressions  coming  from  the  integument  of  the  oppo- 
site side. 

Various  forms  of  Paralysis,  from  lesions  of  the  Cerebro-spinal 
Axis. — In  consequence  of  disease  or  injury  in  di  fie  rent  parts  of  the 
cerebro-spinal  axis,  a  variety  of  symptoms  may  be  produced  affecting 
sensation  and  voluntary  motion.  The  two  most  simple  forms  of  paraly- 
sis from  this  cause  are,  first,  "  paraplegia,"  or  paralysis  of  the  entire 
lower  portion  of  the  body  and  inferior  limbs ;  and  secondly,  "  hemiple- 
gia,"  or  paralysis  of  one  lateral  half  of  the  body,  and  of  one  or  both 
limbs  on  the  corresponding  side. 

I.  In  Paraplegia,  the  injury  affects  the  whole  substance  of  the  spinal 
cord  at  a  particular  level,  and  the  result  is  loss  of  sensation  and  volun- 
tary motion  on  both  sides,  for  the  whole  of  that  part  of  the  body 
supplied  with  nerves  which  originate  at  or  below  the  level  of  the  injury. 
30 


458  THE    SPINAL    CORD. 

The  seat  of  the  lesion  in  the  spinal  cord  is  determined  by  the  line  at 
which  paralysis  of  sensation  and  motion  begins  in  the  external  parts. 
If  the  lesion  occupy  the  lumbar  portion  of  the  cord,  the  legs  and  the 
pelvic  regions  are  paralyzed  and  insensible,  while  the  arms  and  remain- 
ing parts  of  the  trunk  retain  their  feeling  and  power  of  motion.  If  it 
be  in  the  dorsal  region,  a  corresponding  part  of  the  abdomen  and  thorax 
is  also  deprived  of  sense  and  movement ;  and  if  situated  in  the  middle 
cervical  region,  it  produces  at  the  same  time  paralysis  and  insensibility 
of  both  upper  and  lower  extremities,  together  with  that  of  the  chest  and 
intercostal  muscles.  A  paralysis  of  this  kind,  affecting  the  arms  and 
intercostal  muscles,  is  more  dangerous  than  that  of  the  legs  alone ; 
because  a  slight  extension  of  the  lesion  above  the  middle  cervical  region 
will  paralyze  the  fibres  of  origin  of  the  phrenic  nerves,  and  produce 
death  by  stoppage  of  respiration. 

In  complete  paraplegia,  sensation  and  motion  are  both  abolished  in 
the  affected  parts ;  because  the  injury  or  disease,  when  sufficient  to 
destroy  one  of  these  nervous  functions,  almost  necessarily  reaches  those 
portions  of  the  cord  which  preside  over  the  other.  But  in  slight  or 
incomplete  cases,  either  sensibility  or  movement  may  be  more  or  less 
affected,  according  as  the  lesion  is  more  or  less  advanced  in  different 
parts  of  the  thickness  of  the  cord. 

II.  In  Hemiplegia  of  the  simplest  form,  there  is  loss  of  sensation  and 
voluntary  motion  in  the  right  or  left  arm  and  leg,  the  limbs  on  the 
other  side  of  the  body  remaining  uninjured.  Sensibility  and  the  power 
of  movement  are  also  lost  in  the  integument  and  muscles  of  the  chest 
and  abdomen  on  the  corresponding  side.  It  is,  therefore,  a  complete 
paralysis  of  one  lateral  half  of  the  body ;  the  affection  being  usually 
exactly  limited  by  the  median  line,  both  in  front  and  rear.  In  these 
cases  the  paralysis  is  due  to  some  lesion  within  the  cavity  of  the  cra- 
nium, on  the  opposite  side,  and  above  the  decussation  of  the  anterior 
pyramids ;  namely,  in  the  upper  part  of  the  medulla  oblongata,  the  crura 
cerebri,  the  cerebral  ganglia,  or  the  hemispheres.  It  appears  to  be  most 
frequently  seated  in  the  cerebral  ganglia  or  the  hemispheres. 

In  hemiplegia  from  this  cause,  the  loss  of  sensibility  and  of  the  power 
of  motion,  though  occupying  the  same  half  of  the  body,  are  not  necessa- 
rily equal  in  degree.  According  to  Hammond,1  when  the  cause  of  tin 
difficulty  is  a  cerebral  hemorrhage,  they  are  rarely  present  to  the 
extent.  If  the  lesion  be  situated  lower  down,  in  the  crus  cerebri  or  th< 
tuber  annulare,  they  would  be  more  likely  to  resemble  each  other  in  degi 

When  hemiplegia  is  due,  011  the  other  hand,  to  a  lesion  of  the  spinj 
cord  on  one  side,  the  paralysis  of  motion  is  on  the  same  side  of 
body,  and  that  of  sensibility  on  the  opposite  side.     A  number  of  thei- 
cases  have  been  collected  by  Brown-Sequard,  in  most  of  which  it 
ascertained  that  the  injury  was  seated  in  the  lateral  half  of  the  cord 
corresponding  to  the  paralysis  of  motion. 

1  Diseases  of  the  Nervous  System.     New  York,  1871,  p.  77. 


ACTION    AS    A    NEEVOUS    CENTRE.  459 

Action  of  the  Spinal  Cord  as  a  Nervous  Centre. 

So  far  as  the  spinal  cord  is  concerned  in  the  phenomena  of  sensation 
and  voluntary  motion,  it  acts  as  a  medium  of  communication  between 
the  brain,  where  consciousness  and  volition  reside,  and  the  integument 
and  muscles  of  the  external  parts.  Its  complete  division  accordingly  at 
any  point  destroys  this  communication,  and  suspends  the  nervous  func- 
tions dependent  upon  it ;  so  that  the  commands  of  the  will  are  no  longer 
transmitted  to  the  muscles  below,  and  the  individual  is  incapable  of 
perceiving  impressions  made  upon  the  integument  of  the  paralyzed 
parts.  But  after  such  an  operation  motion  is  not  altogether  abolished 
in  the  body  and  limbs ;  and  impressions  conveyed  by  the  sensitive 
nerve  fibres,  though  no  longer  perceived  by  the  individual,  are  still 
capable  of  producing  an  effect,  and  of  exciting  a  reaction  in  the  organs 
of  movement.  These  phenomena,  which  take  place  without  the  inter- 
vention of  the  brain,  are  produced  by  the  action  of  the  spinal  cord  as  a 
nervous  centre,  and  are  due  to  the  independent  properties  of  its  gray 
matter. 

Eeflex  Action  of  the  Spinal  Cord. — If  a  frog  be  decapitated,  and 
allowed  to  remain  at  rest  for  a  few  moments,  until  the  depressing  effects 
of  the  shock  upon  the  nervous  system  have  passed  off,  movements  can 
readily  be  excited  in  either  the  anterior  or  posterior  limbs.  If  the  skin 
of  one  of  the  feet  be  irritated  by  pinching  with  a  pair  of  forceps,  or  by 
immersing  it  in  a  weak  acidulated  solution,  the  leg  is  immediately 
drawn  upward  toward  the  body,  as  if  to  escape  the  source  of  irritation. 
If  the  stimulus  applied  be  of  slight  intensity,  the  corresponding  leg  only 
will  move ;  but  if  it  be  more  severe  in  character,  motion  will  often  be 
produced  in  the  corresponding  limb  on  the  opposite  side,  or  even  in  all 
the  extremities  at  once.  These  phenomena  may  be  repeated  a  great 
number  of  times,  until  the  irritability  of  the  nervous  system  has  been 
exhausted,  or  until  some  structural  change  has  taken  place  in  the 
tissues. 

Two  important  peculiarities  are  noticeable  in  the  movements  thus 
produced  after  decapitation : 

First,  they  are  never  spontaneous  ;  but  are  only  excited  by  the  appli- 
cation of  an  external  stimulus.  The  decapitated  frog,  if  left  to  itself, 
always  remains  perfectly  motionless,  in  a  nearly  natural  attitude,  but 
without  any  tendency  to  alter  its  position.  Each  application  of  a 
stimulus  causes  a  movement,  after  which  the  limbs  again  assume  a  con- 
dition of  quiescence  until  a  repetition  of  the  stimulus  calls  out  a  new 
movement. 

Secondly,  the  muscular  action  thus  manifested  is  not  produced  by  a 
stimulus  directly  applied  to  the  muscles  themselves.  The  stimulus  is 
applied  to  the  integument  of  the  foot,  and  the  muscles  of  the  leg  and 
thigh  are  contracted  in  consequence.  This  shows  that  both  sensitive 
and  motor  nerve  fibres  take  part  in  the  action.  The  sensitive  fibres 
distributed  to  the  integument  first  receive  the  impression  and  convey  it 


460  THE    SPINAL    CORD. 

inward ;  after  which  the  motor  fibres  transmit  an  outward  stimulus  to 
the  muscles  in  a  different  part  of  the  limb.  Even  the  other  limbs,  as 
already  mentioned,  may  be  set  in  motion  by  an  irritation  applied  to 
the  integument  of  one. 

Furthermore,  the  nervous  action  is  not  transmitted,  in  these  cases, 
directly  from  the  integument  to  the  muscles;  it  passes  through  the 
spinal  cord,  which  thus  forms  a  necessary  link  in  the  chain  of  communi- 
cation ;  for  if  the  posterior  limb  be  left  uninjured,  while  its  connection 
with  the  cord  is  severed  by  dividing  the  sciatic  nerve  in  the  cavity  of 
the  abdomen,  no  further  action  can  be  excited,  and  the  limb  remains 
motionless  whatever  irritation  be  applied  to  the  integument. 

Lastly,  if  the  spinal  cord  itself  be  destroyed  by  the  introduction  of  a 
stilet  into  the  spinal  canal,  this  also  puts  an  end  to  the  phenomena,  and 
irritation  of  the  integument  will  no  longer  produce  a  muscular  reaction. 
After  that,  the  muscles  can  only  be  excited  to  contraction  by  a  stimulus 
applied  directly  to  themselves,  or  to  their  motor  nerves. 

All  these  facts  show  that  the  phenomena  in  question  are  due  to  the 
reflex  action  of  a  nervous  centre,  in  which  three  different  nervous  ele- 
ments take  part ;  namely,  first,  the  sensitive  nerve  fibres,  conveying  an 
impression  inward  from  the  integument ;  secondly,  motor  nerve  fibres, 
transmitting  a  stimulus  outward  to  the  muscles  ;  and,  thirdly,  a  nervous 
centre  which  intervenes  between  the  two,  and  in  which  the  reflex  action 
is  accomplished.  The  nervous  centre,  in  this  instance,  is  the  gray  sub- 
stance of  the  spinal  cord. 

It  is  evident,  accordingly,  that  consciousness  is  not  a  necessary  ac- 
companiment to  the  reception  of  sensitive  impressions  by  a  nervous 
centre ;  and  that  a  motor  impulse  may  also  originate  in  a  nervous  centre 
without  the  act  of  volition.  The  reflex  action  of  the  spinal  cord  takes 
place  without  either  consciousness  or  volition  ;  and  yet  it  is  completely 
efficient,  and  produces  muscular  contraction  at  once  on  the  application 
of  a  stimulus  to  the  skin. 

Diminution  or  Increase  of  Beflex  Action  in  the  Cord. — The  reflex 
action  of  the  spinal  cord,  like  other  forms  of  nervous  activity,  may  suffer 
a  temporary  depression,  or  even  total  suspension,  by  any  shock  or  injury 
to  the  system  at  large.  The  operation  of  separating  the  head  from  the 
trunk  in  the  frog  will  often  be  followed,  for  a  few  moments,  by  an 
interval  of  complete  nervous  paralysis,  in  which  no  phenomena  of  reac- 
tion can  be  obtained.  Even  injuries  in  which  the  nervous  centres  are 
not  directly  interested,  such  as  the  opening  of  the  abdomen  and  the 
removal  of  the  abdominal  organs,  may  produce  a  similar  temporary 
effect.  In  some  instances  the  duration  of  this  period  of  depression  is 
very  short,  so  as  to  be  almost  imperceptible ;  in  others  it  lasts  for 
several  minutes.  After  it  has  passed  off,  the  reflex  irritability  of  the 
cord  returns  to  its  natural  condition,  and,  if  the  cord  itself  have  been 
wounded  or  divided,  may  even  be  perceptibly  increased  in  intensity. 

It  is  for  this  reason  that  the  reflex  action  of  the  cord  often  seems  to 
be  more  vigorous  and  prompt  in  the  frog  after  the  removal  of  the  head, 


ACTION    AS    A    NERVOUS    CENTRE.  461 

or  the  transverse  division  of  the  cord  itself  at  its  upper  part.  The 
wound  of  the  nervous  substance  induces  an  increased  excitability  of  its 
gray  matter,  in  consequence  of  which  sensitive  impressions  of  a  moderate 
character  produce  a  more  energetic  muscular  reaction.  This  is  shown 
by  the  observations  of  Tiirck,  Bernard,  and  Yulpian,  in  which,  after  a 
section  of  one  lateral  half  of  the  cord,  the  posterior  leg  on  that  side  is 
withdrawn  more  rapidly  from  an  acidulated  solution  than  the  other ;  and 
in  which  the  reflex  action  of  the  cord,  in  decapitated  animals,  becomes 
more  and  more  marked,  for  the  posterior  limbs,  in  consequence  of  suc- 
cessive transverse  sections  made  from  before  backward,  in  the  cervical 
and  lumbar  regions. 

The  reflex  action  of  the  cord  may  also  be  increased  by  poisonous 
substances.  Strychnine  is  the  most  efficient  in  this  respect,  and  pro- 
duces very  rapidly  an  exalted  condition  of  irritability  in  the  spinal  cord, 
in  consequence  of  which  a  slight  irritation  of  the  skin  is  followed  by 
excessive  muscular  reaction.  If  a  frog  be  simply  decapitated  and  left 
in  repose  for  a  short  time,  the  reflex  action  of  the  cord  manifests  itself, 
as  usual,  in  a  distinct  but  moderate  degree.  Slight  irritations  have  no 
perceptible  effect,  and  the  pinching  of  the  skin  in  one  hind  foot  usually 
causes  retraction  of  that  limb  only.  But  if  a  solution  of  strychnine 
be  injected  underneath  the  skin,  at  the  end  of  ten  or  fifteen  minutes, 
when  absorption  has  taken  place,  the  reflex  irritability  of  the  cord  is 
found  to  be  exaggerated  in  a  very  marked  degree.  The  animal  still 
remains  motionless  if  undisturbed ;  but  the  slightest  irritation  applied 
to  the  skin,  the  contact  of  a  hair  or  feather,  or  the  jar  produced  by 
striking  the  table  upon  which  it  is  placed,  will  often  be  sufficient  to 
throw  it  into  violent  convulsive  action,  in  which  all  the  limbs  take  part. 
As  these  effects  are  produced  in  the  decapitated  animal,  no  influence  can 
be  attributed  to  the  action  of  the  brain.  Strychnine,  accordingly,  is  a 
poison  which  acts  directly  upon  the  spinal  cord  by  increasing  its  excita- 
bility, and  by  thus  causing  convulsive  movements  in  consequence  of 
slight  external  irritation. 

Similar  results  are  known  to  follow  from  wounds  or  injuries  either  of 
the  cord  itself  or  of  peripheral  parts  of  the  nervous  system.  Brown- 
S^quard  has  found1  that  in  Guinea-pigs  a  section  of  one  lateral  half  of 
the  spinal  cord  sometimes  produces,  after  a  few  weeks,  such  a  condition 
of  the  nervous  centres  that  the  animal  becomes  epileptic,  and  that  epi- 
leptiform  convulsions  of  a  very  intense  character  may  be  excited  by 
pinching  the  skin  of  part  of  the  face  and  neck,  on  the  side  corresponding 
with  the  lateral  section  of  the  cord.  The  phenomena  of  tetanus  in  man, 
following  wounds  of  the  peripheral  nerves,  are  also  of  a  reflex  convulsive 
character.  The  tetanic  spasm  is  often,  if  not  always,  excited  by  an 
external  cause ;  but  this  cause  is  so  slight  that  in  the  healthy  condition 
it  would  have  no  perceptible  effect.  The  accidental  movement  of  the 
bedclothes,  the  shutting  of  a  door,  the  passing  of  a  carriage  in  the 

1  Researches  on  Epilepsy.     Boston,  1857. 


462  THE    SPINAL    COED. 

street,  or  even  a  current  of  air  upon  the  skin,  may  be  sufficient  to  throw 
the  muscular  system  into  severe  spasmodic  action.  The  reflex  irrita- 
bility of  the  spinal  cord  may,  therefore,  be  increased  or  diminished  by 
various  causes  acting  upon  it  from  without. 

Reflex  Action  of  the  Cord  in  Warm-blooded  Animals  and  in  Man. — 
In  the  frog,  as  well  as  in  other  cold-blooded  animals,  the  reflex  action 
of  the  spinal  cord  lasts  for  a  comparatively  long  time  after  decapitation 
or  the  stoppage  of  the  circulation ;  continuing  sometimes,  if  the  animal 
be  kept  in  repose  and  sufficiently  cool  and  moist,  for  twenty-four  hours 
or  even  longer.  In  the  warm-blooded  animals,  it  disappears  much  more 
rapidly ;  and  it  must  be  sought  for,  if  at  all,  within  a  very  short  time 
after  death,  since  a  nearly  constant  supply  of  blood  is  essential  in  these 
animals  to  a  continuance  of  the  physiological  action  in  every  part  of  the 
nervous  system.  If  artificial  respiration  be  kept  up,  however,  so  as  to 
maintain  the  circulation,  the  reflex  action  of  the  cord  will  continue  to 
manifest  itself,  independently  of  the  brain ;  and  the  same  thing  may  be 
accomplished,  by  dividing  the  spinal  cord  in  the  lower  cervical  or  upper 
dorsal  region  below  the  origin  of  the  phrenic  nerve.  The  animal  then 
continues  to  breathe  by  means  of  the  diaphragm ;  and  although  deprived 
of  both  sensibility  and  voluntary  motion  in  the  posterior  limbs,  move- 
ments of  the  leg  are  produced  by  pinching  the  skin  of  the  foot. 

Robin  has  observed  the  phenomena  of  reflex  action  of  the  cord,  after 
decapitation,  in  man,  in  the  case  of  an  executed  criminal  whose  body 
was  subjected  to  examination.  The  reflex  muscular  contractions  were 
produced  about  one  hour  after  the  execution.1  "  While  the  right  arm 
was  lying  extended  in  an  oblique  position  by  the  side  of  the  trunk, 
with  the  hand  about  25  centimetres  distant  from  the  upper  part  of  the 
thigh,  I  scratched  with  the  point  of  a  scalpel  the  skin  of  the  chest  at 
the  areola  of  the  nipple,  for  a  space  of  10  or  11  centimetres  in  extent, 
without  making  any  pressure  upon  the  subjacent  muscles.  We  im- 
mediately saw  a  rapid  and  successive  contraction  of  the  great  pectoral 
muscle,  the  biceps,  probably  the  brachialis  anticus,  and  lastly  the  mus- 
cles covering  the  internal  condyle." 

"  The  result  was  a  movement  by  which  the  whole  arm  was  made  to 
approach  the  trunk,  with  rotation  of  the  arm  inward  and  half-flexion  of 
the  forearm  upon  the  arm ;  a  true  defensive  movement,  which  brought 
the  hand  toward  the  chest  as  far  as  the  pit  of  the  stomach.  Neither 
the  thumb,  which  was  half  bent  toward  the  palm  of  the  hand,  nor  the 
fingers,  which  were  half  bent  over  the  thumb,  presented  any  move- 
ments." 

"  The  arm  being  replaced  in  its  former  position,  we  saw  it  again  exe- 
cute a  similar  movement  on  scratching  the  skin,  in  the  same  manner  as 
before,  a  little  below  the  clavicle.  This  experiment  succeeded  four 
times,  but  each  time  the  movement  was  less  extensive  than  before ;  and 

1  Journal  de  1'Anatomie  et  de  la  Physiologic.     Paris,  1869,  p.  90. 


ACTION    AS    A    NERVOUS    CENTRE.  463 

afterward  the  scratching  of  the  skin  over  the  chest  produced  only  con- 
tractions in  the  great  pectoral  muscle  which  hardly  stirred  the  arm." 

The  neck  had  been  severed,  in  the  above  case,  at  about  the  level  of 
the  fourth  cervical  vertebra. 

The  reflex  action  may  also  be  seen  very  distinctly  in  the  human  sub- 
ject, in  certain  cases  of  disease  of  the  spinal  cord.  If  the  upper  portion 
of  the  cord  be  disintegrated  by  inflammatory  softening,  so  that  its 
middle  and  lower  portions  lose  their  natural  connection  with  the  brain, 
paralysis  of  voluntary  motion  and  loss  of  sensation  ensue  in  all  parts 
of  the  body  below  the  seat  of  the  anatomical  lesion.  Under  these  con- 
ditions, the  patient  is  incapable  of  making  any  muscular  exertion  in  the 
paralyzed  parts,  and  is  unconscious  of  any  injury  done  to  the  integu- 
ment in  the  same  region.  But  if  the  soles  of  the  feet  be  gently  irritated 
with  a  feather  or  with  the  point  of  a  needle,  a  convulsive  twitching  of 
the  toes  will  often  take  place,  and  even  retractile  movements  of  the  leg 
and  thigh,  altogether  without  the  patient's  knowledge.  Such  move- 
ments may  frequently  be  excited  by  simply  allowing  the  cool  air  to 
come  suddenly  in  contact  with  the  lower  extremities.  We  have 
repeatedly  witnessed  these  phenomena,  in  a  case  of  disease  of  the  spinal 
cord,  where  the  paralysis  and  insensibility  of  the  lower  extremities 
were  complete.  Many  similar  instances  have  been  reported  by  various 
authors. 

Physiological  Action  of  the  Spinal  Cord,  as  a  Nervous  Centre,  during 
health. — The  physiological  character  of  the  reflex  action  of  the  spinal 
cord,  as  it  takes  place  in  the  healthy  condition,  is  not  easily  brought 
under  observation.  In  animals,  unless  the  head  be  removed  or  the 
spinal  cord  separated  from  the  brain,  the  reflex  and  voluntary  move- 
ments are  liable  to  be  confounded ;  and  in  man  during  health  the  phe- 
nomena of  sensation  and  volition  are  so  prominent,  as  to  conceal  or 
obscure  those  which  are  performed  independently  of  the  consciousness 
and  the  will.  Nevertheless,  the  latter  are  exceedingly  important,  and 
many  of  them  in  almost  constant  operation. 

The  general  character  of  the  reflex  actions  of  the  spinal  cord  is  that 
they  tend  unconsciously  to  the  defence  or  preservation  of  the  body. 
This  character  is  even  seen  in  the  simple  experiments  performed  upon 
the  decapitated  frog.  If  the  frog  in  this  condition  be  suspended  in  the 
air  by  its  anterior  extremity,  the  posterior  limbs  hang  downward  in  a 
perfectly  relaxed  condition.  On  pinching  the  integument  of  a  foot,  or 
immersing  it  in  acidulated  water,  the  limb  is  drawn  upward  by  contrac- 
tion of  its  flexor  muscles,  and  the  result  of  this  movement  is  a  with- 
drawal of  the  foot  from  the  source  of  irritation.  When  the  muscles 
relax,  the  limb  lengthens  until  the  foot  again  touches  the  irritating 
liquid,  when  it  is  again  drawn  up ;  and  so  on,  until  the  irritability  of 
the  cord  is  so  far  diminished,  or  accustomed  to  that  particular  stimulus, 
that  it  no  longer  reacts.  In  this  case,  therefore,  it  is  not  all  the  mus- 
cles of  the  leg  and  thigh  which  are  thrown  into  activity  by  irritating 
the  skin,  but  only  the  flexors,  which  tend  to  withdraw  the  foot  from  the 


464  THE    SPINAL    CORD. 

irritation  to  which  it  is  subjected.  When  an  irritation  is  applied  to  the 
skin  on  the  side  of  the  trunk,  it  is  common  to  see  a  hind  foot  applied  to 
the  irritated  spot,  as  if  to  protect  if  from  a  repetition  of  the  stimulus ; 
and  in  some  instances  the  adaptation  of  reflex  movements  to  accom- 
plish a  definite  result  is  very  marked.  This  cannot  be  attributed  to 
any  faculty  of  perception  belonging  to  the  spinal  cord ;  since  we  know, 
from  pathological  cases  in  man,  that  when  the  cord  is  separated  from 
the  brain  by  disease  or  injury,  the  parts  below  are  left  absolutely  with- 
out conscious  sensibility  or  power  of  volition.  The  character  of  the 
movement  produced  therefore  depends  directly  upon  the  anatomical 
structure  of  the  limbs  and  the  nervous  mechanism  of  the  spinal  cord. 
In  the  case  of  reflex  action  observed  by  Robin  in  a  decapitated  criminal, 
the  effect  of  gentle  irritation  of  the  skin  over  the  front  of  the  chest 
was  a  simple  movement  of  flexion  and  inward  rotation  of  the  arm  and 
forearm;  and  this  necessarily  brought  the  hand  near  the  point  irri- 
tated. It  is  evident  that  the  connection  of  the  sensitive  nerve  fibres 
with  motor  fibres,  through  the  gray  matter  of  the  cord,  may  be  such  as 
to  call  into  action  muscles  which  are  adapted  to  accomplish  a  particular 
movement,  without  the  intervention  of  any  perception  or  voluntary  im- 
pulse. This  is  the  character  of  the  reflex  action  of  the  spinal  cord. 

As  a  general  rule,  movements  of  flexion  are  adapted  to  protect  the 
part  from  external  irritation  or  injury,  and  are  excited  by  ordinary  or 
moderate  causes  ;  those  of  extension  are  calculated  to  repel  the  foreign 
substance  or  to  escape  from  it  by  moving  the  whole  body,  and  are  only 
called  out  by  an  unusual  or  excessive  stimulus.  The  defensive  or  pro- 
tective character  of  these  movements  is  often  to  be  seen,  in  a  state  of 
health,  when  the  brain  takes  no  part  in  their  production.  If  the  surface 
of  the  skin,  for  example,  be  unexpectedly  brought  in  contact  with  a 
heated  body,  the  injured  part  is  often  withdrawn  by  a  rapid  and  con- 
vulsive movement,  before  we  feel  the  pain,  or  even  fairly  understand  the 
cause  of  the  involuntary  act.  When  the  body  by  any  accident  suddenly 
loses  its  balance,  the  limbs  are  thrown  into  a  flexed  position,  calculated 
to  protect  the  exposed  parts  and  to  break  the  fall,  by  a  similar  invol- 
untary and  instantaneous  movement.  Notwithstanding,  therefore,  the 
evident  utility  of  these  actions,  they  have  no  intentional  character,  and 
there  is  not  even  any  distinct  consciousness  of  their  object. 

The  spinal  cord  has  also  an  important  action  in  regard  to  the  attitude 
and  to  locomotion.  The  preservation  of  the  attitude  alone  requires  the 
harmonious  action  of  many  different  muscles,  all  of  which  contribute 
in  various  degrees  to  the  position  of  the  whole  body.  This  is  especially 
the  case  in  man,  where,  in  the  standing  posture,  the  bod}*-  is  balanced 
upon  its  narrow  supports,  in  such  a  way  as  to  preserve  its  equilibrium 
without  attention  or  fatigue.  In  the  movements  of  locomotion  also,  the 
different  flexors  and  extensors  of  the  anterior  and  posterior  limbs  are 
associated  in  a  manner  peculiar  to  each  species  of  animal ;  and  in  man 
the  balancing  of  the  body  requires,  in  progression,  a  still  more  exten- 
sive combination  of  muscular  action  than  when  at  rest. 


ACTION    AS    A    NERVOUS    CENTRE.  465 

The  spinal  cord  by  itself  is  not  sufficient  to  produce  the  muscular 
actions  required  for  standing  and  locomotion;  since  we  know  that  any 
sudden  lesion  which  deeply  injures  the  brain,  or  cuts  off  the  medulla 
oblongata,  or  divides  the  spinal  cord  above  the  cervical  or  lumbar  enlarge- 
ments, either  in  mammalia  or  in  man,  instantly  destroys  the  power  of 
standing  upright,  or  of  making  any  effective  movements  of  locomotion. 
In  the  frog,  an  attitude  very  similar  to  the  natural  one  is  often  preserved 
after  decapitation,  since  the  body  rests  by  most  of  its  under  surface 
upon  the  ground  ;  and  the  contact  of  the  integument,  through  the  reflex 
action  of  the  spinal  cord,  brings  the  limbs  underneath  it  in  a  flexed 
position.  If  such  a  frog  be  held  suspended  in  the  air,  the  limbs  hang 
down  in  a  relaxed  condition,  and  again  assume  the  natural  attitude  of 
flexion,  when  replaced  in  contact  with  a  hard  surface ;  and,  according  to 
Poincare,1  it  can  sometimes  be  made  to  execute  a  series  of  leaps,  each 
concussion,  as  the  body  strikes  the  ground,  giving  a  fresh  stimulus  for 
another  reflex  movement  of  extension  in  the  limbs.  But  in  the  case  of 
the  frog  and  of  the  amphibious  reptiles  generally,  the  muscular  actions 
required,  both  for  the  attitude  and  for  locomotion,  are  of  the  simplest 
character.  In  the  warm-blooded  quadrupeds  and  in  man,  on  the  other 
hand,  the  act  of  volition  is  essential  for  either  standing  or  progression; 
and  both  these  powers  are  abolished  by  cutting  off  the  communication 
of  the  spinal  cord  with  the  brain. 

But,  although  the  voluntary  impulse  is  necessary  to  produce  the  acts 
of  standing  or  walking,  it  does  not  seem  to  be  concerned  in  the  details 
of  their  mechanism.  Once  excited,  the  nervous  action  by  which  walking 
is  accomplished  may  be  kept  up  without  any  mental  effort,  the  attention 
being  directed  to  something  else.  All  we  have  to  do  is,  to  commence 
the  process  by  an  act  of  volition,  and  the  requisite  nervous  machinery 
is  at  once  set  in  motion.  If  we  decide  to  turn  a  corner,  all  the  muscular 
combinations  necessary  for  that  purpose  are  effected  without  the  imme- 
diate intervention  of  the  consciousness  or  the  will.  This  secondary 
action,  by  which  the  different  motor  impulses  are  combined  in  the  limbs 
and  trunk,  is  undoubtedly  dependent  upon  the  integrity  of  the  spinal 
cord. 

The  precise  mode  in  which  this  action  is  accomplished  is  not  positively 
ascertained.  The  most  probable  explanation  at  present  known  is  that 
it  is  due  to  a  constant  reflex  activity  of  the  cord,  by  which  the  muscles 
in  different  parts  of  the  body  and  limbs  are  kept  in  the  proper  degree 
of  tension  or  relaxation ;  and  that  the  different  parts  of  the  cord  are 
united  with  each  other  for  this  purpose  by  longitudinal  commissural 
fibres  which  enter  and  leave  its  gray  substance  at  successive  points. 
Some  authors  (Todd,  Vulpian,  Poincare)  adopt  the  opinion  that  the 
posterior  columns  constitute  such  longitudinal  commissures.  The 
reasons  for  this  opinion  are  not  fully  satisfactory,  since  anatomical 
investigation  has  thus  far  failed  to  show  what  is  the  actual  origin  and 

1  Lecjous  sur  la  Physiologic  dn  Systfeme  Nervcux.     Paris,  1873,  p.  72. 


466  THE    SPINAL    CORD. 

termination  of  the  longitudinal  fibres  of  these  columns ;  but  there  are 
several  facts  which  give  it  a  strong  degree  of  probability.  The  three 
principal  reasons  in  support  of  this  view  are  as  follows : 

I.  The  posterior  columns,  as  fully  shown  by  direct  experiment,  are 
not  the  necessary  organs  of  transmission  for  either  sensation  or  volun- 
tary motion ;  and  they  are,  nevertheless,  composed  of  nerve  fibres  which 
run  in  a  longitudinal  direction.     In  all  the  white  columns  of  the  cord, 
in  their  deeper  parts,  where  they  lie  in  contact  with  the  gray  substance, 
there  are  oblique  or  horizontal  fibres,  entering  or  emerging  from  the 
gray  substance,  which  may  either  belong  to  the  anterior  and  posterior 
nerve  roots,  or  may  be  commissural  fibres  running  lengthwise  from  one 
part  of  the  cord  to  the  other. 

II.  According  to  Yulpian,1  if  the  posterior  columns  be  divided  by 
several  transverse  sections,  at  intervals  of  two  or  three  centimetres  dis- 
tance from  each  other,  the  effect  of  the  operation  is  a  singular  disturb- 
ance in  the  power  of  locomotion,  like  what  would  be  produced  by  a  loss 
of  harmony  in  muscular  action. 

III.  The  most  important  facts,  however,  bearing  on  this  question,  are 
those  connected  with  the  disease  in  man,  known  as  locomotor  ataxia. 
In  this  affection  there  is  a  remarkable  difficulty  in  walking,  of  such  a 
character  that  the  patient's  natural  gait  is  altered,  and  he  is  no  longer 
sure  of  his  movements.     He  loses  more  or  less  the  power  of  equilibrium, 
and  cannot  guide  his  foot  to  a  particular  point  without  looking  at  it 
and  at  the  same  time  making  a  direct  effort  of  the  will.     Consequently 
locomotion,  as  it  is  usually  performed,  becomes  impossible ;  and  yet  the 
patient  has  not  lost  the  power  of  voluntary  movement  in  any  degree, 
since  he  can  often  exert  as  much  muscular  force  as  ever  in  grasping  an 
object  or  in  simply  pushing  or  pulling  with  his  legs  or  arms.     But  he 
has  lost  the  power  of  guiding  his  movements  by  an  involuntary  combi- 
nation, so  as  to  perform  with  ease  the  act  of  ordinary  locomotion.     It 
is  for  this  reason  that  the  affection  is  called  "  ataxia,"  and  not  paralysis. 

In  this  disease  the  only  parts  of  the  nervous  system  which  are  always 
found  to  be  affected  are  the  posterior  columns  of  the  spinal  cord.  They 
are  the  seat  of  a  structural  degeneration  termed  "  sclerosis,"  in  which 
the  elements  of  the  connective  tissue  are  increased  in  quantity  and  den- 
sity, while  the  nerve  fibres  are  altered  and  atrophied,  or  finally  disappear 
altogether.  According  to  Brown -Sdquard,  an  alteration  limited  to  a 
small  extent  of  the  posterior  columns  does  not  usually  affect  the  volun- 
tary movements ;  but  if  it  extend  for  a  few  inches  in  length,  in  either 
the  cervical  or  the  dorso-lumbar  region,  it  always  causes  a  disturbance 
of  these  movements ;  and  when  it  occupies  the  whole  length  and  thick- 
ness of  these  columns,  the  patient  can  neither  stand  nor  walk,  although 
while  lying  down  and  with  the  aid  of  vision  he  can  move  his  limbs 
freely  in  any  direction. 

1  Leqons  sur  la  Physiologie  du  Systfeme  Nerveux.     Paris,  1866,  p.  381. 


ACTION    AS    A    NERVOUS    CENTRE.  467 

Another  important  action  of  the  spinal  cord,  as  a  nervous  centre, 
consists  in  its  control  over  the  sphincters  and  the  organs  of  evacuation. 

While  the  small  intestine,  the  caecum,  and  the  colon  are  supplied  ex- 
clusively with  nerves  from  the  abdominal  plexuses  of  the  sympathetic 
system,  the  lower  portion  of  the  rectum  receives  branches  from  the 
sacral  plexus  of  spinal  nerves,  which  are  distributed  both  to  its  mucous 
membrane  and  its  muscular  apparatus.  The  lower  part  of  the  large 
intestine  acts  in  great  measure  as  a  temporary  reservoir,  in  which  the 
feces,  brought  down  from  above  by  peristaltic  movement,  accumulate 
until  the  time  arrives  for  their  evacuation.  The  rectum,  in  man,  is 
usually  empty,  or  nearly  so,  until  shortly  before  evacuation ;  and  when 
the  feces  begin  to  pass  into  it  from  above,  it  is  still  capable  of  retaining 
them  for  a  certain  period.  Their  retention  and  discharge  are  provided 
for,  in  this  part  of  the  alimentary  canal,  by  two  sets  of  muscular  fibres ; 
namely,  first,  the  sphincter  ani,  which  keeps  the  orifice  of  the  anus 
closed;  and  secondly,  the  levator  ani  and  the  circular  fibres  of  the 
rectum  itself,  which  by  their  contraction  open  the  anus  and  expel  the 
feces.  Both  these  acts  are  regulated  by  the  reflex  influence  of  the 
spinal  cord. 

In  the  natural  condition,  the  sphincter  ani  is  habitually  in  a  state  of 
contraction,  thus  preventing  the  escape  of  the  contents  of  the  intestine. 
Any  external  irritation,  applied  to  the  verge  of  the  anus,  causes  increased 
contraction  of  its  fibres  and  a  more  complete  occlusion  of  its  orifice. 
This  habitual  closure  of  the  sphincter  is  an  entirely  involuntary  act,  as 
efficient  during  profound  sleep  as  in  the  waking  condition,  and  depends 
upon  the  reflex  action  of  the  spinal  cord. 

But  when  the  rectum  is  distended  to  a  certain  point  by  feces  passing 
into  it  from  above,  the  nervous  action  changes.  The  impression  then 
produced  upon  the  mucous  membrane  of  the  rectum,  conveyed  inward 
by  its  sensitive  nerve  fibres  to  the  spinal  cord,  causes  a  relaxation  of 
the  sphincter  ani.  At  the  same  time  the  levator  ani  draws  the  borders 
of  the  relaxed  orifice  upward  and  outward,  and  the  feces  are  expelled  by 
the  contraction  of  the  muscular  fibres  of  the  rectum  itself. 

Both  these  actions  are  in  some  degree  associated,  in  a  state  of  health, 
with  sensation  and  volition.  The  distension  of  the  rectum  which  pre- 
cedes an  evacuation  is  usually  accompanied  by  a  distinct  sensation,  and 
the  resistance  of  the  sphincter  may  be  intentionally  prolonged  for  a  cer- 
tain period.  But  this  voluntary  power  over  the  muscular  contractions 
is  limited.  After  a  time  the  involuntary  impulse,  growing  more  urgent 
with  the  increased  distension  of  the  rectum,  becomes  irresistible ;  and 
the  discharge  finally  takes  place  by  simple  reflex  action  of  the  spinal 
cord. 

If  the  irritability  of  the  cord  be  exaggerated  by  disease,  while  its 
connection  with  the  brain  remains  entire,  the  distension  of  the  rectum 
is  announced  by  the  usual  sensation ;  but  the  reflex  impulse  to  evacua- 
tion is  so  urgent  that  it  cannot  be  controlled  by  the  will,  and  the  patient 


468  THE    SPINAL    CORD. 

is  compelled  to  allow  it  to  take  place  at  once.  The  discharges  are  then 
said  to  be  ''involuntary." 

If  the  cord,  on  the  other  hand,  be  injured  or  divided  in  its  middle  or 
upper  portions,  the  sensibility  and  voluntary  action  of  the  sphincter  are 
lost,  because  its  connection  with  the  brain  has  been  destroyed.  The 
evacuation  then  takes  place  at  once,  by  the  ordinary  mechanism,  as  soon 
as  the  rectum  is  filled,  but  without  any  knowledge  on  the  part  of  the 
patient.  The  discharges  are  then  said  to  be  "  involuntary  and  uncon- 
scious." 

Finally,  if  the  lower  portion  of  the  cord,  in  the  living  animal,  be  broken 
up  by  means  of  an  instrument  introduced  into  the  spinal  canal,  the  tonic 
contraction  of  the  sphincter  ani  at  once  disappears.  The  same  effect  is 
produced,  in  man,  by  disorganization  of  the  lower  part  of  the  spinal 
cord  from  injury  or  disease.  The  sphincter  ani  is  then  permanently 
relaxed,  and  the  feces  are  evacuated  almost  continuously,  without  the 
knowledge  or  control  of  the  patient,  as  fast  as  they  descend  into  the 
rectum  from  the  upper  portions  of  the  intestinal  canal. 

The  urinary  bladder  is  also  an  organ  both  of  reservoir  and  evacua- 
tion, which  is  protected  by  the  circular  bundle  of  muscular  fibres  at  the 
commencement  of  the  urethra,  known  as  the  "  sphincter  vesica?."  While 
the  nerves  distributed  to  the  kidneys  are  derived  exclusively  from  the 
coeliac  plexus  of  the  sympathetic  system,  those  of  the  bladder  consist 
partly  of  sympathetic  filaments  from  the  mesenteric  ganglia,  and  partly 
of  cerebro-spinal  filaments  from  the  lumbar  portion  of  the  spinal  cord, 
both  of  these  sets  having  united  in  the  abdomen  to  form  the  hypogastric 
plexus. 

The  tonic  contraction  of  the  vesical  sphincter  during  health,  by  which 
the  urine  is  retained  in  the  bladder,  is  a  continuous,  involuntary,  and 
unconscious  act,  like  that  of  the  sphincter  ani.  When  the  time  comes 
for  evacuation,  the  sphincter  is  relaxed  by  a  voluntary  impulse,  and  the 
muscular  coat  of  the  bladder  contracts  so  as  to  expel  its  contents;  but 
although  the  commencement  of  this  process  is  a  voluntary  one,  the  sub- 
sequent contraction  of  the  muscular  walls  of  the  bladder  continues  with- 
out any  effort  of  the  will.  According  to  the  experiments  of  Giannuzzi1 
on  dogs,  irritation  of  the  lumbar  portion  of  the  spinal  cord  by  pricking 
with  a  steel  needle,  causes  contraction  of  the  urinary  bladder ;  and 
these  contractions  are  no  longer  produced  after  division  of  the  roots  of 
the  sacral  nerves.  Irritation  of  either  the  sympathetic  or  the  spinal 
nerve  filaments  going  to  the  hypogastric  plexus  produced  contraction 
of  the  bladder,  but  these  contractions  were  more  energetic  in  the  latter 
case  than  in  the  former. 

Diseases  or  injuries  of  the  spinal  cord  which  cause  complete  para* 
plegia,  also  usually  produce  a  paralysis  of  the  bladder.  So  far  as  re- 
gards contraction  of  the  bladder  itself,  therefore,  this  act  is  under  the 
influence  both  of  the  sympathetic  and  cerebro-spinal  systems ;  but  its 

1  Journal  dc  la  Physiologic.     Paris,  1863,  tome  vi.  p.  22. 


ACTION"    AS    A    NERVOUS    CENTRE.  469 

most  energetic  stimulus  is  derived  from  the  spinal  cord  through  the 
sacral  nerves. 

The  closure  or  relaxation  of  the  sphincter  vesicse,  on  the  other  hand, 
is  regulated  by  nervous  influences  coming  from  the  cerebro-spinal  sys- 
tem alone.  The  contraction  of  the  sphincter  offers  a  resistance  to  the 
escape  of  fluid  from  the  bladder,  which  may  be  measured,  and  which 
was  found  by  Kupressow,1  in  the  rabbit,  to  be  equal  to  the  pressure  of 
a  column  of  water  more  than  40  centimetres  in  height.  That  is,  if  in 
the  living  animal  one  of  the  ureters  were  closed  by  a  ligature,  and  an 
upright  tube  fastened  in  the  other,  the  bladder  and  the  upright  tube 
might  be  filled  with  water  to  a  height,  on  the  average,  of  44  centimetres 
without  any  of  it  escaping  by  the  urethra ;  beyond  that  point  the  con- 
tractile power  of  the  sphincter  was  overcome,  and  the  water  was  dis- 
charged by  the  urethral  orifice. 

The  experiments  of  Kupressow  also  show  that  the  nervous  centre 
upon  which  the  sphincter  vesicae  depends  for  its  reflex  stimulus  is  in 
the  lumbar  portion  of  the  spinal  cord.  For  if  the  cord  were  divided  at 
the  level  of  the  first  or  second  lumbar  vertebrae,  no  difference  was  per- 
ceptible in  the  amount  of  resistance  to  pressure  offered  by  the  sphincter ; 
and  sections  at  the  levels  of  the  third  and  fourth  lumbar  vertebrae  made 
a  difference  of  only  two  centimetres.  But  if  the  section  of  the  cord  were 
made  at  the  fifth  lumbar  vertebra,  the  resistance  of  the  sphincter  was  at 
once  reduced  to  14  centimetres;  and  the  same  effect  was  produced  by 
section  at  the  sixth  and  seventh  vertebrae  of  the  same  region.  The 
tonic  contraction,  therefore,  of  the  sphincter  vesicae,  although  it  may  be 
aided  by  an  act  of  volition,  is  directly  dependent  upon  a  nervous  centre 
situated,  in  the  rabbit,  about  the  "middle  of  the  lumbar  portion  of  the 
spinal  cord ;  since  this  contraction  persists  after  the  cord  has  been 
separated  from  the  brain  by  a  section  at  or  above  the  fourth  lumbar 
vertebra,  while  it  disappears  if  the  section  be  made  at  or  below  the  fifth 
lumbar  vertebra,  thus  either  destroying  the  nervous  centre  itself  or 
cutting  off  its  communication  with  the  bladder. 

Both  the  retention  of  the  urine  in  the  bladder  and  its  evacuation  may 
also  be  accomplished  without  the  aid  of  any  voluntary  act.  This  is 
shown  by  the  experiments  of  Goltz,2  who  found  that  after  division  of 
the  spinal  cord,  in  dogs,  between  the  dorsal  and  lumbar  regions,  the 
animals,  though  deprived  of  sensibility  and  voluntary  motion  in  the 
posterior  parts  of  the  body,  could  often  retain  their  urine  for  a  con- 
siderable time,  and  also  evacuate  it  by  a  regular  and  forcible  contrac- 
tion of  the  bladder. 

In  man,  when  the  sensibility  of  the  mucous  membrane  of  the  bladder 
or  neighboring  parts  is  increased  by  inflammation,  the  reflex  impulse  to 
micturition  is  increased  in  intensity,  producing  an  intolerance  of  urine. 
Under  these  circumstances  the  urine  is  discharged  by  a  reflex  act  as 

1  Archiv  fur  die  gesammte  Physiologic.     Bonn,  1872,  Band  v.  p.  291. 

2  Archiv  fur  die  gesammte  Physiologic.     Bonn,  1874,  Band  viii.  p.  474. 


470  THE    SPINAL    CORD. 

soon  as  a  small  quantity  of  it  has  accumulated  in  the  bladder.  The 
impression  which  excites  this  discharge  is  accompanied  by  a  conscious 
sensation,  but  is  too  urgent  to  be  resisted  by  the  will. 

On  the  other  hand,  injury  or  destruction  of  the  spinal  cord  in  the 
dorsal  region  may  cut  off  all  sensibility  and  voluntary  power  over  the 
bladder,  and  yet  the  organ  may  be  evacuated  at  regular  intervals  by 
the  reflex  action  of  the  lumbar  portion  of  the  cord.  But  in  diseases  or 
injuries  affecting  extensively  the  lower  portion  of  the  cord,  a  complete 
paralysis  of  the  bladder  is  often  produced.  The  patient  is  consequently 
unable  to  discharge  his  urine  in  the  ordinary  way,  and  requires  to  be 
relieved  by  the  introduction  of  a  catheter.  If  this  be  not  done,  the 
urine  accumulates  in  the  bladder;  being  retained  for  a  time  by  the 
elastic  tissues  surrounding  the  neck  of  the  bladder  and  the  urethra. 
But  after  the  distension  of  its  walls  has  reached  a  certain  point,  the 
mechanical  resistance  of  the  bladder  becomes  too  great  to  allow  any 
further  accumulation;  and  the  urine  dribbles  away  from  the  urethra  as 
fast  as  it  is  excreted  by  the  kidneys.  Paralysis  of  the  bladder,  accord- 
ingly, first  causes  a  permanent  distension  of  the  organ,  which  is  after- 
ward followed  by  a  continuous,  passive  and  incomplete  discharge  of  its 
contents. 

The  spinal  cord,  therefore,  in  its  character  as  a  nervous  centre,  exerts 
a  general  protective  influence  over  the  whole  body.  It  presides  over 
the  involuntary  movements  of  the  limbs  and  trunk;  it  supplies  the 
requisite  nervous  connection  between  different  muscular  actions  for  the 
attitude  and  locomotion  ;  and  by  its  control  over  the  muscular  appa- 
ratus of  the  rectum  and  bladder,  it  regulates  the  accumulation  and 
discharge  of  the  excrementitious  products  of  the  system. 


CHAPTEE    Y. 

THE    BRAIN. 

THE  brain,  or  encephalon,  comprises  all  that  portion  of  the  cerebro- 
spinal  axis  which  is  contained  within  the  cavity  of  the  cranium.  It 
consists  of  a  variety  of  nervous  centres,  or  collections  of  gray  substance, 
connected  with  each  other  and  with  that  of  the  spinal  cord  by  tracts  of 
longitudinal,  transverse,  oblique,  and  radiating  nerve  fibres.  The  results 
of  experimental  investigation  leave  no  doubt  that  each  one  of  these 
different  nervous  centres  has  a  special  function,  more  or  less  independent 
of  the  others  in  its  immediate  action,  though  necessarily  connected  with 
the  rest  in  the  production  and  external  manifestation  of  the  nervous 
phenomena.  They  are  situated  upon  both  sides  of  the  median  line,  and 
are,  for  the  most  part,  evidently  arranged  in  symmetrical  pairs,  like  the 
hemispheres  of  the  cerebrum,  the  cerebral  ganglia,  the  olfactory  lobes, 
the  tubercula  quadrigemina,  and  the  two  halves  of  the  cerebellum.  The 
largest  of  these  nervous  centres,  forming  in  man  nearly  four-fifths  of  the 
mass  of  the  entire  brain,  are  the  two  convoluted  masses  known  as  the 
"hemispheres"  of  the  cerebrum. 

The  Hemispheres. 

The  hemispheres  form  two  ovoidal  masses  of  nervous  matter,  flattened 
against  each  other  at  the  median  line,  where  they  are  separated  by  the 
great  longitudinal  fissure,  corresponding  to  the  posterior  median  fissure 
of  the  spinal  cord,  and  presenting  on  their  lateral  surfaces  a  general 
rounded  or  hemispherical  form,  whence  their  name  is  derived.  They 
consist  externally  of  a  layer  of  gray  nervous  substance,  and  internally 
of  a  mass  of  white  substance,  the  fibres  of  which  may  be  said  in  general 
terms  to  radiate  from  the  cerebral  ganglia  (corpora  striata  and  optic 
thalami)  toward  the  cortical  layer  of  the  hemispheres.  The  external 
layer  of  gray  substance,  and  consequently  the  surface  of  the  hemis- 
pheres, is  thrown  into  numerous  folds  or  convolutions,  which  are  sepa- 
rated from  each  other  by  fissures,  generally  from  10  to  25  millimetres 
deep.  These  fissures,  like  the  great  longitudinal  fissure  in  the  median 
line,  are  simply  spaces  where  the  opposite  surfaces  of  two  adjacent  con- 
volutions lie  in  contact  with  each  other ;  and  they  indicate  the  points 
at  which  the  external  layer  of  gray  matter  dips  down  toward  the  interior, 
to  return  upon  itself  and  form  the  next  convolution.  The  larger  quan- 
tity of  gray  substance  is,  therefore,  situated  at  the  fissures  rather  than 
at  the  projecting  edges  of  the  convolutions  between  them  ;  and  the  more 

(471  ) 


472 


THE    BRAIN. 


numerous  and  deeper  the  fissures  upon  the  surface  of  a  brain,  the  greater 
is  the  amount  of  gray  substance  which  it  contains. 

Although  the  cerebral  fissures  and  convolutions  are  never  all  precisely 
the  same  in  any  two  brains,  nor  even  exactly  symmetrical  in  the  two 
hemispheres  of  a  single  brain,  yet  the  principal  ones  are  sufficiently 
constant  to  be  regarded  as  essential  features  of  the  organ ;  and  the 
remainder,  while  varying  within  certain  limits,  exhibit  a  general  arrange- 
ment which  is  characteristic  of  the  species  of  animal  to  which  they  belong. 
In  man  they  attain  a  very  high  degree  of  development ;  and  their  nomen- 
clature is  important  as  enabling  us  to  recognize  different  parts  of  the 
cerebral  surface. 


PLAN  OF  THE  FISSURES  AND  CONVOLUTIONS  OP  THE  HUMAN  BRAIN. — The 
fissures  are  designated  by  letters,  the  convolutions  by  numbers.  S.  Fissure  of  Sylvius;  a. 
Anterior  ascending  branch;  b.  Posterior  horizontal  branch.  E.  Fissure  of  Rolando.  P. 
Parietal  fissure.  1.  First  frontal  convolution.  2.  Second  frontal  convolution.  3.  Third 
frontal  convolution.  4.  Anterior  central  convolution.  5.  Posterior  central  convolution. 
6.  Supra-Sylvian,  or  supra-marginal  convolution.  7.  Superior  temporal  convolution.  8. 
Angular  convolution.  9.  Middle  temporal  convolution.  10.  Inferior  temporal  convolution. 
11.  Upper  parietal  convolution.  12.  Occipital  convolutions. 

Next  in  importance  to  the  great  longitudinal  fissure,  which  separates 
the  two  hemispheres  upon  the  median  line,  is  the  Fissure  of  Sylvius  (S). 
This  is  a  much  deeper  cleft  than  the  others,  and  exists,  according  to 
Prof.  Wilder,  in  the  brains  of  all  animals  where  the  cerebral  surface  is 
fissured  at  all.  In  the  human  foetus  it  is  the  first  to  appear,  being  visi- 
ble as  early  as  the  third  month ;  and  in  the  adult  it  forms  a  basis  for 


THE    HEMISPHERES.  473 

the  whole  geographical  division  of  the  hemisheres.  It  commences  as  a 
transverse  indentation  on  the  under  surface  of  the  brain,  running  thence 
outward,  backward,  and  upward,  thus  forming  the  anterior  boundary 
of  the  middle  or  temporal  lobe.  In  the  inferior  animals,  the  whole 
hemisphere  is  seen  to  be  curved  round  this  fissure,  the  convolutions 
generally  following  its  course  and  bending  round  its  upper  extremity  in 
an  arched  form ;  and  in  the  human  brain  this  arrangement  of  the  lateral 
convolutions  is  also  distinctly  visible. 

On  the  outer  side  of  the  cerebral  hemisphere,  where  it  emerges  from 
the  base  of  the  brain,  the  fissure  of  Sylvius  presents,  in  man,  two  dis- 
tinct branches,  namely  a  shorter,  anterior,  ascending  branch  (a),  and  a 
longer,  posterior,  more  horizontal  branch  (6, 6, 6).  At  its  middle  and 
anterior  portions,  this  fissure  is  very  deep,  and  conceals  within  its  folds 
a  projecting  group  of  short  radiating  convolutions,  belonging  to  the 
under  surface  of  the  brain,  between  the  anterior  and  temporal  lobes, 
called  the  "Island  of  Reil." 

The  second  fissure  in  importance,  visible  upon  the  convexity  of  the 
hemisphere,  is  the  Fissure  of  Rolando  (II).  This  fissure  runs  from 
near  the  median  line  transversely  outward  and  somewhat  obliquely  for- 
ward, reaching  nearly  to  the  middle  of  the  fissure  of  Sylvius,  and  form- 
ing the  boundary  line  between  the  frontal  and  parietal  portions  of  the 
hemisphere.  It  is  bordered  b}^  two  convolutions,  one  on  each  side, 
running  parallel  wTith  itself,  namely,  the  anterior  and  posterior  central 
convolutions  (4,  5). 

The  third  principal  fissure  is  the  Parietal  Fissure  (P).  It  starts 
from  immediately  behind  the  posterior  central  convolution,  and  runs 
backward  through  the  parietal  portion  of  the  hemisphere,  curving  some- 
what downward  upon  itself  toward  its  posterior  extremity.  Outside 
and  below  it  are  the  arched  convolutions  about  the  fissure  of  Sylvius; 
inside  and  above  it  is  a  convolution  running  parallel  with  the  great 
longitudinal  fissure. 

Beside  the  three  fissures  just  named  there  are  five  others,  which,  though 
less  deep  and  strongly  marked,  are  constantly  present  and  show  a  con- 
siderable regularity  in  their  position  and  arrangement.  Three  of  them 
are  in  the  anterior  or  frontal  lobe,  in  front  of  the  fissure  of  Rolando. 
The  first  runs  parallel  with  the  fissure  of  Rolando,  and  a  little  in 
advance  of  it,  toward  the  anterior  extremity  of  the  hemisphere.  It  is 
called  the  "prsecentral  fissure."  The  second  runs  through  nearly  the 
whole  length  of  the  frontal  lobe,  in  a  general  direction  parallel  with 
that  of  the  great  longitudinal  fissure.  It  divides  the  upper  from  the 
middle  portion  of  the  frontal  lobe,  and  is  called  the  "  superior  frontal 
fissure."  The  third  is  the  "inferior  frontal  fissure,"  and  surrounds  the 
upper  end  of  the  short  ascending  branch  of  the  fissure  of  Sylvius.  The 
two  remaining  fissures  of  this  grade,  visible  in  a  lateral  view  of  the 
brain,  are  situated  in  the  temporal  lobe,  below  and  behind  the  fissure  of 
Sylvius,  with  which  they  run  in  a  general  parallel  direction. 

In  addition  to  the  fissures  already  described  there  are  many  others 
31 


474:  THE    BKAIN. 

of  secondary  importance  and  more  irregular  in  location,  which  increase 
the  convoluted  aspect  of  the  cerebral  surface.  Some  of  them  run  longi- 
tudinally along  the  middle  of  a  convolution,  dividing  it  into  two  nar- 
rower parallel  folds ;  and  some  of  them  pass  transversely  from  one  of 
the  main  fissures  to  another,  appearing  to  cut  across  the  intervening 
convolution.  But  in  many  instances,  if  the  arachnoid  and  pia  mater  be 
removed,  it  will  be  found  that  these  secondary  fissures  are  merely  super- 
ficial indentations  on  the  surface,  or  furrows  for  the  accommodation  of 
a  vascular  branch ;  and  that  they  do  not,  like  the  others,  penetrate  deeply 
into  the  substance  of  the  brain. 

The  principal  convolutions  to  be  distinguished  on  the  convexities  of 
the  hemispheres  are  as  follows : 

The  First  Frontal  Convolution  (1)  runs  from  the  upper  end  of  the 
anterior  central  convolution,  just  in  front  of  the  commencement  of  the 
fissure  of  Rolando,  forward  along  the  edge  of  the  great  longitudinal 
fissure  to  the  anterior  extremity  of  the  frontal  lobe,  where  it  bends 
downward  and  backward,  terminating  below  in  a  straight  convolution 
next  the  median  line,  and  resting  upon  the  upper  surface  of  the  orbital 
plate.  This  convolution  is  divided  and  folded  in  many  ways  by  secon- 
dary transverse,  oblique,  and  longitudinal  fissures,  but  its  general  direc- 
tion is  easily  recognized.  It  is  bounded  externally  by  the  superior 
frontal  fissure. 

The  Second  Frontal  Convolution  (2)  also  takes  its  origin  at  the  anterior 
central  convolution,  from  which  it  is  more  or  less  completely  separated 
by  the  praecentral  fissure ;  thence  running  downward  and  forward  over 
the  anterior  and  lateral  part  of  the  frontal  lobe.  This  is  the  widest  of 
the  three  frontal  convolutions,  and  the  most  abundantly  variegated  by 
secondary  folds  and  fissures.  It  is  separated  from  the  first  frontal  con- 
volution by  the  superior  frontal  fissure,  and  from  the  third  by  the  inferior 
frontal  fissure. 

The  Third  Frontal  Convolution  (3)  is  situated  at  the  lower  and  outer 
part  of  the  frontal  lobe,  and  curves  round  the  anterior  ascending  branch 
of  the  fissure  of  Sylvius.  It  communicates  posteriorly  with  the  lower 
end  of  the  anterior  central  convolution,  and  by  this  portion  of  its  sub- 
stance helps  to  cover  in  and  conceal  the  island  of  Reil  at  the  bottom  of 
the  fissure  of  Sylvius. 

The  Anterior  Central  Convolution  (4)  runs  transversely  outward  and 
forward  along  the  front  edge  of  the  fissure  of  Rolando.  It  is  usually 
a  single  convolution,  but  is  more  or  less  folded  laterally  by  transverse 
indentations.  It  communicates  with  the  first  frontal  convolution  above 
and  with  the  third  frontal  convolution  below.  It  also  curves  round  the 
lower  end  of  the  fissure  of  Rolando,  to  unite  with  the  following  convo- 
lution, which  may  be  said  to  be  a  continuation  of  it. 

The  Posterior  Central  Convolution  (5)  also  runs  parallel  with  the  fissure 
of  Rolando,  but  behind  it.  Above,  it  turns  backward  and  is  continuous 
with  the  convolutions  of  the  upper  part  of  the  parietal  lobe. 


THE    HEMISPHERES.  475 

The  Supra-Sylman  or  Supra-marginal  Convolution  (6)  starts  from  the 
lower  end  of  the  posterior  central  convolution  and  thence  arches  round 
the  extremity  of  the  fissure  of  Sylvius.  It  then  continues  its  curvilinear 
course,  running  downward  and  forward,  parallel  with  the  inferior  margin 
of  the  fissure  of  Sylvius,  toward  the  anterior  extremity  of  the  temporal 
lobe.  In  this  situation  it  is  known  as  the  First  Temporal  Convolution  (7). 
Throughout  its  course,  it  is  generally  divided  into  two  parallel  convolu- 
tions by  a  secondary  fissure  running  along  its  axis,  and  both  of  these 
secondary  convolutions  are  more  or  less  folded  transversely. 

The  Angular  Convolution  (8)  originates  from  the  preceding  and  follows 
the  inferior  edge  of  the  parietal  fissure  backward  to  its  posterior  extremity, 
where  it  makes  a  rather  sharp  turn  downward  and  forward,  whence  its 
name  of  the  "  angular  convolution."  It  then  becomes  continuous  with 
the  Second  Temporal  Convolution  (9)  running  downward  and  forward  to 
the  extremity  of  the  temporal  lobe.  Below  this  portion,  and  running 
parallel  with  it,  is  the  Third  Temporal  Convolution  (10)  which  forms  the 
inferior  border  of  the  temporal  lobe. 

The  Upper  Parietal  Convolution  (11)  is  situated  above  the  parietal 
fissure,  between  it  and  the  posterior  part  of  the  great  longitudinal 
fissure.  Like  the  corresponding  frontal  convolutions,  it  is  much  divided 
by  irregular  secondary  foldings,  and  is  connected  with  other  convolutions 
which  are  concealed  within  the  great  longitudinal  fissure.  There  are  also 
a  number  of  Occipital  Con  volutions  (12), both  longitudinal  and  transverse, 
but  these  are  not  conspicuous  in  a  lateral  view  of  the  cerebral  hemi- 
spheres. They  are  more  or  less  continuous  with  the  upper  parietal  con- 
volution above,  and  with  the  second  and  third  temporal  convolutions 
below. 

On  a  transverse  horizontal  section  of  the  brain,  the  convolutions  are 
seen  to  penetrate  into  its  substance  for  varying  distances  at  different 
regions.  In  the  anterior  and  posterior  parts  the  foldings  are  more 
nearly  regular  in  depth,  and  leave  a  comparatively  thick  layer  of  white 
substance  between  the  cerebral  ganglia  and  the  gray  matter  of  the  con- 
volutions. But  at  the  sides  of  the  brain,  at  the  situation  of  the  fissures 
of  S}Tlvius,  the  convolutions  reach  to  a  much  greater  depth.  The  cere- 
bral ganglia  are  placed  on  each  side  the  median  line,  near  the  centre 
of  the  brain;  the  corpora  striata  being  separated  from  each  other  ante- 
riorly by  the  septum  lucidum  and  the  cavity  of  the  lateral  ventricles, 
and  the  two  optic  thalami  being  separated  in  a  similar  manner  by  the 
cavity  of  the  third  ventricle,  except  where  they  are  united  by  the- soft 
commissure. 

The  optic  thalami  (Fig.  157, 9 )  are  surrounded  on  their  outer  borders, 
and  separated  from  the  corpora  striata,  by  a  band  of  white  substance, 
the  internal  capsule  (10)  consisting  of  fibres  passing  upward  from  the 
crura  cerebri.  The  corpora  striata  (*,8)  form  on  each  side,  at  their  in- 
ferior portions,  a  continuous  mass  of  gray  substance;  but  for  the  greater 
part  of  their  thickness  they  are  divided  into  two  parts  by  a  tract  of 
white  substance,  continuous  with  the  internal  capsule,  and,  like  it,  con- 


476  THE    BKAIN. 

sisting  of  bundles  of  ascending  fibres  derived  from  the  crura  cerebri. 
The  anterior  and  more  internal  of  the  two  parts  into  which  the  corpus 
striatum  is  thus  divided  is  the  caudate  nucleus  ( 7 ),  so  called  because  a 
horizontal  section  through  its  uppermost  portion  exhibits  a  slender, 

Fig.  157. 


HORIZONTAL  SECTION  OF  THE  HUMAN  BRAIN,  at  the  level  of  the  cerebral  ganglia. 
—1,  2.  Anterior  and  posterior  portions  of  the  great  longitudinal  fissure.  3,  4.  Anterior  and 
posterior  parts  of  the  corpus  callosum.  5.  Fissure  of  Sylvius.  6.  Beginning  of  the  convolu- 
tions of  the  Island  of  Reil.  7,  8.  Corpus  Btriatum.  7.  Caudate  nucleus.  8.  Lenticular 
nucleus.  9.  Optic  thalamus.  10.  Internal  capsule.  11.  External  capsule.  12.  Claustrum. 

tail-like  prolongation  in  a  backward  direction  ;  the  posterior  and  more 
lateral  part  is  called  the  lenticular  nucleus  (s),  from  its  having,  in  a 
section  at  its  mid-level,  a  tolerably  regular  lens-like  figure.  Both  the 
optic  thalamus  and  the  corpus  striatum  are  traversed  b.y  slender  bundles 
of  fibres,  visible  to  the  naked  eye,  and  which  have  a  generally  radiating 
direction  upward  and  outward. 

The  outer  surface  of  the  lenticular  nucleus  is  inclosed  by  a  thin  layer 
of  white  substance,  the  external  capsule  (n),  in  which  is  also  to  be 
seen  a  very  narrow  band  of  isolated  gray  substance,  termed  the  "  claus- 
trum"  (12).  At  this  situation  the  layer  of  gray  substance  at  the  bottom 
of  the  fissure  of  Sylvius  is  separated  from  the  corpora  striata  by  only  a 
very  narrow  interval ;  and  the  fibres  running  outward  and  downward 


THE    HEMISPHERES.  477 

from  these  bodies  would  reach  almost  immediately  the  convolutions  of 
the  Island  of  Reil. 

Intimate  Structure  of  the  Hemispheres.— As  the  longitudinal  tracts 
of  white  substance  pass  upward  and  forward  from  the  medulla  oblongata 
and  tuber  annulare  to  the  base  of  the  hemispheres,  they  form  the  two 
irregularly  cylindrical  masses  known  as  the  "  crura  cerebri."  Their 
fibres  plunge,  for  the  most  part,  directly  into  the  substance  of  the  cor- 
pora striata  in  front,  and  of  the  optic  thalami  behind ;  while  from  these 
two  pairs  of  ganglia  other  fibres  emerge  into  the  white  substance  of  the 
hemispheres.  A  portion  of  the  fibres,  however,  coming  from  the  crura 
cerebri,  pass,  according  to  Vulpian,  Henle,  and  Meynert,  uninterruptedly 
onward,  in  the  internal  capsule  between  the  optic  thalamus  and  corpus 
striatum,  and  between  the  two  nuclei  of  the  corpus  striatum;  thus 
reaching  the  white  substance  of  the  hemispheres  without  having  tra- 
versed the  gray  matter  of  the  ganglia. 

From  this  level,  that  is,  above  and  outside  of  the  cerebral  ganglia,  the 
ascending  divergent  tracts  of  white  substance  form  a  spreading  crown 
of  nerve  fibres,  which  radiate  in  all  directions  to  the  layer  of  gray  sub- 
stance on  the  exterior.  These  fibres  are  of  very  small  size,  as  compared 
with  those  in  the  peripheral  portion  of  the  nervous  system ;  their  aver- 
age diameter,  according  to  Kolliker,  being  4.5,  and  none  of  them  being 
larger  than  6.7  micro-millimetres  in  thickness. 

The  general  direction  of  the  radiating  nerve  fibres  is  easily  seen,  in 
brains  hardened  in  alcohol,  to  be  that  described  above.  At  the  same 
time,  microscopic  examination  shows  that  they  are  abundantly  mingled 
with  other  fibres  which  cross  them  at  right  angles,  or  nearly  so,  and 
which  are  to  be  found  more  or  less  in  every  portion  of  the  white  sub- 
stance of  the  hemispheres.  These  horizontal  or  curvilinear  cross  fibres 
are  derived  in  great  measure  from  the  lateral  expansions  of  the  corpus 
callosum,  the  transverse  fibres  of  which  spread  out  in  various  direc- 
tions, bending  toward  the  convolutions  of  the  upper,  middle,  and  lower 
part  of  the  hemispheres.  As  these  fibres  come  from  the  median  line  at 
the  level  of  the  corpus  callosum.  they  necessarily  cross  those  which  are 
ascending  from  the  cerebral  ganglia  below.  The  corpus  callosum  is 
consequently  a  great  transverse  commissure,  uniting  the  two  hemi- 
spheres of  the  cerebrum  with  each  other.  There  are  also  fibres  imme- 
diately beneath  the  cortical  layer  of  gray  substance,  following  the  curve 
of  the  convolutions  where  they  project  inward  into  the  white  substance. 
These  are  known  as  the  "  arciform  fibres,"  and  are  regarded  as  connect- 
ing filaments  between  the  gray  substance  of  adjacent  convolutions. 

The  gray  substance  of  the  cerebral  convolutions  forms  an  external 
layer,  from  two  to  three  millimetres  in  thickness,  into  which  the  fibres 
of  the  white  substance  penetrate  from  within  in  a  perpendicular  manner. 
It  consists  of  a  uniform  granular  matrix,  in  which  are  imbedded  the 
nerve  cells,  and  through  which  the  fibres  continue  their  course  in  va- 
rious directions.  The  nerve  cells  are  rounded  or  irregular  in  form,  with 
a  varying  number  of  simple  or  branched  prolongations.  In  the  middle 


478 


THE    BRAIN. 


VERTICAL  SECTION  OF  ONE  OP  THE  CE- 
REBRAL CONVOLUTIONS  ;  showing  pyramidal 
cells,  and  bundles  of  fibres  passing  outward  from 
the  white  substance.  Magnified  300  diameters. 
(Henle.) 


portion  of  the  layer  of  gray 
substance,  the  cells  are  distin- 
guished by  their  pyramidal 
form ;  the  pointed  extremity  of 
the  cell  being,  with  few  excep- 
tions, directed  toward  the  surface 
of  the  brain,  and  the  base  toward 
the  white  substance  of  the  inte- 
rior. According  to  Henle,  they 
have  an  average  diameter  of  15 
mmm.  Two,  three,  or  sometimes 
even  four  prolongations  extend 
from  the  angles  at  the  base  of 
the  cell,  running  inward  toward 
the  white  substance,  and  be- 
coming more  or  less  divided  and 
ramified ;  while  the  pointed  ex- 
tremity, on  the  other  hand,  ex- 
tends outward  in  a  single  pro- 
longation toward  the  cerebral 
surface. 

The  fibres,  as  they  penetrate 
from  the  white  into  the  gray 
substance,  are  arranged  in  bun- 
dles, where  they  at  first  run  in 
a  general  direction  parallel  with 
each  other.  But  these  bundles 
rapidly  diminish  in  size,  as  the 
fibres  diverge  laterally  to  pursue 
a  more  or  less  horizontal  course ; 
and  in  the  external  portions  of 
the  gray  substance  there  are 
only  isolated  fibres  running  in 
various  directions.  In  the  gray 
substance,  the  nerve  fibres  be- 
come reduced  to  their  smallest 
dimensions,  measuring,  accord- 
ing to  Kolliker,  from  about  1  to 
2  mmm.  in  diameter.  Some  of 
them  spread  out  at  various  levels 
in  the  cortical  layer,  while  others 
continue  a  vertical  or  oblique 
course  quite  to  the  superficial 
portions  of  the  gray  substance. 

The  immediate  relation  be- 
tween the  fibres  and  cells  of  the 
gray  substance  of  the  hemi- 
spheres has  not  been  determined 


THE    HEMISPHERES.  479 

with  absolute  certainty.  Although  a  few  isolated  instances  have  been 
reported  in  which  a  cell  prolongation  has  been  seen  to  become  con- 
tinuous with  a  medullated  nerve  fibre,  it  is  usually  impossible  to 
demonstrate  this  by  direct  observation,  and  some  of  the  best  micro- 
scopists  have  been  unable  to  see  it  in  a  single  instance.  The  probability 
that  such  a  connection  exists  is  assumed  from  the  fact  that  many  of  the 
nerve  fibres  in  the  gray  substance  become  so  slender  and  pale  as  to 
resemble  very  closely  the  cell  prolongations ;  and,  on  the  other  hand, 
the  cell  prolongations  frequently  run  in  the  same  direction  with  the 
nerve  fibres.  According  to  Henle1  the  prolongations,  given  off  from 
the  bases  of  the  pyramidal  cells,  are  so  often  seen  to  lose  themselves  in 
the  bundles  of  nerve  fibres  coming  from  the  white  substance  as  to  justify 
the  assumption  that  the  fibres  in  these  instances  terminate  in  the  cells. 
The  delicacy  of  texture  of  the  gray  substance  and  the  distance  through 
which  a  cell  prolongation  runs  before  it  attains  the  character  of  a  nerve 
fibre  may  be  sufficient  reason  whjr  the  connection  is  not  more  frequently 
seen  in  microscopic  preparations. 

Physiological  Properties  of  the  Hemispheres. — The  importance  of 
the  hemispheres,  in  connection  with  the  higher  manifestations  of  nervous 
action,  is  sufficiently  indicated  by  their  excessive  development  in  man, 
as  compared  with  the  other  portions  of  the  encephalon.  For  while  in 
the  lower  mammalians  they  are  of  medium  size,  and  often  smooth  or 
sparingly  convoluted  upon  their  surface,  and  in  reptiles  and  fish  are 
sometimes  hardly  larger  than  the  other  nervous  centres  of  the  brain,  in 
man  they  acquire  such  an  extension  as  to  cover  and  surround  almost 
completely  every  other  part  of  the  encephalic  mass,  their  superficial 
layer  of  gray  substance  being  at  the  same  time  still  further  increased  by 
the  multiplied  convolutions  of  its  surface. 

Notwithstanding,  however,  the  evident  importance  of  the  hemispheres 
as  special  parts  of  the  nervous  system,  the  first  fact  certainly  known  in 
regard  to  them  is  that  they  are  not,  even  in  man,  directly  essential  to 
life.  That  is  to  sa}r,  they  do  not  hold  under  their  immediate  control 
any  of  the  physiological  acts,  like  those  of  respiration  and  circulation, 
which  are  necessary  to  the  continuance  of  vitality.  They  often  influ- 
ence these  acts,  in  an  indirect  manner,  by  the  sympathetic  connections 
of  the  nervous  system;  but  life  will  continue  for  a  certain  period  under 
the  influence  of  other  nervous  centres,  without  the  aid  of  the  cerebral 
hemispheres. 

This  is  readily  demonstrated  in  some  of  the  lower  animals  by  the 
entire  removal  of  the  hemispheres  on  both  sides.  In  man,  extensive 
morbid  changes  may  take  place  in  these  parts,  or  severe  mechanical 
injuries,  accompanied  by  greater  or  less  loss  of  substance,  may  be  in- 
flicted upon  them  without  producing  a  fatal  result.  In  a  case  reported 
by  Prof.  Detmold,2  of  abscess  in  the  anterior  lobe  of  the  brain,  a  knife 

1  Anatomie  des  Menschen.     Braunschweig,  1871,  Nervenlehre,  p.  270. 

2  American  Journal  of  the  Medical  Sciences.     Philadelphia,  January,  1850. 


480  THE    BRAIN. 

was  passed  into  the  cerebral  substance,  making  a  wound  one  inch  in 
length  and  half  an  inch  in  depth,  when  the  abscess  was  reached  and  pus 
discharged.  The  patient  immediately  aroused  from  his  comatose  con- 
dition, and  was  able  to  speak;  but  the  collection  of  pus  afterward 
returned,  and  the  patient  finally  died  at  the  end  of  seven  weeks  from 
the  time  of  opening  the  abscess. 

In  another  case,1  a  pointed  iron  bar,  three  feet  and  a  half  in  length, 
and  one  inch  and  a  quarter  in  diameter,  was  driven  through  a  man's 
head  by  the  premature  blasting  of  a  rock.  The  bar  entered  the  left  side 
of  the  face,  near  the  angle  of  the  jaw,  and  passed  obliquely  upward, 
inside  the  zygomatic  arch  and  through  the  anterior  part  of  the  cranial 
cavity,  emerging  from  the  frontal  bone  at  the  median  line,  just  in  front 
of  the  point  of  union  of  the  coronal  and  sagittal  sutures.  The  patient 
became  delirious  within  two  days  after  the  accident,  and  subsequently 
remained  partly  delirious  and  partly  comatose  for  about  three  weeks. 
He  then  began  to  improve,  and  at  the  end  of  rather  more  than  two 
months  from  the  date  of  the  injury  was  able  to  walk  about.  At  the 
end  of  sixteen  months  the  wounds  were  healed,  and  the  patient  had 
recovered  his  general  health,  though  with  loss  of  sight  in  the  eye  of  the 
injured  side. 

The  patient  survived  for  a  little  over  twelve  years,  being  able  to  do 
the  ordinary  work  of  an  ostler,  coachman,  and  farm-laborer,  in  all  of 
which  occupations  he  was  employed  at  various  intervals.  He  died  in 
1861,  after  a  short  illness  accompanied  by  convulsions.  The  skull, 
which  was  subsequently  deposited  in  the  Warren  Anatomical  Museum,2 
shows  the  openings  corresponding  with  the  points  of  entrance  and  exit 
of  the  iron  bar. 

The  conclusions  derived  from  comparative  anatomy,  from  pathological 
observations  in  man,  and  from  experiments  upon  animals,  all  show  that 
the  cerebral  hemispheres  are  especially  connected  with  the  manifesta- 
tions of  conscious  intelligence,  as  distinguished  from  involuntary  reflex 
actions,  simple  sensations,  or  instinctive  movements. 

I.  So  far  as  we  can  judge  of  the  character  and  extent  of  these  mani- 
festations in  the  lower  animals,  they  correspond  directly  with  the  develop- 
ment of  the  hemispheres,  rather  than  with  that  of  any  other  portion  of 
the  encephalon.  In  many  of  the  lower  animals,  muscular  power  and 
endurance,  the  activity  of  some  of  the  special  senses,  and  the  promptitude 
and  certainty  of  the  instincts,  are  much  greater  than  in  man  ;  while  in 
the  human  species,  the  intelligence  is  the  only  faculty  which  is  invari- 
ably superior  to  that  of  animals,  and  which  always  gives  to  man  the 
advantage  over  them.  Even  among  animals,  that  which  especially  cha- 
racterizes certain  species,  and  which  most  nearly  resembles  that  of  man, 
is  a  teachable  intelligence ;  that  is,  one  which  understands  the  meaning 

1  American  Journal  of  the  Medical  Sciences,  Philadelphia,  July,  1850. 

2  J.  B.  S.  Jackson,  Descriptive  Catalogue  of  the  Warren  Anatomical  Museum. 
Boston,  1870,  p.  145. 


THE    HEMISPHERES.  481 

of  impressions  or  objects  presented  to  it,  and  thus  enables  its  possessor, 
by  comprehending  and  retaining  new  ideas,  to  profit  by  experience. 

II.  The  general  result  of  injury,  disease,  or  disorganization  of  the 
hemispheres  in  man,  especially  affecting  the  gray  substance  of  the  con- 
volutions, is  a  disturbance,  diminution,  or  suspension  of  the  intellectual 
faculties.  In  these  cases,  among  the  earliest  and  most  constant  of  the 
morbid  phenomena  is  a  loss  or  impairment  of  memory.  The  patient 
forgets  the  names  of  particular  objects  or  of  particular  persons ;  or  he 
is  unable  to  calculate  numbers  with  his  usual  facility.  His  mental 
derangement  is  often  shown  in  the  undue  estimate  which  he  forms  of 
passing  events.  He  is  no  longer  able  to  appreciate  the  relation  between 
different  objects  and  phenomena.  He  will  show  an  exaggerated  degree  of 
solicitude  about  a  trivial  occurrence,  and  will  pay  no  attention  to  matters 
of  real  importance.  As  the  difficulty  increases,  he  becomes  careless  of 
directions  and  advice,  and  must  be  managed  like  a  child  or  an  imbecile. 
Finally,  when  the  injury  to  the  hemispheres  is  complete,  the  senses  may 
still  remain  active  and  impressible,  while  the  patient  is  completely  de- 
prived of  intelligence,  memory,  and  judgment.  The  constancy  of  these 
results  when  the  lesion  is  situated  in  the  hemispheres,  and  the  fact  that 
they  often  occur  without  being  accompanied  by  any  loss  of  sensibility 
or  motion,  show  the  close  connection  between  the  mental  powers  and 
the  nervous  action  of  this  portion  of  the  brain. 

The  same  connection  is  seen  in  the  existence  of  congenital  idiocy  with 
imperfect  development  of  the  brain.  In  many  cases  the  immediate  con- 
dition upon  which  the  idiocy  depends  is  the  small  size  of  the  brain  as  a 
whole,  particularly  conspicuous  in  the  cerebral  hemispheres.  The  general 
and  special  senses,  and  the  activity  of  the  nervous  system  at  large,  are 
sometimes  fully  developed  in  these  instances,  while  the  intelligence 
proper  remains  at  so  low  a  grade,  that  no  improvement  in  the  mental 
operations  is  possible  and  teaching  is  almost  without  effect. 

This  was  the  case,  in  a  marked  degree,  with  a  pair  of  dwarfed  and 
idiotic  Central  American  children,  who  were  exhibited  at  one  time  in 
the  United  States,  under  the  name  of  the  "  Aztecs."  They  were  a  boy 
and  a  girl,  aged  respectively  about  seven  and  five  years. 

The  antero-posterior  diameter  of  the  boy's  head  was  only  4j  inches, 
the  transverse  diameter  less  than  4  inches.  The  antero-posterior  diameter 
of  the  girl's  head  was  4^  inches,  the  transverse  diameter  only  3|  inches. 
The  habits  of  both,  so  far  as  regards  feeding  and  taking  care  of  them- 
selves, were  those  of  children  two  or  three  years  of  age.  They  were 
incapable  of  learning  to  talk,  and  could  only  repeat  a  few  isolated  words. 
Notwithstanding,  however,  their  limited  intelligence,  they  were  remark- 
ably vivacious  and  excitable.  While  awake  they  were  in  almost  con- 
stant motion,  and  any  new  object  or  toy  presented  to  them  immediately 
awakened  a  lively  curiosity.  They  understood  readily  the  meaning  of 
those  who  addressed  them,  so  far  as  it  could  be  conveyed  by  gesticula- 
tion and  the  tone  of  voice ;  but  they  could  not  be  made  to  comprehend 


482  THE    BRAIN. 

Fig.  159. 


THE  "AZTEC"  IDIOTIC  CHILDREN.  — Taken  from  life,  at  five  and  seven  years  of  age. 

articulate  language,  and,  as  in  other  idiots,  mental  instruction  was  with- 
out result. 

III.  Experiments  performed  upon  the  lower  animals,  by  removal  of 
the  hemispheres,  lead  to  a  similar  result.  In  large  and  full  grown  mam- 
malians the  injury  is  usually  fatal,  owing  in*  great  measure  to  the. 
attendant  hemorrhage ;  but  it  may  be  performed  in  fish,  reptiles,  birds, 
and  sometimes  in  young  quadrupeds  without  producing  death.  Vulpian 
has  succeeded  in  maintaining  life,  after  this  operation,  in  the  frog,  the 
turtle,  the  pigeon,  the  cock,  the  rabbit,  and  the  rat.  The  result  is  that 
these  animals  retain  their  sensibility  and  power  of  motion,  and  continue 
to  maintain  the  normal  attitude  and  to  perform  many  instinctive  and 
reflex  movements  ;  but  spontaneous  action,  and  its  conscious  adaptation 
to  external  conditions,  is  abolished  with  the  removal  of  the  cerebral 
hemispheres. 

The  operation  is  very  readily  performed  upon  the  pigeon,  and  its 
effects  in  this  animal  are  uniform  and  distinctly  marked.  After  removal 
of  both  hemispheres,  the  bird  maintains  without  difficulty  the  standing 
posture,  and  will  even  rest  upon  a  perch  with  security  if  undisturbed ; 
but  he  remains  in  a  state  of  profound  quietude,  almost  completely  indif- 
ferent to  surrounding  objects.  He  stands  upon  the  ground  or  rests 
upon  his  perch,  with  the  eyes  closed  and  the  head  sunk  between  the 
shoulders.  The  plumage  is  smooth  and  glossy,  but  is  uniformly  ex- 
panded, by  erection  of  the  feathers,  so  that  the  body  appears  puffed  out 
and  larger  than  natural.  Occasionally  the  bird  opens  his  eyes,  stretches 
his  neck,  shakes  his  bill  once  or  twice,  or  smooths  down  the  feathers 
upon  his  shoulders,  and  then  relapses  into  his  former  apathetic  condi- 
tion. This  characteristic  state  of  immobility  comes  on  immediately  after 
removal  of  the  hemispheres. 

It  is  not  accompanied,  however,  by  loss  of  either  general  or  special 
sensibility.  If  the  foot  of  the  bird  be  pinched  with  a  pair  of  forceps,  he 
becomes  partially  roused  and  moves  uneasily  once  or  twice  from  side  to 
side,  as  if  to  escape  the  irritation.  Yulpian  has  seen  a  pigeon  within  a 


THE    HEMISPHERES.  483 

short  time  after  the  operation  shake  the  head  briskly  in  consequence  of 
a  fly  having  alighted  on  the  wound.  Hearing  and  sight  also  remain. 
The  discharge  of  a  pistol  behind  the  back  of  the  pigeon  will  often  cause 
him  to  open  his  eyes  and  turn  his  head  partially  round,  giving  evident 
signs  of  having  heard  the  report ;  though  he  immediately  becomes  quiet 
again  and  pays  it  no  further  attention.  In  a  rat  which  had  been  sub- 
jected to  this  operation  by  Yulpian,  a  sharp  hissing  sound  made  by  the 
lips  produced  a  sudden  start  and  movement  of  the  whole  body.  The 
same  observer  found  that  in  a  pigeon,  after  the  animal  had  been  roused 

Fig.  160. 


PIGEON,  AFTER  REMOVAL  OF  THE  CEREBRAL  HEMISPHERES. 

by  pinching  the  foot,  the  sudden  approach  of  a  hand  toward  the  eye 
caused  a  winking  movement  with  partial  turning  of  the  head.  Some- 
times such  a  pigeon  will  fix  his  eye  on  a  particular  object,  and  watch  it 
for  several  seconds  together.  Longet  found  that  by  moving  a  lighted 
candle  before  the  animal's  eyes  in  a  dark  place,  the  head  of  the  bird  would 
often  follow  the  movements  of  the  candle,  showing  that  the  impression 
of  light  was  perceived. 

The  animal  is  still  capable,  therefore,  after  removal  of  the  hemispheres, 
of  receiving  sensations  from  external  objects.  But  these  sensations 
make  upon  him  no  lasting  impression.  He  is  incapable  of  connecting 
with  his  perceptions  any  distinct  succession  of  ideas.  If  he  hears  the 
report  of  a  pistol,  he  is  not  alarmed  by  it ;  for  the  sound,  though  dis- 
tinctly enough  perceived,  does  not  suggest  any  idea  of  danger  or  injury. 
There  is  accordingly  no  power  of  perceiving  the  relation  between  ex- 
ternal objects.  The  memory,  particularly,  is  destroyed,  and  the  recol- 
lection of  sensations  is  not  retained  from  one  moment  to  another.  The 
muscles  are  still  under  the  control  of  the  will ;  but  the  will  itself  is 
inactive,  because  it  lacks  its  usual  stimulus  and  direction.  The  powers 
which  have  been  lost,  therefore,  are  those  of  a  mental  character ;  that  is, 
the  power  of  comparing  different  sensations  or  ideas,  of  perceiving  the 


484  THE    BRAIN. 

proper  relation  between  them,  and  of  originating  in  consequence  an  in- 
telligent volitional  act. 

The  cerebral  hemispheres  as  a  whole  are  therefore  evidently  the 
centres  in  which  the  nervous  mechanism  of  mental  action  is  accom- 
plished. The  mental  endowments  which  are  concerned  in  the  manifesta- 
tions of  the  intelligence  are  mainly  the  memory,  the  reason  and  the 
judgment. 

Memory  is  the  simplest  and  most  essential  of  these  faculties  for  the 
due  performance  of  intelligent  acts.  The  recollection  of  names,  and  of 
the  objects  to  which  they  belong,  is  indispensable  even  to  the  use  of 
articulate  language ;  and  a  deficiency  of  memory  seems  often  to  be  the 
immediate  condition  upon  which  the  incapacity  of  idiotic  children  to 
talk  depends.  It  is  also  constantly  essential  in  the  ordinary  occupations 
of  life,  in  enabling  us  to  retain  past  impressions  as  a  guide  for  imme- 
diate or  future  acts. 

The  reason  may  be  considered  as  the  faculty  by  which  we  appreciate 
the  character  of  the  nervous  impressions  received,  and  are  enabled  to 
refer  them  to  their  external  source.  This  is  quite  different  from  the 
simple  power  of  perception,  which  continues,  as  experiment  has  demon- 
strated, after  the  removal  of  the  cerebral  hemispheres.  The  mental 
action  which  is  excited  by  an  impression  coming  from  without  is  one 
which  transfers  the  attention  from  the  internal  sensation  to  its  external 
source ;  and  when  this  action  is  prompt  and  effectual,  we  at  once  acquire 
an  idea  of  whence  the  impression  originated  and  what  is  its  significance. 
The  perfection  of  this  quality  consists  in  the  certainty  with  which  it 
appreciates  the  relation  between  an  effect  and  its  cause,  and  the  relative 
importance  of  different  phenomena.  This  capacity  is  deficient  or  absent 
in  idiots,  and  consequently  they  cannot  avoid  dangers  or  provide  for 
their  necessities.  For  the  same  reason  it  is  useless  to  punish  an  idiot, 
because,  although  he  may  feel  the  pain  inflicted,  he  does  not  refer  it  as 
a  consequence  to  any  previous  action  of  his  own.  A  deficiency  of  the 
same  quality  in  the  insane,  or  in  those  in  whom  it  is  naturally  imper- 
fect, produces  a  want  of  power  to  comprehend  the  importance  and  connec- 
tion of  different  events.  They  are  said  to  be  "  unreasonable,"  because 
they  expect  results  which  are  unlikely  to  follow  from  certain  causes, 
and  because  they  assume  the  existence  of  causes  which  are  not  realty 
indicated  by  the  results. 

The  judgment  is  the  faculty  by  which  the  appropriate  means  are 
selected  for  the  accomplishment  of  a  particular  end.  Its  exercise  re- 
quires the  existence  of  reason  and  memory,  which  supply  the  necessary 
conditions  upon  which  it  is  based ;  but  its  own  action  is  one  which 
looks  to  the  future  rather  than  to  the  past.  An  individual  in  whom  the 
judgment  is  well  developed  employs,  under  the  guidance  of  experience, 
means  which  are  well  adapted  to  attain  the  end  he  has  in  view ;  one 
who  is  deficient  in  this  respect  resorts  to  means  which  are  insufficient 
or  inappropriate,  and  is  consequent!}'  unsuccessful.  Whether  the  act 
performed  in  this  manner  be  a  simple  mechanical  operation,  like  that  of 


THE    HEMISPHERES.  485 

shutting  a  door  to  exclude  the  cold,  or  a  complicated  plan  involving 
many  parts,  the  mental  process  is  the  same  in  kind,  and  differs  only  in 
degree  ;  its  essential  character  being  that  it  is  an  intelligent  act,  based 
upon  an  understanding  of  the  previous  conditions,  and  intended  to 
accomplish  a  definite  result. 

It  is  evident  that  all  such  manifestations  of  intelligence,  taking  place 
through  the  cerebrum,  are  reflex  actions.  Their  starting  point  is  a  sen- 
sation coming  from  without,  which  gives  rise  in  the  mind  to  a  succession 
of  internal  operations,  terminating  in  an  intelligent  volitional  impulse. 
This  is  reflected  from  within  outward,  and  thus  finally  calls  into  action 
the  nerves  of  voluntary  motion.  There  can  be  little  doubt  that  the 
intermediate  process,  between  the  sensation  and  the  volitional  impulse, 
takes  place  in  the  gray  substance  of  the  cerebral  convolutions. 

Special  Seat  of  the  Facility  of  Articulate  and  Written  Language. — 
Most  of  the  lower  animals  have  the  power  of  communicating  with  each 
other  by  certain  movements  and  vocal  sounds  in  such  a  way  as  to 
attract  their  attention,  and  enable  them  to  act  in  concert.  The  lan- 
guage thus  employed  is  always  a  language  of  expression,  and  consists 
in  such  modifications  of  the  tone  of  voice  or  the  position  of  the  limbs  as 
indicate  pleasure  or  dislike,  excitement  or  alarm,  or  a  friendly  or  hostile 
disposition.  In  man  the  same  methods  are  largely  used  to  express 
similar  feelings,  and  to  represent  others,  such  as  surprise,  contempt, 
amusement,  or  doubt,  which  do  not  seem  to  exist  in  animals  to  an  ap- 
preciable degree. 

But  man  has  also  the  faculty  of  conveying  definite  information  by 
means  of  articulate  speech,  in  which  arbitrary  sounds  are  used  to  indi- 
cate special  objects,  qualities,  or  acts,  as  well  as  all  the  relations  which 
may  exist  between  them.  The  power  of  using  articulate  language,  as  a 
vehicle  for  the  expression  of  the  thoughts,  is  generally  in  proportion  to 
the  development  of  the  intelligence  as  a  whole.  In  order  that  it  may 
be  exercised,  two  faculties  must  come  into  action;  namely,  first,  the 
memory,  by  which  the  particular  words  required  are  brought  to  the 
mind  ;  and,  secondly,  the  voluntary  combination  of  motor  impulses 
necessary  for  their  articulation.  These  acts  are  performed,  in  health, 
with  such  rapidity  that  we  are  not  conscious  of  them ;  and  the  exercise 
of  speech  seems  to  be  a  direct  consequence  of  the  ideas  which  are  to  be 
expressed.  But  pathological  cases  show  that  either  one  or  both  of 
these  faculties  may  be  absent,  while  the  ideas  and  the  desire  to  express 
them  are  as  distinct  as  ever. 

The  affection,  in  these  cases  of  loss  of  the  power  of  language,  is  termed 
aphasia.  It  does  not  depend  upon  a  want  or  confusion  of  ideas,  be- 
cause the  patient  is  often  perfectly  clear  as  to  what  he  wishes  to  say, 
although  he  cannot  say  it.  It  i's  not  due  to  paralysis  of  the  organs  of 
articulation,  since  the  tongue,  lips,  and  palate  can  be  moved  in  every 
direction  with  the  usual  facility.  It  is  a  deficiency  or  suspension  of  the 
power,  either  to  recall  the  word  needed,  or  to  set  in  motion  the  nervous 
actions  required  to  pronounce  it.  In  the  former  instance  it  is  called 


486  THE    BRAIN. 

u  amnesic  aphasia."  The  patient  cannot  say  what  he  wishes,  because 
he  cannot  recollect  the  word  he  wants.  For  the  same  reason  he  is  also 
incapable  of  writing  it.  But  if  the  word  which  he  requires  be  spoken 
to  him,  he  can  repeat  it  immediately,  though  in  a  few  seconds  it  has 
again  escaped  him.  This  disease  is  an  aggravated  form  of  that  condi- 
tion to  which  many  otherwise  healthy  persons  are  occasionally  liable ; 
namely,  that  of  forgetting  for  a  time  a  particular  word  at  the  moment 
they  wish  to  use  it.  In  some  cases  of  aphasia  the  loss  of  power  is  so 
complete  that  the  patient  can  utter  only  two  or  three  words,  which  he 
employs  indiscriminately  whenever  he  speaks  at  all. 

In  the  second  variety  of  the  affection,  the  patient  knows  the  word  he 
wants,  but  cannot  succeed  in  articulating  it.  He  can,  therefore,  express 
himself  by  writing  perfectly  well,  but  cannot  read  aloud  even  what  he 
has  written  himself.  This  is  called  "  ataxic  aphasia,"  because  it  de- 
pends not  upon  an  imperfection  of  memory,  but  upon  a  want  of  power 
to  effect  the  necessary  nervous  combinations. 

There  is  no  question  that  the  power  of  language  resides  somewhere 
in  the  cerebral  hemispheres,  and  many  observations  have  tended  to 
locate  it  more  especially  in  the  convolutions  surrounding  the  lower  end 
of  the  fissure  of  Sylvius,  and  in  those  of  the  Island  of  Eeil.  Broca 
fixes  it  more  especially  in  the  third  frontal  convolution,  surrounding  the 
anterior,  ascending  branch  of  the  fissure  of  Sylvius,  while  others  have 
referred  it  to  the  frontal  lobe  in  general.  The  evidence  for  this  locali- 
zation of  the  faculty  of  language  consists  in  the  number  of  instances  in 
which  aphasia  more  or  less  complete  has  been  found,  on  post-mortem 
examination,  to  be  accompanied  by  lesions  of  the  brain  substance  con- 
fined to  the  points  indicated.  It  is  often  accompanied  by  hemiplegia 
of  the  opposite  side  of  the  body,  but  may  sometimes  exist  independently 
of  any  paralytic  affection. 

According  to  Broca,  it  is,  as  a  rule,  the  third  cerebral  convolution  of 
the  left  hemisphere  alone  which  is  concerned  as  a  nervous  centre  in  the 
production  of  articulate  language.  This  conclusion  is  derived  from  the 
fact,  which  is  generally  conceded  by  pathologists,  that  in  the  large 
majority  of  cases  in  which  aphasia  is  accompanied  by  hemiplegia,  the 
hemiplegia  is  on  the  right  side  of  the  body,  the  lesion  accordingly  occu- 
pying the  left  side  of  the  brain.  But  as  aphasia  is  generally  due  to 
occlusion  of  the  middle  cerebral  artery  by  an  embolism,  and  as  embolism 
is  more  likely  to  occur  on  the  left  side  than  on  the  right,  owing  to  the 
different  angle  at  which  the  vascular  branches  are  given  off,  this  fact  may 
not  indicate  the  exclusive,  or  even  preponderating  influence  of  the  left 
side  of  the  brain  in  the  function  of  articulate  language.  Notwithstand- 
ing some  remarkable  cases  which  would  tend  to  show  a  special  location 
of  this  function  upon  the  left  side,  such  as  that  of  chronic  left  hemiplegia 
without  aphasia,  followed  in  the  same  individual  by  a  sudden  attack  of 
right  hemiplegia  with  aphasia,1  yet  instances  of  an  opposite  kind  are 

Bateman  on  Aphasia.     London,  1870,  p.  152. 


THE    HEMISPHERES.  487 

also  so  numerous  that  the  physiological  question  cannot  be  regarded  as 
settled.  We  are  only  certain  that  aphasia  is  most  frequently  produced 
by  lesions  occupying  the  left  hemisphere,  in  the  convolutions  about 
the  bottom  and  edges  of  the  fissure  of  Sylvius ;  that  is,  in  the  parts 
nourished  by  branches  of  the  middle  cerebral  artery. 

Special  Centres  of  Motion  in  the  Cerebral  Hemispheres.— As  a  rule, 
both  the  white  and  gray  substance  of  the  hemispheres  are  found  to  be 
both  insensible  and  inexcitable  under  the  application  of  ordinary  artifi- 
cial stimulus ;  neither  sensation  nor  motion  being  produced  in  the  living 
animal  by  mechanical  irritation  or  injury  of  these  parts.  In  man,  also, 
it  has  been  repeatedly  observed  that  the  substance  of  the  brain,  when 
exposed  by  accident  or  disease,  gives  no  indication  of  sensibility  or  of 
motor  endowments,  if  subjected  to  external  irritation. 

More  careful  and  extended  observations,  however,  upon  the  lower 
animals,  have  shown  that  under  the  influence  of  galvanic  stimulus  of  a 
low  degree  of  intensity  certain  points  on  the  surface  of  the  cerebral  con- 
volutions will  give  rise  to  definite  movements  in  the  muscles  of  the  head, 
body,  and  limbs.  The  fact  was  first  discovered  by  Fritsch  and  Hitzig 
in  1870,1  and  has  been  subsequently  fully  confirmed  by  other  observers. 
The  experiments  were  performed  first  and  most  frequently  on  dogs ; 
afterward  on  cats,  guinea  pigs,  rabbits,  and  monkeys ;  the  animals  being 
sometimes  stupefied  by  ether,  chloroform,  or  morphine,  sometimes  not 
subjected  to  any  anaesthetic  influence. 

The  general  results  derived  from  these  experiments,  as  given  by 
Hitzig,  are  as  follows : 

I.  One  portion  of  the  convexity  of  the  cerebrum,  in  the  dog,  is  motor ; 
another  portion  is  not  motor. 

II.  The  motor  portion  lies,  in  general  terms,  more  anteriorly;  the 
non-motor  portion  more  posteriorly. 

III.  Electrical  stimulation  of  the  motor  portion  produces  co-ordinated 
muscular  contraction  on  the  opposite  side  of  the  body. 

IY.  With  very  weak  electric  currents,  the  contractions  produced  are 
distinctly  limited  to  particular  groups  of  muscles;  with  stronger  cur- 
rents, the  stimulus  is  communicated  to  other  muscles  of  the  same  or 
neighboring  parts. 

Y.  The  portions  of  the  brain  intervening  between  these  motor  centres 
are  inexcitable  by  similar  means. 

These  conclusions  have  been  verified  by  a  variety  of  observations  in 
Germany,  France,  England,  and  the  United  States.'2  The  experiments, 
which  are  most  readily  performed  on  dogs,  owing  to  the  large  size  of 
the  cerebrum,  and  the  comparatively  little  injury  suffered  from  hemor- 

1  Archiv  fur  Anatomie,  Physiologic  und  Wissenschaftliche  Medicin.     Leipzig, 
1870,  p.  300.     Hitzig,  Untersuchungen  liber  das  Gehirn.     Berlin,  1874. 

2  Report  of  a  Committee  of  the  New  York  Society  of  Neurology  and  Electro- 
logy  on  the  Existence  and  Localization  of  Motor  Centres  in  the  Cerebral  Con- 
volutions.    New  York  Medical  Journal,  March,  1875,  p.  225. 


488  THE    BRAIN. 

rhage,  yield  results  which  are  sufficiently  uniform  to  show  that  they 
depend  upon  important  physiological  conditions.  In  those  performed 
by  the  committee  of  the  New  York  Society  of  Neurology  and  Electro- 
logy,  the  animals  were  etherized  and  kept  more  or  less  completely  under 
the  influence  of  the  anaesthetic  during  the  whole  course  of  the  experi- 
ments. The  stimulus  employed  was  a  galvanic  current  from  a  battery 
of  from  8  to  16  cells,  of  an  intensity  just  sufficient  to  be  distinctly  per- 
ceptible, but  not  painful,  when  applied  to  the  surface  of  the  tongue. 
The  electrodes  were  rounded  platinum  points,  fixed  at  a  distance  of  one 
millimetre  apart.  They  were  applied  to  the  surface  of  the  cerebrum  in 
such  a  manner  as  not  to  wound  but  only  to  touch  it,  and  were  held  in 
contact  with  the  brain  for  about  one  second  only  at  each  application. 
The  applications  were  repeated  at  short  intervals  at  the  same  spot  for 
from  ten  to  forty  times  in  succession,  in  order  to  make  sure  that  the 
reactions  obtained  were  not  accidental.  The  results  show  plainly  that 
there  are  certain  limited  spots,  on  the  surface  of  the  cerebral  convolu- 
tions, at  which  the  application  of  a  faint  galvanic  current  will  cause  dis- 
tinct momentary  contraction  of  separate  muscles,  or  groups  of  muscles, 
on  the  opposite  side  of  the  body.  These  spots  correspond  in  all  essential 
particulars  with  those  discovered  by  Hitzig,  and  are  near!}',  though  not 
quite,  uniform  in  location  on  the  two  opposite  sides,  and  in  different 
animals. 

All  the  centres  of  motion  for  the  anterior  and  posterior  limbs  are 
situated,  in  the  dog,  in  the  convolution  immediately  surrounding  the 
frontal  fissure  (Figs.  161,  162,  F),  a  nearly  transverse  furrow  running 
outward  and  forward  from  the  median  line,  which  may  be  considered 
as  corresponding  to  the  fissure  of  Rolando  in  the  human  brain,  but 
placed  farther  forward  in  the  dog,  owing  to  the  inferior  development  of 
the  frontal  lobe.  In  a  majority  of  cases,  the  motor  centres  for  the 
anterior  limbs  (3,  4)  are  situated  more  in  front,  near  the  outer  extremity 
of  this  fissure  ;  those  for  the  posterior  limbs  (5,  6)  farther  backward  and 
inward.  At  certain  points,  movements  of  flexion  are  produced,  at 
others,  movements  of  extension  ;  sometimes  flexion  of  a  single  paw  alone 
takes  place,  sometimes  flexion  or  extension,  more  or  less  complete,  of  a 
whole  limb  ;  and  sometimes,  at  certain  spots,  there  is  flexion  or  extension 
of  the  fore  and  hind  limbs  together,  or  partial  flexion  of  one,  accompanied 
by  extension  of  the  other.  But  in  the  majority  of  cases,  the  movements 
produced  are  isolated  movements  of  flexion  or  extension  of  a  single  limb. 

The  centre  for  flexion  of  the  head  on  the  neck  in  the  median  line  (1) 
is  in  the  lateral  and  anterior  part  of  the  convolution  situated  in  advance 
of  the  frontal  fissure,  where  this  convolution  bends  downward  and  out- 
ward ;  tha.t  for  flexion  of  the  head  on  the  neck,  with  rotation  toward  the 
side  of  the  stimulus,  is  in  a  part  of  the  same  convolution  (2),  situated 
still  farther  forward  and  downward,  so  as  to  be  invisible  in  a  view  of 
the  brain  taken  from  above. 

The  centre  of  motion  for  the  orbicularis  oculi,  and,  according  to 
Hitzig,  for  the  facial  muscles  generally,  is  in  a  region  situated  upon  the 


THE    HEMISPHERES. 


489 


lateral  part  of  the  hemisphere  (7,  8,  9),  immediately  about  the  supra- 
Sylvian  fissure. 

The  action  of  the  cerebral  convolutions  in  producing  muscular  con- 
traction, when   this  contraction  is  definite  and  limited,  is  always   a 

Fig.  161. 


Fig.  162. 


BRAIN  OF  THE  DOG.— Fig.  161,  view  from  above;  Fig.  162,  profile  view;  showing  the  cen- 
tres of  motion  in  the  cerebral  convolutions.  F.  Frontal  fissure.  S.  Fissure  of  Sylvius.  The 
unshaded  part  is  that  exposed  by  the  opening  in  the  skull,  F.  Frontal  fissure.  S.  Fissure 
of  Sylvius.  1.  Flexion  of  head  on  the  neck,  in  the  median  line.  2.  Flexion  of  head  on  the 
neck,  with  rotation  toward  the  side  of  the  stimulus.  3,4.  Flexion  and  extension  of  anterior 
limb.  5,  6.  Flexion  and  extension  of  posterior  limb.  7,  8, 9.  Contraction  of  orbiciilaiia  oculi, 
and  the  facial  muscles  in  general. 

crossed  action ;  galvanization  of  the  convolutions,  on  either  side  of  the 
brain,  exciting  movement  in   the  muscles,  both  of  the  limbs  and  face,, 
on  the  opposite  side  of  the  body..     On  the  other  hand,,  galvanization  of 
32 


490  THE    BRAIN. 

the  dura  mater  or  other  sensitive  parts,  produces,  by  reflex  action, 
muscular  twitching  on  the  same  side  of  the  body. 

The  existence  of  these  excitable  points  in  the  cerebral  convolutions 
does  not  show  that  they  are  nervous  centres  for  the  immediate  pro- 
duction of  voluntary  movement.  On  the  contrary,  we  know  that  the 
parts  of  the  brain  containing  them,  and,  in  some  animals,  even  the  whole 
hemispheres,  may  be  removed  and  yet  the  power  of  movement  in  the 
limbs  may  be  preserved.  But  they  are  evidently  points  from  which  an 
influence  may  extend  inward  toward  the  central  parts  of  the  brain,  excit- 
ing there  the  immediate  cause  of  motor  action  ;  and  this  influence  is 
transmitted  through  the  cerebral  substance  by  definite  paths,  as  much 
so  as  that  passing  in  the  ramifications  and  fibres  of  the  peripheral  motor 
nerves. 

The  only  doubt  which  has  been  entertained  in  regard  to  the  signifi- 
cance of  these  experiments  is  that  which  attributes  the  muscular  con- 
traction, not  to  the  galvanization  of  the  convolutions  themselves,  but  to 
a  diffusion  of  the  electric  current  from  without  inward,  and  a  consequent 
extension  of  the  galvanic  stimulus  to  the  deeper  parts  of  the  brain,  espe- 
cially the  corpus  striatum  and  ascending  fibres  of  the  crus  cerebri.  But 
the  conditions  of  the  experiment  show  that  this  is  not  the  case.  When 
the  distance  between  the  two  electrodes,  and  consequently  the  length  of 
the  current  traversing  the  surface  of  a  convolution,  is  only  one  milli- 
metre, their  application  to  a  particular  spot  may  produce,  many  times 
in  succession,  a  definite  muscular  contraction ;  and  yet  their  application 
to  other  spots  not  more  than  five  millimetres  distant  from  the  first,  and 
equally  near  the  base  of  the  brain,  may  be  entirely  without  effect. 

Furthermore,  direct  proof  of  the  part  taken  by  the  convolutions  in 
the  production  of  these  phenomena  is  supplied  by  the  experiments  of 
Braun1  and  Putnam.2  In  these  experiments  points  were  found  upon 
the  cerebral  convolutions  which  produced,  under  the  application  of  elec- 
tric stimulus,  the  usual  definite  muscular  contractions.  A  horizontal 
section  was  then  made  at  a  depth  of  one  or  two  millimetres  beneath  the 
surface,  leaving  the  flap  in  place  but  cutting  off  the  anatomical  con- 
tinuity of  brain  tissue.  The  irritation,  being  then  reapplied  to  the 
original  spot,  failed  to  excite  any  muscular  contraction ;  but  if  the  flap 
were  turned  up  and  the  electrodes  applied  to  the  cut  surface  beneath, 
a  current  of  similar  or  slightly  increased  strength  again  produced  the 
same  movements  as  before.  Repeated  trials  of  this  kind,  the  flap  being 
alternately  removed  and  readjusted,  yielded  the  same  results.  It  is 
evident,  therefore,  that  when  the  electrodes,  applied  to  the  surface  of  the 
uninjured  brain,  cause  movements  on  the  opposite  side  of  the  body,  this 
effect  is  not  due  to  a  diffusion  of  the  electric  current  itself  toward  the 
base  of  the  brain,  but  to  a  nervous  stimulus  originating  in  the  convolu- 
tions, and  thence  transmitted  inward  by  the  fibres  of  the  white  substance. 

1  Centralblatt  fur  die  Medicinischen  Wissenschaften.     Berlin,  June  13,  1874, 
p.  455. 

2  Boston  Medical  and  Surgical  Journal,  July  16,  1874. 


THE    CEREBRAL    GANGLIA*  491 

The  Cerebral  Ganglia. 

The  corpora  striata  and  optic  thalami,  from  the  position  which  they 
occupy  at  the  central  part  and  base  of  the  cerebrum,  in  the  course  of 
the  ascending  fibres  of  the  crura  cerebri,  must  be  regarded  as  nervous 
centres  interposed  between  the  medulla  oblongata  below  and  the  hemi- 
spheres above.  According  to  Henle,  the  bundles  of  white  substance 
from  the  posterior  portion  of  the  cms  cerebri,  on  passing  into  the  optic 
thalamus,  spread  out  in  pencil-like  tufts  of  diverging  fibres,  which  become 
generally  distributed  throughout  the  gray  substance  of  the  ganglion, 
and  are  even  mingled  in  its  interior  with  transverse  or  interlacing  fila- 
ments. It  is  conceded  by  both  Kolliker  and  Henle  that  some,  or  even  a 
considerable  proportion,  of  these  fibres  terminate  in  the  gray  substance ; 
while  a  portion,  or  perhaps  other  fibres  originating  in  the  gray  substance, 
pass  outward  again,  from  the  anterior  and  lateral  parts  of  the  thalamus, 
to  continue  their  course  upward  to  the  cerebral  convolutions. 

In  the  corpus  striatum,  the  relation  of  the  fibres  to  the  gray  substance 
is,  in  general,  the  same  as  in  the  thalamus ;  that  is,  they  are  derived 
from  the  ascending  bundles  of  the  crus  cerebri  and  terminate  in  the 
gray  substance  of  the  ganglion.  The  difference  between  the  two  bodies 
is  that  in  the  thalamus  the  mixture  of  the  fibres  with  the  gray  substance 
is  more  intimate  and  uniform  throughout,  while  in  the  corpus  striatum 
the  fibres  are  arranged  in  distinct  bundles,  readily  visible  to  the  naked 
eye,  which  only  disappear,  by  the  dispersion  and  termination  of  their 
filaments,  at  the  distance  of  about  one  millimetre  from  its  outer  edge ; 
so  that  the  ganglion  is  bordered  externally  at  this  situation  by  a 
thin  layer  of  gray  substance  in  which  no  white  striations  are  to  be 
seen.  In  the  corpus  striatum,  as  in  the  optic  thalamus,  there  are  also 
bundles  of  fibres,  according  to  the  observations  of  Kolliker,  which  at 
certain  levels  pass  from  the  gray  matter  of  the  ganglion  into  the  white 
substance  of  the  hemispheres.  Both  the  corpus  striatum  and  optic 
thalamus  contain  nerve  cells  with  ramified  prolongations,  some  of  which 
closely  resemble  the  finest  nerve  fibres  with  which  they  are  mingled, 
and  with  which  many  anatomists  believe  them  to  be  continuous. 

The  exact  physiological  function  of  the  cerebral  ganglia,  as  distin- 
guished from  the  hemispheres  proper,  is  not  precisely  determined.  It 
is  plain  that  they  exert  some  influence,  of  an  intermediate  character, 
between  the  action  of  the  cerebral  hemispheres  above  and  the  direct 
transmission  of  motor  and  sensitive  stimulus  to  or  from  the  parts 
below.  They  have  both  been  found  to  be,  like  the  hemispheres,  insen- 
sible to  ordinary  mechanical  irritation,  unless  this  be  applied  so  deeply 
as  to  reach  the  fibrous  bundles  of  the  crura  cerebri  in  their  inner  and 
deeper  parts.  They  cannot  be  extirpated  or  extensively  injured  with- 
out at  the  same  time  cutting  off  more  or  less  completely  the  connection 
of  the  hemispheres  with  the  peripheral  nervous  system ;  but  they  may 
be  removed  at  the  same  time  with  the  hemispheres,  in  some  of  the  lower 


492  THE    BRAIN. 

animals,  and  yet  the  power  of  motion  and  of  sensibility  may  be  retained 
to  a  considerable  extent. 

It  is  certain,  however,  from  the  known  facts  of  pathology,  that  their 
influence  is  an  important  one,  since,  in  man,  lesions  of  these  ganglia  are 
almost  always  followed  by  more  or  less  complete  hemiplegia  on  the 
opposite  side  of  the  body.  In  general  terms,  the  effect  of  cerebral 
hemorrhage,  whether  from  injury  or  disease,  may  be  said  to  vary  accord- 
ing to  its  location;  hemorrhage  upon  the  surface  of  the  hemispheres 
producing  coma,  that  in  the  cerebral  ganglia  causing  hemiplegia.  The 
usual  significance  attached  to  the  term  "  hemiplegia"  is  that  of  loss  of 
voluntary  motion  on  one  side,  while  a  corresponding  loss  of  sensibility 
is  designated  as  hemiansesfhesia.  In  cases  of  lesion  of  the  cerebral 
ganglia  or  adjacent  parts,  the  loss  of  motion  is  usually  the  most  promi- 
nent symptom,  hemiansesthesia  being  either  entirely  absent  or  disap- 
pearing rapidly,  while  the  motor  paralysis  lasts  a  longer  time.  On  the 
other  hand,  hemiansesthesia  may  continue  after  the  power  of  motion  is 
recovered,  and  it  may  also  be  produced  in  animals  by  lesions  of  the 
brain  without  being  accompanied  by  any  muscular  paralysis. 

Attempts  have  been  repeatedly  made  by  various  authors  to  locate 
more  distinctly  the  physiological  acts  of  sensation  or  motion  in  one  or 
the  other  of  the  cerebral  ganglia  separately ;  but  thus  far  these  attempts 
have  not  been  so  successful  as  to  command  general  assent.  The  most 
exact  experiments  in  regard  to  sensibility  are  those  of  Yeyssiere,1  who 
operated  by  introducing  into  the  brain  of  the  dog  a  slender  trocar 
armed  with  a  spring,  which  could  be  expanded  at  the  bottom  of  the 
wound  and  thus  produce,  by  rotation  of  the  instrument,  a  lesion  of 
the  deeper  parts  of  the  brain  without  serious  injury  of  the  more  super- 
ficial portions.  After  study  of  the  symptoms  caused  by  the  operation, 
the  animal  was  killed,  and  the  exact  location  of  the  injury  ascertained. 
The  observer  found  by  this  means  that  hemiansesthesia,  either  alone  or 
accompanied  by  more  or  less  paralysis  of  motion,  was  produced  by 
lesions  of  the  cerebral  ganglia  and  the  white  substance  included  be- 
tween them ;  but  that  it  was  the  white  substance  of  the  internal  capsule 
which  was  most  constantly  affected  in  these  cases.  The  gray  substance 
of  the  cerebral  convolutions,  as  well  as  that  of  the  cerebral  ganglia, 
might  be  extensively  injured  without  causing  loss  of  sensibility;  but 
this  effect  was  produced  in  proportion  to  the  extension  of  the  injury 
to  the  internal  capsule  and  the  commencement  of  the  expansion  of 
radiating  fibres  derived  from  it. 

The  above  experiments  and  observations  do  not  show  that  the  physio- 
logical functions,  either  of  sensibility  or  voluntary  motion,  are  seated 
in  the  cerebral  ganglia  or  the  internal  capsule.  The  paralysis  of  motion 
and  sensation  resulting  from  injury  to  these  parts  is  due  evidently,  in 
great  measure,  to  the  shock  communicated,  through  descending  fibres, 
to  other  parts  of  the  brain  below  ;  since,  as  in  several  of  Yeyssiere's 

1  Recherches  sur  riTemiansesth^sie  de  cause  c£r6brale.     Paris,  1874. 


THE    CEREBELLUM. 


493 


experiments,  a  hemiplegia  or  hemianaesthesia,  following  laceration  of 
the  brain  substance,  may  disappear  within  a  few  days,  or  even  in  twenty- 
four  hours,  though  the  mechanical  injury  be  not  yet  repaired.  While 
therefore  we  cannot  say  that  either  of  the  cerebral  ganglia  are  the  phys- 
iological organs  of  sensation  or  motion,  yet  their  injury,  both  in  animals 
and  in  man,  generally  produces,  as  its  immediate  result,  hemiplegia  or 
hemiansesthesia,  either  singly  or  combined,  on  the  opposite  side  of  the 
body. 

The  Cerebellum. 

The  cerebellum,  although  in  man  and  the  quadrupeds  much  inferior  in 
size  to  the  cerebrum,  consists,  like  it,  of  a  folded  layer  of  gray  matter 
surrounding  the  mass  of  white  substance  which  forms  its  internal  por- 
tion. The  cortical  layer  of  gray  substance  is  only  about  one-half  as 
thick  as  that  of  the  cerebral  hemispheres;  being  nowhere  over  1.5  milli- 
metre in  thickness.  But  the  convolutions  of  the  cerebellum  are  more 
compactly  arranged  than  those  of  the  cerebrum,  and  penetrate  into  its 
substance  in  the  form  of  thin,  closely  adjacent  laminae  ;  so  that  it  con- 
tains a  comparatively  large  quantity  of  gray  matter  in  proportion  to  its 
mass.  In  the  white  substance  of  the  cerebellum  on  each  side,  not  far 
from  the  median  line,  there  is  an  isolated  deposit  of  gray  matter  in  the 


i.  163. 


VERTICAL  TRANSVERSE  SECTION  OF  THE  HUMAN  CEREBELLUM  AND  ME- 
DULLA OBLONGATA,  a  little  behind  the  pons  Varolii;  posterior  portion.— 1.  Medulla 
oblongata,  showing  the  nucleus  of  the  olivary  bodies.  2.  Fourth  ventricle.  3,  3.  White 
substance  of  the  cerebellum.  4,4.  Corpus  dentatum  of  each  side.  (Henle.) 

form  of  a  thin  lamina,  folded  in  irregular,  tooth-like  convolutions, 
whence  its  name  of  corpus  dentatum.  This  lamina  is  everywhere  closed 
on  its  external  lateral  aspect,  but  presents  an  opening  at  one  point 
toward  the  median  line.  It  seems  to  occupy,  in  the  cerebellum,  a  place 
analogous  to  that  of  the  cerebral  ganglia  above,  and  to  that  of  the 
olivary  nuclei  in  the  medulla  oblongata. 

The  gray  matter  of  the  cerebellar  convolutions  is  penetrated  by  fibres 


494  THE    BRAIN. 

coming  from  the  interior  white  substance,  and  contains  nerve  cells  of 
various  form  and  size.  The  most  characteristic  are  flask-shaped  cells, 
arranged  in  a  single  or  rarely  in  a  double  row ;  the  rounded  extremity 
of  each  cell  being  directed  inward,  the  pointed  extremity  outward. 
According  to  Kb'liiker  and  Henle,  the  cells  usually  give  off  prolonga- 
tions in  two  opposite  directions  ;  that  which  passes  inward  toward  the 
white  substance  being  unbranched  and  resembling  the  axis-cylinder  of 
a  nerve  fibre,  while  that  which  passes  outward  toward  the  surface  of 
the  convolution  divides  into  numerous  fine  ramifications. 

The  cerebellum  is  connected  with  the  rest  of  the  cerebro-spinal  axis 
by,  1st,  the  fibres  of  the  posterior  peduncles,  or  restiform  bodies,  which 
come  from  the  posterior  and  lateral  parts  of  the  medulla  oblongata,  to 
radiate  in  the  white  substance  of  the  cerebellum ;  and  2d,  by  those  of 
the  anterior  peduncles,  orprocessus  e  cerebello  ad  corpora  quadrigemina, 
which  originate  from  the  cerebellum  nearer  the  median  line  than  the 
termination  of  the  restiform  bodies,  and  thence  pass  upward  and  forward, 
joining  the  longitudinal  tracts  of  the  posterior  part  of  the  tuber  annulare 
and  crura  cerebri.  The  two  lateral  halves  of  the  cerebellum  are  further- 
more connected  with  each  other  by,  3d,  the  fibres  of  the  middle  peduncles, 
which  originate  from  the  white  substance  on  each  side,  then  pass  forward 
and  downward  to  meet  in  front  upon  the  under  surface  of  the  tuber 
annulare,  forming  the  arched  commissure  of  the  pons  Varolii. 

Physiological  Properties  of  the  Cerebellum. — The  general  result  of 
experimental  operations  upon  the  cerebellum  shows  that  the  surface  of 
this  organ  is  inexcitable  by  ordinary  means,  and  that  its  mechanical 
irritation  gives  no  evidence  of  sensibility.  Flourens,  Longet,  Yulpian, 
and  experimenters  in  general,  have  recognized  the  fact  that  neither 
sensation  nor  muscular  contractions  are  produced  by  touching  or 
wounding  the  external  gray  substance  of  the  cerebellum ;  while  in  its 
deeper  portions  both  excitability  and  sensibility  become  manifest,  in 
proportion  as  the  irritation  is  applied  nearer  the  medulla  oblongata  and 
the  commencement  of  the  cerebellar  peduncles.  Furthermore,  its  re- 
moval, either  in  part  or  in  whole,  does  not  destroy  nor  essentially 
diminish  either  the  power  of  sensation  or  that  of  movement.  The 
senses  remain  active,  and  the  mental  faculties  are  still  unchanged,  pro- 
vided the  cerebral  hemispheres  have  not  been  injured.  Operations 
upon  this  part  of  the  brain  are  more  difficult  to  perform  than  those 
upon  the  cerebrum,  and  are  much  more  liable  to  produce  a  fatal  result. 
This,  however,  does  not  seem  to  depend  upon  any  direct  influence  of 
the  cerebellum  upon  the  more  vital  functions,  but  is  due  to  its  deeper 
position,  the  difficulty  of  exposing  it  without  causing  too  much  hemor- 
rhage, and  especially  its  proximity  to  the  medulla  oblongata.  If  injury 
from  these  causes  be  avoided,  the  organ  may  be  extensively  wounded 
or  even  totally  removed  without  causing  death.  One-half  or  two-thirds 
of  it  have  often  been  taken  away  without  causing  death  ;  and  in  one  of 
the  experiments  of  Flourens,  a  fowl  lived  for  more  than  four  months 
after  its  complete  extirpation. 


THE    CEREBELLUM.  495 

Aside  from  the  particulars  above  mentioned,  experiments  which  con- 
sist in  mutilation  or  removal  of  the  cerebellum  have  yielded  very  uni- 
form results  of  a  striking  character,  and  not  similar  to  those  caused  by 
injury  to  other  parts  of  the  brain.  These  effects  were  first  described  by 
Flourens  in  1842;1  and  notwithstanding  the  great  activity  of  research 
upon  the  nervous  system  since  that  time,  the  results  obtained  by  him 
have  been  uniformly  corroborated  in  all  essential  particulars  by  subse- 
quent observers.  The  phenomena,  which  are  of  a  similar  nature  in 
different  species  of  animals,  have  been  seen,  by  Flourens  or  others,  in 
the  pigeon,  fowl,  duck,  turkey,  and  other  birds ;  and,  among  quadrupeds, 
in  the  dog,  the  cat,  the  mole,  the  rat,  and  the  guinea  pig. 

The  effect  produced  by  destruction  or  removal  of  the  substance  of  the 
cerebellum  consists  in  a  peculiar  disorder  of  the  movements  of  the  body 
and  limbs,  from  want  of  harmony  in  their  muscular  action.  The  power 
of  associating  the  contractions  of  different  muscles,  in  such  a  way  as  to 
produce  co-ordinated  movements,  is  lost  or  impaired  in  proportion  to 
the  injury  inflicted  upon  the  nervous  centre.  If  in  a  living  pigeon  the 
cerebellum  be  exposed,  and  a  portion  of  its  substance  removed,  the 
animal  exhibits  at  once  a  characteristic  uncertainty  in  the  gait,  and  in 
the  movement  of  the  wings.  If  the  injury  be  more  extensive,  the  bird 
loses  altogether  the  power  of  flight,  and  can  walk,  or  even  stand,  only 
with  difficulty.  This  is  not  owing  to  any  actual  paralysis,  for  the 
movements  of  the  limbs  are  often  quite  rapid  and  energetic ;  but  is  due 
to  a  deficient  control  over  the  muscular  contractions,  similar  to  that 
seen  in  a  man  in  a  state  of  intoxication.  The  movements  of  the  legs 
and  wings,  though  forcible,  are  confused  and  blundering ;  so  that  the 
animal  cannot  direct  his  steps  to  any  particular  spot,  nor  support  him- 
self in  the  air  by  flight.  He  reels  and  tumbles,  but  can  neither  walk 
nor  fly. 

The  senses  and  the  intelligence  are  at  the  same  time  unimpaired,  and 
this  circumstance  causes  a  striking  difference  between  the  phenomena 
produced  by  removal  of  the  cerebrum,  and  those  following  removal  of 
the  cerebellum.  If  these  two  operations  be  done  upon  different  pigeons, 
and  the  two  animals  placed  side  by  side,  the  first  pigeon,  from  which 
the  cerebrum  only  has  been  removed,  remains  standing  firmly  upon  his 
feet,  in  a  condition  of  complete  repose;  and  when  compelled  to  stir, 
he  moves  sluggishly  and  unwillingly,  but  otherwise  acts  in  a  perfectly 
natural  manner.  The  second  pigeon,  on  the  other  hand,  from  which 
the  cerebellum  only  has  been  taken  away,  is  in  a  constant  state  of 
agitation.  He  is  easily  excited,  and  frequently  endeavors,  with  violent 
struggles,  to  escape  from  one  place  to  another ;  but  his  movements  are 
sprawling  and  unnatural,  and  no  longer  under  the  effectual  control  of 
the  will.  If  the  entire  cerebellum  be  destroj'ed,  the  animal  is  incapable 
of  assuming  or  retaining  any  natural  posture.  His  legs  and  wings  are 

1  Recherches  Exp6rimentales  sur  les  Propri6t6s  et  les  Fonctions  du  Systfeme 
Nerveux.  Paris,  1842,  pp.  37,  53,  102,  133. 


496  THE    BKAIN. 

agitated  with  ineffectual  movements,  which  are  evidently  voluntary  in 
character,  but  are  at  the  same  time  irregular  and  confused. 

The  direct  inference  which  may  be  derived  from  these  phenomena  is 
that  the  power  of  co-ordination  or  association  of  voluntary  movements 
of  the  body  and  limbs  resides  in  the  cerebellum  as  a  nervous  centre,  and 
that  this  power  is  accordingly  lost  or  impaired  by  injury  of  its  sub- 
stance. It  is  evident  that  such  a  power  really  exists  under  some  form 
in  the  nervous  system.  No  natural  co-ordinated  movements  are  effected 
by  the  independent  contraction  of  separate  muscles,  but  always  by  a 
number  of  muscles,  or  groups  of  muscles,  acting  in  harmony  with  each 
other.  The  extent  and  variety  of  this  muscular  association  vary  in 
different  classes  of  animals.  They  are  very  considerable  in  birds  and 
quadrupeds  as  compared  with  fish  and  reptiles,  and  reach  in  man  their 
highest  grade  of  development.  Even  in  maintaining  the  ordinary  pos- 
tures of  standing  or  sitting,  many  different  muscles  are  brought  into 
action  together,  in  each  of  which  the  degree  of  contraction  must  be 
accurately  proportioned  to  that  of  the  others.  In  the  motions  of  walk- 
ing and  running,  or  in  the  still  more  delicate  movements  of  the  hands 
and  fingers,  this  harmony  of  action  is  indispensable  to  the  efficiency  of 
the  muscular  apparatus. 

Notwithstanding  the  fact  that  this  power  of  co-ordination  is  invariably 
disturbed  by  injuries  of  the  cerebellum,  it  is  doubted  by  some  writers 
whether  it  can  be  strictly  attributed,  as  a  physiological  function,  to  this 
particular  part  of  the  nervous  system.  The  grounds  upon  which  this 
doubt  is  based  are  twofold ;  first  the  subsequent  recovery  of  the  power 
of  co-ordination  by  animals  after  injury  or  partial  removal  of  the  cere- 
bellum, and  secondly,  the  results  of  certain  pathological  observations 
in  the  human  subject. 

I.  Eestoration  of  the  Co-ordinating  Power  in  Operated  Animals. — 
It  is  certain  that  animals  may  be  affected,  after  partial  extirpation  of 
the  cerebellum,  with  well  marked  loss  of  co-ordinating  power,  and  that 
they  may,  in  some  instances,  subsequently  recover  this  power  without 
regeneration  of  the  lost  nervous  substance.  This  recovery  was  observed 
by  Flourens  in  the  fowl  and  in  the  pigeon,  and  has  been  seen  by  Flint1 
in  the  pigeon  after  removal  of  about  two-thirds  of  the  whole  mass  of  the 
cerebellum.  We  have  also  met  with  four  instances  of  the  same  kind. 
In  the  first,  about  two-thirds  of  the  cerebellum  was  taken  away  by  an 
opening  in  the  posterior  part  of  the  cranium.  Immediately  afterward, 
the  pigeon  showed  all  the  usual  effects  of  the  operation,  being  incapable 
.  of  flying,  walking,  or  even  of  standing  still,  but  only  reeled  and  sprawled 
in  a  perfectly  helpless  manner.  In  five  or  six  days  from  that  time,  he 
had  regained  a  very  considerable  control  over  the  voluntary  movements, 
and  at  the  end  of  sixteen  days  his  power  of  muscular  co-ordination  was 
so  nearly  perfect,  that  its  deficiency,  if  any  existed,  was  imperceptible. 
He  was  then  killed ;  and  on  examination,  it  was  found  that  his  cerebel- 

1  The  Physiology  of  Man ;  Nervous  System.     New  York,  1872,  p.  367. 


THE    CEREBELLUM.  497 

lum  remained  in  nearly  the  same  condition  as  immediately  after  the 
operation;  about  two-thirds  of  its  substance  being  deficient,  with  no 
regeneration  of  the  lost  parts.  The  accompanying  figures  show  the 
appearances  in  this  brain  as  compared  with  that  of  a  healthy  pigeon. 

Fig.  164.  Fig.  165. 


BRAIN  OP  HEALTHY  PIGEON— Pro-  BRAIN    OP    OPERATED     PIGEON  — 

file  view.— 1.  Cerebral  hemisphere.  2.  Optic  Profile  view— showing  the  mutilation  of 

tubercle.    3.  Cerebellum.     4.  Optic  nerve.  the  cerebellum. 
5.  Medulla  oblongata. 

Fig.  166.  Fig.  167. 


BRAIN  OP  HEALTHY  PIGEON— Pos-  BRAIN    OP    OPERATED    PIGEON  — 

terior  view.  Posterior   view— showing  the  mutilation 

of  the  cerebellum. 

In  the  three  remaining  cases  the  quantity  of  nervous  substance 
removed  amounted  to  about  one-half  the  mass  of  the  cerebellum.  The 
loss  of  co-ordinating  power,  immediately  after  the  operation,  though 
less  complete  than  in  the  preceding  instance,  was  perfectly  well  marked ; 
and  in  little  more  than  a  fortnight  the  animals  had  nearly  or  quite 
recovered  the  natural  control  of  their  motions,  so  far  as  could  be  seen 
while  they  were  kept  under  observation. 

It  is  evident  that  in  these  cases,  if  the  cerebellum  be  really  the  seat 
of  a  physiological  co-ordinating  power,  there  are  two  effects  produced 
by  the  operation,  which  should  be  carefully  distinguished  from  each 
other.  The  first  of  these  effects  is  the  shock  due  to  the  sudden  injury 
of  the  cerebellum  as  a  whole.  This  effect  is  temporary,  and  may  be 
recovered  from  in  time,  provided  the  animal  be  sufficiently  strong  to 
survive  the  immediate  mechanical  lesion.  The  remaining  effect  is  that 
due  to  the  loss  of  nervous  substance  ;  and  this  effect  must  of  course  be 
permanent,  unless  the  nervous  matter  be  regenerated.  In  the  cases 
detailed  above,  the  greatest  amount  of  disturbance  seems  to  have 
depended  upon  the  sudden  injury  to  the  nervous  centre  as  a  whole ;  and 
the  animals  recovered,  to  a  great  extent,  their  power  of  co-ordination, 
notwithstanding  that  from  one-half  to  two-thirds  of  the  substance  of 
the  cerebellum  was  permanently  lost. 


498  THE    BKAIN. 

The  recovery  of  a  nervous  function,  after  permanent  loss  of  nervous 
substance,  is  not  peculiar  to  the  cerebellum.  Flourens  has  observed 
the  same  thing  in  regard  to  the  cerebral  hemispheres  in  the  pigeon; 
the  intellectual  and  perceptive  faculties  being  totally  suspended  im- 
mediately after  partial  removal  of  the  hemispheres,  but  again  restored 
after  the  lapse  of  several  days.  But  this  restoration  only  takes  place 
where  the  removal  of  the  nervous  centre  is  partial ;  and  in  the  cerebel- 
lum, as  well  as  in  the  cerebrum,  after  complete  extirpation,  the  loss  of 
function  is  a  permanent  one.  In  the  experiment  of  Flourens,  where  a 
fowl  lived  for  four  months  after  entire  removal  of  the  cerebellum,  there 
was  no  recovery  of  co-ordinating  power. 

It  is  to  be  remembered  that  birds  and  other  animals,  when  confined  to 
the  limited  space  of  a  laboratory,  have  no  opportunity  of  exercising  the 
more  complicated  and  active  movements  natural  to  them  in  a  condition 
of  freedom  ;  and  accordingly,  they  might  not  show  any  great  deficiency 
of  muscular  co-ordination  while  in  confinement,  though  they  might  still 
be  incapable  of  executing  all  the  movements  of  natural  flight.  The 
simpler  motions  may  continue  to  be  performed  with  only  a  part  of  the 
cerebellum  remaining ;  but  we  are  not  sure  that,  even  in  these  cases,  a 
portion  of  the  co-ordinating  power,  corresponding  with  the  destruction 
of  nervous  substance,  has  not  been  permanently  lost. 

II.  Pathological  Observations  in  the  Human  Subject. — The  same  re- 
mark will  apply  to  the  pathological  observations  in  man  which  have  been 
sometimes  considered  as  neutralizing  the  result  of  experiments.  These 
are  mainly  cases  in  which  lesions  of  the  cerebellum,  more  or  less  ex- 
tensive, have  existed  without  recorded  disturbances  of  co-ordination 
similar  to  that  produced  in  animals  by  mechanical  injury  of  the  part. 
In  a  large  majority  of  these  instances  the  patients  were  confined  to  a 
sick-room,  and  in  many  of  them  to  the  bed ;  consequently  there  could 
be  no  opportunity  of  observing  a  want  of  natural  co-ordination  in  the 
more  complicated  movements,  if  any  such  existed.  A  patient,  also,  in 
whom  the  loss  or  diminution  of  a  motor  nervous  function  comes  on 
gradually,  accommodates  himself  to  it  by  abstaining  from  the  attempt 
to  perform  movements  of  which  he  is  incapable,  and  confines  himself  to 
those  which  he  is  still  able  to  perform.  Furthermore,  in  many  cases  of 
disease  of  the  cerebellum,  symptoms  of  want  of  co-ordinating  power 
have  been  distinctly  noticed  and  recorded. 

The  data  derived  from  comparative  anatomy  show  a  general  corre- 
spondence in  the  development  of  the  cerebellum  and  the  variety  and 
complication  of  muscular  action.  In  fish,  as  a  rule,  it  is  of  good  size 
compared  with  other  parts  of  the  brain;  and  although  direct  progression 
in  this  class  is  accomplished  by  a  comparatively  simple  mechanism, 
namely,  the  lateral  flexion  and  extension  of  the  spinal  column  with  its 
expanded  fins  and  tail,  yet  their  movements  through  the  water  or  in 
leaping  out  of  it,  while  pursuing  and  taking  their  prey,  are  remarkably 
rapid  and  vigorous,  and  are  promptly  varied  in  any  direction.  In  the 
frog,  on  the  other  hand,  the  movements  of  progression  consist  of  little 


THE    TUBER    AISTNULARE.  499 

else  than  straightforward  flexion  and  extension  of  the  posterior  limbs ; 
and  the  cerebellum  is  exceedingly  small,  much  inferior  in  size  to  that 
of  fishes,  and  forms  only  a  thin  narrow  ribbon  of  nervous  matter 
stretched  across  the  upper  part  of  the  fourth  ventricle.  In  the  che- 
lonia,  or  turtles,  the  movements  of  the  body  are  accomplished  by  the 
consentaneous  action  of  the  anterior  and  posterior  limbs,  and  those  of 
the  head  and  neck  are  also  much  more  varied  than  in  the  frog,  while  the 
cerebellum  exhibits  a  corresponding  increase  of  development.  In  the 
alligator  and  allied  species,  whose  motions  approximate  more  closely  to 
those  of  the  quadrupeds  than  is  the  case  with  other  reptiles,  the  cere- 
bellum is  also  larger  in  proportion  to  the  remaining  parts  of  the  brain. 
In  birds,  in  quadrupeds,  and  in  man  there  is  a  very  evident  increase  in 
the  size  and  convolutions  of  the  cerebellum,  corresponding  with  the 
greater  variety  and  delicacy  of  movements  which  they  are  capable  of 
performing.  These  facts  are  not  decisive  in  determining  the  physio- 
logical function  of  this  portion  of  the  brain,  since  other  nervous  endow- 
ments also  vary  in  their  degree  of  development  in  different  animals  and 
in  man ;  but  they  show  that  the  assumption  of  a  co-ordinating  power  in 
the  cerebellum  is  not  at  variance  with  the  comparative  anatomy  of  the 
nervous  system. 

Everything  which  we  know  with  certainty,  therefore,  in  regard  to  the 
cerebellum,  indicates  its  close  connection  with  the  power  of  co-ordination 
for  the  movements  of  the  body  and  limbs.  It  cannot  be  regarded  as 
exclusively  presiding  over  this  function  ;  since  there  is  strong  evidence 
that  the  posterior  columns  of  the  spinal  cord  are  in  great  measure 
devoted  to  the  same  purpose,  and  their  morbid  alteration  necessarily 
induces,  in  man,  the  disease  known  as  locomotor  ataxia.  But  the  pos- 
terior columns  of  the  cord  form  by  their  divergence,  at  the  level  of  the 
fourth  ventricle,  the  inferior  peduncles  of  the  cerebellum.  The  cerebel- 
lum accordingly  is  a  highly  developed  and  convoluted  nervous  centre, 
placed  at  the  upper  extremity  of  the  cord,  and  communicating,  by  tracts 
of  white  substance,  with  its  posterior  columns.  The  spinal  cord  itself 
is,  of  course,  essential  to  the  co-ordinated  motions  of  the  body,  arms, 
and  legs,  since  its  posterior  columns  are  for  them  the  direct  agents  of 
control  and  communication ;  but  the  cerebellum  may  also  be  regarded 
as  a  focus  or  nervous  centre  of  reflex  action  for  all  the  more  vigorous 
and  complicated  movements  of  the  trunk  and  limbs. 

The  Tuber  Annulate. 

The  tuber  annulare  is  an  isthmus,  which  makes  connection  between 
the  remaining  parts  of  the  encephalon  above,  and,  through  the  medulla 
oblongata,  with  the  spinal  cord  below.  It  may  be  described  in  general 
terms  as  constituted,  1st,  by  longitudinal  tracts  of  white  substance, 
the  prolongation  of  the  anterior  pyramids  of  the  medulla  oblongata, 
which  pass  through  it  in  a  nearly  straight  course,  becoming  continuous 
above  with  the  crura  cerebri ;  2d,  by  transverse  bundles  of  white  sub- 
stance coming  from  the  two  sides,  and  encircling  it  with  the  superficial 


500  THE    BRAIN. 

band  of  arched  fibres,  known  as  the  pons  Yarolii,  or  great  commissure  of 
the  cerebellum  ;  and  3d,  by  a  deposit  of  gray  substance  contained  in  its 
anterior,  and  more  or  less  mingled  with  its  other  portions.  The  tuber 
annulare  is,  therefore,  like  the  other  central  masses  of  the  encephalon, 
at  the  same  time  a  channel  of  communication  between  the  interior  and 
the  exterior,  and  a  nervous  centre  with  special  endowments  of  its  own. 

In  the  most  superlicial  portions  of  the  pons  Yarolii,  the  transverse 
bundles  of  nerve  fibres  are  closely  packed  together,  without  any  percep- 
tible admixture  of  nerve  cells.  The  deposit  of  gray  substance  commences, 
however,  according  to  Henle*  at  a  short  distance  below  the  surface,  occu- 
pying minute  spaces  between  the  transverse  bundles,  and  containing 
stellate  nerve  cells.  Beneath  the  superficial  transverse  bundles  of  the 
pons  come  the  longitudinal  tracts  of  pyramidal  nerve  fibres,  and  be- 
neath these  again  a  deeper  layer  of  transverse  commissural  fibres.  The 
deposit  of  gray  matter  in  the  pons  is  still  more  abundant  in  its  deep 
than  in  its  superficial  layer ;  often  alternating,  according  to  Henle, 
with  the  transverse  bundles,  in  interspaces  of  J  millimetre  in  thickness. 
It  also  fills  a  space  about  2  millimetres  wide,  on  each  side  the  median 
line,  between  the  two  pyramidal  tracts  of  white  substance. 

Physiological  Properties  of  the  Tuber  Annulare. — In  the  tuber 
annulare  the  phenomena  both  of  excitability  and  sensibility,  under 
artificial  irritation,  become  much  more  marked  than  in  the  great  centres 
of  the  cerebrum  and  cerebellum.  According  to  Longet,  a  galvanic 
stimulus,  when  the  electrodes  are  passed  into  the  substance  of  this 
organ,  produces  distinct  convulsive  movements  even  in  recently  killed 
animals,  although  its  external  surface  does  not  appear  to  be  excitable  by 
similar  means  either  in  front  or  behind.  Yery  slight  irritation  of  its 
posterior  surface  has  been  found,  by  both  Longet  and  Yulpian,  to  give 
rise  in  the  living  animal  to  indications  of  pain ;  but  this  effect  may  be 
partly  due  to  the  contiguity  of  the  sensitive  nerve-roots  which  traverse 
the  nervous  substance  in  this  situation.  Excitability  and  sensibility 
are  also  manifested  on  irritating  the  crura  cerebri,  between  the  tuber 
annulare  and  the  cerebral  ganglia. 

The  nature  of  the  physiological  actions  taking  place  in  the  tuber 
annulare,  as  a  nervous  centre,  can  only  be  studied  by  observing  the 
effects  produced  by  its  injury  or  removal,  in  comparison  with  other 
parts  of  the  encephalic  mass.  It  is  seen  that  the  cerebrum  and  cere- 
bellum may  be  taken  away,  either  together  or  separately,  without  de- 
stroying the  evidences  of  sensibility  or  the  power  of  motion.  According 
to  the  experiments  of  both  Longet  and  Yulpian,  the  cerebral  hemi- 
spheres, the  cerebellum,  the  corpora  striata,  the  optic  thalami,  and  the 
tubercula  quadrigemina  may  all  be  removed,  in  dogs  and  rabbits,  and 
yet  the  signs  of  sensibility  and  the  power  of  motion  in  the  limbs  con- 
tinue to  exist ;  and,  if  the  cerebellum  remain,  the  normal  attitude  of 
the  body  and  limbs,  and  even  the  power  of  progression,  may  still  be 
maintained. 

The  manifestations  of  these  nervous  functions,  however,  are  so  much 


THE    TUBER    ANNULAKE.  501 

diminished  after  extirpation  of  the  cerebral  hemispheres,  that  some 
writers  have  suspected  that  they  might  belong  to  the  category  of  un- 
conscious and  involuntary  reflex  actions.  Longet  and  Vulpian,  on 
the  other  hand,  insist  upon  the  fact,  observed  by  both,  that  after 
removal  of  the  whole  brain,  with  the  exception  of  the  tuber  annulare 
and  medulla  oblongata,  irritation  of  the  external  parts  or  of  a  sensitive 
nerve  will  produce,  in  dogs  and  rabbits,  cries  which  are  evidently  the 
expression  of  a  conscious  sensation.  This  alone  shows  that  the  animals 
after  such  a  mutilation  may  be  still  capable  of  feeling  pain ;  and, 
according  to  Vulpian,1  after  extirpation  of  the  hemispheres  and  the 
cerebral  ganglia  in  the  rat,  movements  of  the  head  and  limbs  were  not 
only  produced  by  pinching  the  integument,  but  blowing  suddenly  upon 
one  of  the  ears  caused  shaking  of  the  head,  accompanied  by  winking  of 
the  eyes  ;  showing  that  the  animal  was  still  sensitive  to  ordinary  tactile 
impressions,  as  well  as  to  those  of  a  painful  character.  The  same 
experimenter  has  found  that  in  a  rat,  after  the  above  operation,  a 
hissing  sound  made  by  the  lips  excited  repeatedly  distinct  signs  of 
agitation.  From  these  facts  it  can  hardly  be  doubted  that  sensations 
are  actually  perceived  by  the  animal  so  long  as  the  tuber  annulare 
remains  uninjured. 

There  is  no  evidence,  however,  that  in  these  cases  there  is  anything 
more  than  the  simple  sensation,  without  conscious  recognition  of  its 
origin  or  significance.  So  far  as  we  can  judge,  the  animal  under  these 
circumstances  may  be  capable  of  feeling  pain,  but  not  of  understanding 
the  cause  by  which  it  was  produced.  He  may  be  conscious  of  the 
sensations  of  light  or  of  sound,  as  existing  in  himself,  without  refer- 
ring them  to  any  external  source.  This  is  the  full  extent  of  sensibility, 
as  it  can  be  supposed  to  exist  in  the  tuber  annulare. 

A  similar  limitation  must  be  placed  on  the  action  of  the  voluntary 
muscles  so  far  as  it  is  excited  by  the  tuber  annulare.  These  motions 
have  the  appearance  of  volition,  so  far  as  they  consist  in  attempts  to 
maintain  or  recover  the  natural  attitude,  or  in  those  of  progression;  but 
it  is  not  a  volition  which  has  any  intelligent  understanding  of  its  pur- 
pose. It  follows  immediately  upon  the  receipt  of  the  sensation  which 
excites  it,  and  is  therefore  a  reflex  action;  but  it  differs  from  the  reflex 
action  of  the  spinal  cord  mainly  in  the  fact,  that  it  is  accompanied  or 
preceded  by  a  conscious  sensation. 

The  evidence  thus  far  in  our  possession  goes  to  show  that  the  tuber 
annulare  is  especially  connected  with  reflex  actions  of  an  emotional  and 
instinctive  character.  These  actions  differ  from  those  connected  with 
the  mental  faculties  in  being  comparatively  little  under  the  control  of 
the  judgment  or  the  will,  and  in  being  directed  by  an  unreasoning  im- 
pulse, where  the  act  follows  immediately  upon  the  receipt  of  the  sensa- 
tion. To  this  class  belong  the  purely  instinctive  acts  performed  by 
animals  or  man,  in  which  there  is  no  direct  recognition  of  their  nlti- 

1  LeQons  sur  la  Physiologie  du  Systfeme  Nerveux.     Paris,  1866,  p.  543. 


502  THE    BRAIN. 

mate  object,  but  only  of  the  immediate  stimulus  upon  which  they  depend. 
All  the  emotions,  and  the  expressions  to  which  they  give  rise,  are  ner- 
vous phenomena  of  this  kind.  The  feelings  of  cheerfulness  or  depres- 
sion, satisfaction,  hilarity,  or  displeasure,  are  expressed,  whenever  they 
reach  a  certain  degree  of  intensity,  by  tears  or  laughter,  by  inarticulate 
sounds,  attitudes  or  movements  of  the  body,  which,  though  not  inten- 
tionally calculated  to  produce  that  effect,  are  at  once  understood  by  all 
who  see  or  hear  them.  Jn  man,  certain  diseases  of  the  brain  induce  a 
condition  in  which  the  emotional  phenomena  are  much  more  easily 
excited  than  in  health,  either  from  an  undue  activity  of  the  nervous 
centre  in  which  they  are  located,  or  from  the  .diminished  influence 
exerted  over  them  by  the  cerebral  hemispheres.  In  these  instances, 
the  individual  is  moved  to  anger,  laughter,  or  tears  on  the  most  trivial 
occasions,  and  from  causes  which  would  not  produce  such  an  effect  in  a 
condition  of  health ;  the  feelings  thus  expressed  being  quite  uncontrol- 
lable for  the  time,  although  the  patient  may  be  conscious  that  they  have 
no  reasonable  motive. 

The  action  of  the  tuber  annulare,  as  the  centre  of  the  emotional  im- 
pulses, is  no  doubt  closely  connected  with  its  influence  over  the  attitude 
and  locomotion.  The  manner  in  which  these  two  functions  are  performed, 
even  in  man,  takes  a  great  share  in  the  manifestation  of  the  emotions,  and 
in  many  of  the  lower  animals  forms  the  principal  means  by  which  they 
are  expressed.  The  normal  postures  of  the  body  and  limbs  and  the 
movements  of  progression,  although  they  are  still  possible  after  de- 
struction of  the  cerebral  hemispheres  and  ganglia,  are  at  once  abolished, 
according  to  Vulpian,  if  the  tuber  annulare  be  removed  or  extensively 
injured. 

There  is  no  doubt,  also,  that  the  other  nervous  faculties  which  have 
been  enumerated  as  connected  with  the  tuber  annulare  come  to  an  end 
as  soon  as  this  organ  is  subjected  to  mutilation.  With  the  destruction 
of  the  tuber  annulare,  according  to  the  general  testimony  of  experi- 
menters, all  indications  of  sensibility  and  volition  disappear,  and  the 
animal  body  is  reduced  to  the  condition  of  a  helpless  and  unconscious 
machine,  in  which  the  functions  of  respiration  and  circulation,  with  cer- 
tain other  involuntary  reflex  phenomena,  are  the  only  remaining  mani- 
festations of  nervous  action. 

The  Medulla  Oblongata. 

The  medulla  oblongata  is  distinguished  from  the  spinal  cord,  of  which 
it  is  a  continuation,  not  only  by  its  external  form,  but  also  by  the  dif- 
ferent arrangement  both  of  the  bundles  of  nerve  fibres  and  of  the  gray 
substance  in  its  interior. 

In  the  spinal  cord,  the  anterior,  middle,  and  posterior  columns  of 
white  substance  all  consist  mainly  of  parallel  fibres  running  in  a  longi- 
tudinal direction ;  while  there  is  a  narrow  band  of  transverse  fibres,  the 
white  commissure,  at  the  bottom  of  the  anterior  median  fissure.  In  the 
medulla  oblongata,  a  much  larger  number  of  horizontal  and  oblique 


THE    MEDULLA    OBLONGATA.  503 

fibres  make  their  appearance,  passing  from  one  side  to  the  other.  The 
greater  part  of  these  fibres  come  from  the  continuations  of  the  lateral 
and  posterior  columns,  and  from  the  posterior  horns  of  gray  matter, 
whence  they  pass  forward  and  inward,  and  cross  each  other  on  the 
median  line  at  the  place  previously  occupied  by  the  white  commissure. 
The  increasing  number  of  these  interchanging  fibres,  and  the  fact  that 
they  cross  the  median  line  in  bundles  of  considerable  size,  and  in  an  ob- 
lique direction  from  below  upward,  produce  the  conformation  visible  at 
the  anterior  surface  of  the  medulla  oblongata,  and  known  as  the  decus- 
xation  of  the  pyramids.  After  crossing  from  one  side  to  the  other,  the 
fibres  again  gradually  take  a  longitudinal  direction,  and  it  is  on  this 
account  that  the  pyramids  increase  in  size  from  below  upward.  The 
pyramids  accordingly  consist  of  fibres  which  are  derived  from  the  lateral 
and  posterior  columns  of  the  opposite  side  of  the  cord.  They  are  not 
the  continuation  of  the  longitudinal  tracts  which  form  the  anterior 
columns  below  j  these  columns,  on  the  contrary,  diminishing  rapidly  in 
size  from  within  outward,  until  they  disappear  almost  completely  above 
the  level  of  the  decussation  of  the  pyramids.  Thus  the  decussation  of 
the  pyramids  represents  that  of  all  the  remaining  longitudinal  fibres  of 
the  spinal  cord,  so  far  as  it  takes  place  in  the  medulla  oblongata. 

The  longitudinal  fibres  of  the  posterior  columns  also  diminish  con- 
siderably in  number  in  the  medulla  oblongata,  as  shown  by  Henle, 
owing  to  their  taking  a  horizontal  direction,  forward  and  inward,  to 
reach  the  decussation  of  the  anterior  pyramids ;  while  the  remaining 
longitudinal  fibres  of  these  columns  pass  into  and  through  the  restiform 
bodies  to  the  white  substance  of  the  cerebellum. 

The  arrangement  of  the  gray  substance  in  the  medulla  oblongata  is 
also  different  from  that  presented  in  the  spinal  cord.  In  the  first  place, 
according  to  the  observations  of  Kolliker,  it  increases  in  quantity  from 
below  upward.  Secondly,  the  central  mass  of  gray  substance,  which  in 
the  cord  surrounds  the  central  canal,  and  sends  out  on  each  side  the 
anterior  and  posterior  horns,  recedes  in  the  medulla  oblongata  farther 
and  farther  backward  ;  the  posterior  horns  spreading  out  laterally,  and 
the  remainder  occupying  the  space  between  them.  The  posterior 
median  fissure  also  becomes  gradually  shallower  and  wider  by  the 
divergence  of  the  posterior  columns ;  and  the  central  canal  approxi- 
mates the  posterior  wall  of  the  medulla,  finally  opening  upon  its  surface 
at  the  lower  part  of  the  fourth  ventricle.  The  gray  substance  of  the 
medulla  oblongata  is  thus  uncovered  posteriorly,  and  forms  a  layer 
spread  out  laterally,  on  each  side  of  the  median  line,  immediately  be- 
neath the  floor  of  the  fourth  ventricle.  It  extends  forward,  without  any 
complete  interruption,  beneath  the  whole  length  of  the  fourth  ventricle 
and  the  aqueduct  of  Sylvius ;  and  it  is  this  layer  of  gray  substance 
which  gives  origin,  at  various  points,  to  the  fibres  of  all  the  cranial 
nerves,  excepting  the  olfactory  and  the  optic. 

Thirdly,  the  medulla  oblongata  is  distinguished  by  the  appearance, 
in  its  interior,  of  other  deposits,  or  nuclei,  of  gray  substance,  detached 


504 


THE    BRAIN. 


from  those  belonging  to  the  spinal  cord.  The  most  marked  of  these  is 
the  olivary  nucleus ;  a  convoluted  lamina  about  one-third  of  a  milli- 
metre in  thickness,  occupying  the  interior  of  the  olivary  body  on  each 
side,  just  below  the  inferior  border  of  the  pons  Yarolii. 


No 


TRANSVERSE  SECTION  OF  HUMAN  MEDULLA  OBLONGATA,  at  the  lower  part 
of  the  fourth  ventricle.— No,  Olivary  nucleus.  E,  Raphe,  at  the  median  line.  Ngl,  Nucleus 
of  the  glosso-pharyngeal  nerve.  Nv,  Nucleus  of  the  pneumogastric  nerve.  Nh,  Nucleus 
of  the  hypoglossal  nerve.  IX,  Roots  of  the  glosso-pharyngeal  nerve  (9th  pair)  at  their  point 
of  emergence  from  the  medulla.  XII,  Roots  of  the  hypoglossal  nerve  (12th  pair)  at  their 
point  of  emergence  from  the  medulla.  Magnified  8  diameters.  (Henle.) 

In  transverse  sections,  near  its  upper  or  lower  extremity,  the  olivary 
nucleus  appears  completely  closed,  but  a  section  through  its  middle 
shows  a  gap  toward  the  median  line.  It  forms,  therefore,  an  ovoid 
sac,  with  its  long  diameter  parallel  to  the  axis  of  the  medulla,  and  an 
opening  at  its  middle  directed  inward.  Through  this  opening  bundles 
of  nerve  fibres  penetrate  from  the  white  substance  of  the  medulla,  and, 


THE    MEDULLA    OBLONGATA.  505 

after  filling  the  space  inclosed  by  its  convoluted  wall,  pass  through  it, 
and  spread  out  laterally  in  a  divergent  direction. 

Physiological  Properties  of  the  Medulla  Oblongata. — The  simplest 
examination  of  the  medulla  oblongata  shows  that  its  physiological  pro- 
perties are  more  distinctly  marked  than  those  of  any  other  part  of  the 
encephalic  mass.  It  is  both  sensitive  and  excitable  to  a  high  degree, 
especially  in  its  posterior  portions.  Artifical  irritation,  by  mechanical 
or  galvanic  stimulus,  causes  at  once  a  painful  sensation,  provided  the 
rest  of  the  brain  be  uninjured,  and  in  the  recently  killed  animal  produces 
general  convulsive  movements  of  considerable  intensity.  These  effects 
are  due  to  the  irritability  of  the  longitudinal  fibres  connecting  the  me- 
dulla with  the  spinal  cord,  and  to  the  roots  of  the  sensitive  and  motor 
cranial  nerves  which  take  their  origin  from  this  part  of  the  encephalic 
mass.  Since  the  medulla  is  the  only  bond  of  nervous  communication 
between  the  brain  and  the  spinal  cord,  its  section  at  any  point  also 
destroys  voluntary  motion  and  sensibility  throughout  the  body  and 
limbs- 

Action  of  the  Medulla  as  a  Nervous  Centre. — The  various  deposits 
of  gray  substance  in  the  interior  of  the  medulla,  and  their  connection 
with  nerves  of  widely  different  distribution  and  functions,  are  the  pecu- 
liar features  of  its  anatomical  structure.  The  results  of  experiment 
show  that  the  reflex  actions  taking  place  in  this  part  of  the  nervous 
system  are  also  of  a  special  and  distinctive  character. 

The  most  important  of  these  actions  is  connected  with  respiration. 
So  long  as  the  medulla  oblongata  is  left  uninjured,  although  the  cranium 
be  emptied  of  all  the  other  nervous  centres,  the  movements  of  respira- 
tion and  circulation  go  on  without  essential  modification.  But  if  the 
medulla  be  destroyed,  respiration  ceases  instantaneously.  This  effect  may 
be  produced,  without  injuring  other  parts  of  the  brain,  in  dogs  or  other 
warm-blooded  animals,  by  introducing  a  steel  instrument  from  behind, 
between  the  edges  of  the  occipital  foramen  and  the  first  cervical  verte- 
bra, carrying  it  forward  in  the  median  line  until  its  point  rests  upon 
the  basilar  process  of  the  occipital  bone.  It  is  then  moved  from  side  to 
side  in  such  a  way  as  to  break  up  the  substance  of  the  medulla  oblon- 
gata, when  all  the  movements  of  respiration  are  at  once  arrested.  The 
circulation  continues,  and  the  pulsations  of  the  heart  are  even  increased 
for  a  time  in  force  and  frequency  ;  but  as  the  deficiency  of  aeration  in 
the  blood  becomes  more  marked,  the  circulation  is  gradually  retarded 
and  after  several  minutes  comes  to  an  end.  The  effect  of  this  operation 
upon  the  two  functions  of  circulation  and  respiration  is  very  different. 
The  circulation  is  interfered  with  and  finally  suspended  in  a  secondary 
manner,  and  only  because  the  blood  is  no  longer  arterialized ;  respira- 
tion is  abolished  instantaneously,  as  the  immediate  result  of  the  destruc- 
tion of  the  medulla  oblongata. 

The  medulla  is,  therefore,  the  most  important  nervous  centre  in  the 
brain  for  the  immediate  preservation  of  the  vital  functions,  and  the 
only  one  whose  injury   or  removal  produces  at   once  a    fatal  result. 
33 


506  THE    BRAIN. 

In  man,  quadrupeds,  and  birds,  it  is  a  vital  point;  since  in  them  the 
function  of  respiration,  over  which  it  presides,  is  necessary  for  the  con- 
tinuance of  life  from  one  moment  to  another. 

The  fact  that  sudden  death  may  be  produced  by  injury  of  the  cerebro- 
spinal  axis  in  this  region  was  known  to  Galen,  who  described  the  method 
of  killing  an  animal  by  section  of  the  spinal  cord  "  at  the  upper  cervical 
vertebrae."  The  respiratory  movements  of  the  chest  and  abdomen  are 
however  necessarily  arrested  by  section  of  the  cord  anywhere  above 
the  third  cervical  vertebra,  since  this  paralyzes  at  once  both  the  dia- 
phragm and  the  intercostal  muscles.  But  movements  of  inspiration, 
simultaneous  with  those  of  the  chest  and  abdomen,  are  also  performed 
by  the  glottis ;  and  in  most  of  the  quadrupeds  there  is  at  the  same  time 
an  expansion  of  the  nostrils,  all  associated  with  each  other  in  the  act 
of  respiration.  If  the  spinal  cord  be  divided  at  the  third  cervical  verte- 
bra the  movements  of  the  chest  and  abdomen  cease,  but  those  of  the 
glottis  and  the  nostrils  continue,  since  the  nerves  supplying  these  parts 
are  still  in  communication  with  the  medulla  oblongata.  Destruction 
of  the  medulla  itself,  on  the  other  hand,  arrests  at  the  same  instant  all 
movements  of  respiration,  both  in  the  trunk,  the  glottis,  and  the  face. 
It  is,  therefore,  a  centre  from  which  the  respiratory  apparatus  in  general 
derives  its  stimulus. 

The  more  exact  location  of  this  centre  was  investigated  by  Flourens1 
by  making  transverse  sections  of  the  medulla  at  different  parts  of  its 
length,  and  observing  the  effect  produced  upon  respiration.  The  result 
showed  that  injuries  of  this  kind,  inflicted  just  behind  the  point  of 
emergence  of  the  pneumogastric  nerves,  destroyed  at  once  all  the  move- 
ments of  respiration  together.  Below  this  point  the  movements  of  the 
chest  and  abdomen  were  stopped,  but  those  of  the  nostrils  and  glottis 
continued  ;  above  it  the  movements  of  the  nostrils  were  arrested,  while 
those  of  the  chest  and  abdomen  went  on. 

Similar  experiments  performed  by  Longet  show  that  the  respiratory 
centre  does  not  extend  through  the  entire  thickness  of  the  medulla; 
since  either  the  anterior  pyramids  in  front  or  the  restiform  bodies 
behind  may  be  destroyed  without  putting  a  stop  to  respiration  ;  while  a 
lesion  passing  through  the  intermediate  layer  at  once  causes  its  sus- 
pension. Flourens  subsequently2  limited  the  position  of  this  centre 
still  more  closely,  and  found  that  in  rabbits  it  occupies  a  space  of  about 
2.5  millimetres  on  each  side  the  median  line,  situated  at  the  lower  end 
of  the  fourth  ventricle,  a  little  in  advance  of  the  divergence  of  the 
posterior  pyramids,  and  just  at  the  point  of  gray  substance  formed  by 
the  ala  cinerea.  A  section  of  the  medulla  at  this  spot,  with  a  double- 
edged  knife  only  5  millimetres  wide,  or  its  perforation  at  the  same 
point  with  a  sharp-edged  canula  not  more  than  3  millimetres  in 

1  Kecherches  Experimentales  sur  les  Proprietes  et  les  Fonctions  du  Systeme 
Nerveux.     Paris,  1842,  pp.  196-204. 

2  Comptes  Kendu  de  1' Academic  des  Sciences.     Paris,  1858,  tome  xlvii.  p.  803. 


THE    MEDULLA    OBLONGATA.  507 

diameter,  caused  immediate  stoppage  of  the  respiration;  while  this 
effect  was  not  produced  by  similar  injuries  inflicted  either  above  or 
below.  This  spot,  which  contains  the  nervous  centre  of  the  movements 
of  respiration,  corresponds  in  level,  in  front  of  the  medulla  oblongata, 
with  the  upper  end  of  the  decussation  of  the  anterior  pyramids,  or  the 
lower  extremity  of  the  olivary  bodies,  and  is  somewhat  below  the 
apparent  origin  of  the  pnenmogastric  nerves. 

Respiration  accordingly  is  an  act  consisting  of  various  associated 
movements,  which  have  their  nervous  centre  in  the  medulla  oblongata. 
The  respiratory  movements  themselves  are  completel3r  involuntary  in 
character ;  for  although  those  of  the  chest  and  abdomen  may  be  for  a 
short  time  increased  in  frequency,  the  surplus  movements  thus  per- 
formed are  not  necessary  to  respiration,  and  soon  produce  a  fatigue  which 
prevents  their  continuance.  Respiration  goes  on  with  its  natural  rhythm, 
and  entirely  unaccompanied  by  fatigue,  under  the  influence  of  the  me- 
dulla, from  the  first  moment  of  birth  and  without  any  necessary  con- 
sciousness of  its  existence.  If  arrested  by  a  voluntary  effort,  the 
internal  stimulus  which  prompts  the  movement  grows  gradually 
stronger,  until  the  will  is  no  longer  capable  of  resisting  its  demands. 
As  soon  as  the  voluntary  resistance  is  overcome  or  discontinued,  the 
respiratory  movements  recommence  by  the  independent  action  of  the 
medulla  oblongata. 

The  action  of  the  medulla  in  respiration  is  one  of  a  reflex  nature. 
The  impression  by  which  it  is  called  out  has  its  origin  in  the  partial 
want  of  arterialization  of  the  blood,  and  especially  in  the  commencing 
accumulation  of  carbonic  acid  in  the  lungs  and  in  the  tissues.  In 
normal  respiration,  this  impression  is  sufficient  to  excite  the  reflex 
action  of  the  medulla  without  producing  a  conscious  sensation ;  and  on 
the  renewal  of  the  air  in  the  lungs  by  inspiration,  the  impulse  is  satisfied, 
the  muscles  relax,  and  expiration  is  accomplished  by  the  passive  col- 
lapse of  the  lungs  and  thorax.  In  a  few  seconds  the  previous  condition 
recurs  and  the  actions  are  repeated  as  before,  causing  in  this  way  the 
regularly  alternating  movements  of  inspiration  and  expiration. 

Since  the  acts  of  inspiration  are  performed  partly  by  the  diaphragm 
and  partly  by  the  intercostal  muscles,  they  will  be  differently  modified 
by  injuries  or  lesions  of  the  nervous  system,  according  to  the  spot  at 
which  they  are  situated.  If  the  spinal  cord  be  divided  or  compressed 
in  the  lower  cervical  region,  all  the  intercostal  muscles  are  necessarily 
paralyzed,  and  respiration  is  then  performed  only  by  the  diaphragm. 
If  the  phrenic  nerve,  on  the  other  hand,  be  divided,  the  diaphragm  alone 
is  paralyzed,  and  respiration  is  performed  altogether  by  the  rising  and 
falling  of  the  ribs.  If  the  injury  inflicted  upon  the  spinal  cord  be  above 
the  origin  of  the  third  cervical  nerve,  both  the  phrenic  and  intercostal 
nerves  are  paralyzed,  and  death  takes  place  from  suffocation.  The  at- 
tempt at  respiration,  however,  still  continues  in  these  cases,  showing 
itself  by  ineffectual  inspiratory  movements  of  the  mouth  and  nostrils. 
Finally,  if  the  medulla  itself  be  broken  up  at  the  situation  of  the 


508  THE    BRAIN. 

respiratory  centre,  both  the  power  and  the  stimulus  to  breathe  are  at 
once  taken  away.  No  attempt  is  made  at  inspiration  and  there  is  no 
appearance  of  suffering.  The  animal  dies  by  want  of  aeration  of  the 
blood,  which  leads  after  some  moments  to  arrest  of  the  circulation. 

An  irregularity  in  the  movements  of  respiration  is  accordingly  one 
of  the  most  threatening  symptoms  in  affections  of  the  brain.  A  sus- 
pension of  the  intellectual  powers  does  not  necessarily  indicate  imme- 
diate danger  to  life.  Even  sensation  and  volition  may  be  impaired 
without  direct  injury  to  the  organic  functions.  Cerebral  apoplexy  at 
the  surface  of  the  hemispheres,  in  the  lateral  ventricles,  or  in  the  cerebral 
ganglia,  is  seldom  immediately  fatal,  however  extensive  may  be  the  in- 
jury of  the  parts.  But  when  occurring  in  the  substance  of  the  medulla 
oblongata  or  its  immediate  neighborhood,  it  produces  death  instan- 
taneously by  the  same  mechanism  as  where  this  part  is  intentionally 
destroyed  by  experiment  in  the  lower  animals.  When  the  medulla  is 
beginning  to  be  implicated,  in  man,  by  a  progressive  disease  or  by 
gradual  failure  of  the  nervous  functions,  the  respiratory  movements 
first  affected  are  those  of  the  nostrils  and  lips,  while  those  of  the  chest 
and  abdomen  go  on  for  a  time  as  usual.  The  cheeks  are  drawn  in  with 
every  inspiration  and  puffed  out  with  every  expiration,  the  nostrils 
sometimes  participating  in  these  abnormal  movements.  A  still  more 
threatening  symptom,  and  one  which  frequently  precedes  death,  is  an 
irregular  and  hesitating  respiration,  sometimes  noticeable  even  before 
the  remaining  cerebral  functions  are  seriously  impaired.  These  phe- 
nomena depend  on  the  connection  between  respiration  and  the  reflex 
action  of  the  medulla  oblongata. 

The  process  of  deglutition  is  also  accomplished  under  the  control  of 
the  medulla.  Mastication  of  the  food  by  the  movements  of  the  jaws, 
and  its  transfer  by  the  tongue  to  the  entrance  of  the  fauces,  are  volun- 
tary actions  which  may  be  continued  or  arrested  at  will.  But  when  the 
food  has  passed  from  the  mouth  into  the  pharynx,  the  act  of  deglutition, 
by  which  it  is  carried  down  into  the  stomach,  is  reflex  and  involuntary 
in  character.  Once  commenced,  it  cannot  be  arrested  by  the  influence 
of  the  will,  as  it  consists  of  a  series  of  muscular  contractions  following 
each  other  in  regular  and  undeviating  succession.  These  contractions 
receive  their  impulse  from  the  medulla  oblongata.  In  the  experiments 
of  Flourens  and  Longet,  fowls  and  pigeons,  after  removal  of  the  cerebral 
hemispheres,  never  picked  up  their  food  spontaneously,  nor  ever  swal- 
lowed it  when  placed  in  the  mouth  at  the  end  of  the  beak;  but  if  carried 
backward  and  placed  in  the  commencement  of  the  pharynx,  it  was  at 
once  embraced  by  the  muscular  walls  of  this  organ,  and  carried  into 
the  stomach  by  a  continuous  movement  of  deglutition.  This  includes, 
not  only  the  associated  contraction  of  the  walls  of  the  pharynx  and 
oesophagus,  but  also  the  stoppage  of  respiration  and  the  closure  of  the 
glottis,  by  which  the  food  is  prevented  from  passing  into  the  larynx. 
According  to  Yulpian,  after  all  parts  of  the  brain  have  been  removed, 
in  cats  or  guinea  pigs,  excepting  the  medulla,  swallowing  may  still  be 


THE    MEDULLA    OBLONGATA.  509 

accomplished  by  reflex  action  ;  but  it  becomes  impossible  as  soon  as 
this  part  is  removed  or  seriously  injured.  The  muscular  combinations 
necessary  to  deglutition  cannot  take  place,  except  under  the  influence 
of  the  medulla  as  a  nervous  centre. 

This  action  may  consequently  be  performed,  in  man,  after  all  sensi- 
bility and  voluntary  power  have  disappeared.  In  cases  of  compression 
of  the  brain  from  injury  or  disease,  when  the  individual  is  in  a  state  of 
complete  unconsciousness,  and  even  when  the  respiration  is  diminished 
in  frequency,  solid  or  liquid  food,  if  carried  into  the  upper  part  of  the 
pharynx,  may  be  successfully  swallowed  by  the  ordinary  movements  of 
deglutition.  When  this  process  is  no  longer  possible,  or  is  accompanied 
by  choking  or  regurgitation,  it  indicates  that  the  medulla  has  become 
seriously  affected,  and  that  death  is  probably  near  at  hand. 

The  medulla  is  furthermore  connected  with  the  act  of  phonation.  The 
production  of  a  vocal  sound  is  usually  the  result  of  a  voluntary  impulse 
derived  from  the  operation  of  the  cerebral  hemispheres.  It  is  sometimes 
also  a  purely  emotional  act,  originating  in  the  excitement  of  the  tuber 
annulare,  and  without  any  reasonable  or  intelligent  motive.  But  in 
these  cases  its  production  is  a  secondary  result,  requiring  the  co-opera- 
tion of  other  nervous  elements,  and  its  immediate  centre  is  located  in 
the  medulla.  This  is  shown  by  the  fact  that  a  cry  may  still  be  produced 
when  the  upper  parts  of  the  encephalon  have  been  destroyed  or  removed, 
and  when  an  irritation  is  applied  to  the  medulla  alone.  If  a  stilet  be 
introduced  into  the  cranium  of  a  frog,  the  cerebral  hemispheres  may 
be  broken  up  without  producing  any  excitement  of  the  vocal  organs ; 
but  when  the  instrument  touches  the  medulla,  its  contact  is  often  fol- 
lowed by  a  distinct  and  spasmodic  cry.  Yulpian  has  shown  that  a  similar 
effect  may  be  produced  in  mammalians,  after  removal  of  the  whole 
encephalon  excepting  the  medulla,  by  a  reflex  action.  A  cry  is  pro- 
duced each  time  the  integument  of  the  foot  is  pinched  by  the  blades  of 
a  forceps.  This  sound,  however,  gives  no  indication  of  consciousness 
or  sensibility  on  the  part  of  the  animal.  It  is  short,  abrupt,  and  momen- 
tary in  duration,  and  is  repeated  only  when  the  irritation  is  again  applied 
to  the  external  parts.  It  is  a  purely  mechanical  effect  of  the  tension  of 
the  vocal  cords  and  the  sudden  expulsion  of  air  through  the  rima  glot. 
tidis.  After  the  destruction  of  the  medulla,  on  the  other  hand,  no  vocal 
sound  can  be  produced,  and  the  same  irritation  of  the  integument  is. 
then  followed  only  by  the  ordinary  spasmodic  movement  of  the  limbs, 
dependent  on  the  reflex  action  of  the  spinal  cord. 

In  the  exercise  of  the  voice,  therefore,  the  preliminary  actions  of  in- 
telligence, volition,  or  emotional  excitement  require  the  co-operation  of 
the  cerebrum  and  the  tuber  annulare ;  but  the  immediate  mechanism  by 
which  a  vocal  sound  is  produced  in  the  larynx  has  its  nervous  centre  in 
the  medulla  oblongata. 

This  part  of  the  brain,  with  the  adjoining  part  of  the  tuber  annulare, 
is  also  the  direct  source  of  the  movements  of  articulation.  It  is  the 
gray  substance  of  this  region  that  gives  origin  to  the  hypoglossal  and 


510  THE    BRAIN. 

facial  nerves  which  animate  the  muscles  of  the  tongue  and  lips,  as  well 
as  the  motor  fibres  which  regulate  the  condition  of  the  rima  glottidis. 
Disease  or  injury  in  this  situation,  sufficient  to  impair  the  action  of  these 
nerves,  consequently  makes  articulation  difficult  or  impossible,  by  para- 
lyzing the  muscles  upon  which  it  is  dependent.  This  affection  is  quite 
distinct  from  "  aphasia,"  which  is  of  cerebral  origin  and  consists  in  a 
loss  or  deterioration  of  mental  faculties  alone,  the  external  mechanism 
of  speech  being  unaffected  and  the  muscles  of  the  tongue  and  lips  re- 
taining their  power  of  movement  in  any  direction.  When  the  difficulty 
is  seated  in  the  medulla,  on  the  other  hand,  the  muscular  paralysis  is 
very  evident,  and  is  distinguished  by  being  more  or  less  confined  to 
those  groups  of  muscles  which  are  concerned  in  articulation  and  phona- 
tion. 

Such  an  affection  is  that  first  described  by  Duchenne  and  now  gene- 
rally recognized  under  the  name  of  glosso-labio-laryngeal  paralysis.1  It 
is  a  paralysis  due  to  chronic  degeneration  of  gray  nervous  tissue  in  the 
medulla  oblongata,  which  affects  the  motor  nerves  of  the  tongue,  the 
face,  the  hanging  palate,  and  the  larynx.  The  first  difficulty  is  generally 
noticeable  in  the  movements  of  the  tongue,  which  cannot  be  applied 
accurately  to  the  upper  teeth  or  to  the  roof  of  the  mouth ;  and  the 
lingual  and  dental  consonants  are  therefore  pronounced  imperfectly  or 
not  at  all.  The  lips  are  next  affected,  so  that  they  cannot  be  brought 
in  contact  with  each  other,  and  B  and  P  are  pronounced  like  Y  or  F. 
As  the  debility  of  the  orbicularis  oris  increases,  the  lips  cannot  even  be 
partially  approximated  and  the  vowels  0  and  U  are  no  longer  sounded ; 
and  by  the  continued  exaggeration  of  these  difficulties  the  patient's 
speech  becomes  at  last  unintelligible.  Deglutition  is  also  affected,  and 
attempts  at  swallowing  are  liable  to  cause  choking,  from  the  imperfect 
protection  of  the  rima  glottidis.  Phonation  becomes  impaired  from 
debility  of  the  laryngeal  muscles,  and  in  advanced  cases  no  vocal  sound 
can  be  produced.  The  disease  is  uniformly  progressive,  and  terminates 
life  usually  by  affecting  the  movements  of  respiration. 

The  medulla  oblongata  is  accordingly  the  seat  of  reflex  actions  which 
are  directly  or  indirectly  connected  with  the  immediate  preservation  of 
life,  since  it  maintains  the  movements  by  which  air  and  food  are  intro- 
duced into  the  interior  of  the  body.  It  also  presides  over  the  immediate 
muscular  combinations  concerned  in  the  production  of  the  voice  and 
articulation,  and  by  this  means  establishes  an  intelligible  communica- 
tion with  the  external  world. 

1  Hammond,  Diseases  of  the  Nervous  System.     New  York,  1871,  p.  676. 


CHAPTEE  YI. 

THE    CRANIAL    NERYES. 

OP  the  twelve  pairs  of  nerves  which  take  their  origin  from  the  brain, 
the  greater  number  present  distinct  analogies,  both  anatomical  and 
physiological,  with  the  spinal  nerves.  All  those  which  are  distributed 
to  the  integument  and  mucous  membranes,  or  to  the  superficial  and  deep 
muscles  of  the  head  and  face,  correspond  in  all  important  characters 
with  the  sensitive  and  motor  nerves  formed  from  the  anterior  and  pos- 
terior spinal  nerve  roots.  Three  of  them,  however,  show  no  resem- 
blance, either  in  their  anatomical  distribution  or  their  physiological 
properties,  with  the  rest.  They  are  the  so-called  olfactory,  optic,  and 
auditory  nerves.  After  leaving  their  points  of  origin  in  the  brain,  they 
are  distributed  neither  to  muscles  nor  to  the  integument  or  mucous 
membranes ;  but  terminate  in  nervous  expansions  of  special  form  and 
structure,  in  which  the  gray  substance  or  collections  of  nerve  cells 
reappear  as  prominent  elements  of  the  tissue.  During  their  passage 
through  the  cavity  of  the  cranium,  these  nerves  are  neither  sensitive 
nor  excitable  in  the  ordinary  sense  of  the  word.  Their  irritation  causes 
no  tactile  or  painful  sensation,  nor  any  direct  muscular  contraction ; 
and  their  section  produces  no  paralysis  of  the  voluntary  muscles,  nor 
any  loss  of  general  sensibility  in  the  neighboring  parts.  They  are  to 
be  considered  rather  in  the  light  of  tracts  or  commissures  than  of  ordi- 
nary nerves,  and  their  physiological  properties  are  those  connected  with 
the  operation  of  the  special  senses  alone. 

The  remaining  cranial  nerves,  on  the  other  hand,  are  similar,  both 
in  structure,  arrangement  and  function,  to  those  in  other  parts  of  the 
cerebro-spinal  system.  Some  of  them,  like  the  oculo-motorius,  the 
patheticus,  and  the  facial,  are  plainly  motor  in  character,  are  distributed 
to  muscles,  produce  convulsive  motion  on  being  irritated,  and,  when 
injured  or  divided,  leave  the  corresponding  parts  in  a  state  of  paralysis. 
Others,  such  as  the  trigeminus,  the  glosso-pharyngeal,  and  the  pneumo- 
gastric,  are  sensitive  nerves,  possessing  either  an  acute  tactile  sensibility, 
like  the  trigeminus,  or  one  of  a  more  obscure  and  special  nature  adapted 
for  the  production  of  involuntary  reflex  actions,  like  the  glosso-pharyn- 
geal and  pneumogastric.  Like  the  posterior  roots  of  the  spinal  nerves, 
these  are  also  provided  with  a  ganglion  situated  at  a  short  distance 
from  their  points  of  emergence  at  the  base  of  the  brain ;  and  they  are 
distributed  either  to  the  integument  or  mucous  membranes  or  to  both. 

The  analogy  in  anatomical  arrangement  between  the  spinal  and  cranial 

(511) 


512  THE    CRANIAL    NERVES. 

nerves  is  in  some  instances  very  marked.  The  fifth  pair  or  trigeminus 
emerges  from  the  tuber  annulare  in  two  distinct  bundles  or  roots,  of 
which  one  is  sensitive,  the  other  motor ;  the  sensitive  root  presenting 
soon  afterward  a  well  developed  ganglion,  with  which  the  fibres  of  the 
motor  root  do  not  mingle.  This  nerve  beyond  the  ganglion,  therefore, 
contains  both  motor  and  sensitive  fibres,  and  is  distributed  both  to 
muscles  and  to  the  integument.  In  a  similar  manner  the  glosso-pha- 
ryngeal  nerve  is  joined,  beyond  its  ganglion,  by  motor  fibres  from  the 
facial;  and  the  pneumogastric  receives  abundant  communications  from 
the  spinal  accessory  and  other  motor  nerves.  Both  the  sensibility  and 
motion  therefore  of  the  parts  to  which  they  are  distributed  are  provided 
for,  in  a  manner  not  essentially  different,  by  both  the  cranial  and  spinal 
nerves. 

The  other  points,  both  of  difference  and  analogy,  in  the  cranial  nerves, 
relate  to  their  origin  and  distribution.  Their  apparent  origin,  that  is, 
the  point  at  which  they  become  detached  from  the  surface  of  the  brain, 
is  not  their  real  origin ;  but  in  every  case  their  fibres  can  be  traced  from 
this  point  inward,  between  other  longitudinal  or  transverse  tracts  of 
white  substance,  until  they  reach  a  mass  of  gray  matter,  often  placed  at 
a  considerable  distance  and  in  quite  a  different  locality  from  their 
apparen  origin.  All  the  cranial  nerves,  excepting  the  olfactory  and 
the  optic,  are  thus  found  to  originate  from  a  mass  of  gray  substance 
upon  and  beneath  the  floor  of  the  fourth  ventricle,  and  extending  forward 
to  surround  the  aqueduct  of  Sylvius.  This  layer  of  gray  substance  is  a 
continuation  of  that  in  the  spinal  cord  ;  but  while  in  the  cord  it  has  the 
form  of  a  central  mass  with  lateral  anterior  and  posterior  horns,  in  the 
medulla  oblongata  it  takes  the  shape  of  a  lamina  occupying  only  the 
posterior  part  of  the  cerebro-spinal  axis.  In  its  various  divisions  and 
expansions,  which  are  rarely,  if  ever,  completely  discontinuous  from 
each  other,  it  forms  the  so-called  "  nuclei"  of  the  cranial  nerves. 

In  their  distribution,  these  nerves  present  also  certain  anatomical 
features  which  are  more  apparent  than  real  in  their  importance.  The 
oculomotorius,  patheticus,  and  abducens  emerge  from  the  substance  of 
the  brain  at  very  different  points,  and,  running  forward  through  the 
cranial  cavity  in  the  form  of  separate  cords,  are  enumerated  as  three 
distinct  nerves.  But  they  all  originate  from  the  layer  of  gray  substance 
already  mentioned,  two  of  them,  the  oculomotorius  and  the  patheticus, 
in  close  proximity  to  each  other ;  they  all  pass  out  of  the  cranium,  into 
the  orbital  cavity,  by  the  sphenoidal  fissure  ;  and  they  are  all  distributed 
to  the  group  of  muscles  moving  the  eyeball.  In  a  physiological  point 
of  view,  therefore,  they  are  branches  of  a  single  nerve,  rather  than  three 
separate  trunks.  Even  when  two  or  more  nerves  emerge  from  the 
cranium  by  different  foramina,  like  the  three  divisions  of  the  trigeminus, 
they  are  nevertheless,  properly  speaking,  parts  of  the  same  nerve,  if  they 
have  similar  physiological  properties  and  are  distributed  to  the  muscles 
or  integument  of  the  same  regions.  It  is  the  ultimate  distribution  of  a 
nerve,  and  not  its  course  through  the  bones  of  the  skull,  that  determines 


THE    OLFACTORY    NERVES. 


513 


its  physiological  character  and  position.  The  details  of  branching  and 
division  of  the  cranial  nerves  vary  in  different  species  of  animals,  or 
even  to  some  extent  in  the  same  individual  on  the  two  opposite  sides 
of  the  body,  but  their  physiological  characters  remain  the  same.  Thus 
in  the  bull-frog,  as  shown  by  Wyman,1  both  the  facial  nerve  and  the 
abducens,  instead  of  existing  as  distinct  trunks,  are  given  off  as  branches 
from  the  fifth  pair ;  and  in  most  of  the  quadrupeds,  the  terminal  frontal 
branches  of  the  ophthalmic  division  of  the  fcrigeminus  are  wanting,  or 
reduced  to  trifling  dimensions,  in  accordance  with  the  absence  of  sensi- 
bility in  the  skin  of  the  forehead  and  vertex. 

The  cranial  nerves  may,  therefore,  be  conveniently  arranged  in  pairs 
according  to  their  distribution  and  functions,  rather  than  the  incidental 
peculiarities  of  their  course  or  subdivision.  The  olfactory,  optic,  and 
auditory  nerves  thus  form  a  group  by  themselves  of  a  specific  character ; 
while  the  remainder  consist  of  the  motor  and  sensitive  nerves,  supply- 
ing the  muscular  apparatus  and  the  integument  or  mucous  membrane 
of  different  regions. 

CRANIAL  NERVES. 
Nerves  of  Special  Sense. 


Distributed  to  the 


Upper,     middle,     and 
lower  facial  regions. 

Tongue  and  pharynx. 
Passages    of    respira- 
tion and  deglutition. 

This  division  of  the  nerves,  though  based  on  their  physiological 
characters  and  distribution,  is  not  absolutely  perfect  in  all  particulars. 
For  while  the  hypoglossal  nerve  supplies  the  muscles  of  the  tongue 
alone,  its  associate,  the  gloss-pharyngeal,  sends  a  part  of  its  sensitive 
fibres  to  the  tongue  and  a  part  to  the  pharynx  ;  and  while  the  trigeminal 
nerve  is  mainly  distributed  to  the  external  parts  of  the  face,  one  of  its 
deeper  branches,  the  lingual,  is  distributed  to  the  tongue.  Notwith- 
standing, however,  these  irregularities,  such  an  arrangement  of  the 
cranial  nerves  is  substantially  correct,  and  may  serve  as  a  useful  guide 
in  the  study  of  their  functions. 

First  Pair.    The  Olfactory  Nerves. 

What  is  called  in  man  the  "  olfactory  nerve,"  is  a  three-cornered  pris- 
matic tract,  composed  of  both  gray  and  white  substance,  running  forward 
in  a  longitudinal  groove  upon  the  inferior  surface  of  the  anterior  cerebral 


1.  Olfactory. 

2.  Optic.     3.  Audil 

Motor  nerves. 

Sensitive  nerves. 

f  Oculomotorius 

Patheticus 

1st   PAIR.   - 

|  Abducens 
Facial 

Trigeminus. 

2d  PAIR. 
3d  PAIR. 

[  Small  root  of  5th  pair 
Hypoglossal 
Spinal  accessory 

Glosso-pharyngeal. 
Pneumogastric. 

1  Nervous  System  of  Rana  pipiens  ;  published  by  the  Smithsonian  Institution. 
Washington,  1853. 


514 


THE    CRANIAL    NERVES. 


lobe,  near  the  median  line,  and  terminating  anteriorly  in  a  flattened 
ovoid  mass  of  gray  substance,  the  "olfactory  bulb."  The  olfactory 
bulb  rests  upon  the  cribriform  plate  of  the  ethmoid  bone,  and  gives  off, 
through  the  perforations  in  this  bone,  the  true  nervous  filaments  sup- 
plying the  olfactory  membrane  in  the  nasal  passages.  The  prismatic 
tract  which  connects  the  olfactory  bulb  with  the  rest  of  the  brain  is  in 
reality,  according  to  both  Henle  and  Meynert,  a  prolongation  of  one  of 
the  cerebral  convolutions.  It  originates  in  a  rounded  eminence  called 
the  "  olfactory  tubercle,"  situated  at  the  back  part  and  under  surface 
of  the  anterior  cerebral  lobe,  just  inside  the  island  of  Reil,  with  which  it 
is  connected.  It  consists,  like  the  other  cerebral  convolutions,  of  gray 
substance  containing  pyramidal  cells.  Its  peculiarity,  as  shown  by 
Henle,  consists  in  the  fact  that  bundles  of  nerve  fibres  from  the  interior 

Fig.  169. 


Cba 


LiOXGITTTDINAL  SECTION  OF  THE  CEREBRAL  HEMISPHERE,  through  the  Situa- 
tion of  the  olfactory  tubercle  and  part  of  the  olfactory  nerve.— 1.  Olfactory  nerve.  2.  Olfac- 
tory tubercle.  Cs.  Corpus  striatum.  Coa.  Anterior  cerebral  com'missure.  Cba.  Anterior 
commissure  of  the  base  of  the  brain.  Magnified  once  and  one  half.  (Henle.) 

pass  through  its  cortical  layer  of  gray  matter,  and  appear  upon  its 
surface  as  more  or  less  distinct  striations  of  white  substance.  It  is 
these  white  striations  which  have  been  designated  as  the  olfactory 
"roots,"  and  which  give  to  the  tract  terminating  in  the  bulb  the  external 
appearance  of  a  nerve.  They  are  derived  from  the  white  substance  of 
the  cerebral  hemispheres,  and  continue  forward  to  the  gray  matter  of 
the  olfactory  bulb.  A  communication  is  established  between  the  olfac- 
tory nerves  of  the  two  opposite  sides  through  the  internal  white  sub- 
stance of  the  olfactory  tubercles.  According  to  Yulpian,  there  is  also 
a  more  direct  communication,  visible  in  the  dog,  the  sheep,  and  the 


THE    OLFACTORY    NERVES.  515 

rabbit,  formed  by  one  of  the  so-called  olfactory  nerve  roots,  which  turns 
inward  and  crosses  the  median  line,  in  company  with  the  fibres  of  the 
anterior  cerebral  commissure. 

Physiological  Properties  of  the  Olfactory  Nerve. — The  olfactory 
nerve  thus  formed  is  a  tract  of  communication  between  the  central 
parts  of  the  brain  and  the  olfactory  bulb.  Its  physiological  connection 
with  the  sense  of  smell  is  indicated  by,  1st,  its  anatomical  relations ; 
2d,  its  comparative  development  in  different  species  of  animals  ;  and  3d, 
the  results  of  its  injury  or  disease. 

I.  The  only  anatomical  connection  of  the  olfactory  nerve,  at  its 
anterior  extremity,  is  with  the  olfactory  bulb;   and  the  nerve  fibres 
given  off  from  this  part  are  distributed  only  to  the  olfactory  region  of 
the  nasal  passages.     In  this  region  ordinary  sensibility  is  but  slightly 
developed,  while  the  parts  are  highly  endowed  with  the  sense  of  smell. 

II.  In  such  of  the  lower  animals  as  possess  a  more  acute  sense  of 
smell  than  man,  like  the  dog,  the  cat,  the  sheep,  and  other  quadrupeds, 
the  olfactory  bulbs  are  increased  in  proportion,  forming  prominent 
masses  at  the  anterior  extremity  of  the  hemispheres ;  while  the  parts 
representing  the  olfactory  nerves  are  of  so  large  a  size  that  they  are 
generally  designated  by  the  name  of  the  u  olfactory  lobes."     They  also 
contain  a  central  tubular  cavity,  which  is  a  prolongation  from  that  of 
the  lateral  ventricles.     There  is   accordingly  a  direct  correspondence 
between  their  development  and  that  of  the  special  sense  with  which 
they  are  connected. 

III.  A  considerable  number  of  cases  are  quoted  by  Longet  in  which 
congenital  absence  of  the  olfactory  nerves,  in  man,  was  accompanied  by 
congenital  incapacity  to  distinguish  odors ;  and  others  in  which  a  loss 
of  the  sense  of  smell  was  also  observed  after  morbid  affections  causing 
compression  or  destruction  of  these  nerves. 

According  to  the  experiments  of  Magendie  upon  dogs,1  the  olfactory 
nerves  are  not  sensitive  to  mechanical  irritation,  since  their  compres- 
sion, puncture,  or  laceration  in  various  directions,  in  the  living  animal, 
causes  no  perceptible  indications  of  sensibility. 

Finally,  experimental  division  or  destruction  of  these  nerves  in  dogs 
abolishes,  so  far  as  observation  can  show,  the  power  of  discriminating 
odors ;  although  it  leaves  the  nasal  mucous  membrane  sensitive  to  the 
irritation  of  pungent  or  caustic  vapors.  In  the  experiments  of  Magendie, 
a  dog,  after  destruction  of  both  olfactory  nerves,  would  disentangle  a 
package  containing  meat  when  openly  presented  to  him;  but  he  did 
not  find  it,  when  placed  near  by  without  his  knowledge.  The  same 
result  was  obtained  by  Vulpian'2  in  operating  upon  hunting  dogs. 
These  animals,  after  recovering  from  the  immediate  effects  of  the 
operation,  were  kept  fasting  from  36  to  48  hours,  and  then  introduced 


Journal  de  Physiologic  Experimental^  et  Pathologique.     Paris,  1825,  tome 
iv.  p.  170. 

2  Legons  sur  la  Physiologic  du  Systeme  Nerveux.     Paris,  1866,  p.  882. 


516  THE    CRANIAL    NERVES. 

into  an  apartment  where  a  piece  of  cooked  meat  was  concealed ;  but 
they  were  never  able  to  discover  it  by  its  odor,  when  the  division  of 
the  nerves  had  been  complete.     Notwithstanding,  therefore,  the  com- 
parative difficulty  of  experimenting  upon  so  obscure  a  function  as  that 
of  smell,  there  is  no  doubt  that  the  olfactory  nerves  and  bulbs  are  really, 
the  internal  organs  of  the  olfactory  sense,  and  that  they  are  disconnectedS 
both  with  ordinary  sensibility  and  the  power  of  motion. 

Second  Pair.    The  Optic  Nerves. 

The  optic  nerves  take  their  first  origin  from  the  anterior  pair  of  the 
tubercula  quadrigemina,  two  small  rounded  prominences,  on  each  side 
of  the  median  line,  situated  just  behind  the  posterior  extremity  of  the 
optic  thalami.  They  consist  essentially  of  swellings  of  the  gray  sub- 
stance which  surrounds  at  this  situation  the  aqueduct  of  Sylvius,  and 
which  is  consequently  continuous  with  that  extending  forward  from  the 
floor  of  the  fourth  ventricle.  Their  surface  is  covered  by  a  layer  of 
white  substance  from  1.5  to  4  millimetres  in  thickness,  consisting  of 
nerve  fibres  which  have  mainly  a  transverse  direction.  Their  gray  sub- 
stance contains  nerve  cells,  some  of  which  are  small  and  rounded,  while 
others,  especially  in  the  anterior  pair,  are  of  larger  size  and  provided 
with  branched  prolongations.  According  to  Henle,  the  fibres  of  origin 
of  the  optic  nerve  pass  from  these  bodies  outward  and  downward  to  the 
corpus  geniculatum  internum,  an  ovoidal  prominence  of  gray  matter 
attached  to  the  posterior  border  of  the  optic  thalamus.  They  cover  the 
surface  of  this  body  in  a  thin  superficial  layer,  and  continue  their  course, 
winding  round  the  lateral  surface  of  the  crus  cerebri ;  where  they  are 
joined  at  an  acute  angle  by  a  second  bundle  of  fibres,  coming  from  the 
corpus  geniculatum  externum,  a  gray  eminence  similar  to  the  last, 
lying  in  contact  with  the  under  part  of  the  optic  thalamus,  but  isolated 
from  its  gray  matter  by  a  thin  investing  layer  of  white  substance. 
These  two  bundles  of  fibres,  coming,  one  from  the  anterior  tubercula 
quadrigemina  and  the  corpus  geniculatum  internum,  the  other  from  the 
corpus  geniculatum  externum,  form  in  man  the  two  roots  of  the  optic 
nerve ;  and  the  collections  of  gray  matter  contained  in  these  bodies  are 
regarded  as  its  "  nuclei,"  or  the  nervous  centres  with  which  it  is  in 
anatomical  communication.  It  also  receives  some  fibres  from  the  sub- 
stance of  the  optic  thalamus  itself. 

The  fibres  derived  from  these  sources  form  a  flattened  band  which 
continues  its  course  in  a  spiral  direction,  winding  round  the  crus  cerebri 
to  the  base  of  the  brain ;  it  thence  runs  forward  and  inward  until  the 
two,  from  the  right  and  left  sides,  meet  upon  the  median  line  in  the 
so-called  "chiasma,"  or  decussation.  From  this  they  again  diverge  out- 
ward and  forward,  leave  the  cavity  of  the  cranium  by  the  optic  fora- 
mina, and,  joining  the  eyeballs,  terminate  in  the  nervous  expansion  of 
the  retina.  That  portion  of  the  optic  nerves  situated  behind  the  decus- 
sation is  sometimes  designated  by  the  special  name  of  the  "optic 
tract." 


THE    OPTIC    NERVES.  517 

Real  Origin  of  the  Optic  Nerves. — The  fibres  of  the  optic  nerves,  in 
man,  as  shown  by  the  above  description,  cannot  all  be  distinctly  traced 
in  a  direct  manner  to  the  tubercula  quadrigemina ;  but  those  of  one 
root  are  evidently  connected  with  the  corpus  geniculatum  externum, 
while  those  of  the  other  pass  to  the  corpus  geniculatum  internum,  and 
through  the  intervention  of  that  body  alone  reach  the  anterior  quadri- 
geminal  tubercule.  And  yet  the  data  derived  from  comparative  anatomy, 
as  well  as  the  results  of  experiments  upon  the  tubercula  quadrigemma, 
show  that  in  the  lower  animals  these  bodies  are  the  real  sources  of  the 
optic  nerves.  In  all  the  mammalian  quadrupeds  the  optic  nerves  are 
readily  seen  to  have  their  direct  origin  in  the  tubercula  quadrigemina. 
In  the  birds,  reptiles,  and  fish  these  bodies  are  divided  only  into  two 
symmetrical  prominences  by  a  shallow,  longitudinal,  median  furrow ; 
and  in  these  classes,  accordingly,  they  are  called  the  "  tubercula  bigem- 
ina."  But  they  are  of  comparatively  larger  size  than  in  the  mammalians, 
and  give  origin  still  more  distinctly  to  the  optic  nerves.  Furthermore, 
their  destruction,  as  shown  by  the  united  testimony  of  all  observers, 
produces  at  once  a  loss  of  sight,  although  the  remaining  parts  of  the 
brain  be  left  uninjured;  while  it  is  certain,  on  the  other  hand,  that 
both  the  hemispheres  and  the  optic  thalami  may  be  removed  without 
destroying  sensibility  to  light.  Even  in  man,  according  to  the  obser- 
vations of  Yulpian,  the  optic  thalami  may  be  the  seat  of  extensive 
lesions,  from  hemorrhage  or  softening,  without  any  sensible  disturb- 
ance of  the  power  of  vision. 

The  apparent  variation  in  man  from  the  general  type,  in  respect  to 
the  origin  of  the  optic  nerves,  is  most  readily  explained  by  the  variation 
in  the  comparative  size  of  the  tubercula  quadrigemina  and  the  optic 
thalami.  In  the  inferior  vertebrate  animals,  namely,  fish  and  reptiles, 
the  tubercula  quadrigemina  or  their  representatives  are  very  large,  and 
the  optic  thalami  are  either  wanting  or  so  slightly  developed  as  to  make 
their  significance  uncertain.  In  birds  the  optic  thalami  are  present,  but 
are  still  inferior  in  size  to  the  tubercula  bigemina.  In  mammalians 
they  increase  in  size  in  the  ascending  series,  but  the  tubercula  quadri- 
gemina are  still,  in  such  animals  as  the  dog  and  cat,  comparatively  con- 
spicuous, and,  throughout  this  class,  consist  of  four  tubercles  instead 
of  two.  In  man  the  optic  thalami  are  very  much  larger  than  the  tuber- 
cula quadrigemina,  which  are  reduced  altogether  to  a  secondary  grade. 
The  corpora  geniculata  probably  represent  in  man  portions  of  gray 
substance  included,  in  the  lower  animals,  in  the  tubercula  quadrigemina 
or  bigemina ;  but  which  in  the  human  brain  are  crowded  outward  and 
backward  by  the  increased  development  of  the  optic  thalami,  and  there- 
fore appear  as  appendages  of  these  bodies. 

Physiological  Properties  of  the  Optic  Nerves. — The  optic  nerves, 
like  the  olfactory,  are  nerves  of  special  sense,  and  may  be  regarded  as 
tracts  of  fibres  connecting  the  gray  matter  of  the  cerebrum  with  the 
retinal  expansion  of  the  globe  of  the  eye.  They  are  destitute  of  sensi- 
bility to  tactile  or  painful  impressions,  and  convey  from  without  inward 


518  THE    CRANIAL    NERVES. 

only  the  impression  produced  upon  the  retina  by  luminous  rays.  In 
the  central  parts  of  the  brain  with  which  they  are  connected,  this  im- 
pression becomes  the  sensation  of  light ;  and  the  optic  nerves  are  there- 
fore the  channels  for  the  sense  of  vision.  Magendie  found  that  in 
quadrupeds  both  the  retina  and  the  optic  nerves  throughout  their 
length  were  insensible  to  mechanical  irritation;  and,  in  man,  that  touch- 
ing the  retina  with  the  point  of  a  cataract  needle  excited  no  perceptible 
sensation.  It  has  also  been  remarked,  in  cases  of  extirpation  of  the 
eyeball,  that  the  section  of  the  optic  nerve  is  not  a  painful  part  of  the 
operation;  and,  according  to  the  observations  of  Longet  upon  animals, 
these  nerves  may  be  pinched,  pricked,  cauterized,  divided,  or  injured  in 
various  ways  without  producing  any  signs  of  pain. 

On  the  other  hand,  division  of  these  nerves  at  once  produces  a  state 
of  blindness.  The  impressions  received  by  the  retina  are  no  longer 
transmitted  to  the  central  organ,  and  the  animal  becomes  insensible  to 
light,  without  losing  any  of  his  ordinary  tactile  sensibility  or  power  of 
voluntary  motion. 

Beside  their  immediate  function  in  the  perception  of  light,  the  optic 
nerves  are  also  channels  for  a  special  reflex  action,  connected  with  the 
mechanism  of  vision ;  namely,  that  of  the  contractile  movements  of  the 
iris.  By  these  movements  the  orifice  of  the  pupil  enlarges  or  diminishes 
according  to  the  intensity  of  the  light  to  which  the  eye  is  exposed.  On 
first  entering  a  dark  room  everything  is  nearly  invisible;  but  gradually, 
as  the  pupil  dilates  and  as  more  light  is  admitted,  objects  show  them- 
selves with  greater  distinctness,  and  at  last  we  can  see  tolerably  well 
where  it  was  at  first  almost  impossible  to  perceive  a  single  object.  On 
the  other  hand,  when  the  eye  is  exposed  to  a  brilliant  light,  the  pupil 
contracts  and  shuts  out  so  much  of  it  as  would  be  injurious  to  the  retina. 

These  movements,  by  which  the  quantity  of  light  admitted  to  the  eye 
is  regulated  to  suit  the  sensibility  of  the  retina,  are  involuntary  in  cha- 
racter, but  are  due  to  impressions  conveyed  inward  by  the  optic  nerve. 
On  the  division  of  these  nerves,  or  the  destruction  of  the  tubercula 
quadrigemina,  not  only  is  the  perception  of  light  abolished,  but  the  pupil 
remains  immovable,  whatever  may  be  the  intensity  of  the  light  to  which 
it  is  exposed.  In  the  production  of  this  reflex  act,  the  impression,  which 
is  first  received  upon  the  retina,  passes  inward  through  the  fibres  of  the 
optic  nerve  to  the  tubercula  quadrigemina.  Its  transformation  into  a 
motor  impulse  is  either  accomplished  in  these  bodies,  or  is  commenced 
in  them  and  completed  by  transmission  to  the  gray  matter  at  the  origin 
of  the  oculomotorius  nerves.  Thus  both  the  optic  nerves  and  the  tuber- 
cula quadrigemina  are  essential  to  the  movements  of  the  pupil  under  the 
influence  of  light.  The  proof  that  this  action  is  of  a  reflex  nature  is 
afforded  by  the  results  of  dividing  and  irritating  the  optic  nerves.  After 
section  of  the  nerve,  according  to  the  experiments  of  Herbert  Mayo  and 
Longet,  upon  pigeons,  dogs,  and  rabbits,  irritation  of  its  peripheral  end, 
that  is,  the  portion  still  connected  with  the  eyeball,  produces  no  effect 
upon  the  pupil ;  but  irritation  of  its  central  portion,  which  is  connected 


THE    OPTIC    NERVES. 


519 


only  with  the  brain,  readily  causes  a  movement  of  contraction.  On  the 
other  hand,  division  of  the  oculomotorius  nerve,  which  paralyzes  the 
iris,  puts  an  end  to  the  movements  of  the  pupil,  although  the  eye  may  be 
otherwise  uninjured  and  the  perception  of  light  unimpaired. 

Decussation  of  the  Optic  Nerves. — The  decussation  of  these  nerves 
forms  one  of  their  most  prominent  anatomical  features,  being  in  all  cases 
readily  visible  on  superficial  examination,  while  in  many  classes  of  the 
lower  animals  and  in  man  it  presents,  on  closer  inspection,  certain  marked 
varieties  of  detail.  In  fish,  as  a  general  rule  (Fig.  1TO),  the  two  optic 
nerves  cross  each  other's  path  from  side  to  side  at  different  levels,  with- 
out any  admixture  or  even  contact  of  their  fibres ;  that  from  the  right  side 
of  the  brain  passing  independently  to  the  left  eye,  and  that  from  the  left 
side  of  the  brain  to  the  right  eye.  In  the  herring,  according  to  Wagner, 
the  optic  nerve  of  the  right  eye  perforates  that  of  the  left,  passing  bodily 
through  it  by  a  distinct  slit,  without  forming  a  chiasma.  In  the  sharks 
and  rays,  which  have  a  higher  general  grade  of  organization  than  other 
fish,  the  fibres  of  the  two  nerves  cross  each  other  in  separate  fasciculi. 


Fig.  170. 


Fig.  171. 


INFERIOR  SURFACE  OF  THE  BRAIN 
OF  THE  COB.— 1.  Optic  nerve  of  right  eye. 
2.  Optic  nerve  of  left  eye.  3.  Right  optic 
tubercle.  4.  Left  optic  tubercle.  5,  6.  Cere- 
bral hemispheres.  7.  Medulla  oblongata. 


INFERIOR  SURFACE  OF  THE  BRAIN 
OF  FOWL. — 1.  Optic  nerve  of  right  eye.  2. 
Optic  nerve  of  left  eye.  3.  Right  optic 
tubercle.  4.  Left  optic  tubercle.  5,  6.  Cere- 
bral hemispheres.  7.  Medulla  oblongata. 


In  birds  the  two  optic  nerves  appear  externally  to  be  united  at  their 
point  of  crossing  (Fig.  171),  but  dissection  shows  that  the  decussation 
of  their  fibres  is  complete.  Those  coming  from  the  left  side  pass,  in 
the  form  of  slender  bundles,  altogether  over  to  the  right,  and  those 
from  the  right  side  pass  in  the  same  manner  over  to  the  left ;  so  that  in 
this  class  each  optic  tubercle  is  connected  exclusively  with  the  eye  of 
the  opposite  side. 

In  man  the  decussation  is  more  complicated,  and  is  arranged  in  such 


520 


THE    CRANIAL    NERVES. 


a  manner  as  to  form  a  connection  at  the  same  time  between  the  two 
opposite  sides,  and  between  the  eye  and  the  quadrigeminal  tubercle  on 
the  same  side.  Here  also  the  apparent  majority  of  the  fibres  cross  each 
other  completely  from  side  to  side,  though  intermingled  at  the  chiasma 
in  such  slender  bundles  that  they  are  distinguishable  only  by  microscopic 
examination.  But  at  each  side  of  the  chiasma  there  is  also  a  layer  of 
fibres,  which,  according  to  Henle,  hardly  exceeds  one-twentieth  of  a 

Fig.  172. 


COURSE  OF  THE  OPTIC  NERVES  IN  MAN.— 1,2.  Right  and  left  eyeballs.    3.  Decussation 
of  the  optic  nerves.    4,4.  Tubercula  quadrigemina. 

millimetre  in  thickness,  passing  continuously  along  its  outer  border  and 
thence  running  forward  with  the  optic  nerve  to  the  eye  of  the  same  side. 
These  fibres,  like  those  of  the  white  substance  in  general,  do  not  keep  the 
same  horizontal  level,  but  follow  a  more  or  less  spiral  course,  winding  suc- 
cessively outward,  downward,  and  inward,  from  the  upper  surface  of  the 
chiasma  to  reach  the  under  surface  of  the  optic  nerve  in  front-  It  is 
not  known  in  what  special  parts  of  the  retina  the  two  sets  of  fibres  on 
each  side,  namely,  the  decussating  and  the  direct,  find  their  termination. 
At  the  anterior  angle  of  the  chiasma  there  are  also  fibres  which  pass 
from  side  to  side  in  a  curved  direction,  running  symmetrically  across 
from  one  optic  nerve  to  the  other,  and  forming  a  transverse  commissural 
baud  between  the  retinae  of  the  two  eyes ;  and  finally  at  the  posterior 
angle  of  the  chiasma  there  are  similar  transverse  commissural  fibres, 
which  pass  forward  on  each  side  with  the  corresponding  optic  tract, 
cross  the  median  line  at  the  chiasma,  and  return  backward  with  the  optic 
tract  of  the  opposite  side.  Thus  there  is  effected  a  fourfold  connection 


THE    OPTIC    NERVES.  521 

between  the  two  eyes  and  their  nervous  centres,  namely,  1st,  that  be- 
tween each  nervous  centre  and  the  opposite  eye ;  2d,  that  between  each 
nervous  centre  and  the  corresponding  eye;  3d,  that  between  the  two 
eyes  by  the  anterior  transverse  commissure;  and  4th,  that  between  the 
two  nervous  centres  by  the  posterior  transverse  commissure. 

The  physiological  significance  of  this  compound  decussation  is  not 
clearly  understood.  When  compared  as  it  presents  itself  in  different 
classes  of  animals,  it  appears  to  be  connected  with  the  decree  of  diver- 
gence or  parallelism  between  the  visual  axes  of  the  two  eyes.  Thus  in 
fish,  where  the  e3^es  are  so  placed  on  opposite  sides  of  the  head  that 
their  axes  cannot  be  brought  into  parallelism  with  each  otherT  the  optic 
nerves  cross  from  side  to  side  as  distinct  cords  going  to  the  opposite 
eyes.  In  birds,  where  the  eyes  have  nearly  the  same  relative  position  as 
in  fish,  the  decussation  is  also  complete,  though  less  evident  externally. 
In  quadrupeds  as  a  class,  the  eyes  are  set  more  obliquely  forward,  while 
in  man  they  are  situated  completely  at  the  front,  so  that  their  visual 
axes  are  both  directed  forward,  and  parallel  with  each  other,  or  may 
even  converge,  and  the  two  eyes  can  thus  be  brought  to  bear  at  the  same 
time  upon  near  objects.  The  quadruple  communication  which  exists  in 
man  is,  therefore,  usually  regarded  as  connected  in  some  way  with  the 
capacity  for  distinct  and  single  vision  with  the  simultaneous  use  of 
both  eyes.  Cases,  however,  like  that  related  by  Yesalius,1  in  which  the 
decussation  was  wanting,  each  optic  nerve  going  independently  to  the 
eye  of  its  own  side,  without  any  noticeable  defect  of  vision,  show  that 
such  a  communication  is  not  directly  or  absolutely  necessary,  even  in 
man,  to  distinct  vision  of  single  objects.  It  more  probably  serves  in  an 
indirect  manner,  by  reflex  action,  to  facilitate  the  harmonious  muscular 
control  of  the  two  eyeballs,  by  which  the  corresponding  parts  of  the 
retina  on  the  two  sides  receive  the  visual  rays  coming  from  a  single 
object. 

Crossed  Action  of  the  Optic  Nerves. — The  results  of  observation 
show  that  the  action  of  the  optic  nerves,  as  channels  for  the  sense  of 
sight,  is  mainly  a  crossed  action.  The  experiments  of  Flourens,  Longet, 
and  Vulpian  coincide  in  this  respect ;  and  in  regard  to  birds  the  fact  is 
easily  established.  If  in  the  pigeon,  as  we  have  frequently  observed, 
the  right  optic  tubercle  alone  be  removed,  when  the  bird  has  recovered 
from  the  immediate  effects  of  the  wound,  the  sight  is  to  all  appearance 
completely  lost  in  the  eye  of  the  opposite  side,  but  remains  unimpaired 
in  the  eye  of  the  same  side.  After  such  an  operation  an  instrument 
may  be  carefully  brought  in  close  proximity  to  the  left  eye,  without 
producing  any  sign  of  its  perception ;  but  the  instant  it  is  moved  a  little 
in  front,  so  as  to  come  within  the  range  of  the  right  eye,  the  animal 
starts  backward  to  avoid  it.  Flourens  obtained  similar  results  in  the 
dog  and  rat,  leading  to  the  conclusion,  which  agrees  with  that  of  Longet, 
that  in  quadrupeds  also  visual  impressions  are  transmitted  by  the  optic 

1  De  Humani  Corporis  Fabrica.     Liber  iv.  cap.  iv. 
34 


522  THE    CRANIAL    NERVES. 

nerves  entirely  in  a  crossed  direction.  There  is  no  question  that  these 
animals  after  destruction  of  the  tubercula  quadrigemina  on  one  side  are 
mainly  blinded  in  the  opposite  eye,  since  they  use  exclusively  the  eye 
of  the  wounded  side  to  guide  them  in  their  motions. 

In  man,  the  partial  blindness  of  both  eyes,  sometimes  observed  in 
cases  of  hemiplegia,  makes  it  probable  that  the  transmission  of  sight 
takes  place  by  both  the  crossed  and  direct  fibres  of  the  optic  tracts. 

The  reflex  influence  which  causes  contraction  of  the  pupil  is  also 
transmitted,  in  the  lower  animals,  in  a  crossed  direction ;  that  is,  the 
stimulus  of  light  falling  upon  the  retina  of  one  eye  passes  to  the  optic 
tubercle  of  the  opposite  side.  But  here,  owing  to  the  transverse  con- 
nections between  the  central  parts  of  the  brain,  the  stimulus  becomes 
duplicated,  and  contractions  are  produced  in  the  pupils  of  both  eyes 
simultaneously.  This  is  because,  although  the  sensitive  impression  is 
conveyed  inward  to  the  nervous  centres  by  one  optic  nerve  only,  when 
transformed  into  a  motor  impulse  it  may  be  sent  outward  by  both 
oeulomotorrus  nerves  at  the  same  time.  Consequently  if,  in  a  pigeon, 
one  eye  be  blinded  by  removal  of  the  opposite  optic  tubercle,  both  pupils 
will  still  contract  under  the  stimulus  of  light  applied  to  the  sound  eye. 
In  examining  one  eye,  therefore,  either  in  animals  or  in  man,  to  ascer- 
tain whether  or  not  its  retina  be  sensitive  to  light,  the  opposite  eye 
should  always  be  covered,  in  order  to  prevent  its  exciting  a  movement 
by  reflex  action. 

Third  Pair.    The  Oculomotorius. 

The  oculomotorius  nerve,  so  called  because  it  supplies  four  out  of  six 
of  the  muscles  moving  the  eyeball,  originates  from  a  collection  of  gray 
substance  situated  next  the  median  line,  beneath  the  tubercula  quadri- 
gemina and  the  aqueduct  of  Sylvius.  As  this  group  of  nerve  cells  is 
continuous  with  that  which  gives  origin  to  the  fourth  nerve  or  pathe- 
ticus,  it  is  sometimes  designated  as  the  common  nucleus  of  the  oculo- 
motorius and  patheticus  nerves.  From  this  nucleus  the  fibres  of  the 
oculomotorius  nerve  pass  downward  and  forward,  through  the  substance 
of  the  crus  cerebri,  until  they  emerge,  in  the  form  of  several  flattened 
bundles,  from  its  inner  border,  a  little  in  front  of  the  anterior  edge  of 
the  pons  Yarolii.  From  this  point,  the  apparent  origin  of  the  nerve, 
its  fibres  unite  into  a  rounded  cord,  which  runs  forward  and  outward, 
to  penetrate  the  cavity  of  the  orbit  by  the  sphenoidal  fissure.  During 
its  transit  along  the  walls  of  the  cavernous  sinus,  it  receives  one  or  two 
fine  twigs  of  sensitive  fibres  from  the  trigeminus  nerve.  In  entering 
the  orbit,  it  divides  into  several  branches,  and  supplies,  the  superior, 
inferior,  and  internal  straight  muscles  of  the  eyeball,  the  inferior  oblique, 
and  the  levator  palpebroe  superioris.  The  oculomotorius  is  accordingly 
concerned  both  in  the  vertical  and  lateral  movements  of  the  eyeball,  and 
in  those  of  rotation;  while  of  the  two  other  muscular  nerves  of  this 
organ,  the  abducens  and  patheticus,  one  is  connected  only  with  the 
movement  of  lateral  abduction,  the  other  only  with  that  of  rotation. 


THE    OCULOMOTORIUS.  523 

Decussation  of  the  Oculomotor ius  Nerve. — According  to  the  observa- 
tions of  Meynert,  a  decussation  takes  place  between  the  oculomotorius 
nucleus  and  the  opposite  side  of  the  brain,  by  means  of  fibres  emerging 
from  the  raphe  upon  the  median  line,  near  which  the  nucleus  is  situated. 
These  fibres  come  originally  from  the  corpus  striatuin,  thence  running 
backward  along  the  inner  border  of  the  crura  cerebri,  into  the  longitu^ 
clinal  lamina  forming  the  raphe  between  them.  Underneath  the  aque^ 
duct  of  Sylvius  they  decussate  with  each  other  at  acute  angles,  those 
from  the  right  corpus  striatnm  passing  to  the  nucleus  of  the  left  side, 
and  vice  versa.  Each  oculomotorius  nerve  is  therefore  in  connection 
with  the  opposite  side  of  the  brain,  not  by  means  of  its  own  fibres,  but 
through  the  intervention  of  its  nucleus  and  the  fibres  which  pass  thence, 
through  the  raphe,  toward  the  opposite  corpus  striatum. 

Physiological  Properties  of  the  Oculomotorius  Nerve. — The  oculomo- 
torius is  in  itself  an  exclusively  motor  nerve,  and  has  been  found  by 
Longet,  when  examined  in  the  living  animal,  near  its  point  of  emergence 
from  the  crus  cerebri,  to  be  insensible  to  mechanical  irritation ;  but  at 
some  distance  farther  forward,  after  receiving  its  branches  of  commu- 
nication from  the  fifth  pair,  it  exhibits  a  certain  degree  of  sensibility. 
Its  excitability,  on  the  contrary,  is  very  manifest ;  and  its  irritation 
within  the  cranial  cavity,  even  after  it  has  been  separated  from  its  con- 
nection with  the  brain,  causes  convulsive  action  in  the  muscles  of  the 
eyeball. 

The  physiological  function  of  this  nerve  is  distinctly  shown  by  the 
nature  of  the  paralysis  following  its  section  either  before  or  after  its 
entrance  into  the  orbit.  These  results  are  for  the  most  part  very  sim- 
ple and  well  marked,  and  are  established  by  the  uniform  testimony  of 
various  observers.  They  consist  of  the  paralysis  of  the  five  muscles  to 
which  the  nerve  is  distributed,  and  induce,  consequently — 

1.  External  strabismus,  from  continued  action  of  the  external  straight 
muscle  of  the  eyeball,  which  is  no  longer  controlled  by  that  of  the 
internal. 

2.  General  immobility  of  the  eyeball,  owing  to  the  abolition  of  its 
natural   upward,    downward,  lateral,  and    rotatory   movements.     For 
although  two  of  the  muscles  of  the  eyeball,  namely,  the  external  rectus 
and    the    superior  oblique,   remain  unparalyzed ;  yet,  as  they  are  no 
longer  antagonized  by  the  remainder,  they  can  only  produce  a  perma- 
nent deviation  of  the  eyeball,  but  no  alternate  movement  in  opposite 
directions.     In  most  of  the  lower  animals   there  is  also   an  unusual 
prominence  of  the  eyeball,  owing  to  the  relaxed  condition  of  the  muscles 
which  serve  for  retraction. 

3.  Drooping  of  the  upper  eyelid.     In  the  ordinary  action  of  opening 
the  eye,  it  is  the  upper  eyelid  alone  which  moves,  being  raised  so  as  to 
uncover  the  cornea  and  pupil,  by  the  contraction  of  the  levator  palpebrse 
superioris.     As  this  muscle  is  animated  by  a  nervous  branch  coming 
from  the  oculomotorius,  it  is  paralyzed  by  section  of  this  nerve  at  the 
same  time  with  the  muscles  moving  the  eyeball.     The  consequence  is 


524  THE    CRANIAL    NERVES. 

that  the  eye  can  no  longer  be  opened  to  its  full  extent ;  although  it  can 
still  be  closed  as  usual  by  the  action  of  the  orbicularis  oculi,  which 
does  not  depend  upon  the  oculomotorius,  but  is  animated  by  branches 
derived  from  the  seventh  pair,  or  facial  nerve.  The  superior  eyelid 
therefore  droops,  resting  by. its  own  weight  in  such  a  position  as  to 
cover  the  upper  portion  of  the  cornea,  and  the  greater  part  or  even  the 
whole  of  the  pupil.  In  man  this  condition  of  the  eyelid  is  known  as 
ptosis,  and  is  one  of  the  consequences  following  paralysis  of  the  oculo- 
motorius  nerve. 

The  influence  of  the  oculomotorius  upon  the  contractile  movements  of 
the  iris  is  important,  though  less  distinct  and  uniform  in  its  action,  as 
shown  by  experiment,  than  that  exerted  upon  movements  of  the  eyeball 
itself.  The  connection  of  the  oculomotorius  with  the  muscular  appa- 
ratus of  the  iris  is  not  a  direct  one,  but  takes  place  through  the  inter- 
vention of  the  ophthalmic  ganglion,  to  which  this  nerve  sends  a  commu- 
nicating motor  branch,  and  which  in  turn  gives  off  the  ciliary  nerves 
destined  for  the  iris.  Some  observers  (Herbert  Mayo,  Longet)  have 
found  well-marked  paralysis  of  the  iris  following  division  of  the  oculomo- 
torius nerve,  and  enumerate,  as  consequences  of  this  injury,  a  permanent 
dilatation  and  immobility  of  the  pupil.  In  the  experiments  of  Longet, 
which  were  performed  on  dogs,  rabbits,  and  pigeons,  irritation  of  the 
cephalic  extremity  of  the  optic  nerve  caused  contraction  of  the  pupil  in 
both  eyes  ;  but  after  division  of  the  oculomotorius  nerve  the  effect  was 
no  longer  produced  upon  the  operated  side.  Bernard  has  also  found 
that  division  of  the  oculomotorius  is  followed,  in  the  rabbit,  by  dilata- 
tion of  the  pupil,  and  that  in  the  operated  e}^e  the  iris  contracts  only 
very  slowly  and  imperfectly  under  the  influence  of  light.  It  is  not, 
however,  completely  paralyzed,  since  it  may  still  move  with  considera- 
ble promptitude  under  the  influence  of  painful  impressions  conveyed  by 
the  fifth  pair.  The  action  of  the  oculomotorius  upon  the  pupil,  there- 
fore, is  energetic  and  constant  in  the  ordinary  reflex  movement  of  con- 
traction under  the  stimulus  of  light ;  but  it  takes  place  through  the 
ophthalmic  ganglion,  to  which  it  communicates,  in  a  certain  degree,  its 
motive  power. 

Fourth  Pair.    The  Patheticus. 

This  nerve  presents  a  variety  of  peculiarities,  which  have  always, 
notwithstanding  its  minute  size,  attracted  to  it  more  or  less  special 
attention.  It  is  distributed  exclusively  to  the  superior  oblique  muscle 
of  the  eyeball ;  its  name  having  been  derived  from  the  mistaken  idea 
that  this  muscle  turned  the  e}re  upward  and  inward.  The  two  oblique 
muscles,  however,  have  been  fully  shown  to  cause  in  the  eyeball  a  nearly 
simple  movement  of  rotation  about  its  longitudinal  axis.  They  are 
antagonistic  to  each  other;  and  by  their  contraction  and  relaxation, 
during  movements  of  inclination  of  the  head  from  side  to  side,  they 
maintain  the  horizontal  planes  of  the  two  eyeballs  in  the  same  position. 
If  this  parallelism  were  not  preserved,  objects  would  appear  to  stand  in 


THE    PATHETICUS.  525 

different  degrees  of  obliquity  to  the  two  eyes,  producing  uncertainty 
and  double  vision. 

The  apparent  origin  of  the  patheticus  nerve  is  directly  behind  the 
tubercula  quadrigemina,  on  the  upper  surface  of  the  valve  of  Vieussens, 
a  thin  lamina  of  white  substance,  extending  from  this  situation  back- 
ward to  the  cerebellum,  and  thus  covering  in  the  anterior  part  of  the 
fourth  ventricle.  The  fibres  of  the  nerve,  however,  can  be  traced  from 
without  inward  in  a  transverse  direction  through  the  substance  of  the 
valve.  According  to  Henle  and  Meynert,  a  great  part  of  these  fibres 
cross  the  median  line,  decussating  with  those  coming  in  the  opposite 
direction  from  the  corresponding  nerve  on  the  other  side;  then,  turning 
downward  and  forward,  they  reach  a  collection  of  gray  matter  seated 
just  behind  the  nucleus  of  the  oculomotorius  nerve,  and  continuous 
with  it  anteriorly.  According  to  Henle,  a  portion  of  the  fibres  also 
remain  upon  the  same  side  of  the  median  line,  and  terminate,  without 
crossing,  in  this  and  another  nucleus  not  far  distant.  The  collection 
of  gray  matter  just  described  is,  however,  regarded  as  the  main  nucleus 
or  point  of  origin  for  the  fibres  of  the  patheticus  nerve.  This  nucleus 
is  situated  beneath  the  aqueduct  of  Sylvius,  near  the  median  line,  and 
at  a  situation  corresponding  with  the  anterior  tubercula  quadrigemina ; 
while  the  point  of  exit  of  the  nerve  is  above  the  aqueduct  of  Sylvius 
and  behind  the  posterior  tubercula  quadrigemina.  Its  fibres,  accord- 
ingly, after  leaving  the  gray  matter  in  which  they  originate,  encircle 
the  lateral  walls  of  the  aqueduct,  running  obliquely  upward  and  back- 
ward, and  then,  curving  inward,  cross  the  median  line  to  their  point  of 
emergence  on  the  opposite  side. 

From  this  point  the  nerve  passes  forward,  as  a  slender,  rounded  fila- 
ment, not  more  than  one  millimetre  in  diameter,  but  containing,  accord- 
ing to  the  estimate  of  Rosenthal,  about  1100  ultimate  nerve  fibres.  It 
passes  along  the  upper  wall  of  the  cavernous  sinus,  where  it  lies  in 
immediate  proximity  to  the  oculomotorius;  and  thence,  entering  the 
cavity  of  the  orbit  by  the  sphenoidal  fissure,  terminates  in  the  sub- 
stance of  the  superior  oblique  muscle  of  the  eyeball. 

The  course  of  the  fibres  of  the  oculomotorius  and  patheticus,  when 
compared  with  each  other,  shows  a  remarkable  relation  between  two 
nerves  which  are  apparently  distinct.  The  fibres  of  both  originate  from 
adjacent  portions  of  the  same  nucleus,  situated  in  the  thickness  of  the 
crus  cerebri.  Those  of  the  oculomotorius  pass  downward  and  forward, 
to  emerge  from  the  inner  free  border  of  the  crus,  at  the  base  of  the 
brain ;  while  those  of  the  patheticus  pass  upward  and  backward,  to 
emerge  from  the  upper  and  posterior  part  of  the  cerebro-spinal  axis, 
between  the  cerebrum  and  cerebellum.  But  the  two  nerves  afterward 
pass  side  by  side,  in  their  passage  toward  the  orbit,  and  are  finally  dis- 
tributed to  muscles  which  are  associated  in  the  accomplishment  of  the 
same  movements. 

Physiological  Properties  of  the  Patheticus  Nerve. — The  anatomical 
distribution  of  this  nerve  to  a  muscle  which  receives  filaments  from  no 


526  THE    CRANIAL    NERVES. 

other  source  indicate  in  great  measure  its  motor  character,  which  is 
furthermore  fully  established  by  the  results  of  observation.  Both  the 
experiments  of  Chauveau  on  the  horse  and  rabbit,  and  those  of  Longet 
on  the  horse,  ox,  and  dog,  show  that  galvanization  of  this  nerve  in 
the  interior  of  the  cranium  produces  always  contraction  of  the  supe- 
rior oblique  muscle  of  the  eyeball,  with  rotation  of  the  eyeball  on  its 
longitudinal  axis  from  without  inward  ;  and  in  those  of  Longet  there 
was  also  a  perceptible  deviation  of  the  pupil  outward.  In  cases  quoted 
by  Longet,  in  the  human  subject,  attributed  to  paralysis  of  this  nerve, 
there  was  incapacity  of  rotation  of  the  eyeball  on  the  affected  side,  and 
consequently  double  vision,  the  image  perceived  by  the  affected  eye  being 
oblique  and  inferior  in  regard  to  the  other ;  but  these  disturbances  of 
vision  disappeared  when  the  head  was  inclined  toward  the  opposite 
side. 

The  patheticus  is,  accordingly,  the  motor  nerve  of  the  superior  ob- 
lique muscle,  and  acts  in  harmony  with  the  oculomotorius  to  preserve 
the  horizontal  plane  of  the  eyeball. 

Fifth  Pair.    The  Trigeminus. 

The  fifth  pair  occupies,  in  every  respect,  a  prominent  place  among 
the  cranial  nerves.  It  is  the  great  sensitive  nerve  of  the  face,  being 
the  only  source  of  general  sensibility  for  the  integument  and  mucous 
membranes  of  this  region ;  and,  by  communicating  branches  sent  to 
the  corresponding  motor  nerves,  it  also  provides  for  the  imperfect 
degree  of  sensibility  belonging  to  the  facial  muscles.  While  in  its  main 
portion,  however,  it  is  thus  pre-eminently  a  sensitive  nerve,  it  also  pos- 
sesses motor  fibres,  derived  from  a  distinct  root,  and  distributed  to 
muscles  of  a  distinct  group.  Before  emerging  from  the  cranial  cavity 
it  separates  into  three  main  divisions,  destined  for  the  corresponding 
regions  of  the  face ;  and  its  name,  trigeminus,  is  derived  from  the  fact 
that  these  three  primary  divisions  of  the  nerve  are  nearly  alike  in  size 
and  importance. 

The  apparent  origin  of  the  fifth  nerve  is  from  the  lateral  portion  of 
the  pons  Yarolii,  where  its  two  roots  emerge  in  close  approximation 
to  each  other,  but  usually  separated  by  a  narrow  band  of  the  trans- 
verse fibres  of  the  pons.  The  anterior  or  motor  root  is  the  smaller, 
being  about  two  millimetres  in  diameter;  the  posterior  or  sensitive  root 
is  the  larger,  and  having  a  diameter  of  about  five  millimetres.  Both 
these  roots  may  be  traced,  through  the  fibrous  bundles  of  the  pons 
Varolii,  backward,  upward,  and  inward  toward  the  gray  substance  be- 
neath the  floor  of  the  anterior  part  of  the  fourth  ventricle.  The  two 
roots,  which  remain  distinctty  separated  throughout  most  of  their  pas- 
sage through  the  pons,  join  each  other  above  and  become  closely  entan- 
gled by  the  interweaving  of  their  bundles ;  though  their  fibres  may  still 
be  distinguished,  on  microscopic  examination,  by  the  generally  larger 
size  of  those  belonging  to  the  motor  root.  They  finally  reach  a  collec- 
tion of  gray  matter,  the  u  nucleus  of  the  fifth  nerve,"  which  is  situated 


THE    TRIG-EMINUS. 


527 


next  behind  that  of  the  oculomotorius  and  patheticus,  but  farther  out- 
ward from  the  median  line,  occupying  the  extreme  lateral  part  of  the 
fourth  ventricle,  where  its  floor  forms  an  angle  with  the  roof.  The 
fibres  of  the  nerve  terminate  partly  in  or  among  the  large,  stellate,  and 
dark-colored  cells  of  the  nucleus.  According  to  Henle,  a  portion  of 
them  also  pass  through  the  nucleus,  nearly  to  the  surface  of  the  floor 
of  the  ventricle,  and  thence  inward  to  the  raphe  at  the  median  line, 
where  they  cross  to  the  opposite  side ;  while  another  portion  still,  re- 
maining upon  the  same  side,  pass  upward  with  the  superior  peduncles 
of  the  cerebellum,  and  lose  themselves  in  the  substance  of  the  tubercula 
quadrigemina.  The  fibres  of  the  fifth  nerve,  accordingly,  which  termi- 
nate in  the  nucleus  proper,  form  partly  a  direct,  and  partly  a  crossed 
connection  between  the  external  organs  and  the  nervous  centres. 

Fig.  173. 


VNt 


TRANSVERSE  SECTION  OP  THE  FLOOR  OF  THE  FOURTH  VENTRICLE,  at -the 
situation  of  the  nucleus  of  the  Trigeminua  Nerve;  Human  brain.— Nt,  Nt',  median  and 
lateral  portions  of  the  nucleus.  V.  Fibres  of  the  nerve  root.  Magnified  8  diameters 
(Henle.) 

After  emerging  from  the  pons  Yarolii,  the  two  roots  of  the  fifth  nerve 
pass  outward  and  forward  in  company  with  each  other,  the  larger,  pos- 
terior, or  sensitive  root  being  placed  above,  the  smaller,  anterior,  or 
motor  root  underneath.  On  reaching  the  apex  of  the  petrous  portion 
of  the  temporal  bone,  a  little  outside  and  behind  the  posterior  clinoid 


528 


THE    CRANIAL    NERVES, 


processes  of  the  sella  turcica,  the  fibres  of  the  sensitive  root  spread  out 
into  a  comparatively  loose  network  of  inosculating  bundles,  and  pass 
into  and  through  the  substance  of  the  Gaxserian  .ganglion.  This  gan- 
glion forms  a  flattened,  crescentic  mass  of  gray  matter,  mingled  with 

Fig.  174. 


DIAGRAM  OF  THE  FIFTH  NERVE  AND  ITS  DISTRIBUTION — 1.  Sensitive  root. 
2.  Motor  root.  3.  Gasserian  ganglion.  I.  Ophthalmic  division.  II.  Superior  maxillary 
division.  III.  Inferior  maxillary  division  4  Supra-orbital  nerve,  distributed  to  the  skin 
of  the  forehead,  inner  angle  of  the  eye,  and  root  of  the  nose.  5.  Infra-orbital  nerve;  to  the 
skin  of  the  lower  eyelid,  side  of  the  nose,  and  skin  and  mucous  membrane  of  the  upper  lip. 
6.  Mental  nerve;  to  the  integument  of  the  chin  and  edge  of  the  lower  jaw,  and  skin  and 
mucous  membrane  of  the  lower  lip.  n,  n.  External  terminations  of  the  nasal  branch  of  the 
ophthalmic  division  ,  to  the  mucous  membrane  of  the  inner  part  of  the  eye  and  the  nasal 
passages,  and  to  the  base,  tip,  and  wing  of  the  nose.  /.  Temporal  branch  of  the  superior 
maxillary  division ;  to  the  skin  of  the  temporal  region,  m.  Malar  branch  of  the  superior 
maxillary  division;  to  the  skin  of  the  cheek  and  neighboring  parts,  b.  Buccinator  branch 
of  the  inferior  maxillary  division  ;  passing  along  the  surface  of  the  buccinator  muscle,  and 
distributed  to  the  mucous  membrane  of  the  cheek,  and  to  the  mucous  membrane  and  skin 
of  the  lips.  I.  Lingual  nerve;  To  the  mucous  membrane  of  the  anterior  two-thirds  of  the 
tongue,  at.  Auriculo-temporal  branch  of  the  inferior  maxillary  division;  to  the  skin  of  the 
anterior  part  of  the  external  ear  and  adjacent  temporal  region,  a?,  #,  x.  Muscular  branches} 
to  the  temporal,  masseter,  and  internal  and  external  pterygoid  muscles,  y.  Muscular  branch ; 
to  the  mylo-hyoid  and  anterior  belly  of  the  digastric  muscles.  /.  Sensitive  branch  of  com- 
munication to  the  facial  nerve. 

the  fibres  derived  from  the  sensitive  root.  According  to  the  observa- 
tions of  Kb'lliker,  the  fibres  of  the  sensitive  root  simply  pass  through 
the  gra3T  matter  of  the  ganglion,  making  no  anatomical  connection  with 
its  nerve  cells ;  while  the  ganglion  cells,  which  are  mostly  unipolar  in 


THE    TRIGEMINUS.  529 

form,  give  off  additional  fibres  in  a  peripheral  direction.  Thus  the 
branches  of  the  fifth  nerve  beyond  the  ganglion  contain,  beside  the  fibres 
derived  from  its  sensitive  root,  others  which  have  originated  from  the 
ganglion  itself.  The  motor  root  passes  underneath  the  ganglion  as  a 
distinct  bundle,  and  neither  gives  to  nor  receives  from  it  any  nerve 
fibres.  At  the  anterior  or  convex  border  of  the  Gasserian  ganglion,  the 
nerve  separates  into  three  nearly  equal  cylindrical  bundles,  namely,  the 
first,  or  ophthalmic;  the  second,  or  superior  maxillary;  and  the  third, 
or  inferior  maxillary  divisions  of  the  fifth  nerve. 

The  ophthalmic  division  passes  forward  through  the  sphenoidal  fis- 
sure into  the  orbit  of  the  eye,  where  it  gives  filaments  to  the  ophthalmic 
ganglion  and  to  the  ej^eball ;  a  nasal  branch  which  supplies  the  integu- 
ment and  mucous  membrane  of  the  inner  part  of  the  eye,  the  mucous 
membrane  of  the  middle  and  inferior  nasal  passages,  and  the  integument 
of  the  root,  wing,  and  tip  of  the  nose;  and  a  branch  to  the  lachrymal 
gland  and  the  integument  of  the  upper  eyelid  and  adjacent  region.  It 
then  emerges  from  the  cavity  of  the  orbit  by  the  supra-orbital  notch, 
and  is  distributed  to  the  skin  of  the  forehead  and  side  of  the  head,  as 
far  back  as  the  vertex. 

The  superior  maxillary  division  passes  out  of  the  cranial  cavity,  by 
the  foramen  rotundum,  at  the  base  of  the  skull,  into  the  spheno-maxil- 
lary  fossa,  where  it  gives  a  sensitive  branch  to  the  spheno-palatine  gan- 
glion of  the  sympathetic,  thence  into  and  through  the  longitudinal 
canal  in  the  floor  of  the  orbit,  giving  off  a  branch  which  runs  upward 
and  outward  to  terminate  in  the  skin  of  the  malar  and  temporal  regions, 
and  numerous  descending  branches,  which  supply  the  teeth,  gums,  and 
adjacent  mucous  membrane  of  the  upper  jaw,  and,  by  a  nasal  filament, 
the  mucous  membrane  of  the  bottom  of  the  nasal  passages.  The  nerve 
then  emerges  upon  the  face  by  the  infra-orbital  foramen,  and  is  distri- 
buted in  abundant  diverging  branches  to  the  integument  of  the  lower 
eyelid  and  the  side  of  the  nose,  and  to  the  skin  and  mucous  membrane 
of  the  upper  lip. 

The  inferior  maxillary  division  leaves  the  anterior  border  of  the 
Gasserian  ganglion  at  a  different  angle  from  the  two  others,  passing 
almost  vertically  downward  through  the  foramen  ovale.  This  division 
receives  all  the  fibres  of  the  motor  nerve  root,  which  become  more 
or  less  intimately  united  to  it  during  and  after  its  passage  through  the 
base  of  the  skull.  While  the  two  other  divisions  of  the  fifth  nerve  are 
therefore  exclusively  sensitive,  the  inferior  maxillary  division  is  a  mixed 
nerve,  containing  both  motor  and  sensitive  fibres.  Its  sensitive  portion, 
however,  is  still  the  most  abundant,  and  all  its  motor  branches  are  given 
off  a  short  distance  below  its  point  of  exit  from  the  skull. 

After  emerging  from  the  foramen  ovale,  this  division  of  the  fifth  pair 
supplies  one  or  two  filaments  to  the  otic  ganglion  of  the  sympathetic, 
which  is  situated  near  its  inner  surface,  and  passes  downward  toward 
the  inferior  dental  canal ;  sending  off,  in  the  mean  time,  two  sensitive 
branches,  namely,  1st,  the  buccinator  branch  (6),  destined  for  the  mucous 


530  THE    CRANIAL    NERVES. 

membrane  of  the  cheek,  and  the  skin  and  mucous  membrane  of  the  lips ; 
and  2d,  the  auricula-temporal  branch  (at),  which  turns  backward  and 
upward  behind  the  neck  of  the  inferior  maxilla,  to  be  distributed  to 
the  integument  of  the  anterior  wall  of  the  external  auditory  meatus, 
the  anterior  part  of  the  external  ear,  and  the  adjacent  temporal  region. 
From  this  branch  a  twig  of  considerable  size  is  given  off  (/"),  which 
turns  forward  to  join  the  facial  nerve,  and  communicates  to  its  branches 
in  front  of  this  point  a  perceptible  degree  of  sensibility. 

Continuing  its  course,  the  nerve  enters  the  dental  canal  of  the  inferior 
maxilla,  through  which  it  runs  from  behind  forward,  giving  off  filaments 
to  the  teeth  and  gums  of  the  lower  jaw.  It  then  emerges  at  the  mental 
foramen,  and  radiates,  like  the  corresponding  portion  of  the  superior 
maxillary  division,  in  diverging  branches  and  ramifications,  which  ter- 
minate in  the  integument  of  the  chin  and  edge  of  the  under  jaw,  and  in 
the  skin  and  mucous  membrane  of  the  lower  lip. 

The  remaining  sensitive  branch  of  this  portion  of  the  fifth  is  the 
lingual  nerve  (/),  which  separates  from  it  before  its  entrance  into  the 
dental  canal,  sends  filaments  to  the  submaxillary  gland,  the  sympathetic 
submaxillary  ganglion,  and  the  adjacent  mucous  membrane  of  the 
mouth,  and  is  finally  distributed  to  the  mucous  membrane  and  papillae 
of  the  tip,  edges,  and  surface  of  the  anterior  two-thirds  of  the  tongue. 
Finally,  the  motor  branches  are  those  (#,  x,  x}  going  to  the  temporal, 
masseter,  and  two  pterygoid  muscles,  and  that  which  is  distributed  (y) 
to  the  mylohyoid  muscle  and  the  anterior  belly  of  the  digastric. 

Physiological  Properties  of  the  Fifth  Pair. — The  most  prominent 
and  important  character  belonging  to  this  nerve  is  that  of  its  general 
sen'sibility.  The  regions  of  the  face  to  which  it  is  distributed,  namely, 
the  skin  of  the  cheeks,  the  eyelids,  the  tip  of  the  nose,  the  lips,  mucous 
surfaces  of  the  anterior  nares,  and  especially  the  tip  of  the  tongue,  possess 
a  tactile  sensibility  of  much  higher  grade  than  most  other  regions  of  the 
body.  The  nerve  itself,  with  all  its  principal  branches,  is  also  acutely 
sensitive  to  mechanical  irritation,  and  will  give  rise  to  indications  of 
sensibility  on  being  wounded  or  galvanized,  under  conditions  when  the 
spinal  nerves  generally  are  nearly  or  quite  inactive. 

But  the  most  direct  and  conclusive  experiment  bearing  on  the  physio- 
logical functions  of  this  nerve  and  its  branches  is  that  of  dividing  them, 
either  separately  or  together,  by  a  transverse  section.  Either  the  infra- 
orbital  or  mental  nerve  maybe  divided,  in  the  quadrupeds, at  the  points 
where  they  emerge  from  the  corresponding  foramina  in  the  maxillary 
bones.  A  more  decisive  method  is  that  of  dividing  the  fifth  nerve  in  the 
interior  of  the  cranium  by  a  section  passing  through  its  trunk  at  the 
situation  of  the  Gasserian  ganglion.  This  operation  was  first  performed 
by  Magendie,  and  has  since  been  frequently  repeated  by  various  ex- 
perimenters. It  may  be  done,  upon  the  cat  or  the  rabbit,  by  means  of 
a  steel  instrument  with  a  slender  shank  and  a  narrow  cutting  blade 
projecting  at  nearly  a  right  angle  from  its  extremity.  The  instrument 
is  introduced  in  a  horizontal  direction  through  the  squamous  portion 


THE    TRIGEMINUS.  531 

of  the  temporal  bone,  and  pushed  inward  and  a  little  forward,  with  its 
cutting  blade  laid  flatwise  upon  the  surface  of  the  petrous  portion,  until 
it  strikes  the  posterior  clinoid  process.  It  is  then  withdrawn  slightly, 
its  cutting  edge  turned  downward,  and  the  fifth  nerve  divided  where  it 
crosses  the  apex  of  the  pyramid  formed  by  the  petrous  portion  of  the 
temporal  bone.  The  instrument  is  again  turned  with  its  cutting  blade 
flatwise,  and  withdrawn  from  the  skull  in  this  position.  When  this 
manoeuvre  is  successfully  carried  out,  all  the  fibres  of  the  fifth  nerve  are 
divided  at  a  single  stroke,  and  the  only  part  of  the  brain  necessarily 
wounded  is  the  inferior  portion  of  the  temporal  lobe.  The  hemorrhage 
is  small  in  amount,  producing  only  a  slight  degree  of  cerebral  compres- 
sion, from  which  the  animal  soon  recovers. 

The  immediate  effect  of  this  operation  is  a  complete  loss  of  sensibility, 
upon  the  operated  side,  in  the  integument  and  mucous  membranes  about 
the  face.  The  cornea  or  conjunctiva  can  be  touched  or  pricked  without 
exciting  an}*-  movement  of  the  eyelids ;  while  upon  the  opposite  side 
these  parts  retain  their  natural  acuteness  of  sensibility.  A  probe  may 
be  deeply  introduced  into  the  nasal  passages,  or  the  upper  or  lower  lip 
may  be  pierced  throughout  its  substance  with  a  steel  needle,  without 
producing  any  indication  of  pain,  or  eliciting  any  sign  of  sensation  on 
the  part  of  the  animal.  At  the  same  time  the  power  of  motion  in  these 
parts  is  unaffected.  The  eyelids  may  be  opened  or  closed  under  the 
influence  of  visual  impressions,  and  the  movements  of  the  lips  and  other 
parts  continue  to  be  performed  in  a  nearly  natural  manner.  In  the  cat, 
the  loss  of  sensibility  and  the  persistence  of  the  power  of  motion  is 
readily  seen  by  irritating  at  different  points  the  integument  of  the  ex- 
ternal ear,  which  in  this  animal  has  naturally  an  acute  tactile  sensibility. 
If  the  point  of  a  steel  instrument  be  brought  in  contact,  upon  the 
operated  side,  with  the  anterior  part  of  the  ear,  which  is  supplied  by 
fibres  from  the  third  division  of  the  fifth  nerve,  no  effect  is  produced. 
But  if  the  same  irritation  be  applied  to  the  back  part  of  the  ear,  which 
is  supplied  by  the  great  auricular  nerve  from  the  cervical  plexus,  a 
vigorous  twitching  movement  is  at  once  excited.  According  to  Longet, 
the  most  violent  injuries,  such  as  exsection  of  the  eyeball,  evulsion  of 
the  hairs  about  the  lips,  extraction  of  the  teeth,  or  destruction  of  the 
integument  by  the  acutual  cautery,  may  be  performed  after  complete 
division  of  the  fifth  nerve  without  causing  any  painful  sensation.  There 
is  entire  anaesthesia  of  all  the  parts  supplied  by  filaments  of  this  nerve. 

The  fifth  pair  is  accordingly  the  exclusive  source  of  sensibility  in  the 
superficial  regions  of  the  face,  and  all  parts  of  the  nasal  and  buccal 
cavities  to  which  it  is  distributed. 

Painful  Affections  of  the  Fifth  Pair. — This  nerve  is  also  the  seat  of 
all  the  neuralgic  painful  affections  about  the  head  and  face.  The  most 
common  of  these  is  headache ;  which  may  be  general,  extending  over 
both  sides  of  the  forehead  and  vertex,  or  confined  strictly  to  one  side. 
It  often  seems  to  be  located  in  the  nerves  supplying  the  periosteum, 


532  THE    CRANIAL    NERVES. 

especially  that  lining  the  orbit  of  the  eye,  or  the  frontal  sinuses.  Where 
the  pain  is  deep  seated,  its  location  may  even  be  in  the  dura  mater  or  the 
bones  of  the  skull ;  since  each  division  of  the  fifth  pair,  either  before  or 
immediately  after  leaving  the  cavity  of  the  cranium,  sends  backward  a 
slender  recurrent  branch,  destined  for  the  dura  mater  and  the  cranial 
bones.  That  from  the  ophthalmic  division  is  traced  backward  into  the 
tentorium,  in  the  substance  of  which  it  ramifies  as  far  as  the  sinuses 
bordering  its  attached  edge. 

In  cases  of  toothache,  which  depends  upon  irritation  of  the  dental 
filaments  of  the  fifth  pair,  the  cause  of  the  neuralgia  is  usually  the 
decay  of  the  bony  substance  of  the  tooth,  and  consequent  exposure  of 
the  tooth  pulp  to  external  injury  or  inflammation.  It  is  usually  con- 
fined to  the  single  tooth  affected  by  decay ;  but  in  severe  cases  the  pain 
may  radiate  to  other  teeth  in  the  immediate  neighborhood,  or  may  even 
spread  over  the  entire  corresponding  side  of  the  maxilla.  Neuralgia  of 
the  teeth  may  also  be  wholly  sympathetic  in  its  origin,  as  where  it  is 
caused,  like  headache,  by  indigestion,  exposure,  or  fatigue;  the  pain 
existing  simultaneously  in  several  teeth,  without  any  morbid  alteration 
of  their  structure. 

The  most  severe  and  persistent  form  of  neuralgia  in  this  nerve  is  that 
known  as  tic  douloureux ;  in  which  the  pain  is  habitually  located  in  one 
of  its  three  principal  divisions  as  they  emerge  upon  the  face.  Here 
also  the  pain  is  not  constant,  but  intermittent,  recurring  in  great 
severity  at  longer  or  shorter  intervals,  and  usually  lasting  but  a  few 
minutes  at  a  time.  It  is  more  frequently  seated  in  the  upper  or  middle 
region  of  the  face,  corresponding  with  the  distribution  of  the  supra  or 
infra-orbital  nerves. 

Lingual  Branch  of  the  Fifth  Pair. — This  branch,  which  is  designated 
by  the  special  name  of  the  "  lingual  nerve,"  possesses  an  especial  interest 
because  it  communicates  to  the  mucous  membrane  of  the  tongue  both 
the  property  of  tactile  sensibility  and  the  special  sense  of  taste.  The 
general  sensibility  of  the  tongue  is  highly  developed  over  the  whole 
of  its  anterior  two-thirds,  where  it  is  supplied  by  the  lingual  nerve ;  and 
at  its  tip  is  more  acute  than  in  any  other  region  of  the  body.  This 
sensibility  disappears  completely  on  the  operated  side,  together  with 
that  of  the  external  portions  of  the  face,  when  the  fifth  nerve  has  been 
divided  in  animals  in  the  interior  of  the  cranium ;  and  Longet  has  found 
that  after  section  of  both  lingual  nerves,  the  surface  of  the  anterior  two- 
thirds  of  the  tongue  may  be  cauterized  with  potassium  hydrate  or  the 
red-hot  iron,  without  producing  any  indication  of  pain.  The  tactile 
sensibility  of  the  tongue  is  of  great  importance  in  man,  and  also  in 
some  of  the  lower  animals,  as  an  aid  in  the  process  of  mastication,  by 
enabling  this  organ  to  appreciate  the  simple  physical  qualities  of  the 
food  introduced  into  the  mouth,  to  perceive  when  it  is  uniformly  re- 
duced to  the  proper  consistency  for  swallowing,  and  to  detect  any 
remnants  left  among  folds  or  crevices  of  the  mucous  membrane.  These 


THE    TRIGEMINUS.  533 

functions  are  therefore  seriously  interfered  with  by  injury  or  destruc- 
tion of  the  sensitive  filaments  supplying  the  tongue. 

The  lingual  nerve  is  also  endowed  with  the  special  sensibility  of 
taste.  This  function  is  a  difficult  one  to  investigate  upon  the  lower 
animals,  owing  to  the  uncertainty  of  its  external  indications  and  the 
difficulty  of  isolating,  for  the  purposes  of  observation,  separate  re- 
gions of  the  cavity  of  the  mouth.  Experiments  upon  man,  however, 
which  are  made  with  comparative  facility,  have  been  performed  by 
Guyot,  Verniere,  Duges,  and  Longet  in  such  a  manner  as  to  leave  no 
doubt  that  the  sense  of  taste  is  highly  developed  in  those  portions  of 
the  tongue  which  are  supplied  exclusively  by  the  lingual  nerve.  These 
experiments  consist  mainly  in  applying  to  different  parts  of  the  mucous 
membrane,  in  the  cavity  of  the  mouth,  a  small  globule  of  lint,  moistened 
with  a  solution  of  some  substance,  like  quinine  or  colocynth,  possessing 
a  distinct  taste  without  irritating  qualities.  In  this  way  it  is  ascertained 
that  the  point,  edges,  and  superior  surface  of  the  tongue,  throughout 
its  anterior  two-thirds,  is  capable  of  perceiving  the  sensations  of  taste, 
without  aid  from  other  parts  of  the  buccal  mucous  membrane.  Accord- 
ing to  the  experiments  of  Bernard  and  Longet  on  animals,  division  of 
the  lingual  nerve  destroys  the  faculty  of  taste  as  well  as  that  of  general 
sensibility  in  the  corresponding  parts  of  the  tongue;  and  similar  obser- 
vations are  quoted  by  Henle,  after  section  of  this  nerve  in  the  human 
subject. 

Muscular  Branches  of  the  Fifth  Pair. — These  branches,  as  enume- 
rated above,  are  given  off  from  the  inferior  maxillary  division,  for  the 
most  part  a  short  distance  below  its  exit  from  the  skull,  and  are  dis- 
tributed to  the  temporal,  the  masseter,  and  the  external  and  internal 
pterygoid  muscles  ;  while  the  mylohyoid  branch,  which  separates  from 
the  trunk  somewhat  farther  down,  supplies  the  muscle  of  the  same 
name  as  well  as  the  anterior  belly  of  the  digastric.  All  these  nerves 
are,  therefore,  concerned  in  the  movements  of  mastication.  The  most 
powerful  of  the  muscles  to  which  they  are  distributed,  namely,  the 
temporal  and  the  masseter,  act  by  bringing  the  teeth  of  the  lower  jaw 
forcibly  in  contact  with  those  of  the  upper.  The  contraction  of  the  two 
pterygoid  muscles  produces  a  lateral  grinding  movement,  by  which  the 
trituration  of  the  food  is  accomplished ;  and  finally  those  supplied  by 
the  mylohyoid  branch  facilitate  the  partial  separation  of  the  jaws,  to 
allow  a  repetition  of  the  former  motions.  In  different  species  of 
animals  these  movements  vary  in  their  relative  importance.  In  the 
carnivora,  it  is  the  closure  of  the  jaws  which  preponderates  over  the 
rest,  enabling  the  animal  to  seize  and  tear  his  prey,  by  means  of  the 
pointed  canine  and  sharped-edged  molar  teeth.  In  the  herbivora,  on 
the  other  hand,  the  lateral  grinding  movements  are  more  important  for 
the  complete  comminution  of  the  seeds,  grains,  or  other  hard  vegetable 
tissues  upon  which  they  feed.  In  man,  both  movements  coexist  in  a 
nearly  equal  degree. 

The  movements  of  mastication  are  accordingly  paralyzed  by  section 


5,'U  TIIK     (MiANIAI,     NKKVES. 

of  the  fifth  pair,  and  :uv  tin-  only  muscular  functions  directly  interfered 
with  liy  this  operation.  There  is  a  diHerenec,  ho\\  ever,  in  Mir  ultimate 
consequences  uhich  follow  |>:i  ralysis  of  mast  icat  ion,  according  to  the 
species  of  animal  alfcctcd.  If  the  fifth  pair,  or  its  inferior  maxillary 
division,  \\civ  destroyed  on  both  sides  in  either  u  carnivorous  or 
herbivorous  animal,  death  would  follow  from  inanition,  owing  to  the 
impossibility  of  preparing  the  food  for  deglutition.  If  the  injury  were 
inllictcd  upon  one  side  only,  it,  would  be  equally  fatal  in  the  hcrbivora, 
by  preventing  the  alternate  lateral  movements  of  the  jaw;  while  in  a 
carnivorous  animal  the  vertical  movements,  which  are  more  import-nut, 
would  be  less  seriously  alleetcd,  since  they  might  still  be  performed, 
though  imperfectly,  by  the  muscles  of  the  opposite  side. 

I'.iit  the  most  peculiar  secondary  result,  of  paralysis  of  the  muscles  of 
mastication  on  one  side  is  seen  in  the  rodcntia.  In  these  animals  the 
most  important  teeth  are  the  four  incisors,  two  in  the  upper  and  two  in 
Mir  lower  jaw,  which  are  used  for  gnawing  through  hard  substances,  and 
which  grow  continuously  from  the  tooth  pulp  below,  thus  supplying  the 
waste  caused  by  wearing  away  their  edges.  The  tooth  move  against 
each  other  in  an  exact  vertical  plane,  the  upper  and  lower  incisors  on 
each  side  meeting  e:ich  other,  and  thus  by  mutual  attrition  keeping  their 
chisel  like  edges  at  a  con  espoiiding  level.  If  the  fifth  nerve  be  divided 
in  I  hese  animals,  the  lower  jaw  becomes  deviated  toward  the  operated 
side  in  consequence  of  the  paralysis  of  the  corresponding  petrygoid 
muscles.  The  edges  of  the  four  incisor  teeth  then  no  longer  correspond 
with  each  other,  but  are  so  shifted  that  one  of  those  in  the  upper  and 
one  in  the  lower  jaw  do  not  meet  \\ith  any  opposing  edge,  and  are  con- 
sequently no  longer  worn  away.  According  to  the  experiments  of  Ber- 
nard on  rabbits,  (he  line  of  junction  between  the  edges  of  t  he  teeth, 
instead  of  being  hori/.ontal,  then  becomes  oblique,  being  directed  from 
abo\e  downward,  from  the  operated  toward  the  sound  side,  and  the 
same  fact  has  been  observed  by  Hint.1  If  the  animal  survive  for  a 
considerable  time,  tin-  teeth  which  are  no  longer  worn  away,  as  they 
continue  to  grow  from  the  tooth-pulp  below,  may  become  excessively 
elongated.  \\'e  have  seen  an  instance  in  the  woodchuck  ( A  ret omys 
monax)  of  lateral  deviation  of  the  teeth  from  a  reunited  fracture  of  the 
lower  jaw,  in  which  the  upper  incisor  on  one  side  and  the  lower  on  the 
other  had  increased  to  live  or  six  times  their  natural  length,  and  had 
probably  caused  the  death  of  the  animal  by  penetrating  the  soft  pails 
about,  the  head  and  interfering  with  the  movement  of  the  jaws. 

Antixtainoh'c  lirtuicln-K  <>/'  fhc  /•'//'//»  /'rt/>. —  Although  the  separate 
regions  of  the  face  are  supplied  in  a  general  way  by  the  three  great 
divisions  of  this  nerve,  there  is  yet  more  or  less  communicat  ion  between 
them  by  intermingled  filaments  from  (litl'erent  sources,  and  the  separate 
branches  of  each  division  communicate  with  considerable  frequency. 
Thus  the  infra-orbital  nerve,  which  sends  filaments  to  the  lower  eyelid, 

1  Physiology  of  Man  ;  Nervous  Svstem.     Now  York.  1872,  p.  198. 


THE    TRIGEMINUS.  f>;>f> 

inosculates  by  a  distinct  twig  with  one  of  the  nasal  branches  of  the  oph- 
thalmic division.  The  integument  of  tlio  11OSO  is  supplied  by  the  nasal 
branches  of  tin'  ophthalmic  division,  and  also  by  tllOSC  coming  from  the 
infraorbital  nerve.  The  upper  :md  lower  lips  arc  supplied  both  from 
tlu-  infraorhital  Mild  mental  nerves  on  t  ho  outside,  and  from  the  terminal 
filaments  of  (he  buccinator  nerve  on  the  inside;  ;ind  the  temporal  region 
receives  branches  both  from  the  superior  and  inferior  maxillary  divisions. 
A  most  important,  Miiastomotic  branch  of  the  fifth  pair  is  that  which  its 
inferior  maxillary  division  sends  to  the  facial  nerve  (Fig.  It4,y),  and 
by  means  of  \\hich  it  .supplies  sensitive  filaments  to  the  great  motor 
ncrvo  of  the  face.  As  a  general  rule,  nerves  which  are  distributed 
exclusively  to  muscles  receive  at  some  part,  of  their  origin  or  course 
sensitive  filaments  which  accompany  them  to  their  destination.  The 
muscular  tissue  consequently  has  a  certain  degree  of  sensibility  ;  and  it, 
is  this  sensibility,  sometimes  called  the  u  muscular  sense,"  \\  Inch  enables 
us  to  appreciate  the  existence  and  degree  of  contraction  in  any  particular 
muscle  or  group  of  muscles.  Many  of  the  sensitive  filaments  supplied 
to  the  facial  nerve  by  tlu4  communicating  branch  of  the  fifth  are  un- 
doubtedly destined  to  reach  the  muscles  of  the  face  \\ilh  the  terminal 
branches  of  this  nerve;  but  there  are  also  abundant  anastomoses  be- 
tween the  facial  nerve  and  the  fifth  near  the  final  distributions  of  the 
latter  nerve.  These  anastomoses  are  quite  numerous,  between  the 
branches  of  the  infraorbital  and  mental  nerves  and  those  of  the  facial; 
and  certain  regions  of  the  integument  may,  therefore,  be  supplied  with 
sensibility  by  filaments  from  both  these  sources-  The  observations  of 
1/Mtievant1  have  shown  that  ii  is  impossible  to  abolish  the  sensibility 
of  any  extended  region  of  the  face  by  section  of  either  division  of  tin' 
fifth  pair  alone.  A  complete  anaesthesia  can  only  be  produced  by  divi- 
sion of  the  whole  nerve  within  the  cranial  cavity.  This  destroys  at 
once  not,  only  the  sensibility  supplied  directly  by  the  fifth  pair,  but  also 
that  communicated  to  the  facial  by  its  anastomotic  branch. 

According  to  llenle,  there  is  still  a  portion  of  the  side  of  the  face 
which  may  derive  a  certain  degree  of  sensibility,  apart  from  that  due  to 
the  fifth  pair,  from  the  great  auricular  nerve  of  the  cervical  plexus ;  since 
the  anterior  branch  of  this  nerve,  after  supplying  the  under  part  of  the 
lobe  of  the  ear,  sends  some  slender  filaments  anteriorly  to  the  integu- 
ment, of  the  cheeks,  running  in  some  instances  as  far  forward  as  the 
neighborhood  of  the  malar  bone. 

In  lli« -nee  of  the  Fifth  Pair  on  the  Special  Senses The  results  of 

experiment  show  that  this  nerve  has  an  important  influence  upon  the 
special  senses,  since  they  are  always  more  or  less  interfered  with,  and  in 
some  instances  practically  destroyed,  by  its  division  or  injury.  This 
influence,  however,  is  mainly  not  a  direct  but  an  indirect  one;  and  shows 
itself  by  a  disturbance  of  nutrition  in  the  tissues  of  the  organ.  For  the 
perfect  action  of  any  of  the  special  senses,  two  different  conditions  are 

1  Trait6  des  Sections  Nervcuscs.     Paris,  1873,  p.  179. 


636  THE    CRANIAL    NERVES. 

requisite :  first  the  peculiar  sensibility  of  its  own  special  nerveT  and 
secondly  the  integrity  of  the  component  parts  of  the  organ  itself.  As 
the  nutrition  of  the  organ  is  affected  by  injury  or  disease  of  the  fifth 
pair,  this  necessarily  causes  a  derangement  in  its  physiological  action 
and  thus  interferes  with  the  exercise  of  the  special  sense  belonging  to  it. 
These  effects  seem  to  depend,  not  so  much  upon  the  division  of  the  ordi- 
nary sensitive  fibres  of  the  fifth  nerve,  as  of  those  which  are  derived 
from  the  nerve  cells  of  the  Gasserian  ganglion,  or  which  are  supplied 
by  the  fifth  pair  to  the  special  sympathetic  ganglia  connected  with  the 
organs  of  sense. 

Influence  on  the  Sense  of  Smell. — The  nasal  passages  are  supplied 
by  two  different  nerves  derived  from  the  cerebro-spinal  S3rstem,  namely, 
the  olfactory  nerve  distributed  to  their  upper  portions,  and  endowed 
with  its  own  special  sensibility;  and  the  nasal  branches  of  the  fifth  pair, 
distributed  in  the  lower  portions,  to  which  they  communicate  the  gene- 
ral sensibility  of  the  mucous  membrane.  The  mucous  membrane  also 
contains  filaments  from  the  spheno-palatine  ganglion  of  the  sympathetic  ; 
and  this  ganglion  receives  its  sensitive  root -from  the  superior  maxillary 
division  of  the  fifth  pair. 

The  general  sensibility  of  the  nasal  passages  may  accordingly  remain 
after  the  special  sense  of  smell  has  been  destroyed.  If  the  fifth  pair, 
however,  be  divided,  not  only  is  general  sensibility  destroyed  in  the 
Schneiclerian  membrane,  but  a  disturbance  also  takes  place  in  its  nutri- 
tion, by  which  the  power  of  smell  is  also  lost*  The  mucous  membrane 
becomes  swollen,  and  the  nasal  passage  is  obstructed  by  an  accumula- 
tion of  mucus.  According  to  Longet,  the  membrane  also  assumes  a 
fungous  consistency,  and  is  liable  to  bleed  at  the  slightest  touch.  The 
effect  of  this  alteration  is  to  blunt  or  destroy  the  sense  of  smell.  It  is 
owing  to  a  similar  condition  of  the  mucous  membrane  that  the  power 
of  smell  is  impaired  in  cases  of  influenza.  The  olfactory  nerves  become 
inactive  in  consequence  of  the  alteration  in  their  mucous  membrane  and 
its  secretions. 

Influence  on  the  Sense  of  Sight. — The  anterior  parts  of  the  eyeball 
are  also  supplied  with  nerves  of  ordinary  sensibility  from  the  fifth  pair, 
while  the  special  impressions  of  light  are  transmitted  exclusively  by  the 
optic  nerve.  In  addition,  the  iris  and  cornea  are  supplied  by  filaments 
coming  from  the  ophthalmic  ganglion  of  the  sympathetic,  which  re- 
ceives its  sensitive  root  from  the  fifth  pair.  If  this  nerve  be  divided 
within  the  cranium,  by  a  section  passing  in  front  of  or  through  the  Gas- 
serian ganglion,  a  change  of  nutrition  often  follows  in  the  cornea,  by 
which  its  tissue  becomes  the  seat  of  vascular  congestion  and  ulceration, 
and  which  frequently  goes  on  to  complete  and  permanent  destruction 
of  the  eye.  These  changes  may  be  observed  in  the  cat,  after  intra- 
cranial  section  of  the  fifth  nerve  by  the  usual  method.  Immediately 
after  the  operation  the  pupil  is  contracted  and  the  conjunctiva  loses  its 
sensibility.  At  the  end  of  twent}r-four  hours  the  cornea  begins  to  be- 
come opaline,  and  by  the  second  day  the  conjunctiva  is  visibly  congested, 


THE    TRIGEMINUS.  537 

and  discharges  a  purulent  secretion.  This  process,  after  commencing 
in  the  cornea,  increases  in  intensity  and  spreads  to  the  iris,  which  be- 
comes covered  with  an  inflammatory  exudation.  The  cornea  grows 
more  opaque,  until  it  is  at  last  altogether  impermeable  to  light,  and 
vision  is  consequently  suspended.  Sometimes  the  diseased  action  goes 
on  until  it  results  in  sloughing  and  perforation  of  the  cornea  and  dis- 
charge of  the  humors  of  the  eye;  sometimes,  after  a  few  days,  the 
inflammatory  appearances  subside,  and  the  eye  is  finally  restored  to  its 
natural  condition. 

According  to  the  observations  of  Bernard,  although  these,  conse- 
quences usuall3r  follow  division  of  the  fifth  nerve  when  performed  at  the 
situation  of  the  Gasserian  ganglion,  or  between  it  and  the  eyeball,  they 
are  either  retarded  in  their  appearance  or  altogether  wanting  when  the 
section  is  made  posteriorly  to  the  ganglion,  between  it  and  the  base  of 
the  brain.  Thjs  indicates  that  the  influence  exerted  by  this  nerve  upon 
the  nutrition  of  the  eyeball  does  not  reside  in  its  own  proper  fibres,  but 
in  additional  filaments  derived  from  the  Gasserian  ganglion. 

Influence  on  the  Sense  of  Taste. — The  lingual  branch  of  the  fifth 
pair  communicates  to  the  anterior  portion  of  the  tongue  at  the  same 
time  its  acute  general  sensibility  and  its  sensibility  of  taste ;  both  of 
which  are,  of  course,  abolished  by  its  division.  Whether  both  kinds  of 
sensibility  reside  in  the  same  or  in  different  fibres  cannot  yet  be  deter- 
mined ;  but  cases  which  have  been  observed  in  man,  of  impairment  of 
the  sense  of  taste,  while  tactile  sensibility  remains  entire,  make  it  pos- 
sible that  there  may  be  two  distinct  sets  of  fibres  in  the  lingual  nerve, 
one  devoted  to  general  sensibility,  the  other  to  that  of  taste.  How- 
ever that  may  be,  it  is  evident  that  the  exercise  of  the  sense  of  taste  is 
facilitated  by  the  presence  of  general  sensibility  in  the  mucous  mem- 
brane of  the  tongue,  and  is  influenced  by  the  state  of  the  local  circula- 
tion and  the  buccal  secretions.  In  a  tongue  which  is  dry  or  coated,  as 
in  the  febrile  condition,  taste  is  practically  abolished ;  as  much  so  as 
the  sense  of  sight  from  opacity  of  the  cornea.  The  sense  of  taste, 
accordingly,  depends  for  its  exercise,  not  only  upon  the  special  sensi- 
bility of  the  lingual  nerve,  but  also  upon  all  the  physiological  conditions 
requisite  for  the  integrity  of  the  mucous  membrane. 

Influence  upon  the  Sense  of  Hearing. — The  influence  of  the  fifth  pair 
upon  the  sense  of  hearing  is  less  certainty  known  than  that  exerted 
upon  the  other  special  senses,  and  is  only  to  be  surmised  from  the  simi- 
larity of  its  anatomical  relations.  This  nerve  provides  for  the  general 
sensibility  of  the  external  ear  by  twigs  from  its  auriculo-temporal  branch, 
which  supply  the  skin  of  the  anterior  border  of  the  concha  and  that  of 
the  anterior  wall  of  the  external  auditory  meatus.  Its  relation  with  the 
deeper  parts  of  the  organ  is  established  by  means  of  the  otic  ganglion 
of  the  sympathetic,  which  receives  a  few  short  fibres  from  the  inferior 
maxillary  division  of  the  fifth  pair,  and  which  sends  a  filament  back- 
ward to  join  the  tj'mpanic  plexus  on  the  inner  surface  of  the  membrane 
of 'the  tympanum.  This  plexus  is  also  supplied  with  filaments  from 
35 


538 


THE    CRANIAL    NERVES. 


the  ganglion  situated  upon  the  trunk  of  the  glosso-pharyngeal  nerve; 
and  is  consequently  made  up  of  interlacing  fibres  derived  from  both 
these  sources.  Its  peripheral  sensitive  fibres  terminate  in  the  mucous 
membrane  lining  the  cavity  of  the  middle  ear.  The  secretions,  both  of 
this  cavity  and  of  the  external  auditory  meatus,  are  important  for  the 
preservation  of  the  integrity  of  the  parts  and  for  the  mechanism  of 
audition ;  and  they  are  undoubtedly  in  great  measure  under  the  control 
of  the  nervous  supply,  of  which  a  considerable  portion  is  derived  from 
the  fifth  pair. 

Sixth  Pair.    The  Abducens. 

The  abducens  nerve,  so  called  because  it  is  distributed  only  to  the 
single  muscle  which  causes  the  movement  of  abduction  of  the  eyeball, 
originates  mainly  from  a  collection  of  gray  matter  on  the  floor  of  the 
fourth  ventricle,  near  its  widest  part  and  at  a  point  corresponding  with 
the  posterior  section  of  the  pons  Varolii.  It  is  situated  next  the  median 


TRANSVERSE  SECTION  OF  THE  FLOOR  OF  THE  FOURTH  VENTRICLE  of  the 
Human  Brain,  showing  the  nucleus  and  roots  of  the  abducens  and  facial  nerves.— Nf,  Nu- 
cleus of  gray  matter.  VI',  Fibres  of  the  abducens  nerve  (6th  pair).  VII',  Fibres  of  the  facial 
nerve  (7th  pair).  VII",  Bundle  of  longitudinal  fibres,  connected  with  the  root  of  the  facial 
nerve.  R,  Raphe,  at  the  median  line,  showing  transverse  or  decussating  fibres  from  the 
facial  nerve  roots.  Magnified  35  diameters.  (Henle.) 

line,  and  is  indicated  on  each  side  by  a  longitudinal  prominence,  known 
as  the  "  fasciculus  teres."  This  collection  of  gray  matter  is  the  common 
nucleus  of  the  abducens  and  facial  nerves ;  since  the  fibres  of  both  these 
nerves  are  traced  to  a  connection  with  it,  although  running  in  some- 
what different  directions.  The  fibres  of  the  abducens,  as  shown  by  Dean, 
Meynert,  and  Henle,  originate  from  the  inner  border  of  the  nucleus 
without  showing  any  apparent  decussation  with  those  of  the  opposite 
side.  They  then  pass  almost  directly  downward  and  forward,  in  a  verti- 
cal longitudinal  plane,  through  the  substance  of  the  tuber  annulare,  to 
their  point  of  emergence  at  the  base  of  the  brain,  at  the  posterior  edge 


THE    FACIAL.  539 

of  the  pons  Yarolii.  From  this  point,  the  nerve,  which  is  about  two  mil- 
limetres in  thickness,  runs  nearly  straight  forward,  beneath  the  under 
surface  of  the  pons,  passes,  in  company  with  the  oculomotorius  and 
patheticus,  along  the  wall  of  the  cavernous  sinus  and  through  the 
sphenoidal  fissure,  into  the  cavity  of  the  orbit,  where  it  terminates  in 
the  external  straight  muscle  of  the  eyeball. 

Physiological  Properties  of  the  Abducens. — The  physiological  pro- 
perties of  this  nerve  have  been  examined,  in  the  experiments  of  Longet 
on  rabbits,  and  in  those  of  Chauveau  on  rabbits  and  horses,  by  irritating 
its  trunk  within  the  cranium  and  at  its  point  of  emergence  from  the 
pons  Yarolii.  The  abducens  is  thus  shown  to  be,  at  its  origin  and  for 
some  distance  beyond,  exclusively  a  motor  nerve  ;  since  its  galvanization 
produces  at  once  continued  contraction  in  the  external  straight  muscle 
of  the  eyeball,  and  mechanical  or  other  irritation  applied  to  its  fibres 
causes  no  indication  of  suffering.  In  the  experiments  of  Longet,  which 
were  performed  upon  the  living  animal,  the  difference  in  this  respect 
between  the  abducens  nerve  and  the  trigeminus  was  very  marked ;  irrita- 
tion of  the  trigeminus  always  giving  rise  to  signs  of  acute  sensibility, 
while  that  of  the  abducens  had  no  other  effect  than  local  muscular  con- 
traction. 

Division  of  this  nerve  causes  internal  strabismus  from  paralysis  of 
the  external  straight  muscle,  and  loss  of  the  lateral  motion  of  the  eye- 
ball in  a  horizontal  plane ;  although  its  vertical  movements  are  still 
preserved,  owing  to  the  continued  activity  of  the  oculomotorius  nerve. 
Cases  of  internal  strabismus,  in  man,  are  recorded,  with  the  accompa- 
nying symptoms  mentioned  above,  which  were  apparently  due  to  com- 
pression of  the  abducens  nerve  by  morbid  growths  within  the  cranial 
cavity. 

Seventh  Pair.    The  Facial. 

With  regard  to  the  innervation  of  the  external  parts  of  the  face,  this 
nerve  holds  an  equal  rank  with  the  fifth  pair,  and  may  be  regarded  as 
complementary  to  it  in  physiological  endowments.  As  the  fifth  pair  is 
the  nerve  of  sensation  for  the  integument  of  this  region,  the  facial  is  the 
motor  nerve  for  its  superficial  muscles.  It  is  the  nerve  of  facial  expres- 
sion, by  which  the  features  are  animated  in  their  varying  movements, 
corresponding  with  the  different  phases  of  mental  or  emotional  activity. 
Although  at  its  origin  an  exclusively  motor  nerve,  it  receives,  soon  after 
its  emergence  from  the  cranium,  a  communicating  branch  from  the  fifth 
pair,  which  gives  to  it,  and  to  the  muscles  in  which  it  terminates,  a  cer- 
tain share  of  sensibility. 

The  facial  nerve  has  its  principal  source  in  a  collection  of  gray  matter, 
which  has  already  been  described  as  also  giving  origin  to  the  fibres  of 
the  abducens  (Fig.  175).  This  nucleus  extends  for  a  short  distance 
longitudinally  along  the  floor  of  the  fourth  ventricle  near  the  median  line, 
as  a  layer  about  1.5  millimetre  in  thickness,  and  containing,  according 


540  THE    CRANIAL    NERVES. 

to  Dean,1  stellate,  oval,  or  fusiform  nerve  cells,  among  which  the  nerve 
fibres  penetrate.  The  nucleus  constitutes,  at  this  situation,  the  gray 
matter  of  the  "  fasciculus  teres."  The  fibres  of  the  abducens  and  facial 
nerves  are  given  off  from  its  internal  and  external  borders  respectively ; 
those  of  the  abducens  passing  directly  downward  through  the  tuber 
annulare,  near  the  median  plane,  those  of  the  facial  first  passing  out- 
ward and  then  bending  downward,  to  reach  their  point  of  emergence  at 
the  posterior  edge  of  the  lateral  portion  of  the  pons  Varolii. 

According  to  Dean,  Meynert,  and  Henle,  a  considerable  portion  of  the 
root  fibres  of  the  facial  nerve  communicate,  either  directly  or  through 
the  nucleus,  across  the  median  line,  with  the  opposite  side  of  the  brain. 

After  emerging  from  the  posterior  edge  of  the  pons  Varolii,  the  facial 
nerve,  in  company  with  the  auditory,  passes  into  and  through  the  in- 
ternal auditory  meatus.  It  then  enters,  by  itself,  the  aqueduct  of  Fal- 
lopius,  and,  following  the  course  of  this  canal  through  the  petrous 
portion  of  the  temporal  bone,  comes  out  at  the  stylomastoid  foramen 
and  turns  forward  upon  the  side  of  the  face.  It  spreads  out  between 
the  lobules  of  the  parotid  gland  into  a  number  of  branches,  which  by 
their  mutual  interlacement  form  the  well-known  "  parotid  plexus,"  or 
"  pes  anserinus,"  of  this  nerve.  Its  branches  then  diverge  upward,  for- 
ward, and  downward,  to  be  distributed  to  the  superficial  muscles  of  the 
facial  region.  It  also  supplies,  by  branches  given  off  immediately  after 
its  emergence  from  the  stylomastoid  foramen,  the  muscles  of  the  exter- 
nal ear,  as  well  as  the  stylohyoid  and  the  posterior  belly  of  the  digastric ; 
and  by  a  twig  which  descends  below  the  jaw  to  the  submaxillary  region, 
it  supplies  filaments  to  the  upper  part  of  the  platysma  myoides  muscle, 
and  communicates  with  an  ascending  branch  of  the  superficial  cervical 
nerve  from  the  cervical  plexus. 

Physiological  Properties  of  the  Facial  Nerve. — The  facial  is  shown, 
by  the  result  of  abundant  corresponding  investigations,  to  be,  at  its 
origin  and  in  its  main  physiological  characters,  an  exclusively  motor 
nerve.  Not  only  is  the  tactile  sensibility  of  the  facial  region  imme- 
diate^ destroyed  by  the  section  of  the  fifth  pair  within  the  skull, 
though  the  facial  itself  remain  uninjured,  but,  according  to  the  ex- 
periments of  Magendie  and  Bernard,  the  trunk  of  this  nerve,  when  irri- 
tated at  its  source  in  the  living  animal,  after  opening  the  cranial  cavity, 
shows  no  sign  of  sensibility,  although  that  of  the  sensitive  cranial 
nerves  is  at  the  same  time  perfectly  manifest.  On  the  other  hand, 
Chaveau  has  found  that  in  the  recently  killed  animal,  galvanization  of 
the  intracranial  portion  of  the  facial  nerve  causes  at  once  contraction 
of  the  muscles  of  the  face  and  of  the  external  ear.  This  nerve  is  accord- 
ingly, at  its  source,  insensible  and  excitable. 

Furthermore,  the  most  decisive  results  are  obtained  from  division  of 
the  facial  nerve  at  various  parts  of  its  course.  This  may  be  done,  in 

1  Gray  Substance  of  the  Medulla  Oblongata  and  Trapezium.  Washington, 
1864,  pp.  58,  61. 


THE    FACIAL.  541 

most  quadrupeds,  at  the  point  of  exit  of  the  nerve  from  the  stylomas- 
toid  foramen,  or,  as  practised  by  Bernard,  during  its  passage  through 
the  aqueduct  of  Fallopius,  by  means  of  a  cutting  instrument  intro- 
duced into  the  cavity  of  the  tympanum,  thus  reaching  the  nerve  through 

Fig.  176. 


DIAGRAM  OP  THE  FACIAL  NERVB  AND  ITS  DISTRIBUTION. — 1.  Facial  nerve  at 
its  entrance  into  the  internal  auditory  meatus.  2.  Its  exit,  at  the  stylomastoid  foramen. 
3,  4.  Temporal  and  posterior  auricular  branches,  distributed  to  the  muscles  of  the  external 
ear  and  to  the  occipitalis.  5.  Branches  to  the  frontalis  muscle.  6.  Branches  to  the  stylohyoid 
and  digastric  muscles.  7.  Branches  to  the  upper  part  of  the  platysma  myoides.  8.  Branch 
of  communication  with  the  superficial  cervical  nerve  of  the  cervical  plexus. 

its  upper  wall.  The  effect  of  this  section  is  to  paralyze  at  once  all  the 
superficial  muscles  of  the  face  on  the  corresponding  side.  The  visible 
effects  vary  in  the  different  facial  regions,  according  to  the  function  of 
the  muscles  which  have  lost  their  power  of  motion, 

Effect  upon  the  Eye. — The  orbicularis*  oculi  being  paralyzed,  the  eye 
upon  the  affected  side  cannot  be  closed,  but  remains  permanently  open ; 
even,  according  to  the  observation  of  Bernard,  while  the  animal  is 
asleep.  This  depends  upon  the  fact  that  the  two  muscles  serving  to 
open  and  close  the  eyelids  are  animated  by  two  different  nerves ;  the 
levator  palpebrae  superioris,  which  lifts  the  upper  eyelid,  being  supplied 
by  the  ocnlomotorius,  while  the  orbicularis  oculi  receives  its  nervous 


542  THE    CRANIAL    NERVES. 

filaments  from  the  facial.  After  paralysis  of  this  nerve,  therefore, 
complete  closure  of  the  lids  becomes  impossible,  although  the  move- 
ments of  the  eyeball  are  unaffected,  and  the  pupil  is  capable  of  dilata- 
tion and  contraction  as  before. 

At  the  same  time  the  motion  of  winking  is  suspended  upon  the 
affected  side.  This  movement  is  an  involuntary  reflex  action,  excited 
by  the  contact  of  air  with  the  surface  of  the  cornea,  and  the  accumula- 
tion of  the  tears  along  the  edge  of  the  lower  eyelid.  At  short  intervals 
this  produces  an  instantaneous  contraction  of  the  orbicularis,  by  which 
the  edges  of  the  eyelids  are  brought  together,  and  again  immediately 
separated ;  thus  spreading  the  moisture  of  the  lachrymal  secretion  uni- 
formly over  the  cornea  and  protecting  its  surface  from  dryness  or  irri- 
tation. After  section  of  the  facial  nerve,  this  movement  ceases,  and 
on  thrusting  a  solid  body  suddenly  toward  the  face  of  the  animal  it  can 
be  seen  that  the  eye  on  the  sound  side  instinctively  closes,  while  the 
other  remains  open.  Even  touching  the  conjunctiva  or  the  cornea  on 
the  operated  side  fails  to  cause  contraction  of  the  eyelids,  although  the 
animal  shrinks  and  the  eyeball  turns  in  the  orbit;  showing  that  the 
motor  power  of  the  orbicularis  alone  has  been  affected  while  sensibility 
remains. 

Two  precisely  opposite  effects,  accordingly,  are  produced  upon  the 
movements  of  the  eye,  by  section  of  the  fifth  nerve,  or  its  ophthalmic 
branch,  and  by  that  of  the  facial.  After  division  of  the  fifth  nerve, 
touching  the  cornea  fails  to  produce  closure  of  the  eyelids  because  the 
sensibility  of  its  surface  has  been  destroyed,  though  the  power  of  motion 
remains.  When  the  facial  has  been  divided,  it  is  the  muscular  action 
which  is  paralyzed,  the  sensibility  of  the  parts  remaining  entire. 

Effect  on  the  Nostrils. — In  some  animals,  as  in  man,  the  nostrils  are 
more  or  less  rigid  and  nearly  inactive  in  the  ordinary  condition.  They 
expand,  however,  with  considerable  vigor  when  the  movements  of 
respiration  are  increased  in  frequency,  or  when  the  air  is  forcibly  in- 
spired to  assist  in  the  sense  of  smell.  In  many  species,  furthermore, 
as  in  most  graminivorous  quadrupeds,  and  especially  in  the  horse,  they 
alternately  expand  and  collapse  in  a  regular  and  uniform  manner,  with 
each  inspiration  and  expiration ;  executing  in  this  way  a  series  of 
respiratory  movements  synchronous  with  those  of  the  chest  and  abdo- 
men. Even  in  man  the  expansion  of  the  nostrils,  at  the  time  of  in- 
spiration, becomes  very  marked  whenever  the  breathing  is  hurried  or 
laborious,  owing  to  increased  muscular  exertion  or  to  any  accidental 
obstruction  of  the  air-passages. 

All  these  movements  are  suspended  by  section  of  the  facial  nerve. 
The  muscles  by  which  they  are  performed  being  paralyzed,  the  nostril 
on  the  affected  side  becomes  flaccid,  and,  instead  of  opening  for  the 
admission  of  air  into  the  nares,  it  collapses  and  forms  more  or  less  of 
an  obstruction  to  its  entrance.  As  the  partial  dyspnoea  thus  induced 
tends  to  accelerate  the  breathing,  the  paralyzed  nostril  is  still  further 
compressed  by  the  air  in  the  movement  of  inspiration;  while  at  the 


THE    FACIAL.  643 

time  of  expiration,  on  the  other  hand,  it  is  forced  outward  by  the  exit 
of  the  air.  The  natural  movements  of  the  nostril  in  respiration,  are 
therefore  reversed  by  paralysis  of  the  facial  nerve.  In  the  normal  con- 
dition they  exhibit  an  active  expansion  in  inspiration,  and  a  partial 
collapse  in  expiration.  After  section  of  the  nerve  the  nostril  collapses 
in  inspiration,  and  partially  opens  in  expiration ;  moving  passively 
inward  and  outward,  like  an  inert  valve,  with  the  changing  direction  of 
the  current  of  the  air. 

Effect  on  the  Lips. — In  the  lower  animals  generally,  but  especially 
in  the  herbivora,  the  movements  of  the  lips  are  mainly  serviceable  in 
the  prehension  of  the  food  ;  and  if  these  movements  be  paralyzed  on 
the  two  sides  at  once,  by  section  of  both  the  facial  nerves,  the  conse- 
quent incapacity  to  introduce  food  into  the  mouth  may  be  sufficiently 
serious  to  cause  death  by  inanition.  In  the  carnivora  the  motions  of 
retraction  and  elevation  of  the  lips,  by  which  the  canine  teeth  are  un- 
covered, have  also  a  marked  effect  on  the  expression  of  the  face.  In 
most  of  these  animals,  after  division  of  the  facial  nerve,  the  change  in 
the  appearance  of  the  corresponding  side,  even  in  the  quiescent  condi- 
tion, is  distinctly  perceptible.  The  lips  are  flaccid  and  motionless,  and 
the  corner  of  the  mouth  hangs  down  and  cannot  be  completely  closed, 
owing  to  the  paralysis  of  the  orbicularis  oris  muscle. 

Effect  on  the  Ears. — In  most  of  the  quadrupeds  the  action  of  the 
external  ears  is  much  more  important  than  in  man,  owing  to  their 
superior  mobility  and  the  greater  development  of  the  corresponding 
muscles.  In  all,  the  varying  position  of  these  organs  is  of  great  influ- 
ence in  modifying  the  expression  ;  and  their  rapid  and  extensive  move- 
ments are  also  serviceable  as  an  essential  aid  to  the  sense  of  hearing. 
When  the  facial  nerve  has  been  divided,  the  ear  on  the  corresponding 
side  becomes  flaccid  and  motionless ;  and  in  species  where  the  organ  is 
long  and  narrow,  as  in  the  hare  and  rabbit,  it  can  no  longer  be  main- 
tained in  the  erect  position. 

All  the  superficial  muscles  accordingly  of  the  head  and  face,  which 
are  supplied  by  filaments  from  this  nerve,  are  paralyzed  by  its  section ; 
while  the  sensibility  of  the  skin,  in  the  corresponding  parts,  is  pre- 
served entire. 

Facial  Paralysis  in  Man. — Facial  paralj'sis,  from  disease  involving 
the  nerve  itself,  its  sources  of  origin  in  the  brain,  or  the  walls  of  its  bony 
canal  in  the  cranium,  is  not  an  uncommon  affection  in  the  human  sub- 
ject. It  is  usually  confined  to  one  side,  being  limited  by  the  median 
line,  and  produces  accordingly  a  marked  difference  in  the  appearance 
of  the  two  sides  of  the  face.  In  particular  cases,  where  the  cause  of 
the  difficulty  is  located  in  the  branches  of  the  nerve,  certain  portions 
of  the  muscular  apparatus  may  be  affected  to  the  exclusion  of  others ; 
and  the  muscles  about  the  lips  may  be  paralyzed  without  any  percepti- 
ble loss  of  motion  in  the  parts  above.  Or  the  affection  may  be  fully 
developed  in  one  region  of  the  face,  and  only  partial  in  the  remainder. 
But  when  the  disease  is  seated  upon  the  trunk  of  the  nerve  within  the 


544 


THE    CRANIAL    NERVES. 


aqueduct  of  Fallopius,  or  involves  the  whole  of  its  central  origin,  its 
consequences  extend  uniformly  over  one  side  of  the  face,  forming  a  com- 
plete unilateral  facial  paralysis. 

The  external  signs  of  paralysis  of  the  facial  nerve  from  disease  in 
man  are,  in  general,  the  same  with  those  which  follow  experimental 
division  of  this  nerve  in  animals.  The  main  peculiarity  depends  upon 
the  greater  development  of  the  facial  muscles  in  man  as  the  organs  of 
expression.  The  most  marked  effect,  therefore,  of  this  disease  in  the 
human  subject,  is  a  loss  of  expression  on  the  paralyzed  side  of  the  face. 

Fig.  177. 


FACIAL  PARALYSIS  of  the  right  side. 

All  the  features  have  a  collapsed  and  flaccid  appearance.  The  eyelids 
remain  motionless,  and  the  eye  is  constantly  open,  not  only  on  account 
of  the  impossibility  of  bringing  down  the  upper  e^yelid,  but  also  because 
the  lower  lid  sinks  down  more  or  less  below  the  level  of  the  cornea ; 
thus  giving  to  the  eye  a  staring,  vacant  appearance.  The  act  of  winking 
is  no  longer  performed  upon  the  affected  side.  Owing  to  the  paralyzed 
condition  of  the  frontalis  and  superciliary  muscles,  all  the  characteristic 
lines  and  wrinkles  on  this  side  disappear,  and  the  forehead  and  eyebrow 
become  smooth  and  expressionless.  The  same  thing  is  true  of  the 


THE    FACIAL.  545 

cheek,  which,  as  well  as  the  nostril,  is  flattened  and  collapsed.  The 
corner  of  the  mouth  hangs  downward,  and  the  lips  cannot  be  kept  in 
contact  with  each  other  at  this  point,  sometimes  allowing  the  saliva  to 
escape  by  drops  from  the  cavity  of  the  mouth. 

Beside  these  symptoms  there  is  also,  in  man,  a  deviation  of  the  mouth 
towards  the  sound  side,  owing  to  the  facial  muscles  on  that  side  being 
no  longer  antagonized  by  those  opposite.  In  many  instances  this  de- 
viation is  not  observable  during  a  state  of  quiescence,  since  both  sets 
of  muscles  are  then  equally  relaxed  ;  and  it  becomes  evident  only  when 
the  patient  begins  to  move  the  muscles  of  the  sound  side,  as  in  speaking 
or  laughing,  or  when  the  emotions  are  excited.  But  in  some  cases,  where 
the  face  has  naturally  an  abundance  of  expression,  the  distortion  of  the 
features,  and  the  consequent  difference  between  the  two  sides  of  the 
face,  are  distinctly  shown  even  in  the  quiescent  condition,  and  become 
still  more  marked  when  the  patient  is  excited  or  engages  in  conversa- 
tion. 

Another  secondary  effect  of  facial  paralysis  in  man  is  difficulty  in 
drinking  and  in  mastication.  The  first  is  due  to  the  impossibility  of 
contracting  the  orbicularis  oris  on  the  affected  side ;  so  that  the  lips  at 
this  corner  of  the  mouth  cannot  be  kept  firmly  in  contact  with  the  sides 
of  the  goblet.  The  consequence  is  that  a  portion  of  the  fluid  escapes 
and  runs  over  the  lower  part  of  the  face,  unless  the  patient  take  the 
precaution  to  aid  the  paralyzed  part  by  pressure  with  his  fingers.  The 
difficulty  in  mastication  is  not  owing  to  any  paralysis  of  the  muscles 
moving  the  lower  jaw.  These  muscles  are  animated  by  the  inferior 
maxillary  division  of  the  fifth  pair,  and  are  unaffected  in  disease  of  the 
facial  nerve.  It  results  from  the  paratysis  of  the  buccinator  muscle, 
and  the  relaxed  condition  of  the  side  of  the  cheek.  In  consequence  of 
this,  the  food  in  mastication  lodges  partially  in  the  space  between  the 
outside  of  the  gum  and  the  inside  of  the  cheek;  and  the  patient  is  often 
obliged  to  remove  it  by  mechanical  means  in  order  to  complete  its 
mastication. 

The  loss  of  power  in  the  orbicularis  oris  also  produces  an  imperfect 
articulation.  The  lips  cannot  be  brought  together  with  sufficient  pre- 
cision, and  consequently  the  labials,  such  as  B  and  P,  are  imperfectly 
pronounced.  If  the  paralysis  be  bilateral,  existing  on  both  sides  of  the 
face  at  a  time,  cases  of  which  have  been  sometimes  observed,  the  features 
are  no  longer  deviated  from  their  symmetrical  position,  but  the  diffi- 
culty of  articulation  becomes  much  increased,  extending  not  only  to 
the  labials  proper,  but  also  to  such  of  the  vowels,  as  0  and  U,  which 
require  a  certain  contraction  of  the  orbicularis  oris.  This  affection  is 
distinguished  from  that  known  as  "  glosso-labio-laryngeal  paralysis."  in 
which  articulation  is  also  impaired.  In  the  latter  disease,  which  is  of 
central  origin,  the  paralysis  affects  the  muscles  of  the  tongue  and  larynx 
as  well  as  those  of  the  lips ;  in  facial  paralysis  it  is  confined  to  those 
which  receive  their  filaments  from  the  facial  nerve.  Facial  paralysis 
ma}T  therefore  exist  without  danger  to  life. 


546  THE    CRANIAL    NERVES. 

Crossed  Action  of  the  Facial  Nerve. — The  results  of  minute  examina- 
tion of  the  mode  of  origin  of  this  nerve  give  indications  of  a  transverse 
communication  by  decussating  nerve  fibres,  between  its  nucleus  at  the 
floor  of  the  fourth  ventricle  and  the  opposite  side  of  the  tuber  annulare. 
It  has  not  yet  been  possible,  however,  to  follow  with  certainty  the  indi- 
vidual fibres  to  their  termination,  or  to  decide  whether  the  decussating 
fibres  are  part  of  the  original  root  fibres  which  have  simply  passed 
through  the  nucleus,  or  whether  they  originate  anew  from  the  nerve 
cells  of  the  nucleus  and  thence  pass  to  the  opposite  side.  The  opinion 
usually  adopted  by  anatomists  from  the  examination  of  microscopic  sec- 
tions is  that  a  part  of  the  fibres  of  each  cranial  nerve  root  terminate  in 
the  nucleus  of  the  same  side,  and  a  part  cross  over,  as  decussating  fibres, 
to  the  opposite  side.  This  is  plainly  shown  in  the  case  of  the  patheticus, 
which  is  the  only  one  of  the  cranial  nerves,  beside  the  optic,  exhibiting 
a  distinct  decussation  of  its  root  fibres  outside  their  connection  with 
the  nucleus. 

That  the  action  of  the  facial  nerve  is  in  great  part  a  crossed  action  is 
evident  from  the  results  of  pathological  observation.  Facial  paralysis 
is  a  frequent  accompaniment  of  hemiplegia;  and  in  the  great  majority 
of  instances,  that  is,  when  the  cerebral  lesion  is  situated  above  the  tuber 
annulare,  the  hemiplegia  of  the  body  and  limbs  and  the  paralysis  of 
the  face  are  upon  the  same  side  with  each  other.  The  injury  to  the 
brain,  therefore,  in  these  cases,  produces  both  hemiplegia  and  facial 
paralysis  on  the  opposite  side.  When  the  injury  is  seated  lower  down, 
on  the  contrary,  in  the  substance  of  the  tuber  annulare,  it  may  affect  at 
the  same  time  the  roots  of  the  facial  nerve  outside  its  nucleus,  and  the 
longitudinal  tracts  of  the  anterior  pyramids  above  their  decussation ; 
and  may  cause  in  this  way  a  facial  paralysis  on  the  same  side  and 
hemiplegia  on  the  opposite  side.  It  thus  appears  that  the  facial  par- 
alysis is  on  the  same  side  with  the  injury  when  this  is  seated  externally 
to  the  nucleus,  and  on  the  opposite  side  when  it  is  seated  above  the 
nucleus  and  near  the  central  parts  of  the  brain.  This  shows  that  for 
a  large  part  of  its  functions,  the  action  of  the  facial  nerve. is  entirely  a 
crossed  action. 

The  communication,  however,  between  the  nucleus  and  the  opposite 
side  of  the  brain,  upon  which  this  crossed  action  depends,  does  not  affect 
all  the  fibres  of  the  nerve,  nor  the  whole  of  the  physiological  functions 
which  are  under  its  control.  The  only  decussation  of  the  nerve  fibres 
connected  with  the  facial  known  to  exist,  is  that  which  takes  place  at 
the  raphe  on  the  floor  of  the  fourth  ventricle.  If  all  the  fibres  of  the 
nerve  root  or  their  continuations  crossed  at  this  point,  from  right  to 
left  and  from  left  to  right,  then  a  longitudinal  section  at  the  raphe, 
following  the  median  line  between  the  two  nuclei,  would  completely 
paralyze  both  sides  of  the  face  at  the  same  time.  But  this  effect  is  not 
produced ;  since,  in  the  experiments  of  Yulpian,1  who  has  performed  this 

1  Lemons  sur  la  Physiologic  du  Systeme  Nerveux.     Paris,  1866,  p.  480. 


THE    FACIAL.  547 

operation  on  dogs  and  rabbits,  the  animals  were  still  capable  of  wink- 
ing with  both  eyes ;  only  the  action  of  the  two  nerves  was  no  longer 
simultaneous,  and  the  closure  of  each  eye  was  performed  at  irregular 
intervals  independently  of  the  other. 

It  is  evident,  therefore,  that  the  reflex  act  of  winking  takes  place  for 
each  eye  upon  the  same  side,  undoubtedly  in  the  gray  matter  of  the 
facial  nucleus ;  and  the  two  nuclei  habitually  act  in  harmony  with  each 
other  by  means  of  the  commissural  fibres  passing  between  them.  But 
the  mental  and  emotional  influences,  which  cause  the  movement  of  the 
features  in  expression  or  in  voluntary  acts,  are  transmitted  by  decus- 
sating fibres  from  the  opposite  side  of  the  brain. 

This  is  still  further  indicated  by  the  different  effects  caused  by  peri- 
pheral and  central  lesions  of  the  facial  nerve.  In  man,  as  in  animals,  if 
this  nerve  be  divided  or  destroyed  during  or  after  its  passage  through 
the  aqueduct  of  Fallopius,  all  the  movements  of  the  facial  muscles  are 
paralyzed  together.  But  in  cases  of  facial  paralysis  depending  upon  a 
lesion  in  the  cerebrum  itself,  that  is,  above  the  situation  of  the  nucleus, 
it  is  generally  observed,  according  to  Yulpian  and  Hammond,1  that  the 
loss  of  movement  is  not  complete;  but  that,  while  all  the  other  parts  of 
the  face  are  paralyzed,  the  patient  retains  the  power  of  winking  on  the 
affected  side.  This  peculiarity  is  even  given  as  a  means  of  diagnosis 
between  facial  paralysis  dependent  upon  injury  of  the  nerve  itself  and 
that  caused  by  a  lesion  in  the  brain. 

Sensibility  of  the  Facial  Nerve. — Although  this  nerve  is  exclusively 
motor  at  its  origin,  it  receives  filaments  of  communication  from  the  fifth 
pair,  which  give  it  a  certain  degree  of  sensibility.  The  most  important 
of  these  branches,  given  off  from  the  inferior  maxillary  division  of  the 
fifth  nerve,  joins  the  facial  soon  after  its  emergence  from  the  stylo- 
mastoid  foramen,  and  runs  forward  with  its  principal  branches  and  rami- 
fications. The  facial  nerve,  therefore,  according  to  the  united  testimony 
of  all  modern  experimenters,  if  examined  upon  the  side  of  the  face,  is 
found  to  be  sensitive  to  mechanical  irritations,  although  the  degree  of 
its  sensibilty  is  much  less  than  that  of  the  fifth  pair.  Owing  to  this 
communication,  the  pain,  in  cases  of  tic  douloureux,  sometimes  follows 
the  course  of  the  horizontal  branches  of  the  facial  nerve.  The  proof, 
however,  that  the  sensitive  fibres  of  this  nerve  are  derived  from  its 
anastomoses  and  do  not  orginally  form  a  part  of  its  trunk,  is  that  the 
sensibility  of  the  facial  regions  to  which  it  is  distributed  disappears 
completely  after  division  of  the  fifth  pair,  notwithstanding  that  the  facial 
nerve  itself  remains  entire. 

Beside  the  principal  communication  above  mentioned,  this  nerve  con- 
tracts abundant  anastomoses,  at  the  anterior  part  of  the  face,  with  the 
radiating  filaments  of  the  supraorbital,  infraorbital,  and  mental  branches 
of  the  fifth  pair. 

1  Diseases  of  the  Nervous  System.     New  York,  1871,  p.  78. 


548  THE    CRANIAL    NERVES. 

Twigs  and  Communications  of  the  Facial  Nerve  in  the  Aqueduct  of 
Fallopius. — While  passing  through  its  canal  in  the  petrous  portion  of 
the  temporal  bone,  the  facial  nerve  gives  off  a  number  of  slender  fila- 
ments by  which  it  communicates  with  other  nerves  or  with  ganglia 
belonging  to  the  sympathetic  system.  The  physiological  character  of 
most  of  these  filaments  is  imperfectly  understood ;  but  certain  facts  have 
been  established  in  regard  to  them,  and  they  are  of  interest  because 
they  are  usually  involved  in  injury  or  disease  of  the  nerve  within  its 
bony  canal,  and  thus  other  secondary  symptoms  are  produced  in  addi- 
tion to  those  of  external  facial  paralysis. 

Fig.  178. 


THE  FACIAL  NERVE  AND  ITS  CONNECTIONS,  within  the  aqueduct  of  Fallopius.— 
1.  Fifth  nerve,  with  the  Gasserian  ganglion.  2.  Ophthalmic  division  of  the  fifth  nerve.  3. 
Superior  maxillary  division  of  the  fifth  nerve.  4.  Lingual  nerve.  5.  Sphenopalatine  gan- 
glion. 6.  Otic  ganglion.  7.  Submaxillary  ganglion.  8.  Facial  nerve  in  the  aqueduct  of  Fal- 
lopius. 9.  Great  superficial  petrosal  nerve.  10.  Small  superficial  petrosal  nerve.  11  Stapedius 
branch  of  facial  nerve  12.  Branch  of  communication  with  pneumogastric  nerve.  13.  Branch 
of  communication  with  glossopharyngeal  nerve.  14.  Chorda  tympani. 

At  the  elbow  formed  ~by  the  anterior  bend  of  the  facial  nerve,  soon 
after  its  entrance  into  the  aqueduct  of  Fallopius,  there  is  a  minute  col- 
lection of  gray  matter,  known  as  the  u  ganglion  geniculatum."  From 
this  point  a  slender  filament,  the  great  superficial  petrosal  nerve  (Fig. 
178,  9),  runs  forward,  passing  obliquely  through  the  base  of  the  skull, 
and  terminates  in  the  sphenopalatine  ganglion.  This  ganglion,  which  is 
also  in  connection,  by  another  root,  with  the  Superior  maxillary  division 
of  the  fifth  nerve,  lends  filaments  to  the  mucous  membrane  of  the  pos- 
terior part  of  the  nasal  passages  and  that  of  the  hard  and  soft  palate 
and  to  the  levator  palati  and  uvular  muscles ;  that  is,  to  the  dilators  of 
the  isthmus  of  the  fauces. 

This  nerve,  which  forms  communication  between  the  facial  and  the 
sphenopalatine  ganglion,  is  without  doubt  the  motor  root  of  the  gan- 
glion, supplying  motive  force  from  the  facial  to  the  muscular  branches 
given  off  from  it  beyond.  This  conclusion  is  derived  from  the  phe- 
nomena of  paralysis  of  the  palatal  muscles  accompanying  certain  cases 


THE    FACIAL.  549 

of  facial  paralysis,  where  the  lesion  is  deep  seated.  The  paralysis  is 
recognized  by  an  incapacity  to  lift  the  soft  palate,  which  hangs  down  in 
a  passive  manner,  and  by  the  deviation  of  the  uvula,  which,  according  to 
the  observations  recorded  by  Longet,  is  always  toward  the  sound  side. 
The  levator  palati,  and  especially  the  uvular  muscle,  being  paralyzed,  its 
fellow  in  contracting  draws  the  uvula  into  an  oblique  position,  with  its 
point  directed  toward  the  non-paralyzed  side.  As  there  is  no  other 
communication  between  the  facial  nerve  and  the  palatal  muscles,  than 
that  through  the  sphenopalatine  ganglion  by  the  great  superficial  petro- 
sal  nerve,  this  nerve  must  be  regarded  as  containing  motor  fibres  running 
from  the  facial  to  the  ganglion. 

A  little  below  the  origin  of  the  last-mentioned  filament,  the  facial  nerve 
gives  off  a  second,  the  small  superficial  petrosal  nerve  do ),  which  com- 
municates both  with  the  otic  ganglion  and  with  the  plexus  of  nerve 
filaments  on  the  inner  wall  of  the  tympanum,  known  as  the  "  tympanic 
plexus,"  which  supplies  nerve  fibres  to  the  lining  membrane  of  the 
tympanic  cavity,  while  the  otic  ganglion  sends  a  motor  filament  to  the 
tensor  tympani  muscle. 

From  the  concave  border  of  the  facial  nerve,  as  it  bends  downward,  a 
fine  motor  filament,  the  stapedius  branch  (n),  passes  forward  to  supply 
the  stapedius  muscle.  The  facial  nerve,  therefore,  in  this  part  of  its 
course,  has  an  influence  on  the  mechanism  of  hearing,  through  the 
muscles  which  regulate  the  position  of  the  bones  of  the  middle  ear,  and 
consequently  the  tension  of  the  membrana  tympani.  This  influence  is 
exerted  directly  by  its  stapedius  branch,  and  indirectly,  through  the  otic 
ganglion,  by  the  filament  supplied  to  the  tensor  tympani.  Cases  of 
facial  paralysis  have  been  known  to  be  accompanied,  sometimes  by  par- 
tial deafness,  and  sometimes  by  abnormal  sensibility  to  sonorous  im- 
pressions ;  but  it  has  not  been  determined  how  far  these  symptoms  were 
due  to  the  implication  of  other  parts,  or  how  far  to  paralysis  of  the 
muscles  of  the  middle  ear  from  disease  of  the  facial. 

From  its  descending  portion,  the  facial  nerve  gives  off  two  small 
branches  of  communication  ( 12,  13 ),  one  to  the  pneumogastric  and  one 
to  the  glossopharyngeal  nerve.  They  are  usually  regarded  as  motor 
filaments,  which  transmit  to  these  two  nerves  the  power  of  causing  mus- 
cular contraction.  This  seems  nearly  certain  in  regard  to  the  branch 
communicating  with  the  glossopharyngeal  nerve ;  since  Cruveilhier  de- 
scribes a  separate  filament  of  the  facial  passing  to  the  styloglossus  and 
palato-glossus  muscles,  and  Longet  cites  an  instance  in  which  a  branch 
of  the  facial,  on  one  side,  without  making  any  connection  with  the  glosso- 
pharyngeal nerve,  was  distributed  directly  to  the  palato-glossal  and 
glossopharyngeal  muscles ;  that  is,  to  the  constrictors  of  the  isthmus 
of  the  fauces. 

,  Finally  the  facial  nerve,  shortly  before  its  exit  from  the  stylomastoid 
foramen,  gives  off  from  its  concave  border  another  slender  branch  of 
considerable  interest,  the  chorda  tympani  (u).  It  first  passes  upward 
and  forward,  in  a  recurrent  direction,  traverses  the  cavity  of  the  tym- 


550  THE    CRANIAL    NERVES. 

panum  near  the  inner  surface  of  the  membrana  tympani,  curves  down- 
ward and  forward,  and  joins  the  descending  portion  of  the  lingual  nerve. 
It  is  certain  that  some  of  its  fibres  again  leave  the  lingual  nerve  at  the 
situation  of  the  subm axillary  ganglion,  to  reach  this  ganglion  and  the 
tissue  of  the  submaxillary  gland  ;  and  it  is  also  certain  that  some  of 
them  continue  onward  with  the  lingual  nerve,  and  accompany  it  to  its 
distribution  in  the  tongue. 

The  most  positive  knowledge  in  our  possession  with  regard  to  the 
physiological  character  of  the  chorda  tympani  is  that  it  is  distinctly  a 
motor  nerve,  influencing  the  acts  of  circulation  and  secretion.  This 
results  from  the  numerous  experiments  of  Bernard1  on  the  dog  and  cat, 
which  show  that,  in  these  animals,  galvanization  of  the  chorda  tympani 
increases  at  the  same  time  the  activity  of  the  circulation  and  the  secre- 
tion of  saliva  in  the  submaxillary  gland.  The  gland,  with  its  excretory 
duct  and  nervous  connections,  is  exposed  in  the  living  animal.  It  is  then 
seen  that  the  introduction  of  vinegar  into  the  fauces  causes,  by  reflex 
action,  an  increased  current  of  blood  through  the  vessels  of  the  gland, 
and  excites  an  abundant  flow  of  submaxillary  saliva.  But  if  the  chorda 
tympani  be  tied  or  cut  across,  the  action  above  described  no  longer  takes 
place,  and  the  gland  remains  inexcitable  under  the  influence  of  a  sapid 
substance  introduced  into  the  fauces.  On  the  other  hand,  if  the  peri- 
pheral extremity  of  the  nerve  be  galvanized,  this  stimulus  excites  the 
circulation  and  secretion  as  before ;  and  the  same  effect  is  produced  by 
stimulating,  either  the  lingual  nerve  itself,  or  the  filament  which  it  sends 
to  the  submaxillary  gland.  Finally,  while  section  of  the  chorda  tym- 
pani in  the  cavity  of  the  tympanum,  or  evulsion  of  the  facial  nerve  from 
the  aqueduct  of  Fallopius,  will  arrest  the  secretive  activity  of  the  sub- 
maxillary gland,  section  of  the  facial  at  the  stylomastoid  foramen  does 
not  have  this  effect,  but  only  paralyzes  the  muscles  of  the  face.  A  dif- 
ference accordingly  exists,  in  the  effects  produced  by  injury  of  the  facial 
nerve,  according  to  its  location,  within  the  aqueduct  of  Fallopius  or  out- 
side of  this  canal.  If  the  lesion  be  external,  there  is  simple  paralysis  of 
the  facial  muscles.  If  it  be  internal,  there  is  also  a  diminished  activity 
of  circulation  and  secretion  in  the  submaxillary  gland. 

Another  symptom  sometimes  observed  in  deep-seated  lesions  of  the 
facial  nerve,  which  is  also  dependent  on  injury  of  the  chorda  tympani, 
is  a  diminution  or  disturbance  of  the  sense  of  taste  in  the  tip  and  sur- 
face of  the  tongue.  In  this  affection,  the  taste  is  not  absolutely  abol- 
ished, but  is  diminished  in  acuteness,  and  especially  in  promptitude. 
In  a  person  presenting  this  difficulty,  or  in  an  animal  after  division  of 
the  chorda  tympani,  if  a  bitter  substance  be  placed  alternately  upon 
the  two  sides  of  the  tongue,  it  is  perceived  almost  immediately  upon 
the  sound  side,  but  only  after  a  considerable  interval  on  the  side  of  the 

1  Systeme  Nerveux.  Paris,  1858,  tome  ii.  pp.  150-157.  Liquides  de  TOrganisme 
Paris,  1859,  tome  i.  pp.  310-315. 


THE    AUDITORY.  551 

paralysis.  Various  explanations  are  given  to  account  for  these  phe- 
nomena. By  some  writers  they  are  referred  exclusively  to  the  motor 
properties  of  the  chorda  tympani.  If  the  fibres  of  this  nerve  which 
accompany  the  branches  of  the  lingual  in  their  peripheral  distribution 
have  an  influence  upon  the  circulation  and  secretion  in  the  tongue 
similar  to  that  which  they  exert  in  the  submaxillary  gland,  it  is  plain 
that  when  these  actions  are  depressed  by  section  of  the  chorda  tym- 
pani, the  sense  of  taste  may  be  diminished  in  the  corresponding  parts 
as  an  indirect  result  of  its  paralysis.  Others,  on  the  contrary,  attri- 
bute this  effect  to  sensitive  fibres  in  the  chorda  tympani,  which  convey 
the  impressions  of  sapid  substances  directly  from  without  inward,  and 
which,  of  course,  cease  their  action  when  the  nerve  is  divided.  The 
indications  obtained  by  experiment  on  this  point  are  as  yet  too  obscure 
to  allow  of  a  decisive  opinion.  The  precise  manner  in  which  the  chorda 
tympani  takes  a  share  in  the  exercise  of  the  sense  of  taste  is  more  or 
less  a  matter  of  uncertainty.  But  there  is  no  question  that  its  paralysis 
interferes,  to  an  appreciable  degree,  with  this  sense;  and  an  alteration 
of  the  taste,  accompanying  facial  paralysis  upon  the  same  side,  is  a 
symptom  which  fixes  the  location  of  the  nervous  lesion  at  some  point 
inside  the  stylomastoid  foramen. 

Eighth  Pair,    The  Auditory. 

On  the  posterior  surface  of  the  medulla  oblongata,  a  little  behind  the 
widest  part  of  the  fourth  ventricle,  a  number  of  white  striations  run 
from  the  neighborhood  of  the  median  line,  transversely  outward,  toward 
the  posterior  edge  of  the  peduncles  of  the  cerebellum.  These  striations, 
which  are  sometimes  exceedingly  distinct,  represent  the  commencement 
of  the  roots  of  the  auditory  nerve.  The  nucleus  from  which  they 
originate  is  a  mass  of  gray  substance  situated  directly  beneath  them, 
containing  nerve  cells  of  various  form  and  size,  some  of  which  belong 
to  the  smaller  variety,  while  some  of  them,  according  to  Dean,  are 
among  the  largest  of  those  met  with  in  the  nervous  system.  The  gray 
matter  of  the  nucleus,  at  its  lateral  portion,  extends  outward  and  upward 
toward  the  white  substance  of  the  cerebellum,  with  which  it  is  connected 
by  numerous  bundles  of  radiating  fibres. 

The  fibres  originating  from  this  ganglion  partly  run  directly  outward 
in  a  superficial  course,  forming  the  white  striations  visible  at  this  point, 
and,  uniting  with  each  other,  curve  round  the  posterior  border  of  the 
peduncles  of  the  cerebellum  to  reach  the  lateral  surface  of  the  medulla 
at  the  lower  edge  of  the  pons  Varolii.  Some  of  them  follow  a  deeper 
course,  passing  obliquely  through  the  substance  of  the  medulla  outward 
and  downward  to  the  same  point.  These  fibres,  united  with  each  other, 
form  the  posterior  root  of  the  auditory  nerve. 

The  anterior  root  consists  of  fibres  which  are  traced  backward  from 
their  point  of  emergence,  partly  to  the  floor  of  the  fourth  ventricle,  but 
also  in.  great  measure,  according  to  Clarke,  Dean,  and  Henle,  into  the 
white  substance  of  the  cerebellum,  where  they  mingle  with  fibres  coming 


552  THE    CRANIAL    NERVES. 

from  the  interior  of  this  organ.  The  main  anatomical  peculiarity, 
therefore,  which  distinguishes  the  central  origin  of  the  auditory  from 
that  of  the  other  cranial  nerves,  is  its  abundant  and  direct  connection 
with  the  substance  of  the  cerebellum 

The  auditory  nerve,  formed  by  the  union  of  these  two  bundles  of  root 
fibres,  emerges  from  the  lateral  surface  of  the  medulla  oblongata,  at  the 
inferior  edge  of  the  pons  Yarolii,  and  immediately  outside  the  facial 
nerve.  In  company  with  the  facial  it  then  passes  forward  and  outward, 
enters  the  internal  auditory  meatus,  penetrates  through  the  perforations 
at  the  bottom  of  this  canal,  and  terminates  in  the  nervous  expansions 
of  the  internal  ear. 

Physiological  Properties  of  the  Auditory  Nerve. — The  auditory 
nerve  is  evidently  a  nerve  of  special  sense,  and  serves  to  communicate 
to  the  brain  the  impression  of  sonorous  vibrations.  In  the  experiments 
of  Magendie  upon  dogs  and  rabbits,  the  auditory  nerve,  when  exposed 
in  the  cranial  cavity,  was  found  to  be  insensible  to  the  severest  me- 
chanical irritation,  although  the  roots  of  the  fifth  pair  exhibited  at  the 
same  time  an  acute  sensibility.  Its  exclusive  distribution  to  the  inter- 
nal ear,  for  which  it  forms  the  only  nervous  connection  with  the  bitf  in, 
leaves  no  doubt  that  its  function  is  that  of  transmitting  to  the  central 
organ  the  nervous  influences  which  produce  the  sensation  of  sound. 

Behind  the  situation  of  the  auditory  there  commences  a  special  divi- 
sion of  the  cranial  nerves,  which  differ  in  great  measure  from  the  pre- 
ceding. All  the  foregoing  nerves,  excepting  those  of  special  sense,  are 
either  distinctly  motor  or  have  a  highly  developed  general  sensibility ; 
they  are  distributed  to  the  integument  and  to  muscles  which  are  con- 
cerned in  the  execution  of  voluntary  movements  ;  and  they  are  all  asso- 
ciated in  the  production  of  nervous  action  in  the  various  regions  of  the 
face. 

The  second  division  of  the  cranial  nerves,  on  the  other  hand,  com- 
prising the  glossopharyngeal,  the  pneumogastric,  and  the  spinal  acces- 
sory, are  distributed  to  the  deeper  parts  about  the  commencement  of 
the  digestive  and  respiratory  passages,  where  the  general  sensibility  is 
comparatively  deficient,  and  the  movements  are,  for  the  most  part, 
involuntary ;  and  they  exhibit  phenomena  which  have  more  especially 
the  character  of  reflex  actions.  Externally,  they  show  a  marked  simi- 
larity of  anatomical  arrangement,  originating  one  behind  the  other,  in 
a  continuous  line,  along  the  lateral  furrow  of  the  medulla  oblongata 
and  the  side  of  the  spinal  cord,  each  by  a  series  of  separate  filaments ; 
and  in  such  juxtaposition  that  it  is  in  some  instances  difficult  to  say, 
from  external  inspection,  where  the  root  fibres  of  one  terminate,  and 
those  of  the  other  begin.  The  two  sensitive  nerves  belonging  to  this 
group,  namely,  the  glossopharyngeal  and  the  pneumogastric,  have  their 
source  in  two  nuclei  which  are  continuous  with  each  other  at  the  pos- 
terior surface  of  the  medulla  oblongata ;  and,  according  to  the  observa- 


THE    GLOSSOPHARYNGEAL.  553 

tions  of  Dean,  in  the  medulla  of  the  sheep,  the  transition  between  the 
pneumogastric  and  glossopharyngeal  roots  or  nuclei  is  so  gradual  that 
it  is  impossible  to  point  out  any  exact  line  of  demarcation.  Each  of 
these  nerves  has  upon  its  trunk  a  distinct  ganglion,  situated  within  its 
point  of  emergence  from  the  cranium.  The  motor  portion  of  the  group, 
or  the  spinal  accessory,  originates  from  a  special  nucleus  of  its  own, 
and  sends  branches  of  communication  to  both  the  other  nerves.  While 
the  three  nerves  of  this  group,  therefore,  can  hardly  be  regarded  as  a 
single  pair,  they  have  nevertheless  a  close  mutual  relation  both  in  ana- 
tomical arrangement  and  in  their  physiological  properties. 

Ninth  Pair.    The  Glossopharyngeal, 

The  fibres  of  the  glossopharyngeal  nerve  originate  from  a  nucleus 
situated  a  little  behind  and  below  that  of  the  auditory,  and  near  the 
outer  border  of  the  fasciculus  teres,  by  which  it  is  separated  from  the 
median  line.  This  nucleus  is  continuous  posteriorly  with  that  of  the 
pneumogastric  nerve,  which  projects  above  it  on  the  floor  of  the  fourth 
ventricle  (Fig.  168,  Ngl,  Nv).  The  nerve  fibres,  after  leaving  the  nu- 
cleus, pass  downward  and  outward  through  the  substance  of  the  medulla, 
and  emerge  from  its  lateral  surface,  next  behind  the  auditory  nerve,  in 
a  series  of  five  or  six  filaments  which  soon  afterward  unite  into  a  single 
cord.  The  nerve  then  passes  into  and  through  the  jugular  foramen,  in 
company  with  its  associated  nerves,  the  pneumogastric  and  spinal 
accessor}*.  While  passing  through  this  opening  in  the  skull,  it  presents 
a  ganglionic  enlargement,  similar  to  those  of  the  posterior  spinal  nerve 
roots,  and  known  as  the  petrosal  ganglion,  from  its  occupying  a  shallow 
depression  in  the  petrous  portion  of  the  temporal  bone.  At  the  situa- 
tion of  the  petrosal  ganglion  it  gives  off  a  small  branch,  the  "  nerve  of 
Jacobson,"  which  is  distributed  to  the  mucous  membrane  of  the  tym- 
panum and  Eustachian  tube,  and  sends  a  filament  of  communication  to 
the  otic  ganglion  of  the  sympathetic  system.  The  trunk  of  the  glosso- 
pharyngeal nerve  then  passes  downward  and  forward,  receiving  branches 
of  communication  from  both  the  facial  and  the  pneumogastric  nerves, 
after  which  it  separates  into  two  main  divisions,  one  of  which  is  des- 
tined for  the  tongue,  the  other  for  the  pharynx;  a  double  distribution, 
to  which  the  nerve  owes  its  name.  The  portion  passing  to  the  tongue 
is  distributed  to  the  mucous  membrane  of  the  posterior  third  of  this 
organ,  namely,  to  that  portion  situated  behind  the  V-shaped  row  of  cir- 
cumvallate  papillae,  and  to  these  papillae ;  it  also  supplies  filaments  to 
the  tonsils  and  to  the  mucous  membrane  of  the  pillars  of  the  fauces  and 
of  the  soft  palate.  The  remaining  portion  of  the  nerve  is  distributed 
to  the  mucous. membrane  of  the  pharynx  and  certain  of  the  adjacent 
muscles,  namely,  the  digastric  and  stylopharyngeal  muscles,  by  union 
with  a  branch  of  the  facial  to  the  styloglossal  muscle,  and  by  union 

1  Gray  Substance  of  the  Medulla  Oblongata  and   Trapezium.     Washington. 
1864,  p.  30. 
36 


554  THE    CRANIAL    NERVES. 

with  branches  of  the  pneumogastric  to  the  mucous  membrane  and  the 
superior  and  middle  constrictors  of  the  pharynx.  The  muscles,  accord- 
ingly, to  which  this  nerve  is  directly  or  indirectly  distributed  are  those 
by  which  the  tongue  is  drawn  backward  (styloglossal),  the  larynx  and 
pharynx  elevated  (digastric  and  stylopharyngeal),  and  the  upper  part 
of  the  pharynx  contracted  (superior  and  middle  constrictors) ;  that  is, 
those  concerned  in  the  act  of  deglutition. 

Physiological  Properties  of  the  Glossopharyngeal. — The  glossopha- 
ryngeal  nerve  is  evidently  for  the  most  part  a  nerve  of  sensibility.  Its 
origin  from  the  tract  of  gray  matter  in  the  medulla  oblongata  correspond- 
ing to  the  posterior  horns  of  gray  matter  in  the  spinal  cord,  the  distinct 
ganglion  located  upon  its  trunk  in  the  jugular  foramen,  and  the  fact  that 
it  is  mainly  distributed  to  the  mucous  membranes  of  the  tongue  and 
pharynx,  all  indicate  its  resemblance  in  anatomical  arrangement  to  other 
well  known  sensitive  nerves  or  nerve  roots.  The  result  of  direct  experi- 
ment corroborates  this  view.  Longet,  in  irritating  the  glossopharyngeal 
nerve  within  the  cranium,  was  never  able  to  produce  muscular  contrac- 
tion ;  and  although  Chauveau,  in  experimenting  upon  this  nerve  in  the 
same  situation  in  recently  killed  animals,  saw  its  galvanization  followed 
by  contraction  of  the  upper  part  of  the  pharynx,  the  effect  may  have 
been  due  to  reflex  action,  since  the  nerve  w~as  still  in  connection  with 
the  medulla  oblongata.  This  conclusion  is  rendered  certain  by  the  in- 
vestigations of  Reid,1  who  found  that  irritation  of  the  glossopharyngeal 
nerve  produced  movements  of  the  throat  and  lower  part  of  the  face ; 
but  that  these  movements  were,  in  a  great  measure,  reflex  and  not 
direct,  since  they  were  also  produced  after  the  nerve  had  been  divided, 
by  applying  the  irritation  to  its  cranial  extremity.  Its  sensibility  to 
mechanical  or  galvanic  irritation,  however,  appears  to  be  of  a  low  grade, 
as  compared  with  that  of  the  trigeminal  nerve.  While  some  observers 
(Reid)  found  its  irritation  in  the  living  animal,  outside  the  jugular  fora- 
men, give  rise  to  evident  signs  of  pain,  others  (Panizza)  have  failed  to 
see  any  indications  of  suffering  from  this  cause ;  and  others  still  (Longet) 
speak  of  the  signs  of  pain,  thus  produced,  in  a  more  or  less  uncertain 
manner.  This  variation  in  the  observed  results  is  sufficient  to  show  the 
inferior  capacity  of  the  glossopharyngeal  nerve  for  the  receipt  of  painful 
impressions;  since  no  experimenter  has  ever  doubted  the  acute  sensibility 
of  the  fifth  pair. 

But  notwithstanding  the  comparative  deficiency  of  the  nerve  itself, 
and  the  parts  to  which  it  is  distributed,  in  ordinary  sensibility,  it  serves 
to  transmit  sensitive  impressions  of  a  special  character,  which  are  con- 
nected with  two  different  but  associated  functions,  namely :  1.  The  sense 
of  taste,  and,  2.  The  reflex  act  of  deglutition. 

Connection  with  the  Sense  of  Taste. — The  power  of  perceiving  sensa- 
tions of  taste  exists  not  only  in  the  anterior  portion  of  the  tongue  which 

1  Todd's  Cyclopaedia  of  Anatomy  and  Physiology.  Article,  Glossopharyngeal 
Nerve. 


THE    GLOSSOPHARYNGEAL.  555 

contains  filaments  derived  from  the  lingual  branch  of  the  fifth  pair,  but 
also  at  the  base  of  the  organ,  throughout  its  posterior  third,  and  in  the 
mucous  membrane  of  the  arches  of  the  palate,  which  are  supplied  only 
by  the  fibres  of  the  glossopharyngeal.  The  difference  between  these  two 
regions  is  that  while  that  supplied  by  the  fifth  pair  possesses  tactile 
sensibility  of  a  high  grade  in  addition  to  that  of  taste,  in  the  posterior 
region  the  general  sensibility  is  less  acute  than  the  special  sensibility  to 
impressions  of  taste.  The  appreciation  of  savors  is  provided  for  by 
both  the  lingual  and  glossopharyngeal  nerves,  each  in  its  separate  de- 
partment of  the  oral  cavity.  The  sense  of  taste  accordingly,  in  the 
experiments  of  Reid,  was  never  completely  abolished  by  division  of 
either  one  of  these  nerves.  For  its  complete  suspension,  both  of  them 
must  be  destroyed  on  both  sides.  The  method  adopted  by  Longet  for 
examining  the  condition  of  the  taste  in  dogs,  before  and  after  division 
of  the  glossopharyngeal  nerves,  was  to  place  upon  the  base  of  the  tongue 
a  few  drops  of  a  concentrated  solution  of  colocynth.  Although  this 
always  produced  in  the  animals,  while  in  their  natural  condition,  mani- 
fest signs  of  disgust,  it  had  no  such  effect,  as  a  general  rule,  after  sec- 
tion of  the  glossopharyngeal  nerves  on  both  sides,  provided  the  solution 
were  applied  only  to  the  posterior  part  of  the  tongue  and  the  pharynx ; 
while  if  even  a  minute  quantity  came  in  contact  with  the  tip  or  edges 
of  the  tongue  it  caused  brisk  movements  of  the  jaws  with  all  the  in- 
dications of  a  sense  of  repugnance.  While  in  the  anterior  and  more 
movable  parts  of  the  tongue,  accordingly,  the  sensations  of  taste  are 
appreciated,  during  the  process  of  mastication,  by  the  filaments  of  the 
lingual  nerve  which  are  distributed  there,  the  glossopharyngeal  is  the 
nerve  of  taste  for  the  posterior  part  of  the  organ.  It  is  called  into  ac- 
tivity after  mastication  is  accomplished  and  at  the  moment  when  the 
food  is  carried  backward  and  compressed  by  the  base  of  the  tongue,  the 
pillars  of  the  fauces^  and  the  walls  of  the  pharynx. 

Connection  with  the  Reflex  Act  of  Deglutition. — In  the  fauces  and 
pharynx,  the  glossopharyngeal  nerve  also  possesses  a  peculiar  sensibility 
to  certain  impressions,  which  excite  at  once  the  muscles  of  the  neigh- 
boring parts  and  bring  into  play  the  complicated  mechanism  of  degluti- 
tion. This  consists  in  drawing  backward  and  upward  the  base  of  the ' 
tongue,  thus  bringing  the  masticated  food  into  and  through  the  isthmus 
of  the  fauces.  The  muscles  of  the  pillars  of  the  fauces  (palato-glossal 
and  palato-pharj'iigeal)  afterward  contract  and  close  the  opening  of  the 
isthmus,  while  the  soft  palate  is  drawn  backward  and  extended  across 
the  upper  end  of  the  pharynx,  thus  shutting  off  its  communication  with 
the  posterior  nares ;  and  the  contraction  of  the  constrictor  muscles  of 
the  pharynx  then  forces  its  contents  downward  into  the  beginning  of  the 
oesophagus.  This  process  is  an  involuntary  one.  Both  the  contraction 
of  the  special  muscles,  and  their  regular  co-ordination  in  the  necessary 
series  of  successive  movements,  are  actions  which  do  not  depend  on  the 
exercise  of  the  will,  but  which  take  place  even  in  a  state  of  unconscious- 
ness under  the  stimulus  supplied  by  contact  of  food  or  liquids  with  the 


556  THE    CKANIAL    NERVES. 

inner  surface  of  the  fauces  and  pharynx.  This  contact  produces  an  im- 
pression which  is  conveyed  by  the  glossopharyngeal  nerve  inward  to  the 
medulla  oblongata,  whence  it  is  reflected  outward  in  the  form  of  a  motor 
impulse.  The  sensibility  which,  by  the  contact  of  masticated  food  or 
nutritious  liquids,  thus  produces  the  movements  of  swallowing,  if  sub- 
jected to  the  influence  of  nauseous  or  irritating  substances,  will  cause  an 
inverted  muscular  reaction,  equally  involuntary  in  character. 

Natural  stimulants,  therefore,  applied  to  the  mucous  membrane  of  the 
pharynx,  excite  deglutition;  unnatural  stimulants  excite  vomiting.  If 
the  linger  be  introduced  into  the  fauces  and  pharynx,  or  if  the  mucous 
membrane  of  these  parts  be  irritated  by  tickling  with  the  end  of  a 
feather,  the  sensation  of  nausea,  conveyed  through  the  glossopharyngeal 
nerve,  is  sometimes  so  great  as  to  produce  immediate  vomiting.  This 
method  may  be  employed  in  cases  of  poisoning,  when  it  is  desirable  to 
excite  vomiting  rapidly,  and  when  emetic  medicines  are  not  at  hand. 

Motor  Properties  of  the  Glossopharyngeal. — Although  this  nerve  is 
shown,  by  the  result  of  observation,  to  be  exclusively  sensitive  at  its 
origin,  it  is  found,  if  examined  outside  the  cavity  of  the  cranium,  to 
possess  motor  properties.  In  the  experiments  of  Herbert  Mayo  upon 
the  ass,  confirmed  by  those  of  Longet  on  the  horse  and  the  dog,  irritation 
of  this  nerve  in  the  neck  produced  contraction  in  the  stylopharyngeal 
muscles  and  in  the  upper  part  of  the  pharynx.  These  movements  were 
not  the  result  of  reflex  action,  but  were  excited  through  the  nerve  from 
within  outward;  since,  in  the  experiments  of  Longet,  they  were  called 
out  after  the  nerve  had  been  divided,  by  applying  the  irritation  to  its 
peripheral  extremity. 

The  glossophaiyngeal,  therefore,  after  its  exit  from  the  jugular  fora- 
men, is  a  mixed  nerve.  In  addition  to  its  own  original  sensitive  fila- 
ments, it  has  received  a  branch  of  communication  from  the  facial  which 
is  undoubtedly  of  a  motor  character,  and  also  a  branch  from  the  pneu- 
mogastric.  The  pneumogastric  branch  is  also  regarded,  on  anatomical 
grounds,  as  really  made  up,  wholly  or  in  part,  of  motor  fibres  derived 
from  the  spinal  accessory,  through  its  anastomosis  with  the  pneumogas- 
tric. According  to  Cruveilhier.  it  sometimes  comes  directly  and  exclu- 
sively from  the  anastomotic  branch  of  the  spinal  accessory;  sometimes 
partly  from  this  and  partly  from  the  pneumogastric  itself.  The  results 
obtained  by  experiment  also  indicate  a  double  source  for  the  motor 
fibres  which  join  the  glossopharyngeal  before  its  exit  from  the  skull. 
If  these  fibres  were  derived  exclusively  from  the  facial  or  exclusively 
from  the  spinal  accessory,  the  division  or  destruction  of  one  or  the 
other  of  these  nerves  above  its  communicating  branch  would  abolish 
entirely  the  motor  power  of  the  glossopharyngeal.  But  the  experiments 
of  Bernard  upon  rabbits,  in  which  the  facial  nerve  was  divided  in  the 
aqueduct  of  Fallopius,  and  those  of  Bernard  and  Longet  on  cats  and 
rabbits,  in  which  the  spinal  accessory  was  destroyed  on  both  sides, 
show  that  the  process  of  deglutition,  though  more  or  less  retarded,  is 
not  abolished  by  either  of  these  ope  rations. 


THE    PNEUMOGASTRIC.  557 

Beside  the  anastomotie  branches  received  by  the  glossopharyngeal, 
near  its  origin,  from  the  facial  and  the  spinal  accessory,  it  also  has  com- 
munication with  both  these  nerves  near  its  peripheral  distribution.  It 
is  joined  by  a  branch  of  the  facial,  which  accompanies  it  to  the  stylo- 
glossal  muscle,  and  perhaps  also  to  the  pillars  of  the  fauces ;  and,  accord- 
ing to  Cruveilhier,  a  branch  derived  from  the  spinal  accessoiy  takes 
part  in  the  formation  of  the  pharyngeal  plexus  which  supplies  the  upper 
constrictor  muscles  of  the  pharynx.  The  process  of  deglutition,  there- 
fore, is  excited  at  its  commencement  by  sensitive  impressions  conveyed 
through  the  glossopharyngeal  nerve  ;  but  its  movements  are  executed 
by  a  reflex  impulse  transmitted  through  the  motor  fibres  of  several 
distinct  branches  of  communication. 

Tenth  Pair.    The  Pneumogastric. 

The  pneumogastric  nerve,  remarkable  for  its  varied  and  extensive 
course  and  the  distribution  of  its  fibres  to  a  number  of  different  locali- 
ties, has  received  its  name  from  the  two  most  important  organs  in  which 
it  terminates,  the  lungs  and  stomach.  It  arises  from  the  side  of  the 
medulla  oblongata  by  a  series  of  from  ten  to  fifteen  separate  filaments, 
arranged  in  a  linear  series,  continuously  with  those  of  the  glossopha- 
ryngeal. The  nucleus  from  which  these  fibres  take  their  origin  is  an 
extended  tract  of  gray  matter  running  in  a  longitudinal  direction 
along  the  posterior  surface  of  the  medulla  oblongata,  just  outside  the 
lower  extremity  of  the  fasciculus  teres.  This  collection  of  gray  matter 
(Fig.  168,  Nu)  which  is  uncovered  by  the  divergence  of  the  posterior 
columns  of  the  cord,  and  is  thus  exposed  to  view  on  the  floor  of  the 
fourth  ventricle,  is  known  as  the  ala  cinerea.  At  its  anterior  ex- 
tremity it  covers,  and  is  continuous  with,  the  nucleus  of  the  preceding 
nerve,  the  glossopharyngeal ;  and  at  its  posterior  extremity  it  joins 
that  of  the  following  nerve,  the  spinal  accessory.  From  its  deep  sur- 
face it  gives  out  the  fibres  of  origin  of  the  pneumogastric  nerve,  which 
run  downward  and  outward  through  the  substance  of  the  medulla,  and 
emerge,  as  above  mentioned,  in  a  series  of  filaments  from  its  lateral 
surface. 

The  filaments  of  the  pneumogastric,  after  leaving  the  side  of  the 
medulla  oblongata,  unite  into  a  single  trunk  which  passes  out  of  the 
cranium,  in  company  with  the  glossopharyngeal  and  the  spinal  accessory, 
by  the  jugular  foramen  (Fig.  179).  Here  it  presents  upon  its  trunk  a  gan- 
glionic  swelling,  known  as  the  "jugular  ganglion."  At  or  immediately 
beyond  the  situation  of  the  ganglion,  the  nerve  is  joined  by  an  important 
motor  branch  of  communication  from  the  spinal  accessory  ;  and  it  after- 
ward receives  filaments  from  four  other  sources;  namely,  the  facial,  the 
hypoglossal,  and  the  anterior  branches  of  the  first  and  second  cervical 
nerves. 

While  passing  down  the  neck  the  pneumogastric  nerve  takes  part,  by 
an  anastomotic  branch,  in  the  formation  of  the  pharyngeal  plexus.  Its 
first  important  branch  of  distribution  is  the  superior  larynyeal  nerve. 


,"58 


THE    CRANIAL    NERVES. 


Fig.  179. 


which  runs  downward  and  forward,  penetrates  the  larynx  by  an  open- 
ing in  the  side  of  the  thyro-hyoid  membrane,  and  is  distributed  to  the 
mucous  membrane  covering  the  epiglottis  and  lining  the  interior  of  the 
laryngeal  cavity.  This  is  the  main  portion  of  the  nerve,  and  it  is  sensi- 
tive in  character;  providing  for  the  peculiar  sensibility  of  the  glottis  and' 
epiglottis  and  for  that  of  the  inner  surface  of  the  larynx  in  general. 
The  nerve  gives  off,  however,  a  small  muscular  branch  which  terminates 
in  the  inferior  constrictor  of  the  pharynx  and  in  the  crico-thyroid  mus- 
cle of  the  larynx.  It  also  supplies  several  filaments,  which 'unite  with 
others  coming  from  the  great  sympathetic,  to  form  the  laryngeal  plexus  ; 
and  by  this  plexus  the  superior  laryngeal  branch  of  the  pneumogastric 
furnishes  filaments  to  the  upper  cardiac  nerves  of  the  cervical  portion 

of  the  sympathetic.  Other  filaments 
pass  off  from  the  trunk  of  the  pneumo- 
gastric while  passing  down  the  neck, 
which  also  join  the  cardiac  branches 
of  the  sympathetic,  and  which  in  some 
instances,  according  to  Cru  veilhier,  pass 
directly  downward,  to  unite  with  the 
cardiac  plexus  beneath  the  concavity 
of  the  arch  of  the  aorta. 

The  next  branch  is  the  inferior 
laryngeal  nerve,  which  separates  from 
the  trunk  of  the  pneumogastric  after 
entering  the  cavity  of  the  chest,  curves 
round  the  subclavian  artery  on  the 
right  side  and  the  arch  of  the  aorta  on 
the  left,  and  ascends,  in  the  groove 
between  the  trachea  and  oesophagus, 
to  the  larynx,  giving  off  branches  to 
the  oesophagus  and  the  inferior  con- 
strictor muscle  of  the  pharynx.  In 
the  larynx  it  is  distributed  to  all  the 
muscles  of  this  organ,  excepting  the 
crico-thyroid,  which  is  supplied  by  the 
superior  laryngeal.  The  larynx  is 
therefore  supplied  by  two  different 
branches  of  the  pneumogastric  nerve, 
which  are  mainly  distinct  from  each 
other  in  their  properties  and  functions. 
The  superior  laryngeal  branch  is  for 
the  most  part  a  sensitive  nerve,  sup- 

ORIGIN  AND  COURSE  OF  THE  G-LOSSOPHARYNGE  A  L,  PNETTMOGASTRIC,  AND 
SPINAL  ACCESSORY  NERVES.— 1.  Facial  nerve.  2.  Glossopharyngeal.  3.  Pneumogastric. 
4.  Spinal  accessory.  5.  Hypoglossal.  6.  External  (muscular)  branch  of  the  spinal  accessory. 
7.  Superior  laryngeal  branch  of  the  pneumot-astric.  8.  Pharyngeal  plexus.  9.  Laryngeal 
plexus  and  uppercardiac  branches  of  the  pneumogastric.  10.  Tympanic  plexus,  from  a  branch 
of  the  glossopharyngeal.  (Hirschfeld.) 


THE    PNEUMOGASTRIC.  559 

plying  the  mucous  membrane  of  the  larynx;  the  inferior  laryngeal 
branch  is  a  motor  nerve,  and  is  essential  to  the  activity  of  nearly  all 
the  muscles  of  the  organ. 

After  entering  the  cavity  of  the  chest,  the  most  important  dependency 
of  the  pneumogastric  nerve  is  the  pulmonary  plexus,  formed  by  the 
separation  of  the  nerve  into  a  considerable  number  of  inosculating 
branches  which  send  their  terminal  filaments  along  the  course  of  the 
bronchi  and  their  subdivisions,  to  the  ultimate  bronchi  and  lobules  of 
the  lungs.  In  the  inferior  portion  of  the  chest,  the  inosculating  fila- 
ments on  both  sides  surround  the  oesophagus  with  the  cesophageal 
plexus,  from  which  fibres  are  supplied  to  the  mucous  membrane  and 
muscular  coat  of  this  organ. 

The  two  pneumogastric  nerves,  after  being  reconstructed  by  the  union 
of  their  branches  below  the  pulmonary  plexus,  penetrate  the  cavity  of 
the  abdomen  and  spread  out  in  two  sets  of  gastric  branches,  which 
supply  the  mucous  membrane  and  muscular  coat  of  the  stomach.  Those 
belonging  to  the  left  pneumogastric  nerve  supply  the  anterior  wall  of  the 
organ,  and,  extending  toward  the  right  as  far  as  the  pylorus,  send  a  con- 
tinuation of  nervous  filaments  to  the  transverse  fissure  of  the  liver,  into 
which  they  penetrate,  together  with  those  of  the  hepatic  plexus  of  the 
sympathetic  ;  those  belonging  to  the  right  pneumogastric  send  filaments 
to  the  posterior  wall  of  the  stomach,  and  finally  communicate  with  the 
solar  plexus  of  the  sympathetic. 

The  pneumogastric  nerve,  therefore,  is  distributed,  by  its  various 
branches,  to  the  mucous  membranes  and  muscular  apparatus  of  the  pas- 
sages by  which  air  and  food  are  introduced  into  the  interior  of  the  body. 
It  also  forms  connection  at  several  points  with  branches  of  the  great 
sympathetic,  and,  through  it,  sends  fibres  to  the  central  organ  of  the  cir- 
culation, and  to  the  radiating  sympathetic  plexuses  of  the  abdominal 
organs. 

Physiological  Properties  of  the  Pneumogastric. — According  to  the 
results  obtained  by  Longet,  the  pneumogastric  is,  at  its  origin,  exclu- 
sively a  sensitive  nerve.  Galvanic  irritation  applied  to  the  nerve  roots, 
carefully  separated  from  the  medulla  and  from  adjacent  filaments,  was 
not  found  to  produce  any  muscular  contractions ;  but  when  applied  to 
the  trunk  of  the  nerve  at  a  lower  level,  muscular  contractions  were 
readily  excited.  At  this  situation  the  nerve  already  contains  motor 
fibres  derived  from  inosculation  with  the  spinal  accessory,  the  facial  and 
the  hypoglossal,  and  from  the  loop  of  communication  between  the  two 
upper  cervical  nerves.  In  its  trunk,  accordingly,  it  has  the  characters 
of  a  mixed  nerve,  and  is  capable  of  providing  both  for  movement  and 
sensibility  in  the  organs  to  which  it  is  distributed. 

The  sensibility  of  the  pneumogastric  nerve,  however,  to  mechanical 
irritation  and  to  painful  impressions,  is  but  slightly  marked,  as  shown 
by  the  experience  of  all  observers.  It  may  frequently  be  divided  in 
the  middle  of  the  neck  in  the  living,  unetherized  animal,  without  any 
sign  of  pain  being  manifested ;  and  this  want  of  reaction  is  at  times  so 


560  THE    CRANIAL    NERVES. 

complete  as  to  indicate  an  entire  absence  of  ordinary  sensibility.  This 
does  not  seem  to  be  invariably  the  case ;  but  although  Bernard  has 
found  in  some  instances  a  well-marked  sensibility  in  this  nerve,  and  in 
others  only  a  very  indistinct  one,  it  is  not  possible  to  say  with  certainty 
upon  what  special  conditions  the  difference  depends.  As  a  general 
rule,  the  pneumogastric  nen'e  is  decidedly  deficient  in  that  kind  of  sen- 
sibility which  produces  pain ;  and  we  know  that  the  organs  to  which  it 
is  distributed  have  but  little  appreciation  of  tactile  impressions.  Never- 
theless, there  is  abundant  evidence  that  this  nerve  is  endowed,  in  its 
various  divisions,  with  sensibility  of  a  peculiar  kind,  and  one  which  is  of 
the  highest  importance  for  the  due  performance  of  the  vital  functions. 

Connection  with  the  movements  of  Respiration. — The  most  important 
endowment  of  the  pneumogastric  nerve  is  undoubtedly  that  by  which  it 
is  connected  with  the  reflex  movements  of  expansion  and  collapse  of 
the  chest  in  respiration.  Its  influence  in  this  respect  is  at  once  made 
evident  by  the  results  which  follow  the  division  of  both  nerves  in  their 
course  through  the  neck.  This  may  be  readily  done  in  adult  dogs  by 
etherizing  the  animal  and  exposing  the  nerves  in  the  middle  of  the  neck 
during  the  continuance  of  insensibility.  After  the  etherization  has 
passed  off,  and  the  circulation  and  respiration  are  restored  to  a  quies- 
cent condition,  both  nerves  may  be  simultaneously  divided,  and  the 
effects  of  the  operation  observed. 

After  the  nerves  have  been  divided,  and  the  slight  disturbance  which 
immediately  follows  their  section  has  subsided,  the  most  striking  change 
produced  in  the  condition  of  the  animal  is  a  diminished  frequency  in 
the  movements  of  respiration.  The  respirations  sometimes  fall  at  once 
to  ten  or  fifteen  per  minute,  becoming,  in  an  hour  or  two,  still  further 
reduced.  Respiration  is  performed  easily  and  quietly  ;  and  the  animal, 
if  undisturbed,  remains  usually  crouched  in  a  corner,  without  any  spe- 
cial sign  of  discomfort.  If  he  be  aroused  and  compelled  to  move,  the 
frequency  of  respiration  is  temporarily  augmented ;  but  as  soon  as  he 
is  again  quiet,  it  returns  to  its  former  standard.  By  the  second  or 
third  day  the  respirations  are  often  reduced  to  five,  four,  or  even  three 
per  minute ;  when  the  animal  usually  appears  very  sluggish,  and  is 
roused  with  difficulty  from  his  inactive  condition.  Respiration  is  also 
performed  in  a  peculiar  manner.  The  movement  of  inspiration  is  slow, 
easy,  and  silent,  occupying  several  seconds  in  its  accomplishment; 
while  that  of  expiration  is  sudden  and  audible,  and  is  accompanied  by 
a  well  marked  effort,  which  has,  to  some  extent,  a  convulsive  character. 
The  intercostal  spaces  sink  inward  during  the  lifting  of  the  ribs ;  and 
the  whole  movement  of  respiration  has  an  appearance  of  insufficiency, 
as  if  the  lungs  were  not  thoroughly  filled  with  air.  This  is  undoubtedly 
owing  to  a  peculiar  alteration  in  the  pulmonary  texture,  which  has  by 
this  time  already  commenced. 

Death  takes  place  from  one  to  six  days  after  the  operation,  according 
to  the  age  and  strength  of  the  animal.  The  only  marked  symptoms 
which  accompany  :*  are  a  steady  failure  of  the  respiration,  with  increas- 


THE    PNEUMOGASTRICc  561 

ing  sluggishness.  There  are  no  convulsions,  nor  any  evidences  of  pain. 
After  death  the  lungs  are  found  in  a  peculiar  state  of  solidification. 
They  are  not  swollen,  but  rather  appear  smaller  than  natural.  They 
are  of  a  dark  purple  color,  leathery,  and  resisting  to  the  touch,  destitute 
of  crepitation,  and  infiltrated  with  blood.  Pieces  of  the  lung  cut  out 
sink  in  water.  The  pleural  surfaces,  at  the  same  time,  are  bright  and 
polished,  and  their  cavity  contains  no  effusion  or  exudation.  The  lungs 
are  simply  engorged  with  blood,  and,  to  a  greater  or  less  extent,  empty 
of  air;  their  tissue  having  undergone  no  other  alteration. 

These  phenomena  point  to  the  pneumogastric  nerves  as  the  main 
channels  through  which  the  stimulus  which  excites  the  movements  of 
respiration  is  conveyed  inward  to  the  medulla  oblongata.  Respiration 
is  a  reflex  act,  consisting,  like  other  nervous  manifestations  of  a  similar 
character,  of  two  different  elements;  namely,  first,  an  impression  con- 
veyed from  without  inward  by  a  sensitive  nerve  to  the  appropriate 
nervous  centre;  and,  secondly,  of  a  motor  impulse  transmitted  thence 
through  motor  nerves  to  the  muscular  apparatus.  But  by  dividing  the 
pneumogastric  nerves  in  the  neck,  neither  the  intercostal  muscles  nor 
the  diaphragm  are  paralyzed.  The  muscular  apparatus  which  effects 
the  expansion  of  the  lungs  remains  untouched,  and  yet  the  movements 
of  respiration  become  gradually  slower  until  they  cease  altogether.  At 
the  same  time  the  disturbance  of  respiration,  under  these  circumstances, 
although  sufficient  to  produce  death  after  a  short  interval,  is  not  accom- 
panied by  any  apparent  sense  of  suffocation.  The  retarded  breathing, 
and  the  consequent  imperfect  aeration  of  the  blood,  are  not  felt  by  the 
animal,  and  he  accordingly  makes  no  attempt  to  compensate  for  them 
by  voluntary  effort. 

In  dividing  the  pneumogastric  nerves,  therefore,  it  is  not  the  motor, 
but  the  sensitive  element  in  the  reflex  act  of  respiration  which  is  inter- 
fered with.  The  experiments  of  Waller  and  Prevost1  show  conclusively 
that  this  is  the  part  performed  by  the  nerves  in  question.  In  these 
experiments  the  pneumogastric  nerve  was  exposed  in  the  living  dog, 
and  divided  in  its  course  down  the  neck;  after  which,  galvanization  of 
its  central  extremity  produced  a  succession  of  forcible  inspirations  and 
expirations,  expelling  the  air  through  the  trachea  with  an  audible  sound. 
The  respiratory  impulse,  therefore,  is  propagated  through  the  pneu- 
mogastric nerve  in  a  centripetal,  not  in  a  centrifugal  direction.  The 
impression  which  normally  originates  in  the  lungs,  and  is  thence  con- 
veyed through  these  nerves  to  the  medulla  oblongata,  produces  in  the 
nervous  centre,  though  unperceived  as  a  conscious  sensation,  the  stimu- 
lus which  calls  into  activity  the  muscles  of  respiration.  If  this  impres- 
sion be  not  at  once  satisfied  by  filling  the  lungs  with  air,  it  increases  in 
intensity ;  and  if  the  breath  be  voluntarily  suspended  or  forcibly  ob- 
structed, the  impression  soon  becomes  perceptible  as  a  sensation  of 
distress,  or  "  demand  for  breath,"  which  reacts  upon  the  entire  system. 

1  Archives  de  Physiologic  normale  et  pathologique.     Paris,  1870,  p.  190. 


562  THE    CRANIAL    NERVES. 

On  the  other  hand,  if  the  pneumogastric  nerves  be  cut  off,  the  customary 
impression  is  no  longer  conveyed  from  the  lungs  to  the  medulla,  and 
the  movements  of  respiration  are  consequently  retarded.  The  imperfect 
aeration  of  the  blood  thus  induced  reacts  in  turn  upon  the  medulla,  as 
well  as  upon  the  other  nervous  centres,  diminishing  its  sensibility,  and 
rendering  it  less  able  to  respond  to  impressions  of  any  kind.  Thus  the 
difficulty,  which  consists  in  a  want  of  the  nervous  reaction  necessary 
for  respiration,  increases  from  hour  to  hour,  the  breathing  becomes  con- 
stantly more  imperfect  and  sluggish,  and  at  last  ceases  altogether.  The 
alteration  in  the  tissue  of  the  lungs,  their  engorgement  and  solidifica- 
tion, add  to  the  difficulty  in  aeration  of  the  blood,  and  probably  have, 
at  last,  a  considerable  share  in  producing  the  fatal  result. 

It  is  evident,  however,  that  the  pneumogastric  nerves,  although  the 
principal  means  for  conveying  to  the  medulla  the  stimulus  for  respira- 
tion, are  not  the  only  ones.  If  they  were  so,  respiration  would  stop 
instantly  after  section  of  these  nerves,  as  it  does  after  destruction  of  the 
medulla  itself.  The  lungs  are,  no  doubt,  especially  sensitive  to  the  want 
of  oxygen  and  accumulation  of  carbonic  acid  in  the  blood ;  and  the 
nervous  impression  thus  produced  is  accordingly  first  felt  in  them. 
There  is  reason  to  believe  that  all  the  vascular  organs  are  more  or  less 
capable  of  originating  this  impression,  and  that  all  the  sensitive  nerves 
are  capable,  to  some  extent,  of  transmitting  it.  Although  the  first  dis- 
agreeable sensation,  on  holding  the  breath,  makes  itself  felt  in  the 
lungs,  yet  if  we  persist  in  suspending  respiration,  the  feeling  of  dis- 
comfort soon  spreads  to  other  parts  ;  and  at  last,  when  the  accumula- 
tion of  carbonic  acid  has  become  excessive,  all  parts  of  the  body  are 
pervaded  by  a  general  feeling  of  distress.  It  is  easy,  therefore,  to  under- 
stand why  respiration  should  be  retarded,  after  section  of  the  pneumo- 
gastrics,  since  the  chief  source  of  the  stimulus  to  respiration  is  cut  off; 
but  the  movements  still  go  on,  though  more  slowty  than  before,  because 
the  other  sensitive  nerves,  which  continue  to  act,  are  in  some  measure 
capable  of  conveying  a  similar  impression. 

In  order  that  the  movements  of  respiration  should  go  on  with  the 
requisite  frequency  to  maintain  the  aeration  of  the  blood,  it  is  necessary 
that  the  pnenmogastric  nerves,  which  are  especially  endowed  with  this 
kind  of  sensibility,  retain  their  integrity  as  nervous  conductors  between 
the  lungs  and  the  medulla  oblongata.  In  this  function,  they  act  alto- 
gether as  sensitive  nerves;  while  the  muscles  of  respiration  receive 
their  reflex  motor  stimulus  by  way  of  the  spinal  nerves. 

Connection  with  the  Respiratory  Movements  of  the  Glottis. — The 
respiratory  movements  of  the  glottis,  already  described  in  a  former 
chapter  (p.  277)  are  essential  parts  of  the  mechanism  of  respiration. 
They  consist  in  the  active  opening  of  the  glottis  in  inspiration,  followed 
by  its  partial  collapse  at  the  time  of  expiration.  The  opening  of  the 
glottis,  which  is  requisite  for  the  free  admission  of  air  into  the  trachea, 
is  effected  by  the  action  of  the  posterior  crico-arytenoid  muscles.  These 
muscles,  in  contracting,  rotate  the  arytenoid  cartilages  outward,  and 


THE    PNEUMOGASTRIC.  563 

thus  separate  the  vocal  chords  from  each  other  and  largely  increase  the 
transverse  diameter  of  the  orifice  of  the  glottis.  When  they  relax  at 
the  time  of  expiration,  the  arytenoid  cartilages  return  to  their  former 
position,  and  the  opening  of  the  glottis  is  again  narrowed  by  the  passive 
approximation  of  the  vocal  chords.  As  the  movements  of  expansion 
are  accomplished  by  the  action  of  the  laryngeal  muscles,  they  depend 
upon  the  influence  of  the  pneumogastric  nerve  and  its  inferior  laryngeal 
branch. 

Both  the  movements  of  the  glottis  in  respiration  and  their  dependence 
upon  nervous  influence  may  be  seen  in  the  dog  by  means  of  an  operation 
which  consists  in  making  a  dissection  along  the  side  of  the  neck,  in 
such  a  way  as  to  expose  the  pharynx  and  a  considerable  portion  of  the 
oesophagus.  The  superior  laryngeal  nerve  on  that  side  is  necessarily 
cut  across,  but  the  inferior  laryngeal,  as  well  as  the  trunk  of  the  pneu- 
mogastric, are  left  uninjured.  By  a  longitudinal  incision  through  the 
pharynx  and  oesophagus,  the  upper  and  posterior  surfaces  of  the  larynx 
are  then  exposed,  and,  notwithstanding  the  previous  division  of  the 
superior  laryngeal  nerve,  the  alternate  movements  of  expansion  and 
collapse  of  the  glottis  are  seen  going  on  in  their  natural  order,  and 
keeping  pace  with  the  corresponding  respiratory  movements  of  the 
chest.  If  now  the  inferior  laryngeal  nerve  be  divided  upon  either  the 
right  or  the  left  side,  the  vocal  chord  of  that  side  becomes  motionless, 
while  that  of  the  opposite  side  continues  to  move  as  before.  If  the  re- 
maining laryngeal  nerve  be  divided,  all  movements  of  expansion  in  the 
vocal  chords  instantly  cease  ;  and  the  same  effect  is  produced  by  section 
of  both  pneumogastric  nerves  in  the  middle  of  the  neck,  since  the  in- 
ferior laryngeals  are  given  off  as  branches  below  that  point. 

If  the  section  of  both  pneumogastric  nerves,  or  of  their  inferior  laryn- 
geal branches,  be  made  simultaneously  under  these  circumstances  while 
the  breathing  is  tolerably  rapid,  the  injurious  effect  of  laryngeal  paralysis 
upon  respiration  at  once  becomes  manifest.  Both  vocal  chords  being 
then  deprived  of  the  active  control  of  their  muscles,  the  borders  of  the 
rima  glottidis  are  left  in  a  condition  of  passive  flexibility.  They  have 
not  only  lost  the  power  of  separating  from  each  other  and  thus  opening 
the  glottis  at  the  time  of  inspiration,  but  they  are  also  drawn  downward 
and  inward  by  the  current  of  air  passing  into  the  trachea,  and  thus,  like 
a  double  membranous  valve,  they  occlude  more  or  less  completely  the 
orifice  of  the  glottis,  and  offer  a  physical  obstacle  to  the  free  entrance 
of  the  air.  In  very  young  animals,  where  there  is  but  little  rigidity  of 
the  laryngeal  cartilages,  the  occlusion  of  the  glottis  thus  produced  after 
section  of  the  inferior  laryngeal  nerves,  may  be  so  complete  as  to  produce 
immediate  death  by  suffocation ;  in  adult  animals  the  occlusion  is  only 
partial,  but  is  still  sufficient  to  diminish  perceptibly  the  capacity  of  res- 
piration. 

The  natural  movements  of  the  glottis  in  breathing  are  therefore 
reversed  after  section  of  the  inferior  laryngeal  nerves.  Before  this 
operation,  in  the  normal  condition,  the  glottis  is  opened  at  inspiration 


564:  THE    CRANIAL    NERVES. 

and  collapses  in  expiration ;  after  the  section  of  the  nerves,  it  is  nar- 
rowed  in  inspiration  and  passively  opened  in  expiration  by  the  forcible 
expulsion  of  the  air.  The  effects  thus  produced  on  the  glottis,  by  division 
of  the  inferior  laryngeal  nerves,  are  the  same  with  those  which  take  place 
in  the  nostrils  after  division  of  the  facial  nerves.  Both  these  sets  of 
movements  are  connected  with  the  mechanism  of  respiration,  and  both 
are  influenced  in  a  similar  manner  by  division  of  their  motor  nerves. 

As  the  laryngeal  muscles  are  necessarily  paralyzed  by  division  of  the 
pneumogastric  nerves  in  the  middle  of  the  neck,  the  effects  of  this  mus- 
cular paralysis  are  necessarily  added  to  those  which  result  from  in- 
terruption of  the  sensitive  function  of  the  pneumogastric  branches  in 
the  lungs.  In  very  young  animals,  as  mentioned  above,  the  effects  due 
simply  to  laryngeal  paralysis  are  more  marked  than  m  adults ;  and  in 
order  to  determine  the  extent  of  its  influence  upon  the  lungs  we  have 
performed  a  comparative  experiment,  in  the  following  manner.  Two 
pups  were  taken  belonging  to  the  same  litter,  and  of  the  same  size  and 
vigor,  about  two  weeks  old.  In  one  of  them  (No.  1)  a  section  was  made 
of  both  pneumogastric  nerves  in  the  middle  of  the  neck ;  in  the  other 
(No.  2), the  inferior  laryngeal  nerves  only  were  divided,  the  pneumogas- 
trics  being  left  untouched.  In  No.  1,  therefore,  the  natural  stimulus  to 
respiration  was  diminished  at  the  same  time  that  the  muscles  of  the 
larynx  were  paralyzed  ;  in  No.  2,  there  was  laryngeal  paralysis  alone, 
the  sensibility  to  the  demand  for  respiration  remaining  the  same.  For 
the  first  few  seconds  after  the  operation  there  was  but  little  difference  in 
the  condition  of  the  two  animals,  the  laryngeal  symptoms  being  most 
prominent  in  both.  There  was  the  same  obstruction  at  the  glottis  owing 
to  paralysis  of  the  lar}rngeal  muscles,  the  same  difficulty  of  inspiration, 
and  the  same  frothing  at  the  mouth.  Very  soon,  however,  in  No.  1,  the 
respiratory  movements  became  quiescent,  and  at  the  same  time  much 
reduced  in  frequency,  falling  to  ten,  eight,  and  five  respirations  per 
minute,  as  usual  after  section  of  the  pneumogastrics ;  while  in  No.  2 
the  respiration  continued  frequent  as  well  as  laborious,  and  the  general 
signs  of  agitation  and  discomfort  were  kept  up  for  one  or  two  hours,  after 
which  there  followed  diminished  excitability  of  the  nervous  centres,  and 
the  animal  became  exhausted,  cool,  and  partially  insensible,  like  the 
other.  They  both  died  between  thirt}7  and  forty  hours  after  the  opera- 
tion. On  post-mortem  inspection  it  was  found  that  congestion  and 
solidification  of  the  lungs  existed  to  a  similar  extent  in  each  instance; 
and  the  only  appreciable  difference  between  the  two  bodies  was  that  in 
No.  1  the  blood  was  coagulated,  and  the  abdominal  organs  natural,  while 
in  No.  2  the  blood  was  fluid  and  the  abdominal  organs  congested.  The 
alteration  in  the  tissue  of  the  lungs,  therefore,  after  the  pneumogastric 
nerves  have  been  divided,  is  not  a  direct  effect,  produced  by  cutting  off 
the  influence  of  these  nerves  upon  the  pulmonary  tissue,  but  results 
indirectly  from  the  diminished  activity  of  respiration  and  imperfect 
aeration  of  the  blood. 


THE    PNEUMOGASTRIC.  565 

Protection  of  the  Glottis  from  the  Intrusion  of  Foreign  Substances. — 
The  influence  of  the  pneumogastric  nerve  in  the  larynx  is  not  confined 
to  its  motor  action  upon  the  muscles ;  it  also  supplies,  by  its  superior 
laryngeal  branch,  a  peculiar  sensibility  to  the  mucous  membrane  of  these 
parts,  which  is  essential  for  the  protection  of  the  respiratory  passages. 
In  the  first  place,  it  stands  as  a  sort  of  guard,  or  sentinel,  at  the  entrance 
of  the  larynx,  to  prevent  the  intrusion  of  foreign  substances.  If  a  crumb 
of  bread  fall  within  the  aryteno-epiglottidean  folds,  or  on  the  edges  of 
the  vocal  chords,  or  upon  the  posterior  surface  of  the  epiglottis,  the 
sensibility  of  the  parts  excites  an  expulsive  cough,  by  which  the  foreign 
body  is  dislodged.  The  impression  received  and  conveyed  inward  by 
the  sensitive  fibres  of  the  superior  laryngeal  nerve,  is  reflected  upon  the 
expiratory  muscles  of  the  chest  and  abdomen,  by  which  the  movements 
of  coughing  are  accomplished.  Touching  the  above  parts  with  the  point 
of  a  needle,  or  pinching  them  with  the  blades  of  a  forceps,  will  produce 
the  same  effect.  This  reaction  is  dependent  on  the  sensibility  of  the 
laryngeal  mucous  membrane  ;  and  it  can  no  longer  be  produced  after 
section  of  the  superior  laryngeal  branch  of  the  pneumogastric  nerve. 

Connection  with  the  Formation  of  the  Voice. — In  addition  to  its  func- 
tion in  the  mechanism  of  respiration,  the  larynx  is  also  an  organ  for 
the  production  of  vocal  sounds.  The  formation  of  the  voice  can  be 
studied  in  the  lower  animals  by  exposing  the  larynx  and  glottis. in  the 
manner  described  above,  and  in  man  by  the  use  of  the  laryngoscope ; 
that  is,  a  small  mirror  held  at  a  suitable  angle  at  the  back  of  the  pharynx 
in  such  a  way  as  to  reflect  a  more  or  less  complete  view  of  the  laryngeal 
orifice.  The  first  important  fact  to  be  observed  in  this  respect  is  that 
the  voice  is  formed  always  in  expiration,  never  in  inspiration.  It  is 
the  column  of  outgoing  air  which  is  set  in  vibration  to  produce  a  vocal 
sound,  and  which  continues  and  modifies  its  resonance  while  passing 
through  the  pharynx,  mouth,  and  nasal  passages.  Secondly,  it  requires 
an  active  tension  and  close  approximation  of  the  vocal  chords,  so  that 
the  orifice  of  the  glottis  is  narrowed  to  a  comparatively  minute  crevice. 
So  long  as  the  vocal  chords  preserve  their  relaxed  condition  during 
expiration,  nothing  is  heard  except  the  faint  whisper  of  the  air  passing 
through  the  cavity  of  the  larynx.  When  a  vocal  sound,  however,  is  to 
be  produced,  the  chords  are  suddenly  made  tense  and  applied  closely  to 
each  other,  thus  diminishing  considerably  the  diameter  of  the  orifice : 
and  the  air,  driven  by  forcible  expiration  through  the  glottis,  in  passing 
between  the  vibrating  vocal  chords,  is  itself  thrown  into  vibrations  which 
produce  the  sound  required.  The  tone,  pitch,  and  intensity  of  this  sound 
vary  with  the  conformation  of  the  larynx,  the  degree  of  tension  and 
approximation  of  the  vocal  chords,  and  the  force  of  expiration.  The 
narrower  the  opening  of  the  glottis,  and  the  greater  the  tension  of  the 
chords,  the  more  acute  the  sound  ;  while  a  wider  opening  and  a  less 
degree  of  tension  produce  a  graver  note.  The  quality  of  the  sound  is 
also  modified  by  the  length  of  the  column  of  air  included  between  the 
glottis  and  the  mouth,  the  tense  or  relaxed  condition  of  the  walls  of  the 


566  THE    CRANIAL    NERVES. 

pharynx  and  fauces,  and  the  state  of  dryness  or  moisture  of  the  mucous 
membrane  lining  the  passages. 

The  actual  formation  of  the  voice,  or  the  production  of  sonorous 
vibrations,  takes  place,  therefore,  exclusively  in  the  larynx;  while 
articulation,  or  the  division  of  the  vocal  sound  into  words  and  phrases 
by  vowels  and  consonants,  is  accomplished  by  the  aid  of  the  lips, 
tongue,  teeth,  and  palate.  Consequently,  division  of  the  pneumogas- 
tric  nerve  or  of  its  inferior  laryngeal  branch  on  both  sides,  by  para- 
lyzing the  muscles  of  the  larynx  which  serve  to  approximate  and  extend 
the  vocal  chords,  produces  among  its  other  effects  a  loss  of  voice.  Fur- 
thermore, as  the  two  functions  of  vocalization  and  articulation  are 
accomplished  by  distinct  nervous  and  muscular  actions,  they  may  be 
deranged  independently  of  each  other,  by  injury  or  disease  of  different 
parts  of  the  nervous  system.  That  of  articulation  is  regulated  by  the 
action  of  the  facial  and  hypoglossal  nerves  ;  while  vocalization  is  under 
the  control  of  the  pneumogastric. 

Connection  with  Deglutition. — The  reflex  act  of  deglutition,  which 
commences  in  the  fauces  and  pharynx  under  the  control  of  the  glosso- 
pharyngeal  nerve,  is  continued  and  completed  by  the  lower  portion  of 
the  pharynx  and  the  tube  of  the  oesophagus.  These  parts  receive  both 
their  sensitive  and  motor  filaments  exclusively  from  the  pneumogastric 
nerve,  and  it  is  under  its  influence  that  the  food,  once  started  upon  its 
downward  passage,  is  conducted  by  the  peristaltic  action  of  the  oesoph- 
agus into  the  stomach. 

The  inferior  constrictor  muscle  of  the  pharynx  and  the  cervical  por- 
tion of  the  oesophagus  both  receive  filaments  from  the  inferior  laryngeal 
nerve ;  while  the  thoracic  portion  of  the  oesophagus  is  supplied  entirely 
from  the  trunk  of  the  pneumogastric.  Some  fibres  are  also  sent  to  the 
inferior  constrictor  of  the  pharynx  by  the  superior  laryngeal  nerve. 
Deglutition,  therefore,  becomes  incomplete,  as  shown  by  the  experiments 
of  Bernard  upon  dogs,  horses,  and  rabbits,  by  division  of  the  pneumo- 
gastric nerves  in  the  middle  of  the  neck.  The  masticated  food  is  still 
conveyed,  by  the  action  of  the  pharynx,  from  the  fauces  into  the 
oesophagus ;  but  here  it  accumulates,  distending  the  inert  walls  of  the 
paralyzed  canal,  and  finding  its  way  into  the  stomach  only  in  small 
quantities  and  by  the  imperfect  effect  of  compression  from  above.  In 
the  natural  condition,  the  process  of  swallowing  is  a  connected  series 
of  rapidly  succeeding  contractions,  beginning  at  the  fauces  and  ending 
at  the  cardiac  orifice  of  the  stomach.  Each  portion  of  the  mucous 
membrane  receives  in  turn  a  stimulus  from  the  contact  of  the  food, 
which  is  followed  by  excitement  of  the  corresponding  muscles ;  so  that 
the  alimentary  mass  is  carried  rapidly  from  above  downward  by  an 
action  which  is  reflex  in  character  and  independent  of  voluntary  control. 
Section  of  the  pneumogastric  nerves  destroys  at  once  sensibility  and 
motive  power  in  the  whole  of  the  oesophagus,  and  thus  interferes  with 
complete  deglutition. 

There  is  no  doubt  that  the  sensitive  nerves  of  the  cesophageal  mucous 


THE    PNKUMOGASTRIO.  567 

membrane  take  their  shun'  in  exciting  tlui  action  of  its  muscular  coat. 
The  general  sensibility  of  this  canal,  however,  is  very  slight,  as  coin- 
pared  with  the  parts  above,  and  is  not  usually  sntlicient  to  cause  a 
perceptible  impression  from  the  food  in  the  a.ct  of  swallowing.  Its 
muscular  contraction  takes  place,  as  a  general  rule,  without  any  ell'ect 
on  the  consciousness;  and  it  is  only  when  the  food  is  very  cold  or  very 
hot,  or  when  it  contains  pungent  or  irritating  ingredients,  that  it8 
passage  through  the  (esophagus  produces  a  distinct  sensation. 

Jt  appears  that  the  filaments  of  the  superior  laryngeal  nerve,  dis- 
tributed about  the  anterior  surface  of  the  epiglottis  and  borders  of  the 
larynx,  take  an  active  part  in  exciting  the  movements  of  deglutition. 
In  the  experiments  of  Waller  and  I'revost  on  dogs  and  cats,  galvaniza- 
tion of  the  superior  laryngeal  nerve  produced,  in  many  repeated  trials, 
rhythmical  movements  of  deglutition,  consisting  of  contraction  of  the 
pharynx  and  elevation  of  the  larynx,  followed  by  peristalt  ic  motion  of 
the  whole  length  of  the  oesophagus.  All  the  sensitive  fibres  of  the 
pneumogMsl.ric,  therefore,  distributed  to  the  parts  concerned  in  the  net 
of  swallowing,  undoubtedly  assist  in  exciting  the  necessary  muscular 
contractions, 

1'ntlccfion  of  Ike  Glottis  in  the  act  of  Deglutition. —  As  the  larynx 
communicates,  by  its  superior  orifice,  directly  with  the  cavity  of  the  pha- 
rynx, and  as  all  solids  and  liquids,  in  the  act  of  swallowing,  necessarily 
pass  over  its  surface,  portions  of  the  food  would  be  constantly  liable  to 
find  their  way  through  the  rima  glottidis  into  the  respiratory  passages, 
unless  then'  were  some  provision  against  it.  The  epiglottis,  which 
stands  in  front  of  the  glottis  ill  a  nearly  upright  position,  and  which 
shuts  down  over  its  orifice  like  a  cover  when  the  base  of  the  tongue  is 
drawn  back  at  the  time  of  deglutition,  might  seem  to  be  adapted  to 
secure  protection  in  this  respect 

Kxperienee  shows,  however,  that  the  epiglottis  is  not  essential  for 
the  safety  of  the  glottis  in  deglutition.  The  entire  organ  may  be  cut 
off  in  dogs,  as  we  have  verified  by  repeated  experiments,  without  any  dif- 
ficulty being  afterward  exhibited  by  the  animal  in  swallowing  either 
liquid  or  solid  food.  The  epiglottis,  furthermore,  is  an  organ  which 
exists  only  in  mammalians,  being  absent,  in  all  the  remaining  classes  of 
vertebrate  animals.  In  birds  especially,  the  orifice  of  the  glottis  can  IK; 
readily  seen  on  opening  the  beak,  unprotected  by  anything  similar  to 
an  epiglottis,  and  performing  the  alternate  movements  of  expansion 
and  collapse  connected  with  respiration.  Finally,  the  existence  of  the 
epiglottis  in  man  does  not  prevent  foreign  substances  from  passing  into 
the  glottis  whenever  the  other  conditions  of  normal  deglutition  are  sus- 
pended or  dist  urbed.  The  protection  of  the  glottis  against  the  entrance 
of  solid  or  liquid  food  does  not  depend  upon  a  mechanical  obstacle,  but 
upon  a  definite  association  of  nervous  acts. 

The  first  requisite  for  the  act,  of  swallowing  is  the  sunjHtnuion  of  respi- 
ration. This  takes  place,  at  the  beginning  of  deglutition,  by  a  nervous 
influence  which  it  is  difficult  to  describe,  but  which  may  be  designated 


568  THE    CRANIAL    NERVES. 

as  an  "action  of  arrest."  The  same  nervous  impression  which  excites 
by  reflex  action  the  constrictors  of  the  pharynx,  suspends  for  a  time 
the  movements  of  inspiration.  This  effect  is  very  perceptible  in  the 
ordinary  act  of  swallowing,  and  was  witnessed  by  Waller  and  Prevost  in 
many  of  their  experiments  on  this  subject ;  galvanization  of  the  central 
extremity  of  the  superior  laryngeal  nerve  causing  immediate  relaxation 
of  the  diaphragm,  with  stoppage  of  its  movements. 

The  effect  of  the  arrest  of  breathing  upon  the  glottis  is  to  prevent  the 
customary  opening  of  its  orifice  at  the  time  of  inspiration.  As  the  res- 
piratory movements  of  the  glottis  are  coincident  with  those  of  the  chest, 
and  are  excited  and  maintained  by  the  same  nervous  influence,  the 
impression  which  puts  a  stop  to  one  suspends  the  other  also.  The  glot- 
tis consequently,  not  being  opened  at  the  time  the  food  enters  the 
pharynx,  its  liability  to  admit  any  portion  of  the  alimentary  mass  is 
much  diminished  by  the  mere  fact  of  its  passive  condition.  But  this 
condition  furthermore  allows  the  rima  glottidis  to  be  completely  closed 
by  the  contraction  of  the  inferior  constrictor  of  the  pharynx,  the  most 
active  muscle  in  the  apparatus  of  deglutition ;  since  the  fibres  of  this 
muscle  are  attached  laterally  to  the  external  surface  and  free  borders 
of  the  thyroid  cartilage,  and  thus  compress  the  larynx  on  both  sides  at 
the  moment  the  food  is  carried  downward  by  their  contraction.  It  is 
by  this  means  alone  that  the  glottis  is  protected  in  birds  and  in  other 
animals  where  the  epiglottis  is  wanting,  and  it  is  also  the  essential  part 
of  the  same  process  in  man  and  in  mammalians. 

The  accident  in  which  food  or  foreign  substances  sometimes  gain 
access  to  the  larynx  is  always  produced  by  a  sudden  attempt  at  in- 
spiration. This,  which  cannot  take  place  during  deglutition  in  the 
ordinary  condition  of  the  nervous  system,  may  nevertheless  be  produced 
in  many  instances  by  an  unexpected  shock  or  excitement,  which  disturbs 
momentarily  the  harmonious  -co-ordination  of  the  reflex  actions.  Any 
sudden  impression  produces  in  general,  as  its  first  effect,  a  spasmodic 
movement  of  inspiration ;  and  if  this  take  place  while  food  is  contained 
in  the  pharynx,  a  portion  of  it  almost  necessarily  passes  in,  together 
with  the  current  of  air,  through  the  widely  open  orifice  of  the  glottis. 

Connection  with  the  Stomach  and  Stomach  Digestion. — The  effect 
produced  upon  the  stomach  and  digestion  by  division  of  the  pneumo- 
gastric  nerve  shows  that  its  influence  upon  this  organ  is  in  the  main 
similar  to  that  which  it  exerts  on  the  oesophagus ;  that  is,  it  confers  on 
its  mucous  membrane  a  certain  sensibility  to  the  presence  of  food,  and 
provides  for  the  peristaltic  action  of  its  muscular  coat.  After  experi- 
mental section  of  both  pneumogastric  nerves  in  the  region  of  the  neck, 
the  sensations  of  hunger  and  thirst  remain  ;  the  animals  often  exhibiting 
a  desire  for  food  and  drink,  and  sometimes  taking  it  in  considerable 
quantity,  although  little,  if  any,  reaches  the  stomach,  owing  to  the 
paralysis  of  the  muscular  walls  of  the  oesophagus.  In  the  experiments 
of  Bernard  on  dogs,  the  secretion  of  gastric  juice  was  suspended  after 
this  operation,  and  food  introduced  into  the  stomach  through  a  gastric 


THE    PNEUMOGASTRIC.  569 

fistula  remained  undigested.  But  Longet  has  found  that  if  food  be 
introduced  under  these  circumstances  in  small  quantity,  it  may  cause 
the  secretion  of  gastric  juice,  and  may  be  finally  digested  and  absorbed* 
These  results  indicate  that  the  functions  of  secretion  and  digestion  in 
the  stomach  are  not  immediately  under  the  control  of  the  pneumogastric 
nerve,  but  that  they  become  deranged  after  its  section  and  practically 
suspended,  owing  to  the  indirect  influence  of  other  causes. 

On  the  other  hand,  the  muscular  contractions  of  the  organ  and  the 
sensibility  of  its  mucous  membrane  are  both  directly  abolished  by 
division  of  the  pneumogastrics.  According  to  the  observations  of 
Bernard,  the  finger,  introduced  into  the  cavity  of  the  stomach  through 
a  gastric  fistula  in  the  dog,  is  compressed  with  considerable  force  by 
the  walls  of  the  organ ;  but  this  pressure  disappears  completely  if  the 
pneumogastric  nerves  be  divided.  The  absence  of  muscular  power  in 
the  paralyzed  stomach  is  of  itself  sufficient  to  account  for  the  failure 
of  digestion  when  the  influence  of  these  nerves  has  been  cut  off.  The 
peristaltic  action  of  the  organ  is  essential  to  the  digestive  process,  in 
order  to  bring  successive  portions  of  the  food  in  contact  with  its  mu- 
cous membrane1,  and  to  cause  the  intimate  admixture  of  the  gastric 
juice  with  all  parts  of  the  alimentary  mass.  The  natural  movement 
and  agitation  of  the  food,  by  the  action  of  the  muscular  coat,  is  no 
doubt,  also,  an  important  stimulus  to  the  continued  secretion  of  the 
gastric  juice ;  and  when  it  no  longer  takes  place,  the  digestive  fluid  will 
necessarily  be  supplied  in  smaller  quantity.  It  is  evident,  therefore, 
that  the  pneumogastric  nerves  supply  to  the  walls  of  the  stomach  a 
certain  amount  of  sensibility  and  a  motor  power,  which  are  practically 
essential  to  the  process  of  digestion. 

Influence  on  the  Action  of  the  Heart. — The  pneumogastric  nerve,  as 
already  shown,  gives  off  a  number  of  filaments  which  are  destined  for 
the  cardiac  plexus,  and  ultimately  for  distribution  in  the  substance  of 
the  heart.  One  or  two  of  these  filaments  come  from  the  superior 
laryngeal  branch  of  the  pneumogastric,  and  immediately  join  the  upper 
cardiac  nerve  derived  from  the  superior  cervical  ganglion  of  the  sympa- 
thetic. Several  others  are  furnished  by  the  main  trunk  of  the  pneumo- 
gastric in  the  neck,  which  inosculate  with  each  other  and  with  the  con- 
tinuation of  the  upper  cardiac  nerve.  The  inferior  laryngeal  branch,  in 
its  reascending  course  through  the  lower  part  of  the  neck,  supplies  so 
many  inosculating  filaments  to  the  same  plexus  of  cardiac  nerves  that, 
according  to  Cruveilhier,  it  appears  in  some  instances  to  be  distributed 
in  almost  equal  proportions  to  the  larynx  and  to  the  keart.  Finally 
other  small  branches  are  supplied  by  the  pneumogastric  in  the  cavity 
of  the  chest,  which  lose  themselves  at  once  in  the  cardiac  plexus  proper, 
beneath  the  arch  of  the  aorta.  All  the  filaments,  accordingly,  which 
are  finally  distributed  to  the  heart  through  the  cardiac  plexus,  originate 
from  the  sympathetic  and  the  pneumogastric  nerves;  and  the  entire 
group  is  characterized  by  the  frequent  and  intimate  admixture  of  the 
fibres  derived  from  these  two  sources.  A  considerable  proportion  of 
37- 


570  THE    CRANIAL    NERVES. 

the  cardiac  filaments  are,  therefore,  made  up  of  fibres  originally  belong- 
ing to  the  pneumogastric  nerve. 

The  effect  produced  upon  the  heart's  action  by  irritating  the  pneumo- 
gastric in  the  region  of  the  neck  is  precisely  the  opposite  to  that  usually 
caused  by  irritating  the  nerves  going  to  a  muscular  organ.  This  effect 
may  be  seen  by  opening  the  chest,  and  exposing  the  heart  to  view,  at  the 
same  time  that  the  pneumogastric  nerves  are  separated  from  their  con- 
nections in  the  neck  for  a  sufficient  distance  to  apply  to  them  the  poles 
of  a  galvano-electric  apparatus.  In  the  cold-blooded  animals,  as  the 
frog  or  the  turtle,  no  other  precaution  is  required;  in  the  dog  and 
other  warm-blooded  species,  artificial  respiration  must  be  maintained 
by  the  nozzle  of  a  bellows  inserted  in  the  trachea. 

When  a  galvano-electric  current  of  moderate  strength  is  applied  to 
the  pneumogastric  nerves  prepared  in  this  way,  the  cardiac  pulsations 
are  reduced  in  frequency ;  and  if  the  current  be  increased  in  strength, 
the  heart's  action  stops  altogether,  and  remains  suspended  so  long  as 
the  stimulus  continues  to  be  applied  to  the  nerve.  When  the  galvani- 
zation ceases,  the  cardiac  pulsations  recommence ;  and  the  same  thing 
may  be  repeated  for  an  indefinite  number  of  successive  trials. 

There  are  two  important  facts  to  be  noted  in  regard  to  these  effects 
of  irritating  the  pneumogastric : 

1.  When  the  heart  ceases  its  movements  under  the  galvanization  of 
the  nerves,  its  walls  are  not  in  a  contracted  condition,  but  in  a  state  of 
relaxation.    Neither  are  its  cavities  distended  with  blood  ;  but  the  organ 
simply  remains  quiescent,  lying  at  rest  without  any  indication  of  mus- 
cular activity. 

2.  If  the  pneumogastric  nerves  be  divided  at  their  point  of  exposure 
in  the  middle  of  the  neck,  and  if  the  central  extremities  be  galvanized, 
no  effect  is  produced  upon  the  heart.     But  if  the  stimulus  be  applied  to 
their  peripheral  extremities,  the  above  phenomena  are  reproduced,  the 
heart  remaining  flaccid  so  long  as  the  galvanization  is  continued.     The 
effect  in  question,  therefore,  is  not  due  to  reflex  action,  but  to  a  direct 
influence  convej^ed  through  the  pneumogastric  filaments  to  the  muscu- 
lar substance  of  the  heart.     This  conclusion  is  fully  confirmed  by  the 
fact  that  a  similar  retardation  or  stoppage  of  the  cardiac  pulsations  is 
caused  in  frogs  and  turtles  by  galvanization  of  the  medulla  oblongata 
itself,  the  pneumogastric  nerves  remaining  entire  ;  but  if  the  nerves  be 
previously  divided,  no  such  effect  is  produced.     On  the  other  hand, 
division   of  the   pneumogastric  nerves,  or  sudden  destruction  of  the 
medulla  oblongata,  causes  increased  rapidity  of  the  cardiac  pulsations. 
Section  of  these  nerves,  accordingly,  in  the  warm-blooded  animals,  pro- 
duces opposite  effects  upon  the    respiration  and  the  pulse,  one  being 
accelerated   and   the   other   retarded.      According   to    Bernard,  these 
effects,  though  opposite  in  direction,  are  produced  in  similar  propor- 
tions ;  so  that,  if  the  respirations  are  diminished  one-half,  the  cardiac 
pulsations  are  increased  to  double  their  former  frequency.     Thus  when 
the  influence  of  the  pneumogastric  nerve  is  cut  off,  the  motions  of  the 


THE    SPINAL    ACCESSORY.  571 

heart  increase  in  rapidity,  when  it   is  stimulated,  they  experience  a 
retardation. 

This  influence,  exerted  upon  the  heart  by  the  pneumogastric  nerve,  is 
of  the  peculiar  kind  known  as  the  "action  of  arrest."  Such  a  power 
certainly  exists  in  the  nervous  system,  though  its  nature  is  not  easy 
of  explanation.  An  instance  of  it  has  already  been  given  in  the  fact, 
observed  b}"  Waller  and  Prevost,  of  suspension  of  the  movements  of 
the  diaphragm  by  galvanizing  the  trunk  of  the  superior  laryngeal  nerve. 
The  natural  stoppage  of  respiration  in  the  act  of  swallowing,  and  the 
relaxation  of  the  sphincters  preliminary  to  the  evacuation  of  the  rectum 
and  the  bladder,  are  effected  by  nervous  influences  of  a  similar  kind. 
There  are  evidently  nervous  fibres  which  transmit  their  stimulus  di- 
rectly to  the  muscles,  and  which,  in  this  respect,  belong  to  the  category 
of  motor  nerves ;  but  which,  when  called  into  activity,  instead  of  ex- 
citing muscular  contraction,  serve  to  moderate  or  even  suspend  it.  The 
most  palpable  instance  of  this  mode  of  action  is  that  of  the  pneumogas- 
tric nerves  in  their  relation  with  the  heart ;  but  there  is  evidence  that 
it  occurs,  in  a  more  obscure  manner,  in  various  other  parts  of  the 
nervous  system. 

Eleventh  Pair.    The  Spinal  Accessory. 

This  nerve,  which  has  received  its  name  from  the  singularity  of  its 
origin  and  subsequent  course,  consists  of  filaments  which  emerge  from 
the  side  of  the  cervical  portion  of  the  spinal  cord,  from  the  level  of  the 
fourth  or  fifth  cervical  nerve  upward  (Fig.  179,4).  These  filaments 
unite  into  a  slender,  rounded  cord,  which  ascends  in  a  vertical  direction 
between  the  anterior  and  posterior  roots  of  the  cervical  spinal  nerves, 
gradually  increasing  in  size  from  the  addition  of  new  root  fibres  from 
the  spinal  cord,  to  the  level  of  the  foramen  magnum,  where  it  enters  the 
cranial  cavity.  Here  it  receives  a  new  supply  of  accessory  root  fibres 
from  the  side  of  the  medulla  oblongata,  which  emerge  in  a  continuous 
line  with  those  of  the  pneumogastric  nerve.  The  nerve  trunk,  thus  con- 
stituted by  the  union  of  its  spinal  and  its  medullary  roots,  joins  the 
pneumogastric  and  glossopharyngeal  nerves  in  their  passage  through 
the  jugular  foramen. 

The  central  origin  of  the  root  fibres  of  this  nerve  is  a  collection  of 
nerve  cells  situated  in  the  upper  portion  of  the  spinal  cord  and  the  com- 
mencement of  the  medulla  oblongata,  on  the  outer  and  posterior  aspect  of 
the  anterior  horn  of  gray  matter.  In  the  remainder  of  the  medulla,  this 
nucleus  is  situated  farther  backward,  receding  from  front  to  rear  with 
the  rest  of  the  gray  matter  in  this  part  of  the  nervous  centres.  At  its 
anterior  extremity,  it  becomes  continuous  with  the  nucleus  of  the  pneu- 
mogastric. From  the  gray  matter  of  its  nucleus,  the  fibres  of  the  spinal 
accessory  nerve  curve  downward  and  outward  until  they  emerge,  as 
above  mentioned,  in  a  series  of  bundles,  from  the  lateral  surface  of  the 
medulla. 

While  passing  through  the   foramen  lacerum,  the   spinal  accessory 


572  THE    CRANIAL    NERVES. 

becomes  adherent  externally  to  the  jugular  ganglion  of  the  pneumogas- 
tric,  but  without  taking  any  part  in  its  formation,  except  by  furnishing 
one  or  two  small  filaments  of  communication.  Immediately  upon  its 
exit  from  the  foramen  it  divides  into  two  main  branches;  namely,  1st, 
the  internal,  or  anastomotic  branch,  which  joins  the  trunk  of  the  pneu- 
mogastric  and  becomes  more  or  less  intimately  blended  with  it,  and 
2dly,  the  external,  or  muscular  branch,  which  passes  downward  and 
outward  and  is  distributed  to  the  sterno-mastoid  and  trapezius  muscles. 
According  to  many  different  observers  (Bernard,  Cruveilhier,  Henle, 
Longet)  the  internal  or  anastomotic  branch  is  made  up  of  nerve  fibres 
coming  from  the  medulla  oblongata ;  the  external  or  muscular  branch 
consists  of  those  originating  from  the  spinal  cord. 

The  spinal  accessory  is  without  question  a  motor  nerve.  According 
to  the  experiments  of  Longet  on  dogs,  its  mechanical  irritation  in  the 
cranial  cavity  does  not  give  rise  to  signs  of  pain,  and  although  Bernard 
found  evidences  of  sensibility  on  galvanizing  the  uninjured  nerve  in 
the  same  situation,  if  it  were  divided  and  the  irritation  applied  to  its 
central  extremity  no  indications  of  sensibility  were  manifest.  On  the 
other  hand  its  fibres  may  be  traced  in  great  part  directly  to  their  termi- 
nation in  muscular  tissues,  and  its  division  or  evulsion  induces  effects 
which  consist  exclusively  in  loss  of  motive  power. 

The  most  complete  method  of  experimenting  upon  the  effects  pro- 
duced by  destruction  of  this  nerve  is  that  first  adopted  by  Bernard, 
namely,  its  evulsion,  For  this  purpose,  the  muscular  branch  of  the 
nerve  is  followed  by  dissection  from  without  to  its  point  of  emergence 
from  the  jugular  canal,  where  it  separates  from  the  anastomotic  branch. 
The  combined  trunk  is  then  seized  between  the  blades  of  a  forceps,  and 
by  a  steady  and  continuous  traction  the  whole  of  the  nerve,  witli  both 
its  medullary  and  spinal  roots,  may  be  separated  from  their  central 
attachments  and  extracted  entire.  By  appropriate  variations  of  the  pro- 
cedure, either  the  medullary  portion  with  the  anastomatic  branch,  or  the 
cervical  portion  with  the  external  branch,  may  be  taken  away  separately, 
and  the  comparative  effects  of  the  two  operations  observed.  But  when 
the  entire  trunk  is  extracted  as  above,  the  source  of  the  fibres  destined 
both  for  anastomosis  with  the  pneumogastric,  and  for  the  muscular 
branch  of  the  nerve,  is  destroyed  at  the  same  time. 

The  most  striking  effects  of  this  operation  are  due  to  paralysis  of  the 
internal  or  anastomotic  branch.  It  is  this  branch  which  supplies  to  the 
pneumogastric  nerve  a  large  share  of  its  motor  fibres ;  and  those  espe- 
cially which  form  the  pharyngeal  branch  of  the  pneumogastric  nerve,  are 
shown  by  dissection  to  be  derived  from  the  anastomotic  branch  of  the 
spinal  accessory.  According  to  Cruveilhier,  the  pharyngeal  filament  is 
sometimes  given  off  exclusively  from  the  anastomotic  branch  of  the 
spinal  accessory,  sometimes  partly  from  this  branch  and  partly  from  the 
pneumogastric  itself.  Beyond  the  pharyngeal  branch,  the  fibres  of  the 
pneumogastric  nerve  derived  from  the  spinal  accessory  can  no  longer 
be  followed  with  certainty  by  means  of  dissection  ;  but  the  results  of 


THE    SPINAL    ACCESSORY.  573 

experiment  show  that  they  are  finally  distributed,  through  the  inferior 
laryngeal  branch,  to  the  muscles  of  the  larynx,  where  they  preside  over 
its  actions  as  a  vocal  organ. 

After  the  spinal  accessory  nerve  has  been  torn  away  on  both  sides  in 
the  manner  above  described,  the  most  noticeable  result  is  a  loss  of 
power  to  produce  vocal  sounds.  The  other  movements  of  the  larynx 
are  not  interfered  with.  Especially  those  of  respiration  go  on  in  a  natu- 
ral manner.  But  the  voice  is  completely  lost,  as  much  so  as  if  the  infe- 
rior laryngeal  nerves,  or  the  pneumogastric  trunks  themselves,  had  been 
divided.  The  difference  between  the  two  cases,  however,  is  very  impor- 
tant. Section  of  the  pneumogastrics,  or  of  their  inferior  laryngeal 
branches,  paralyzes  at  once  all  the  movements  of  the  glottis,  those  of 
respiration  as  well  as  those  of  phonation ;  since  these  nerves  contain  all 
the  motor  fibres  distributed  to  the  larynx,  except  those  of  the  crico-thy- 
roid  muscles.  On  the  other  hand,  section  or  evulsion  of  the  spinal 
accessory  nerves  paralyzes  the  movements  of  phonation  alone,  namely, 
those  in  which  the  vocal  chords  are  approximated  and  the  rima  glottidis 
narrowed,  while  it  leaves  untouched  the  movements  of  respiration,  in 
which  the  vocal  chords  are  separated  and  the  rima  glottidis  opened. 

Thus  the  muscular  apparatus  of  the  lar}7nx,  which  is  destined  to  per- 
form separately  two  distinct  functions,  is  supplied  with  motor  nerves 
from  two  different  sources.  Those  which  preside  over  the  production 
of  vocal  sounds  originate  exclusively  from  the  spinal  accessory ;  those 
which  excite  the  movements  of  respiration  are  derived  from  the  other 
motor  nerves  (facial,  hypoglossal,  cervical)  which  also  inosculate  with 
the  pneumogastrics. 

The  special  function  of  the  external  or  muscular  branch  of  the  spinal 
accessory  nerve  is  not  so  fully  understood.  The  stern o-mastoid  and 
trapezius  muscles,  to  which  its  fibres  are  distributed,  also  receive  fila- 
ments from  the  cervical  spinal  nerves ;  and  they  still  retain  the  power 
of  motion  after  division  or  evulsion  of  the  spinal  accessory  on  both 
sides.  The  sterno-mastoid  and  trapezius  muscles  have  no  such  peculiar 
and  easily  recognizable  mode  of  action  as  that  of  the  larynx  in  the  for- 
mation of  the  voice  ;  and  consequently  it  has  not  been  easy  to  distin- 
guish with  certainty  what  special  movement  of  these  muscles  is  para- 
lyzed by  division  of  the  spinal  accessory,  and  what  remains  unaffected. 
The  most  plausible  conclusions  are  those  derived  by  Bernard  from 
continued  observation  of  animals  preserved  for  some  time  after  the 
division  of  these  nerves. 

According  to  this  explanation,  the  fibres  of  the  external  branch  of 
the  spinal  accessory,  like  th6se  of  the  internal  branch,  perform  a  func- 
tion which  is  antagonistic  to  the  movements  of  respiration.  Respira- 
tion is  naturally  suspended  in  all  steady  and  prolonged  muscular  efforts. 
In  the  acts  of  straining,  lifting,  pushing,  and  the  like,  respiration  ceases, 
the  spinal  column  is  made  rigid,  and  the  head  and  neck  are  placed  in  a 
fixed  position  largely  by  the  aid  of  the  sterno-mastoid  and  trapezius 


574:  THE    CRANIAL    NERVES. 

muscles.  Such  efforts  cannot  be  made  with  success  if  the  muscles  in 
question  are  paralyzed.  In  the  lower  animals,  according  to  the  obser- 
vations of  Bernard,  they  also  take  part  in  the  production  of  a  cry,  or 
prolonged  vocal  sound.  If  the  entire  spinal  accessory  be  destroyed,  as 
already  shown,  the  voice  is  completely  abolished  by  loss  of  power  in 
the  laryngeal  muscles.  If  the  external  branch  alone  be  divided,  the 
animal  can  still  produce  a  sound  in  the  larynx ;  but  this  sound  cannot 
be  prolonged  into  a  cry,  and  the  voice  is  confined  in  duration  to  the 
ordinary  length  of  an  expiratory  movement.  Although  the  animals, 
furthermore,  are  not  apparently  inconvenienced  by  this  operation  so 
long  as  they  remain  quiet,  any  increased  exertion,  as  in  running  or 
leaping,  causes  a  want  of  harmony  between  the  movements  of  respira- 
tion and  those  of  the  limbs,  which  results  in  unusual  shortness  of 
breath. 

The  sterno-mastoid  and  trapezius  muscles,  like  those  of  the  larynx, 
are  therefore  animated  by  two  sets  of  motor  nerve  fibres.  One  set, 
coming  from  the  cervical  spinal  nerves,  provides  for  all  the  movements 
connected  with  ordinary  changes  of  attitude  and  locomotion ;  the 
others,  derived  from  the  spinal  accessory,  supply  the  requisite  stimulus 
for  continuous  muscular  exertion,  or  for  a  prolonged  vocal  sound. 

Twelfth  Pair.    The  Hypoglossal. 

The  hypoglossal  nerve,  the  motor  nerve  of  the  tongue,  emerges  from 
the  anterior  part  of  the  medulla  oblongata  by  a  linear  series  of  ten  or 
twelve  slender  filaments  in  the  furrow  between  the  outer  edge  of  the 
anterior  pyramids  and  the  rounded  'projection  of  the  olivary  bodies 
(Fig.  179,5).  The  vertical  line  along  which  these  filaments  make  their 
appearance  corresponds  exactly  with  the  line  of  origin  of  the  anterior 
roots  of  the  cervical  spinal  nerves  below ;  and  the  whole  external  aspect 
of  their  anatomical  relations  resembles  that  of  a  motor  nerve  root. 

The  central  origin  of  the  hypoglossal  root  fibres,  according  to 
Clarke,  Dean,  Kolliker,  Henle,  and  Meynert,  is  a  nucleus  of  gray  matter 
situated  at  the  posterior  part  of  the  medulla  oblongata  next  the  median 
line,  at  the  inferior  extremity  of  the  fourth  ventricle.  This  collection  of 
gray  matter  has  an  elongated,  irregularly  cylindrical  form,  extending 
longitudinally  from  about  the  level  of  the  divergence  of  the  posterior 
columns  upward  and  forward  to  that  of  the  auditory  nucleus.  It  is, 
therefore,  parallel  in  its  position  with  the  spinal  accessory  and  pneumo- 
gastric  nuclei,  but  situated  between  them  and  the  median  line.  In 
transverse  sections  of  the  medulla,  made  successively  from  below  up- 
ward, this  nucleus  is  first  seen  (Fig.  180)  to  be  placed  immediately 
about  the  central  canal,  which  is  already  approaching  the  posterior  sur- 
face of  the  medulla ;  and  the  roots  of  the  nerve  run  in  a  curvilinear 
course  downward  and  outward  to  their  point  of  emergence. 

Above  this  point,  after  the  central  canal  has  opened  into  the  cavity 
of  the  fourth  ventricle  (Fig.  181),  the  hypologlossal  nucleus  has  itself 
receded  quite  to  the  posterior  surface  of  the  medulla,  where  it  occupies 


THE    HYPOGLOSSAL. 


575 


upon  the  floor  of  the  fourth  ventricle,  on  each  side  of  the  median  line, 
the  longitudinal  eminence  known  as  the  "  fasciculus  teres."  Its  root 
fibres  thence  run  downward  through  the  whole  thickness  of  the  medulla 


180. 


*** 


Xli 


TRANSVERSE  SECTION  OP  THE  HUMAN  MEDULLA  OBLONG  ATA,  just  belowthe 
divergence  of  the  posterior  columns,  and  through  the  inferior  extremity  of  the  olivary 
nucleus.— Cc.  Central  canal.  R.  Raphe.  No.  Olivary  nucleus.  Nh.  Nucleus  of  the  hypo- 
glossal  nerve.  XII'.  Hypoglossal  nerve  roots.  Magnified  8  diameters.  (Henle.) 

at  this  part,  passing  for  some  distance  in  a  nearly  vertical  plane,  and 
then  curving  outward,  to  reach  the  furrow  between  the  olivary  bodies 
and  the  anterior  pyramids,  where  they  emerge. 

During  the  passage  of  the  hypoglossal  nerve  roots  through  the  medulla 
oblongata,  they  pass  along  the  surface  of  the  olivary  nucleus,  between  it 
and  the  anterior  pyramid,  and  in  great  measure  between  the  folds  or 
even  through  the  substance  of  its  convoluted  wall.  It  is  shown  by 
Dean1  that  although  a  direct  continuity  cannot  be  made  out  between 
the  root  fibres  of  the  nerve  and  the  stellate  cells  of  the  olivary  nucleus, 
yet  prolongations  of  the  cells  can  sometimes  be  traced  for  a  consider- 

1  Gray  Substance  of  the  Medulla  Oblonsrata  and  Trapezium.  Washing-ton, 
1864,  p.  36. 


576 


THE    CRANIAL    NERVES. 


able  distance  upward  and  inward,  in  company  with  the  nerve  roots,  to- 
ward the  hypoglossal  nucleus ;  and  in  the  sheep,  the  tracts  of  fibres  con- 
necting the  two  nuclei  are  very  evident.  According  to  Henle,  in  some 


No 


xn 


TRANSVERSE  SECTION  OF  THE  HUMAN  MEDULLA  OBLONGATA,  through  the 
middle  of  the  hypoglossal  nucleus  and  the  olivary  body. — No.  Olivary  nucleus.  R.  Raphe 
Ngl.  Nucleus  of  the  glossopharyngeal  nerve.  Nv.  Nucleus  of  the  pneumogastric  nerve. 
Nh.  Nucleus  of  the  hypoglossal  nerve.  IX.  Glossopharnygeal  nerve  roots.  XII.  Hypoglossal 
nerve  roots.  Magnified  8  diameters.  (Henle.) 

transverse  sections  through  the  hilum,  or  opening  of  the  olivary  body 
(Fig.  182),  fibres  from  the  hypoglossal  nerve  roots  may  be  seen  bending 
round  the  inner  border  of  the  nucleus  into  its  interior ;  while  other  fibres 
emerge  in  a  corresponding  manner  from  the  opposite  edge  of  the  hilum 
and  continue  onward,  with  the  main  root-bundles,  to  the  hypoglossal 
nucleus.  Although  the  details  of  minute  anatomical  structure  in  these 
parts  have  not  been  fully  made  out,  it  is  evident  that  a  close  relation  of 
some  kind  exists  between  the  gray  matter  of  the  olivary  bodies  and  the 
liypoglossal  nucleus  and  roots. 


THE    HYPOGLOSSAL. 


577 


Fig.  182. 


Kolliker  regards  the  roots  of  the  hypoglossal  nerves  as  decussating 
completely  with  each  other  through  the  raphe,  at  the  level  of  the  nuclei. 
According  to  both  Clarke  and 
Dean,  on  the  other  hand,  a 
portion  of  the  fibres  of  each 
root  terminate  in  the  corre- 
sponding nucleus,  while  an- 
other portion  bend  inward 
and  cross  the  raphe  at  the 
median  line,  decussating  with 
those  of  the  opposite  side, 
Henle  describes  a  few  thin 
bundles  of  fibres  which  con- 
nect the  roots  of  the  nerve  on 
each  side,  at  their  point  of 
emergence,  with  the  raphe  in 
front  of  the  medulla.  It  is 


certain  that  the   hypoglossal, 
like  the  other  cranial  nerves, 


xn 


TRANSVERSE  SECTION  ov  THE  HTTMA.N 
MEDULLA  OBLONGATA,  through  the  olivary 
nucleus  and  root  of  the  hypoglossal  nerve.— A  p. 
Anterior  pyramid.  XII.  Hypoglossal  nerve  roor. 
Magnified  8  diameters.  (Henle.) 


has,  in  some  way,  a  connec- 
tion with  the  opposite  side  of 
the  brain  ;  since  cases  of  facial 
paralysis  from  cerebral  hemor- 
rhage are  often  accompanied  by  paralysis  of  the  tongue  on  the  same 
side  with  that  of  the  face,  and  on  the  opposite  side  to  that  of  the  lesion. 
One  of  the  genio-hyo-glossal  muscles  having  lost  its  power,  while  the 
other  remains  active,  if  the  patient  attempts  to  protrude  the  tongue  in 
such  cases,  its  point  is  deviated  toward  the  paralyzed  side. 

After  leaving  the  anterior  surface  of  the  medulla  oblorigata  the  fibres 
of  the  hypoglossal  nerve  become  parallel  with  each  other,  and,  passing 
through  the  anterior  condyloid  foramen  of  the  occipital  bone,  emerge 
from  the  skull  in  the  form  of  a  cylindrical  cord.  Immediately  after 
escaping  from  the  condyloid  foramen  it  presents  one  or  two  branches 
of  inosculation  with  the  pneumogastric,  at  the  point  where  it  crosses  the 
track  of  this  nerve.  According  to  Cruveilhier,  the  dissection  of  the  parts, 
after  maceration  in  dilute  nitric  acid,  shows  distinctly  that  this  inoscula- 
tion consists  of  fibres  which  leave  the  hypoglossal  nerve  and  join  those 
of  the  pneumogastric,  running  with  them  in  a  peripheral  direction.  The 
hypoglossal  nerve  then  passes  downward,  nearly  to  the  level  of  the  hyoid 
bone,  where  it  curves  forward,  giving  filaments  to  the  styloglossal  and 
hyoglossal  muscles,  and  to  those  immediately  beneath  the  hyoid  bone; 
after  which  it  turns  upward,  penetrates  the  tongue  from  below,  inoscu- 
lates by  two  or  three  filaments  with  the  lingual  branch  of  the  fifth  pair, 
and  is  finally  distributed  to  all  the  muscles  of  the  substance  of  the 
tongue.  It,  therefore,  animates  not  only  the  lingual  muscles  proper, 
but  also  those  which  draw  the  tongue  backward  and  upward  (stylo- 
glossal),  and  backward  and  downward  (hyoglossal  and  infra-hyoid  mus- 


578  THE    CRANIAL    NERVES. 

cles).  The  trunk  of  the  nerve  also  receives  communicating  filaments 
from  the  first  and  second  cervical  spinal  nerves,  which,  according  to 
Cruveilhier,  are  filaments  of  reenforcement,  accompanying  the  hypo- 
glossal  nerve  toward  its  peripheral  termination. 

Physiological  properties  of  the  Hypoglossal  Nerve. — The  motor  char- 
acter of  the  hypoglossal  nerve  is  easily  established  by  the  results  which 
follow  its  irritation  and  division.  If  the  nerve  be  exposed  in  the  living 
or  recently  killed  animal  at  the  top  of  the  neck,  where  it  runs  parallel 
to  and  a  little  above  the  hyoid  bone,  pinching  or  wounding  its  fibres,  or 
the  application  of  the  galvanic  stimulus,  produces  immediately  convul- 
sive action  of  the  muscles  of  the  tongue.  The  same  effect  follows  if  the 
trunk  of  the  nerve  be  divided  at  this  point,  and  the  irritation  applied  to 
its  peripheral  extremity ;  showing  that  the  contractions  thus  produced 
are  not  due  to  reflex  action,  but  to  a  direct  stimulus  conveyed  through 
the  hypoglossal  nerve  to  the  muscular  fibres.  The  excitability  of  the 
nerve  is  consequently  beyond  question.  Whether  it  possess  also  any 
sensitive  fibres  of  its  own  is  not  so  certain.  Longet  obtained  in  this 
respect  only  negative  results ;  the  division  of  the  filaments  of  origin  of 
the  nerve,  in  his  experiments  on  dogs,  through  the  space  between  the 
occiput  and  the  atlas,  not  producing  perceptible  signs  of  pain.  The 
trunk  of  the  hypoglossal  nerve  outside  the  cranial  cavity,  certainly  pos- 
sesses some  degree  of  sensibility,  according  to  the  testimony  of  nearly  all 
experimenters  ;  but  this  is  regarded  as  derived,  like  that  of  other  motor 
nerves,  from  inosculations  beyond  its  point  of  origin,  especially  from 
those  of  the  first  and  second  cervical  spinal  nerves  near  the  base  of 
the  skull,  and  from  branches  of  the  fifth  pair  near  its  terminal  distri- 
bution. Whatever  sensibility  it  may  possess  is  destined  only  for  the 
muscular  substance  of  the  tongue,  and  not  for  its  mucous  membrane; 
since,  in  the  first  place,  division  of  the  lingual  branch  of  the  fifth  pair 
and  of  the  glossopharyngeal  nerve  destroys  both  tactile  and  gustatory 
sensibility  over  the  whole  surface  of  the  tongue,  though  the  hypoglossal 
be  left  untouched  ;  and  secondly,  according  to  the  experiments  of  Lon- 
get, after  division  of  both  hypoglossal  nerves  in  the  dog  the  surface  of 
the  tongue,  when  touched  with  the  point  of  a  needle,  evinces  its  ordinary 
tactile  sensibility,  the  application  of  bitter  solutions  causes  signs  of  dis- 
gust, and  the  contact  of  foreign  bodies  at  the  base  of  the  organ  excites 
the  action  of  vomiting. 

The  distinct  and  uniform  result  of  section  of  both  hypoglossal  nerves 
is  a  loss  of  muscular  power  in  the  whole  substance  of  the  tongue,  while 
its  tactile  and  gustatory  sensibilities  are  preserved.  In  the  experiments 
of  Panizza,  confirmed  by  those  of  Longet,  the  animals  upon  which  this 
operation  had  been  performed  were  unable  to  move  the  tongue  in  any 
direction,  or  even  to  restore  it  to  its  natural  position  when  it  was  turned 
back,  except  by  hanging  the  head  downward  and  shaking  it,  thus  allow- 
ing the  organ  to  fall  forward  by  its  own  weight,  as  a  helpless  mass.  In 
the  movements  of  the  jaws,  which  were  not  interfered  with,  the  tongue 


THE    HYPOGLOSSAL.  579 

was  liable  to  be  caught  between  the  teeth  and  wounded  ;  an  accident 
which  evidently  caused  suffering  to  the  animal,  thus  showing  the  con- 
tinued sensibility  of  the  paralyzed  organ. 

Connection  of  the  Hypoglossal  Nerve  with  Mastication  and  Degluti- 
tion.— Although  the  movements  of  the  tongue  do  not  take  a  direct  part 
in  mastication,  they  are  yet  of  essential  importance  to  its  accomplish- 
ment, by  bringing  successive  portions  of  the  food  between  the  teeth  and 
removing  those  which  have  already  undergone  tritu  ration.  In  species 
where  liquids  are  introduced  into  the  mouth  by  the  act  of  lapping,  this 
movement  becomes  also  impossible  after  section  of  the  hypoglossal 
nerves ;  and  both  liquid  and  solid  food,  the  latter  already  reduced  to  a 
pulp,  must  be  introduced  far  backward  into  the  fauces  in  order  to  allow 
of  their  deglutition.  The  natural  action  of  the  lingual  muscles  is  prac- 
tically of  so  much  importance  that,  according  to  Longet,  it  requires  a 
great  expenditure  of  time  and  patience,  in  animals  with  paralysis  of  the 
tongue  from  division  of  the  hypoglossal  nerves,  to  supply  them  with 
sufficient  nourishment  for  the  support  of  life. 

Connection  of  the  Hypoglossal  Nerve  with  Articulation. — In  man, 
another  important  function  is  performed  by  the  tongue  as  a  muscular 
organ,  namely,  that  of  articulation.  As  the  lingual  muscles  take  an 
important  part  in  the  pronunciation  of  all  the  consonants  except  the 
labials  (6,  ?n,  p}  and  the  labio-dentals  (/,  v),  as  well  as  in  that  of  the 
vowels  a,  e,  t,  and  y,  their  paralysis  will  necessarily  produce  a  nearly 
complete  incapacity  of  articulation.  In  man,  disease  or  injury  of  the 
hypoglossal  nerve  alone  is  a  rare  occurrence,  and  is  almost  invariably 
confined  to  one  side.  In  the  glosso-labio-laryngeal  paralysis,  described 
in  connection  with  the  functions  of  the  medulla  oblongata  (p.  510),  the 
disease  is  of  central  origin,  and  affects,  in  various  proportions,  other 
muscles  as  well  as  those  of  the  tongue.  Here,  however,  according  to 
Hammond,  the  earliest  signs  of  imperfect  action  show  themselves  in  the 
lingual  muscles,  and  when  the  disease  is  fully  developed  the  tongue 
becomes  completely  paralyzed,  and  all  power  of  articulation  is  lost. 

The  hypoglossal  nerve,  accordingly,  though  one  of  the  simplest  of 
the  cranial  nerves  in  the  nature  of  its  physiological  endowments,  is 
essential  for  the  expression  of  ideas  by  articulate  language,  and  is  also 
important  as  an  aid  in  the  mastication  and  deglutition  of  the  food. 

General  Arrangement  and  Mode  of  Origin  of  the  Cranial  Nerves 

Notwithstanding  the  apparent  irregularity  in  source  and  distribution 
of  the  cranial  nerves,  as  compared  with  the  spinal,  an  examination  of 
their  internal  origin  shows  that  they  are  arranged  on  a  definite  plan, 
not  essentially  dissimilar  to  that  of  the  spinal  nerves.  The  difference 
between  them  depends  only  upon  the  changed  position  of  the  gray 
substance  in  the  medulla  oblongata  as  compared  with  that  in  the  spinal 
cord.  When  the  central  canal  of  the  cord  opens  into  the  cavity  of  the 
fourth  ventricle,  just  above  the  point  of  divergence  of  the  posterior 
columns,  the  gray  matter  surrounding  it  becomes  posterior  instead  of 


580 


THE    CRANIAL    NERVES. 


Fig.  183. 


central  in  its  position;  what  corre- 
sponds to  the  posterior  horns  of 
gray  matter  in  the  cord  spreading 
out  lateral!}',  and  what  corresponds 
to  the  anterior  horns  following  the 
central  canal  as  it  recedes,  and  at 
last  occupying  the  middle  of  the 
floor  of  the  fourth  ventricle,  next  the 
median  line.  All  the  sensitive  and 
motor  cranial  nerves  take  their  origin 
from  this  layer  of  gray  matter,  or  its 
continuation,  from  the  commence- 
ment of  the  fourth  ventricle  to  the 
aqueduct  of  Sylvius  beneath  the  tu- 
bercula  quadrigemina.  The  relations 
of  origin  between  the  motor  and  sen- 
sitive nerve  roots  are  still  preserved. 
In  the  spinal  cord,  the  motor  roots 
originate  from  the  anterior  horns  of 
gray  matter,  the  sensitive  roots  from 
the  posterior  horns.  In  the  medulla 
oblongata  and  tuber  annulare,  the 
nuclei  of  the  motor  cranial  nerves 
form  a  series  near  the  median  line; 
those  of  the  sensitive  nerves  are 
placed  farther  outward.  A  series  of 
sections  of  the  spinal  cord,  medulla 
oblongata,  and  tuber  annulare,  made 
in  succession  from  below  upward, 
show  that  the  collections  of  gray 
matter,  or  nuclei,  in  the  medulla 
oblongata  and  tuber  anuulare,  from 
which  the  different  motor  or  sensitive 
nerves  take  their  origin,  are  not  com- 
pletely disconnected  from  each  other 
any  more  than  the  successive  portions 
of  gray  matter  in  the  spinal  cord; 


I.  Transverse  Section  of  the  Tuber  Annulare,  through  the  lower  border  of  the  pons  Varolii. 
1.  Nucleus  of  the  facial  and  abducens  nerves.     2.  Nucleus  of  the  auditory  nerve.     F.   Facial 
nerve.    Ab.  Abducens  nerve. 

II.  Transverse  section  of  the  medulla  oblonjata,  through  the  middle  of  the  olivary  bodies, 
and  just  above  the  opening  of  the  central  canal.     1.  Hypoglossal  nucleus.     2  Pneumogastric 
nucleus.    H.  Hypoglossal  nerve.     Pn.  Pneumogastric  nerve. 

III.  Transverse  section  of  the  medulla,  through  the  lower  end  of  the  olivary  bodies,  and 
just  below  the  opening  of  the  central  canal.     1.  Hypocrlossal  nucleus.     2.    Pneumogastiic 
nucleus.     H.  Hypoglossal  nerve.     Pn.  Pneumogastric  nerve. 

IV.  Transverse  section  of  the  medulla,  through  the  decussation  of  the  anterior  pyramids. 
Sp.  Spinal  accessory  nerve. 

V.  Transverse  section  of  the  spinal  cord  in  the  dorsal  region,     a,  a.  Anterior  nerve  roots. 
p,  p.  Posterior  nerve  roots. 


THE    CKANIAL    NERVES  581 

but  at  certain  points,  the  gray  substance  takes  on  a  special  degree  of 
development,  and  presents  an  abundant  collection  of  nerve  cells.  These 
collections  are  called  the  "nuclei"  of  the  nerves,  on  account  of  their 
evident  importance  as  points  of  origin  from  which  the  nerve  roots  can 
be  traced  to  their  points  of  emergence  at  the  base  of  the  brain.  The 
foregoing  diagram  shows  the  changes  in  external  form  of  the  cerebro- 
spinal  axis,  and  in  the  position  of  its  gray  matter,  as  examined  at  differ- 
ent levels  in  the  cranium  and  spinal  canal. 


CHAPTEE    VII. 

THE   SYMPATHETIC   SYSTEM. 

THE  sympathetic  system  of  nerves,  when  compared  with  the  cerebro- 
spinal  system,  presents  anatomical  peculiarities  of  arrangement  and 
distribution  so  distinct  and  noticeable,  that  it  is  naturally  regarded  as 
occupying  a  place  by  itself.  The  slender  double  cord  of  its  main  trunk 
extending  throughout  the  great  cavities  of  the  body,  the  number  and 
scattered  position  of  its  ganglia,  which  are  united  with  each  other  only 
by  filaments  of  small  size,  the  frequent  and  plexiform  arrangement  of 
its  branches,  and  the  distribution  of  its  terminal  fibres  to  the  organs 
of  circulation  and  nutrition,  all  form  a  well  marked  group  of  features 
by  which  it  is  easily  recognized.  But  notwithstanding  the  general  im- 
portance of  these  characters,  the  sympathetic  nerves  and  ganglia  do  not 
constitute  a  separate  and  independent  nervous  system.  Neither  the 
minute  structure  of  their  anatomical  elements,  nor  their  external  con- 
nections, are  essentially  different  from  those  of  the  cerebro-spinal  nerves 
and  nervous  centres.  The  sympathetic  trunks  and  branches  contain 
medullated  nerve  fibres  of  the  same  anatomical  character  as  those  of 
the  spinal  cord  and  its  nerves ;  and  its  ganglia  are  provided  with  nerve 
cells  which  send  off  one  or  more  prolongations  in  the  form  of  nerve 
fibres.  The  main  peculiarity  of  intimate  structure  in  the  sympathetic 
nerve  fibres  is  that  they  are,  as  a  rule,  of  small  diameter,  though  not 
smaller  than  the  average  of  those  in  the  cerebro-spinal  nerves.  The 
cells  of  the  sympathetic  are  also  generally  of  comparatively  small  size, 
never,  according  to  Kb'lliker,  equalling  the  largest  of  those  in  the  gray 
substance  of  the  spinal  cord  or  the  brain ;  and  they  are  also  charac- 
terized by  the  frequency  with  which  they  send  out  only  a  single  pro- 
longation, thus  apparently  becoming  a  source  of  new  fibres. 

But,  on  the  other  hand,  the  cerebro-spinal  system  contains  both 
fibres  and  nerve  cells  of  small  as  well  as  large  size.  The  posterior  roots 
of  all  the  spinal  nerves  have  connected  with  them  ganglia  which  are 
similar  in  structure  to  those  of  the  sympathetic  system;  the  fibres 
which  come  from  the  spinal  cord  simply  passing  through  them,  as 
shown  by  the  observations  of  Kolliker,  and  being  joined  by  other  fibres 
originating  from  the  gray  matter  of  the  ganglion  itself.  The  same 
arrangement  exists  in  the  ganglia  of  the  cranial  nerves,  as,  for  instance, 
in  the  Gasserian  ganglion  of  the  fifth  pair.  Thus  all  the  sensitive  and 
mixed  cerebro-spinal  nerves  contain  some  fibres  of  ganglionic  origin,  in 
addition  to  those  derived  directly  from  the  brain  or  spinal  cord. 
Furthermore,  all  the  sympathetic  ganglia  receive  filaments  of  communi- 
(582) 


THE    SYMPATHETIC    SYSTEM.  583 

cation  from  the  cerebro-spinal  nerves,  which,  there  is  every  reason  to 
believe,  consist  of  fibres  coming  from  the  brain  or  spinal  cord,  and  pass- 
ing through  the  ganglion  to  form  part  of  the  peripheral  branches  of  the 
sympathetic  system.  This  conclusion  is  drawn  not  only  from  the  fact 
that  many  of  these  fibres  cannot  be  shown  by  microscopic  examination 
either  to  originate  or  terminate  in  the  substance  of  the  ganglion,  but 
also  from  the  paralyzing  effect  produced  upon  muscular  organs  supplied 
with  sympathetic  fibres,  by  division  of  the  cerebro-spinal  nerve  which 
communicates  with  its  ganglion.  This  is  more  particularly  shown  by 
the  paralysis  of  the  iris  following  division  of  the  oculomotorius  nerve, 
which  gives  a  motor  branch  to  the  ophthalmic  ganglion.  The  numerous 
branches  of  communication  supplied  by  the  pneumogastric  nerve  to  the 
cardiac  branches  of  the  sympathetic,  and  to  the  cardiac  plexus  itself, 
afford  an  equally  striking  instance  of  the  same  kind. 

The  ganglia  seated  upon  the  spinal  and  cranial  nerve  roots  are  there- 
fore undoubtedly  analogous,  in  their  anatomical  relations,  with  the 
detached  ganglia  of  the  sympathetic  system  proper ;  and  the  whole  of 
this  system  may  be  considered  as  made  up  of  a  set  of  nervous  centres 
disseminated  throughout  the  great  cavities  of  the  body,  and  of  nervous 
filaments  which  both  receive  fibres  from  the  cerebro-spinal  centres,  and 
communicate  by  some  of  their  own  with  the  cerebro-spinal  nerves.  All 
the  organs  in  the  body,  accordingly,  are  supplied  with  fibres  from  both 
sources ;  the  difference  consisting  in  the  proportions  in  which  one  kind 
or  the  other  are  present  in  particular  parts.  The  cerebro-spinal  nerves 
are  supplied  in  the  greatest  abundance,  and  manifest  their  most  striking 
properties,  in  the  organs  and  functions  of  animal  life  ;  those  of  the  sym- 
pathetic system  preponderate  in  the  organs  of  vegetative  life,  and  in 
their  influence  upon  the  functions  of  nutrition,  secretion,  and  growth. 

Anatomical  Arrangement  of  the  Sympathetic  System. — The  sympa- 
thetic system  consists  of  a  double  chain  of  nervous  ganglia,  running 
from  above  downward  along  the  front  and  sides  of  the  spinal  column, 
and  connected  with  each  other  by  longitudinal  filaments.  Each  gan- 
glion is  reenforced  by  motor  and  sensitive  fibres  from  the  cerebro-spinal 
system,  and  thus  the  organs  under  its  influence  are  brought  indirectly 
into  communication  with  external  objects  and  phenomena.  Its  nerves 
are  distributed  to  glands  and  mucous  membranes,  many  of  which  are 
destitute  of  general  sensibility,  and  to  muscular  parts  which  are  re- 
moved from  the  control  of  the  will.  The  sympathetic  ganglia  are 
situated  successively  in  the  head,  neck,  chest,  and  abdomen;  and  in 
each  of  these  regions  are  connected  with  special  organs  by  their  fibres 
of  distribution. 

The  first  sympathetic  ganglion  in  the  head  is  the  ophthalmic  gan- 
glion, situated  within  the  orbit  of  the  eye,  on  the  outer  aspect  of  the 
optic  nerve.  It  communicates  by  slender  filaments  with  the  carotid 
plexus,  and  receives  a  motor  root  from  the  oculomotorius  nerve,  and  a 
sensitive  root  from  the  ophthalmic  branch  of  the  fifth  pair.  Its  fila- 
ments of  distribution,  known  as  the  "  ciliary  nerves,"  pass  forward  upon 


584 


THE    SYMPATHETIC    SYSTEM. 


Fig.  184. 


the  eyeball,  pierce  the  scelerotic,  and  terminate  in  the  muscular  tissue 
of  the  iris. 

The  next  is   the   xpheno-palatine  ganglion,   situated  in  the  spheno- 

maxillary  fossa.  It  commu- 
nicates, like  the  preceding, 
with  the  carotid  plexus,  and 
receives  a  motor  root  from 
the  facial  nerve,  and  a  sensi- 
tive root  from  the  superior 
maxillary  branch  of  the  fifth 
pair.  Its  filaments  are  dis- 
tributed to  the  levator  palati 
and  uvular  muscles,  to  the 
mucous  membrane  of  the  pos- 
terior part  of  the  nasal  pas- 
sages, and  to  that  of  the  hard 
and  soft  palate. 

The  third  sympathetic  gan- 
glion is  the  submaxillary ) 
situated  upon  the  submaxil- 
lary  gland.  It  communicates 
with  the  superior  cervical  gan- 
glion of  the  sympathetic  by 
filaments  which  accompany 
the  facial  and  external  carotid 
arteries.  It  derives  its  sensi- 
tive filaments  from  the  lingual 
branch  of  the  fifth  pair,  and 
its  motor  filaments  from  the 
facial  nerve,  by  means  of  the 
chorda  tympani.  Its  branches 
of  distribution  pass  mainly  to 
the  subm  axillary  gland  and 
Wharton's  duct. 

The  last  sympathetic  gan- 
glion in  the  head  is  the  otic 
ganglion.  It  is  situated  be- 
neath the  base  of  the  skull, 
on  the  inner  side  of  the  third 
division  of  the  fifth  pair.  It 
receives  filaments  of  communication  from  the  carotid  plexus ;  a  motor 
root  from  the  facial  by  means  of  the  small  superficial  petrosal  nerve, 
as  well  as  one  or  two  short  fibres  from  the  inferior  maxillary  division 
of  the  fifth  pair ;  and  a  sensitive  root  from  the  glossopharyngeal  by 
the  nerve  of  Jacobson.  Its  branches  are  sent  to  the  internal  muscle  of 
the  malleus  in  the  middle  ear  (tensor  tympani),  to  the  circurnflexus  palati, 
and  to  the  mucous  membrane  of  the  tympanum  and  Eustachian  tube. 


GANGLIA  AND  NERVES  OP  THE  SYMPA- 
THETIC  SYSTEM. 


THE    SYMPATHETIC    SYSTEM.  585 

The  continuation  of  the  sympathetic  nerve  in  the  neck  consists  of 
two  and  sometimes  three  ganglia,  the  superior,  middle,  and  inferior. 
These  ganglia  communicate  with  each  other,  and  also  with  the  anterior 
branches  of  the  cervical  spinal  nerves.  Their  filaments  follow  the 
course  of  the  carotid  artery  and  its  branches,  and  are  distributed  to  the 
substance  of  the  thyroid  gland,  and  to  the  walls  of  the  larynx,  trachea, 
pharynx,  and  oesophagus.  By  the  superior,  middle,  and  inferior  cardiac 
nerves  they  also  supply  sympathetic  fibres  to  the  cardiac  plexus,  and, 
through  it,  to  the  substance  of  the  heart. 

In  the  chest,  the  sympathetic  ganglia  are  situated  on  each  side  the 
spinal  column,  just  over  the  heads  of  the  ribs.  Their  communications 
with  the  spinal  nerves  in  this  region  are  double  ;  each  ganglion  receiving 
two  filaments  from  the  intercostal  nerve  next  above  it.  The  filaments 
originating  from  the  ganglia  are  distributed  upon  the  thoracic  aorta, 
and  to  the  lungs  and  oesophagus. 

In  the  abdomen,  the  continuation  of  the  sympathetic  S37stem  consists 
mainly  of  the  aggregation  of  ganglionic  enlargements  situated  upon  the 
coeliac  artery,  known  as  the  semilunar  or  cceliac  ganglion.  From  this 
ganglion  a  multitude  of  radiating  and  inosculating  branches  are  sent  out, 
which,  from  their  common  origin  and  their  diverging  Bourse,  are  termed 
the  "  solar  plexus."  From  this,  other  plexuses  originate,  which  accom- 
pany the  abdominal  aorta  and  its  branches,  and  are  distributed  to  the 
stomach,  small  and  large  intestine,  spleen,  pancreas,  liver,  kidneys, 
supra-renal  capsules,  and  internal  organs  of  generation. 

Beside  the  above  ganglia  there  are  in  the  abdomen  four  other  pairs, 
situated  in  front  of  the  lumbar  vertebrae.  Their  filaments  join  the 
plexuses  radiating  from  the  semilunar  ganglion. 

In  the  pelvis,  the  sympathetic  system  is  continued  by  four  or  five  pairs 
of  ganglia,  situated  on  the  anterior  aspect  of  the  sacrum,  and  terminat- 
ing, at  the  lower  extremity  of  the  spinal  column,  in  the  u  ganglion  impar," 
which  is  probably  to  be  regarded  as  a  fusion  of  two  separate  ganglia. 

The  entire  sympathetic  series  is  thus  composed  of  numerous  small 
ganglia  connected  throughout,  first  with  each  other;  secondly,  with  the 
cerebro-spinal  system ;  and  thirdly,  with  the  viscera. 

Physiological  Properties  of  the  Sympathetic  Ganglia  and  Nerves. — 
The  properties  and  functions  of  the  sympathetic  nerves  have  been  less 
successfully  studied  than  those  of  the  cerebro-spinal  system,  owing, 
perhaps,  to  the  anatomical  difficulties  in  the  way  of  reaching  and  ope- 
rating upon  them  for  purposes  of  experiment  The  principal  part  of 
the  sympathetic  S3^stem  is  situated  in  the  interior  of  the  chest  and  abdo- 
men ;  and  the  mere  opening  of  these  cavities,  to  reach  the  ganglionic 
centres,  causes  such  a  disturbance  in  the  functions  of  vital  organs,  and 
such  a  shock  to  the  system  fit  large,  that  the  results  of  these  experiments 
are  liable  to  be  more  or  less  unsatisfactory,  The  connections  of  the  sym- 
pathetic ganglia  with  each  other  and  with  the  cerebro-spinal  axis  are  so 
numerous  and  scattered,  that  these  ganglia  cannot  be  completely  isolated 
without  resorting  to  a  still  more  extensive  operation.  And  finally,  the 
38 


586  THE    SYMPATHETIC    SYSTEM. 

sensible  phenomena  obtained  by  experimenting  on  the  sympathetic 
nerves  are,  in  many  cases,  slow  in  making  their  appearance,  and  not 
particularly  striking  or  characteristic  in  their  nature. 

Notwithstanding  these  difficulties,  however,  some  facts  have  been 
ascertained  with  regard  to  this  part  of  the  nervous  system,  which  give 
a  certain  degree  of  insight  into  its  character  and  functions. 

Influence  on  Movement  and  Sensibility. — The  sympathetic  system  is 
endowed  both  with  sensibility  and  the  power  of  exciting  motion  ;  but 
these  properties  are  less  active  than  in  the  cerebro-spinal  system,  and 
are  exercised  in  a  different  manner.  If  we  irritate  a  sensitive  spinal 
nerve  in  one  of  the  limbs,  or  apply  the  galvanic  current  to  its  posterior 
root,  the  evidences  of  pain  or  of  reflex  action  are  decisive  and  instanta- 
neous. There  is  no  appreciable  interval  between  the  application  of  the 
stimulus  and  the  sensation  which  results  from  it.  On  the  other  hand, 
in  experiments  upon  the  sympathetic  ganglia  and  nerves,  evidences  of 
sensibility  are  also  manifested,  but  much  less  acutely,  and  only  after 
somewhat  prolonged  application  of  the  irritating  cause.  These  results 
correspond  with  what  we  know  of  the  physiological  properties  of  the 
organs  supplied  by  the  sympathetic  system.  These  organs  are  insen. 
sible,  or  nearly  so,  to  ordinary  impressions.  We  are  not  conscious  of 
the  changes  going  on  in  them,  so  long  as  the}7  retain  a  normal  character. 
But  they  are  still  capable  of  perceiving  unusual  or  excessive  irritations, 
and  may  even  give  rise  to  acute  pain  when  in  a  state  of  inflammatory 
alteration. 

There  is  the  same  peculiar  character  in  the  action  of  the  motor  nerves 
belonging  to  the  sympathetic  system.  If  the  facial  or  hypoglossal,  or 
the  anterior  root  of  a  spinal  nerve,  be  irritated,  the  convulsive  movement 
which  follows  is  instantaneous,  spasmodic,  and  momentary  in  duration. 
But  if  the  semilunar  ganglion  or  its  nerves  be  subjected  to  a  similar 
experiment,  no  immediate  effect  is  produced.  It  is  only  after  a  few 
seconds  that  a  slow,  vermicular,  progressive  contraction  takes  place  in 
the  corresponding  part  of  the  intestine,  which  continues  for  some  time 
after  the  exciting  cause  has  been  removed. 

Morbid  changes  taking  place  in  organs  supplied  by  the  sympathetic 
present  a  similar  peculiarity  in  their  production.  If  the  body  be  exposed 
to  cold  and  dampness,  congestion  of  the  kidneys  shows  itself  perhaps  on 
the  following  day.  Inflammation  of  any  internal  organ  is  rarely  estab- 
lished within  twelve  or  twenty-four  hours  after  the  application  of  the 
exciting  cause.  The  internal  processes  of  nutrition,  together  with  their 
derangements,  which  are  more  especially  under  the  control  of  the  sym- 
pathetic, require  a  longer  time  to  be  influenced  by  incidental  causes, 
than  those  which  are  regulated  by  the  cerebro-spinal  system. 

Connection  with  the  Special  Senses. — In  the  head,  the  sympathetic 
has  an  important  connection  with  the  special  senses.  This  is  noticeable 
more  particularly  in  the  case  of  the  eye,  in  the  influences  regulating  the 
expansion  and  contraction  of  the  pupil.  The  ophthalmic  ganglion  sends 
off  a  number  of  ciliary  nerves,  distributed  to  the  iris,  and  receives  a 


THE    SYMPATHETIC    SYSTEM.  587 

motor  root  from  the  oculomotorius.  The  reflex  action,  by  which  the 
pupil  contracts  under  the  influence  of  light  and  expands  under  its 
diminution,  takes  place,  accordingly,  through  this  ganglion.  The  impres- 
sion conveyed  by  the  optic  nerve  to  the  tubercula  quadrigemina,  and  • 
reflected  outward  by  the  fibres  of  the  oculomotorius,  is  not  transmitted 
directly  by  the  last  named  nerve  to  the  iris  ;  but  passes  first  to  the 
ophthalmic  ganglion,  and  is  thence  conveyed  to  its  destination  by  the 
ciliary  nerves. 

The  reflex  movements  of  the  iris  exhibit  consequently  a  somewhat 
sluggish  character,  which  indicates  the  intervention  of  the  sympathetic 
system.  The  changes  in  the  size  of  the  pupil  do  not  take  place  instan- 
taneously with  the  variation  in  the  amount  of  light,  but  require  an 
appreciable  interval  of  time.  If  we  suddenly  pass  from  a  light  into  a 
dark  room,  we  are  unable  to  distinguish  surrounding  objects  until  a 
certain  time  has  elapsed,  and  the  expansion  of  the  pupil  has  taken 
place  ;  and  vision  even  continues  to  grow  more  distinct  for  a  consider- 
able period  afterward,  as  the  expansion  of  the  pupil  becomes  more  com- 
plete. If  we  cover  the  eyes  of  another  person  with  the  hand  or  a  folded 
oloth,  and  then  suddenly  expose  them  to  the  light,  we  can  see  that  the 
pupil,  which  is  at  first  dilated,  contracts  somewhat  rapidly  to  a  certain 
extent,  and  afterward  continues  to  diminish  in  size  for  several  seconds, 
until  its  equilibrium  is  fairly  established.  Furthermore,  if  we  pass  sud- 
denly from  a  dark  room  into  bright  sunshine,  we  are  immediately  con- 
scious of  a  painful  impression  in  the  eye,  which  results  from  the  inability 
of  the  pupil  to  contract  with  sufficient  rapidity.  All  such  exposures 
should  therefore  be  made  gradually,  in  order  that  the  movements  of  the 
iris  may  keep  pace  with  the  varying  quantity  of  stimulus,  and  thus 
protect  the  eye  from  injurious  impressions. 

The  reflex  movements  of  the  iris,  though  accomplished  through  the 
medium  of  the  ophthalmic  ganglion,  derive  their  original  stimulus, 
through  the  motor  root  of  this  ganglion,  from  the  oculomotorius  nerve. 
For  if  the  oculomotorius  nerve  be  divided  between  the  brain  and  the 
eyeball,  the  pupil  becomes  sensibly  dilated,  and  loses  in  great  measure 
its  power  of  contracting  under  the  influence  of  light.  The  motive  power, 
originally  derived  from  the  brain,  is,  therefore,  modified  by  passing 
through  the  ophthalmic  ganglion  before  reaching  its  destination  in  the 
iris. 

Three  organs  of  special  sense,  the  eye,  the  nose,  and  the  ear,  are 
each  provided  with  two  sets  of  muscles,  superficial  and  deep,  which 
regulate  the  quantity  of  stimulus  admitted  to  the  organ  and  the  mode 
in  which  it  is  received.  The  superficial  set  is  animated  by  branches  of 
the  facial  nerve ;  the  deep-seated  or  internal  set,  by  filaments  from  a 
sympathetic  ganglion. 

Thus,  the  front  of  the  eyeball  is  protected  by  the  orbicularis  and 
levator  palpebrse  superioris  muscles,  which  open  or  close  the  eyelids  at 
will,  and  allow  a  larger  or  smaller  quantity  of  light  to  reach  the  cornea. 
These  muscles  are  supplied  by  the  oculomotorius  and  facial  nerves,  arid 


588  THE    SYMPATHETIC    SYSTEM. 

are  mainly  voluntary  in  their  action.  The  iris,  on  the  other  hand,  is  a 
deep-seated  muscular  curtain,  which  regulates  the  quantity  of  light 
admitted  through  the  pupil.  It  is  supplied  by  filaments  from  the  oph- 
thalmic ganglion,  and  its  movements  are  involuntary. 

Division  of  the  sympathetic  nerve  in  the  middle  of  the  neck  has  a 
marked  effect  on  the  muscular  apparatus  of  the  eye.     Within  a  few 
seconds  after  this  operation  has  been  performed  upon  the  cat,  the  pupil 
of  the  corresponding  eye  becomes  contracted,  and  remains  in  that  con- 
dition.    At  the  same  time  the  third 
Fig.  185.  ..     .  t.t     . 

eyelid,  or  "  nictitating  membrane," 

with  which  these  animals  are  pro- 
vided, is  drawn  partially  over  the 
cornea,  and  the  upper  and  lower 
eyelids  also  approximate  to  each 
other;  so  that  all  the  apertures 
guarding  the  eyeball  are  percep- 
tibly narrowed,  and  the  expression 
of  the  face  on  that  side  is  altered 
in  a  corresponding  degree.  This 
effect  has  been  explained  by  sup- 
posing the  circular  fibres  of  the 

OAT,  after  section  of  the  right  sympathetic.       .   .  ,    .    ,  •, 

iris,  or  the  constrictors,  to  be  ani- 
mated by  filaments  derived  from  the  oculomotorius,  and  the  radiating 
fibres,  or  the  dilators,  to  be  supplied  by  the  sympathetic;  so  that,  while 
division  of  the  oculomotorius  would  produce  dilatation  of  the  pupil  by 
paralysis  of  the  circular  fibres  only,  division  of  the  sympathetic  would 
be  followed  by  exclusive  paralysis  of  the  dilators,  and  consequently  by 
contraction  of  the  pupil.  This  explanation,  however,  is  not  entirely 
satisfactory ;  since,  after  division  of  the  sympathetic  nerve  in  the  cat, 
not  only  is  the  pupil  contracted,  but  both  the  upper  and  lower  eyelids 
and  the  nictitating  membrane  are  also  drawn  partially  over  the  cornea, 
and  assist  in  excluding  the  light.  The  last-named  effect  cannot  be 
owing  to  direct  paralysis,  from  division  of  the  fibres  of  the  sjonpathetic. 
It  is  more  probable  that  the  section  of  this  nerve  operates  by  exaggerat- 
ing for  a  time  the  sensibility  of  the  retina,  owing  to  vascular  congestion; 
and  that  the  partial  closure  of  the  eyelids  and  pupil  is  a  consequence 
of  that  condition. 

In  the  olfactory  apparatus,  the  superficial  set  of  muscles  are  the  com- 
pressors and  elevators  of  the  alee  nasi,  which  are  animated  by  filaments 
of  the  facial  nerve.  By  their  action,  odoriferous  vapors  are  snuffed  up 
and  directed  into  the  upper  part  of  the  nasal  passages,  where  they  come 
in  contact  with  the  sensitive  portions  of  the  olfactory  membrane ;  or, 
if  too  pungent  or  disagreeable  in  flavor,  are  excluded  from  entrance. 
These  muscles  are  not  very  important  in  the  human  species ;  but  in 
many  of  the  lower  animals,  as  in  the  carnivora,  they  play  a  very  im- 
portant part  in  the  mechanism  of  olfaction.  Furthermore,  the  levators 
and  depressors  of  the  velum  palati,  which  are  deep-seated,  serve  to  open 


THE    SYMPATHETIC    SYSTEM.  589 

or  close  the  posterior  nares,  and  accomplish  a  similar  office  with  the 
muscles  already  named  in  front.  The  levator  palati  and  uvular  muscles 
are  supplied  by  filaments  from  the  spheno-palatine  ganglion,  and  are 
involuntary  in  character. 

The  ear  has  two  sets  of  muscles,  similarly  supplied.  The  superficial 
set  are  those  attached  to  the  external  ear.  They  are  comparatively 
inactive  in  man,  but  in  many  of  the  lower  animals  are  well  developed 
and  important.  In  the  horse,  the  deer,  the  sheep,  and  various  other 
species,  they  turn  the  ear  in  different  directions  to  catch  more  distinctly 
feeble  sounds,  or  to  exclude  those  which  are  disagreeable.  These  mus- 
cles are  supplied  by  filaments  of  the  facial  nerve,  and  are  voluntary  in 
their  action. 

The  deep-seated  set  are  the  muscles  of  the  middle  ear.  Sounds  are 
transmitted  to  the  middle  ear  through  the  membrane  of  the  tympanum, 
which  may  be  made  more  or  less  sensitive  to  sonorous  impressions  by 
varying  its  condition  of  tension  or  relaxation.  This  condition  is  regu- 
lated by  the  two  muscles  of  the  middle  ear,  namely,  the  tensor  tympani 
and  the  stapedius.  The  first  named  muscle  is  supplied  with  nervous 
filaments  from  the  otic  ganglion  of  the  sympathetic.  By  its  contraction, 
the  handle  of  the  malleus  is  drawn  inward,  bringing  the  membrana  tym- 
pani with  it,  and  thus  increasing  its  tension.  On  the  relaxation  of  the 
muscle,  the  chain  of  bones  returns  to  its  ordinary  position,  and  the  pre- 
vious condition  of  the  tympanic  membrane  is  restored.  This  action,  so 
far  as  we  can  judge,  is  purely  involuntary.  The  stapedius  muscle,  on 
the  other  hand,  is  supplied  by  a  branch  of  the  facial  nerve  (p.  549).  It 
is  probable  that  its  contraction  serves  to  relax  the  membrana  tympani, 
and  enables  us  to  make  a  certain  degree  of  voluntary  exertion  in  listen- 
ing for  faint  or  distant  sounds. 

Connection  with  the  Circulation. — Perhaps  the  most  important  fact 
concerning  the  sympathetic  S3rstem  is  that  of  its  influence  over  the 
vascularity  of  the  parts  supplied  by  it.  In  the  first  place,  division  of 
the  sympathetic  trunk  produces  a  vascular  congestion  in  the  corre- 
sponding parts.  If  this  nerve  be  divided,  in  any  of  the  warm-blooded 
quadrupeds,  in  the  middle  of  the  neck,  a  vascular  congestion  of  all  parts 
of  the  head,  on  the  corresponding  side,  immediately  follows.  This  con- 
gestion-is most  distinctly  evident  in  the  rabbit,  in  the  thin  and  trans- 
parent ears;  and  within  a  few  minutes  after  the  operation,  the  difference 
in  their  appearance  on  the  two  sides  is  strongly  pronounced.  All  the 
vessels  of  the  ear  on  the  affected  side  become  turgid  with  blood ;  and 
many  which  were  before  imperceptible,  are  distinctly  apparent.  This 
effect,  which  was  first  pointed  out  by  Bernard,  and  has  been  observed  by 
many  other  experimenters,  we  have  often  verified.  It  lasts  for  a  con- 
siderable time,  and  may  even  be  very  distinct  at  the  end  of  three  weeks. 
It  remains  longer  when  a  portion  of  the  nerve  has  been  cut  out,  or  the 
cervical  ganglion  extirpated,  than  when  its  filaments  have  been  simply 
divided  by  a  transverse  section.  It  finally  disappears  when  the  separated 
filaments  have  reunited  and  regained  their  functional  activity. 


590  THE    SYMPATHETIC    SYSTEM. 

The  vascular  congestion  thus  produced  by  division  of  the  sympathetic 
nerve  is  accompanied  by  three  important  phenomena,  all  intimately  con- 
nected with  each  other. 

First,  the  quantity  of  blood  circulating  in  the  part  is  increased,  and 
its  movement  accelerated.  It  is  not  a  state  of  passive  congestion  ;  but 
all  the  vessels  are  simultaneously  dilated,  a  larger  quantity  of  blood 
passes  through  the  capillaries  in  a  given  time,  and  returns  by  the  veins 
in  greater  abundance  than  before. 

Secondly,  there  is  a  remarkable  elevation  of  temperature  in  the  affect- 
ed  part.  This  elevation  of  temperature  is  very  perceptible  to  the  touch, 
both  in  the  ear  and  in  the  integument  of  the  corresponding  side  of  the 
head.  Measured  by  the  thermometer,  it  has  been  found  by  Bernard  to 
reach,  in  some  cases,  4.5  or  5  degrees  (8°  or  9°  F.).  It  results  from 
the  increased  quantity  of  blood  circulating  in  the  vessels ;  since  the 
blood  coming  from  the  interior  and  warmer  parts  of  the  body  supplies 
more  heat,  in  proportion  to  the  abundance  and  rapidity  with  which  it 
traverses  the  vascular  tissues. 

Thirdly,  the  color  of  the  venous  blood  becomes  brighter.  This  effect 
is  also  due  to  increased  rapidity  of  the  circulation.  The  blood  is  de- 
prived of  its  oxygen  and  darkened  in  color  by  the  changes  of  nutrition 
which  take  place  in  the  tissues.  But  if  the  rapidity  of  the  circulation 
be  suddenly  increased,  a  certain  proportion  of  the  blood  escapes  deoxi- 
dation,  and  its  change  in  color,  from  arterial  to  venous,  is  incomplete. 
The  blood  accordingly  returns  by  the  veins  of  the  affected  part  in  greater 
abundance,  of  a  higher  temperature,  and  of  a  more  ruddy  color,  than  in 
the  corresponding  parts  on  the  opposite  side. 

When  a  local  vascular  congestion  has  thus  been  produced  by  divi- 
sion of  the  sympathetic  nerve,  if  that  portion  of  the  divided  nerve 
which  remains  in  connection  with  the  tissues  be  galvanized,  all  the  above 
effects  rapidly  disappear  ;  the  bloodvessels  of  the  ear  and  corresponding 
side  of  the  head  contract  to  their  previous  dimensions,  the  quantity  of 
blood  circulating  through  the  tissues  is  diminished,  the  temperature  is 
reduced  in  a  corresponding  degree,  and  the  blood  in  the  veins  returns 
to  its  ordinary  dark  color.  The  variations  in  the  rapidity  of  the  circu- 
lation, dependent  on  the  condition  of  the  sympathetic  nerve,  have  been 
shown  by  Bernard'  in  the  following  manner.  In  a  living  rabbit  the  upper 
part  of  one  ear  is  cut  off  with  a  pair  of  very  sharp  scissors,  so  that  the  blood 
may  escape  in  jets  from  the  divided  ends  of  the  small  arteries.  The 
force  and  height  of  the  arterial  jets  having  been  observed,  the  sym- 
pathetic nerve  is  then  divided  in  the  middle  of  the  neck  on  the  corre- 
sponding side  Immediately  the  blood  escapes  from  the  wounded  ear  in 
greater  abundance,  and  the  arterial  jets  rise  to  double  or  even  triple 
their  former  height.  The  galvanic  current  is  then  applied  to  the  di- 
vided extremity  of  the  sympathetic,  above  the  point  of  section,  when  the 
streams  of  blood  escaping  from  the  wound  diminish  or  disappear ;  but 

1  Journal  de  la  Physiologie  de  1'Uomme  et  des  Animaux.     Paris,  1862,  p.  397. 


THE    SYMPATHETIC    SYSTEM.  591 

they  recommence  and  again  increase  in  intensity  so  soon  as  the  gal- 
vanization of  the  nerve  is  suspended. 

The  same  author  has  shown  that  a  similar  influence  is  exerted  by  the 
sympathetic  nerve  upon  the  circulation  in  the  limbs.1  If  the  lumbar 
nerves  of  one  side  be  divided,  in  the  dog,  within  the  cavity  of  the  spinal 
canal,  paralysis  of  motion  and  sensibility  is  produced  in  the  correspond- 
ing limb,  but  there  is  no  change  in  its  vascularity  or  temperature ;  while 
if  the  lumbar  portion  of  the  sympathetic  be  divided  or  excised,  without 
disturbing  the  spinal  nerves,  all  the  signs  of  increased  temperature  and 
activity  of  the  circulation  are  manifested  in  the  limb  below,  without  loss 
of  motion  or  sensibility.  Exsection  of  the  first  thoracic  ganglion  of  the 
sympathetic  produces  similar  effects  in  the  anterior  extremity ;  and 
these  effects  are  diminished  or  suspended  by  electric  irritation  of  the 
divided  nerve. 

Division  of  the  sympathetic  nerve,  accordingly,  produces  dilatation 
of  the  bloodvessels  and  consequent  increased  rapidity  of  the  circula- 
tion, and  causes  the  blood  to  retain  its  red  color  in  the  veins  ;  while  gal- 
vanization of  the  same  nerve  produces  contraction  of  the  vessels,  dimin- 
ishes the  quantity  of  the  circulating  fluid,  and  causes  the  change  in 
color  of  the  blood,  from  arterial  to  venous. 

The  same  thing  takes  place  in  the  glandular  organs.  If  the  submax- 
illary  or  parotid  gland  be  exposed  in  the  living  animal,2  so  long  as  the 
gland  is  in  its  ordinary  condition  the  blood  passing  through  it  is  seen 
to  undergo  the  usual  changes,  and  returns  dark  colored  by  the  veins. 
But  if  the  sympathetic  filament  which  accompanies  the  external  carotid 
artery  be  divided,  the  quantity  of  blood  flowing  through  the  gland  is  at 
once  increased,  and  appears  of  a  red  color  in  the  veins.  The  same 
changes  occur  when  the  gland  is  excited  to  secretion  by  stimulating 
the  organs  of  taste. 

An  apparent  antagonism  exists,  in  regard  to  the  circulation,  between 
the  sympathetic  nerve  and  those  derived  from  the  cerebro-spinal 
system.  If  the  chorda  tympani,  which  sends  filaments  to  the  submax- 
illary  ganglion,  be  galvanized,  it  causes  an  excitement  of  the  secretion3 
in  the  submaxillary  gland,  increased  activity  of  the  circulation,  and  a 
red  color  of  the  blood  in  the  veins.  The  division  of  this  nerve  is  followed 
by  a  contrary  result.  The  effects  produced,  therefore,  by  galvanization 
of  the  chorda  tympani  are  those  produced  by  division  of  the  sympa- 
thetic ;  and  the  effects  produced  by  galvanizing  the  sympathetic  are 
those  which  follow  division  of  the  chorda  tympani. 

The  vascularity  of  the  parts,  accordingly,  as  well  as  the  glandular 
activity  of  vascular  organs,  are  under  the  control  of  the  nervous  system. 
The  filaments  of  the  sympathetic  nerve  accompany  everywhere  the  blood- 
vessels, enveloping  the  arterial  branches  with  an  abundant  plexus,  and 

1  Journal  de  la  Physiologic  de  PHomme  et  des  Animaux.     Paris,  1862,  p.  397. 

2  Bernard,  Legons  sur  les  Liquides  de  I'Organisme.    Paris,  1859,  tome  i.  p.  230. 
9  LeQons  sur  les  Liquides  de  1'Organisme.     Paris,  1859,  tome  i.  p.  312. 


592  THE    SYMPATHETIC    SYSTEM. 

following  them  to  their  minutest  ramifications.  They  appear  to  act  by 
causing  a  contraction  in  the  organic  muscular  fibres  of  the  small  arteries, 
thus  regulating  the  resistance  of  the  vessels,  and  the'  passage  of  the 
blood  through  them.  When  the  sympathetic  nerve  is  excited,  the  vessels 
contract,  the  blood  passes  through  them  slowly,  and  is  fully  converted, 
during  its  passage,  into  venous  blood.  When  the  influence  of  this  nerve 
is  diminished  or  suspended,  the  vessels  dilate,  and  the  blood,  passing 
through  them  with  greater  rapidity,  is  not  completely  changed  from  the 
arterial  to-  the  venous  condition. 

Connection  with  Reflex  Actions. — The  influence  of  the  sympathetic 
nerve  upon  the  thoracic  and  abdominal  viscera  has  been  only  imperfectly 
investigated.  It  undoubtedly  serves  as  a  medium  of  reflex  action  between 
the  sensitive  and  motor  portions  of  the  digestive,  excretory,  and  gene- 
rative apparatus ;  and  it  is  certain  that  it  takes  part  in  reflex  actions 
in  which  the  cerebro-spinal  system  is  also  interested.  There  are  accord- 
ingly three  different  kinds  of  reflex  action,  taking  place  wholly  or  par- 
tially through  the  sympathetic  system,  which  may  occur  in  the  living 
body. 

1.  Reflex  actions  taking  place  from  the  internal  organs,  through  the 
sympathetic  and  cerebro-spinal  systems,  to  the  voluntaiy  muscles  and 
sensitive  surfaces. — The  convulsions  of  children  are  often  due  to  the 
irritation  of  undigested  food  in  the  intestinal  canal.     Attacks  of  indi- 
gestion  may  also  produce  temporary  amaurosis,  double  vision,  stra- 
bismus, and  even  hemiplegia.     Nausea,  and  a  diminished  or  capricious 
appetite,  are  prominent  symptoms  of  early  pregnancy,  induced  by  the 
condition  of  the  uterine  mucous  membrane. 

2.  Reflex  actions  taking  place  from  the  sensitive  surfaces,  through 
the  cerebro-spinal  and  sympathetic  systems,  to  the  involuntary  muscles 
and  secreting  organs. — Exposure  of  the  integument  to  cold  and  wet  is 
often  a  determining  cause  of  diarrhoea.     Mental  and  moral  impressions, 
excited  through  the  special  senses,  will  affect  the  motions  of  the  heart, 
and  disturb  the  acts  of  digestion  and  secretion.     Terror,  or  an  absorb- 
ing interest  of  any  kind,  will  produce  dilatation  of  the  pupil,  and  com- 
municate in  this  way  an  unusual  expression  to  the  eye.     Disagreeable 
sights  or  odors,  or  even  unpleasant  occurrences,  are  capable  of  hastening 
or  arresting  the  menstrual  discharge,  or  of  inducing  premature  delivery. 

3.  Reflex  actions  taking  place,  through  the  sympathetic  system,  from 
one  part  of  the  internal  organs  to  another. — The  contact  of  food  with 
the  mucous  membrane  of  the  intestine  excites  a  peristaltic  movement  in 
its  muscular  coat.     The  mutual  influence  of  the  digestive,  urinarj',  and 
internal  generative  organs   upon   each  other  is   exerted    through  the 
medium  of  the  sympathetic  ganglia  and  nerves.     The  variations  of  the 
capillary  circulation  in  different  abdominal  viscera,  corresponding  with 
the  activity  or  repose  of  their  associated  organs,  are  due  to  a  similar 
nervous  influence.     These  phenomena  are  not  accompanied  by  conscious 
sensation,  nor  by  any  apparent  intervention  of  the  cerebro-spinal  system. 


CHAPTEE    VIII. 

THE   SENSES. 

THE  senses  are  the  endowments  by  which  we  perceive  the  physical 
properties  of  external  objects  and  the  phenomena  produced  by  their 
various  reactions,  such  as  solidity,  pressure,  smoothness  or  inequality  of 
surface,  temperature,  light,  sound,  and  sapid  and  odoriferous  qualities. 
All  our  information  with  regard  to  the  objects  of  nature  is  obtained 
through  these  channels,  which  are  consequently  the  primitive  source 
of  all  conscious  relation  with  the  external  world.  Sensation  alone  in- 
dicates merely  the  perception  of  some  impression  derived  from  without, 
whatever  may  be  its  nature.  The  senses,  on  the  other  hand,  form  so 
many  subdivisions  of  the  main  function,  each  of  which  is  devoted  to 
the  perception  of  a  particular  class  of  physical  properties  or  reactions. 
They  are  divided  into  five  different  groups,  namely :  1.  General  sensi- 
bility. 2.  The  sense  of  taste.  3.  The  sense  of  smell.  4.  The  sense  of 
sight.  5.  The  sense  of  hearing. 

General  Sensibility. 

General  sensibility  is  that  by  which  we  appreciate  the  simpler  physi- 
cal properties  of  external  objects,  such  as  their  consistency,  roughness 
or  smoothness  of  surface,  temperature,  and  mass.  It  is  so  called  be- 
cause it  is  generally  diffused  over  the  external  integument,  beside  being 
present  in  most  of  the  mucous  membranes  near  the  surface.  Notwith- 
standing that  this  endowment  includes  the  power  of  perceiving  several 
different  kinds  of  impression,  they  are  all,  so  far  as  we  know,  communi- 
cated to  the  perceptive  centres  by  the  same  nerves ;  and  the  grade  of 
sensibility  for  all  varies,  as  a  general  rule,  in  the  same  direction  and  to 
the  same  degree  in  different  parts  of  the  body.  The  sensations  thus 
produced,  though  presenting  some  peculiarities  by  which  they  may  be 
distinguished  from  each  other,  are  therefore  naturally  comprised  under 
the  single  head  of  general  sensibility. 

Sensations  of  Touch. — This  is,  perhaps,  the  least  complicated  form 
of  sensory  impression,  and  is  known  as  "tactile  sensibility."  It  is 
produced  by  the  simple  contact  of  a  foreign  body  with  the  sensitive 
surface,  and  gives  information  as  to  its  solidity,  its  external  configura- 
tion, and  its  indifferent  or  irritating  qualities.  Although  there  is  a 
certain  variety  in  these  impressions,  yet  they  evidently  belong  to  the 
same  group,  and  there  is  no  essential  difference  in  the  effect  produced 
by  the  contact  of  sharp-pointed  instruments,  and  that  caused  by  irri- 
tating substances,  like  mustard,  applied  to  the  skin,  the  continuous  or 

(593) 


594  THE    SENSES. 

interrupted  galvanic  current,  pungent  liquids  placed  upon  the  tongue, 
or  pungent  vapors  in  the  nasal  passages.  These  are  all  impressions  of 
tactile  sensibility,  and  depend  upon  a  similar  irritation- of  the  peripheral 
nervous  extremities. 

The  structures  especially  devoted  to  the  exercise  of  tactile  sensibility 
are  minute  bulbous  organs  developed  upon  the  terminal  extremities  of 
the  nerve  fibres  in  the  papillae  of  the  skin  and  adjacent  mucous  mem- 
branes, in  each  of  which  two  situations  they  present  certain  distinguish- 
ing features,  though  their  essential  character  is  the  same  in  both.  In 
the  skin,  these  organs  are  known  as  the  tactile  corpuscles.  They  are 
elongated  oval  bodies,  measuring,  according  to  Kolliker,  about  -^  of  a 
millimetre  in  length  by  ^0  of  a  millimetre  in  thickness.  They  are 
situated  in  the  substance  of  certain  of  the  papillae,  with  their  long  axes 
placed  longitudinally,  and  extending  nearly  to  the  free  extremity  of  the 
organ.  They  are  not  to  be  found  in  all  of  the  papillae,  since  even  at  the 
end  of  the  index  finger,  where  they  are  most  abundant,  according  to 
the  observations  of  Meissner,  not  more  than  one  papilla  in  four  is  pro- 
vided with  a  tactile  corpuscle.  The  papillae  containing  the  corpuscles 
are  not  supplied  with  bloodvessels ;  while  the  remainder,  constituting 
the  large  majority,  contain  capillary  blood- 
vessels, but  no  tactile  corpuscles.  The  tactile 
corpuscle  itself  consists,  1st,  of  a  sheath,  ex- 
hibiting a  number  of  transverse  nuclei,  and 
considered  as  representing  a  form  of  connec- 
tive tissue;  2d,  of  an  inclosed  mass  of  trans- 
parent, homogeneous  material ;  and,  3d,  of 
one  or  two  medullated  nerve  fibres,  which  pass 
upward  from  the  superficial  plexus  of  the  skin 
through  the  substance  of  the  papilla,  reach  the 
tactile  corpuscle,  wind  round  it  in  a  spiral 
direction  toward  its  apex,  and  finally,  losing 
their  medullary  layer,  terminate  in  some  man- 
™r  »<*  7*  disti"'«y  ascertained.  Tactile 
puscie  and  nerve  fibres.  (Koi-  corpuscles  have  been  found,  in  man,  upon  the 
dorsal  and  palmar  surfaces  of  the  hand  and 

foot,  upon  the  nipple,  and  upon  the  anterior  part  of  the  forearm.  As 
their  abundance  in  these  different  regions  corresponds  with  the  local 
acuteness  of  sensibity,  they  are  undoubtedly  to  be  regarded  as  the  special 
organs  of  touch,  though  not  perhaps  the  only  form  of  nerve  structure 
capable  of  exercising  this  function. 

In  the  conjunctiva,  the  red  portion  of  the  lips,  the  tongue,  the  sub- 
lingual  mucous  membrane,  and  the  glans  penis,  the  organs  of  touch  are 
constituted  by  the  terminal  bulbs  of  the  nerve  fibres  in  these  regions. 
These  organs  differ  from  the  tactile  corpuscles  mainly  in  their  smaller 
size  and  the  greater  simplicity  of  their  structure.  In  man,  according  to 
Kolliker,  they  are  for  the  most  part  nearly  spherical  in  form,  though 
in  the  inferior  animals  they  are  often  elongated  and  club-shaped.  They 


GENERAL    SENSIBILITY.  595 

consist  of  a  very  thin,  external  envelope  of  connective  tissue,  inclosing, 
as  in  the  tactile  corpuscle,  a  mass  of  homogeneous  or  finely  granular 
substance.  The  medullated  nerve  fibre  which  penetrates  the  bulb,  loses 
its  medullary  layer  at  its  entrance,  and  runs  through  the  central  homo- 
geneous substance,  to  terminate  by  a  free  extremity  near  its  apex. 
Both  the  tactile  corpuscles  and  the  terminal  bulbs  are  therefore  anatomi- 
cal forms,  in  which  the  axis  cylinder  of  the  sensitive  nerve  fibre  termi- 
nates, after  divesting  itself  of  its  medullary  layer. 

The  tactile  sensibility  varies  considerably  in  different  regions  of  the 
integument.  The  best  method  of  appreciating  this  variation  is  that 
adopted  by  Weber  and  Valentin.  It  consists  in  applying  to  different 
parts  the  points  of  a  pair  of  compasses,  tipped  with  suitable  pieces  of 
cork.  If  these  points  be  applied  to  the  skin  when  fixed  at  very  short 
distances  apart,  the  two  sensations  cannot  be  accurately  distinguished 
from  each  other  but  are  blended  into  one ;  and  the  impression  thus  pro- 
duced is  that  of  a  single  contact.  The  minimum  distance  at  which  the 
two  points  can  be  distinguished  by  the  integument  thus  becomes  a 
measure  of  its  sensibility  at  that  spot.  The  observations  of  Valentin,1 
which  are  the  most  varied  and  complete  in  this  respect,  give  the  follow- 
ing as  the  limits  of  distinct  perception  in  different  regions : 

DISTANCE  AT  WHICH  TWO  POINTS  MAY  BE  SEPARATELY  DISTINGUISHED. 

At  the  tip  of  tongue 1.00  millimetre. 

"        palmar  surface  of  tips  of  fingers    .         .  1.50 

"  "  "       of  second  phalanges       .  3.24          " 

of  first  phalanges  .        .  3.44 

"        dorsum  of  tongue 5.22  " 

"        dorsal  surface  of  fingers          ...  8.12  " 

cheek 9.46 

back  of  hand 14.50 

skin  of  throat 17.27 

dorsum  of  foot 26.10 

"        front  of  sternum 33.07          " 

middle  of  back 50.43 

This  method  does  not  necessarily  give  an  absolute  measure  of  tho 
aculeness  of  sensibility  in  the  different  regions,  since  the  two  points 
might  be  less  easily  distinguished  from  each  other  in  any  one  region, 
and  yet  the  absolute  amount  of  sensation  produced  might  be  as  great 
as  in  the  surrounding  parts;  but  it  undoubtedly  affords  an  accurate 
estimate  of  the  delicacy  of  tactile  sensation,  by  which  we  distinguish 
slight  inequalities  in  the  surface  of  solid  bodies.  There  is  every  reason 
to  believe  that  the  two  qualities  of  delicacy  and  acuteness  of  local  sensi- 
bility correspond  with  each  other  in  their  degree  of  development  in 
various  localities;  since  the  regions  where  tactile  sensibility  is  most 
delicate  are  frequently  found  to  be  also  those  where  the  amount  of 
sensation  is  the  greatest.  A  feeble  galvanic  current  msy  be  perceived 

1  In  Todd's  Cyclopaedia  of  Anatomy  and  Physiology,  vol.  iv.,  article  on  Touch. 


596  THE    SENSES. 

when  applied  to  the  tips  of  the  fingers,  though  it  will  produce  no  impres- 
sion on  the  rest  of  the  limbs  or  trunk ;  and  one  which  is  too  faint  to  be 
distinguished  by  the  fingers  may  be  perceptible  at  the  tip  of  the  tongue. 

Certain  parts  of  the  body,  furthermore,  are  especially  well  adapted 
for  use  as  organs  of  touch,  not  only  on  account  of  their  acute  sensibility, 
but  also  owing  to  their  conformation  and  mobility.  In  man,  the  hands 
are  the  most  favorably  constructed  for  this  purpose,  by  the  numerous 
articulations  and  varied  power  of  movement  of  the  fingers,  b}r  wMch 
they  may  be  applied  to  solid  surfaces  of  any  form,  and  brought  succes- 
siveljT  in  contact  with  all  their  irregularities  and  depressions.  We  are 
thus  enabled  to  obtain  the  most  precise  information  as  to  the  texture, 
consistency,  and  configuration  of  foreign  bodies. 

But  the  hands  are  not  the  exclusive  organs  of  touch,  even  in  man, 
and  in  the  lower  animals  the  function  is  mainly  performed  by  other  parts. 
In  the  cat  and  in  the  seal,  the  long  bristles  seated  upon  the  lips  are  used 
for  this  purpose,  each  bristle  being  connected  at  its  base  with  a  nervous 
papilla ;  and  in  the  elephant  the  end  of  the  nose,  which  is  developed 
into  a  flexible  and  sensitive  proboscis,  is  employed  as  the  principal  organ 
of  touch.  This  function,  therefore,  may  be  performed  by  one  part  of 
the  body  or  another,  provided  the  accessory  organs  be  developed  in  a 
favorable  manner. 

About  the  head  and  face,  the  sensibility  of  the  skin  is  principally  de- 
pendent upon  branches  of  the  fifth  pair.  In  the  neck,  trunk,  and  extre- 
mities it  is  due  to  the  sensitive  fibres  of  the  cervical,  dorsal,  and  lumbar 
spinal  nerves.  It  exists,  to  a  considerable  extent,  in  the  mucous  mem- 
branes of  the  mouth  and  nose,  and  of  other  passages  leading  to  the  in- 
terior. The  sensibility  of  the  mucous  membranes  is  most  acute  in  parts 
supplied  by  branches  of  the  fifth  pair,  namely,  the  conjunctiva,  anterior 
part  of  the  nares,  inside  of  the  lips  and  cheeks,  and  the  anterior  two- 
thirds  of  the  tongue.  The  tactile  sensibility,  which  is  resident  in  the 
skin  and  in  a  certain  portion  of  the  mucous  membranes,  diminishes  in 
degree  from  without  inward,  and  disappears  altogether  in  the  internal 
organs  which  are  not  abundantly  supplied  with  nerves  from  the  cerebro- 
spinal  sj'stem. 

While  the  general  sensibility  of  the  skin,  and  of  the  mucous  mem- 
branes, varies  in  acuteness  in  different  parts  of  the  bod3r,  it  is  every- 
where the  same  in  kind.  The  tactile  sensations  produced  by  the  con- 
tact of  a  foreign  body  are  of  the  same  nature,  whether  they  be  felt  by 
the  tips  of  the  fingers,  the  dorsal  or  palmar  surfaces  of  the  hands,  the 
lips,  cheeks,  or  any  other  part  of  the  integument.  Their  only  difference 
is  in  the  intensity  and  distinctness  of  the  impressions  produced. 

The  appreciation  of  the  weight  or  mass  of  a  foreign  body  is  obtained 
from  the  degree  of  pressure  which  it  causes  upon  the  integument,  when 
supported  by  the  hand  or  other  part  of  the  body.  It  does  not  appear 
that  any  other  kind  of  sensation  is  necessary  for  this  purpose,  although 
we  generally  also  employ,  in  estimating  a  weight,  the  degree  of  muscular 
effort  required  to  sustain  it.  If  the  hand,  however,  be  rested  upon  some 


GENEKAL    SENSIBILITY.  597 

solid  support,  and  the  foreign  body  placed  upon  it,  its  weight  is  then 
appreciated  solely  by  the  amount  of  pressure  which  it  causes.  The 
sensation  of  muscular  contraction  is  itself  a  result,  so  far  as  we  can 
judge,  of  the  physical  impression  produced  upon  the  sensitive  nerve 
fibres  in  the  muscular  tissue ;  and  there  is  nothing  to  indicate  that  it 
differs  essentially  from  that  caused  by  pressure  upon  the  nerves  of  the 
integument. 

Sensations  of  Temperature. — The  appreciation  of  temperature  is  also 
most  highly  developed,  as  a  general  rule,  in  those  parts  which  have  the 
greatest  share  of  tactile  sensibility.  The  difference  in  this  respect  be- 
tween the  integument  of  the  face  and  that  of  the  scalp  is  very  marked  ; 
since  hot  applications  may  be  readily  borne  upon  the  scalp,  which  would 
be  nearly  or  quite  intolerable  upon  the  face.  The  extent  of  surface  ex- 
posed to  a  given  temperature  has  also  an  influence  upon  the  effect  pro- 
duced, and  a  moderate  degree  of  either  warmth  or  cold  applied  over  a 
considerable  portion  of  the  skin  is  much  more  readily  perceived  than 
if  confined  to  a  limited  region.  There  is  evidence  that  the  impres- 
sions of  temperature  and  those  of  touch,  if  transmitted  by  the  same 
fibres,  depend  upon  two  different  forms  of  nervous  excitation,  or  are 
received  by  different  peripheral  nervous  structures ;  since  abundant 
instances  have  been  observed  in  which  one  of  these  two  kinds  of  sensi- 
bility was  impaired  independently  of  the  other.  In  various  forms  of 
paralysis,  tactile  sensibility  may  be  lost  while  that  of  temperature  re- 
mains ;  or,  on  the  other  hand,  the  power  of  appreciating  temperatures 
may  disappear  while  impressions  of  contact  continue  to  be  perceived.1 

Sensations  of  Pain. — The  sense  of  pain  is  different  in  character  from 
that  caused  by  tactile  impressions  or  by  variations  in  temperature.  It 
is  caused  by  any  exaggerated  mechanical  irritation  or  by  the  application 
of  excessive  heat  or  cold ;  but  in  all  these  instances,  when  the  intensity 
of  the  impression  rises  above  a  certain  point,  the  ordinary  perceptions 
produced  by  it  disappear,  and  that  of  pain  takes  their  place.  Thus  if 
the  blade  of  a  knife  or  the  point  of  a  needle  be  placed  gently  in  contact 
with  the  skin,  we  perceive,  by  means  of  tactile  sensibility,  the  character 
and  form  of  its  surface.  But  if  the  pressure  be  increased  beyond  a  cer- 
tain degree,  or  if  the  integument  be  actually  wounded,  we  obtain  no  pre- 
cise information  of  the  physical  qualities  of  the  foreign  body,  and  are 
only  conscious  of  the  pain  which  results.  The  appreciation  of  cold  or 
warmth,  in  like  manner,  is  only  possible  within  moderate  limits ;  and 
when  the  variations  are  so  excessive  as  to  produce  pain,  all  accurate 
perception  of  the  degree  of  temperature  is  lost.  The  contact  of  a  red- 
hot  iron  and  that  of  one  much  below  the  freezing  point  of  water  produce 
sensations  which  are  not  essentially  different  from  each  other,  and  which 
are  marked  only  by  their  painful  character. 

It  is  not  known  whether  the  sensation  of  pain  be  confined  to  nerve 

1  Brown-Sequard,  Physiology  and  Pathology  of  the  Central  Nervous  System. 
Philadelphia,  1860,  pp.  84,  98,  125. 


598  THE    SENSES. 

fibres  which  are  distinct  from  those  endowed  with  other  forms  of  general 
sensibility,  but  it  is  certain  that  it  may  be  preserved  or  lost  independently 
of  the  other  varieties.  The  anaesthesia  which  is  produced  by  the  inha- 
lation of  ether  or  chloroform  may  be  carried  to  such  a  point  that  the 
capacity  for  feeling  pain  is  abolished,  while  tactile  sensibility  remains ; 
so  that  the  wounds  caused  by  puncturing  or  cutting  instruments  may 
be  felt,  though  unaccompanied  by  any  sense  of  suffering.  Similar  ob- 
servations have  been  made  in  cases  of  paralysis  where,  it  is  well  known, 
the  patient  may  perceive  the  contact  of  foreign  bodies  or  the  prick  of 
a  pin,  but  at  the  same  time  may  not  experience  from  them  any  painful 
sensation ;  or,  on  the  other  hand,  the  sense  of  pain  may  persist  in  the 
affected  parts,  while  that  of  touch  is  diminished  or  lost.1  Notwith- 
standing this  apparent  independence  of  the  immediate  conditions  neces- 
sary for  the  sensation  of  pain,  it  is  transmitted  by  fibres  of  the  same 
nerves,  belonging  to  the  cerebro-spinal  system,  which  convey  ordinary 
impressions ;  and  nerves  which  are  endowed  with  the  most  acute  tactile 
sensibility,  like  the  branches  of  the  fifth  pair,  are  also  capable,  when 
irritated  by  injury  or  disease,  of  giving  rise  to  the  severest  painful  im- 
pressions. 

Mode  of  Action  of  the  Senses  in  general. — There  are  certain  facts 
connected  with  the  exercise  of  general  sensibility  which  are  also  com- 
mon to  the  operation  of  all  the  senses,  and  which  are  of  sufficient  im- 
portance to  be  considered  by  themselves. 

In  the  first  place,  an  impression  of  any  kind,  made  upon  a  sensitive 
organ,  remains  for  a  short  time  after  the  removal  of  its  immediate 
cause.  The  state  of  excitement  produced  in  the  nervous  expansions 
and  fibres  has  a  certain  degree  of  persistence,  which  is  longer  in  duration 
for  some  organs  than  for  others,  but  which  exists  in  some  degree  for 
all.  The  sense  of  simple  contact  or  pressure  of  a  foreign  body  upon 
the  skin,  especially  if  it  be  somewhat  forcible  and  continued,  remains 
for  a  perceptible  interval  after  the  foreign  body  is  removed.  The  feel- 
ing of  cold  or  warmth,  from  the  application  of  ice  or  heated  liquids, 
lasts  more  or  less  after  the  application  is  discontinued.  Even  in  the 
case  of  sight  and  hearing  it  is  easy  to  verify  the  same  fact ;  and  the 
duration  of  continuance  of  the  nervous  impression,  though  very  short, 
has  been  found  in  many  instances  susceptible  of  measurement. 

Secondly,  the  organs  of  sense  after  a  time  become  accustomed  to  a  con- 
tinued impression,  so  that  the}7  no  longer  perceive  its  existence.  If  a 
uniform  pressure  be  exerted  upon  any  part  of  the  body,  the  compressing 
substance  at  last  fails  to  excite  sensation,  and  we  remain  unconscious  of 
its  existence.  In  order  to  attract  our  notice,  it  is  necessary  to  increase 
or  diminish  the  pressure  or  to  change  its  locality  or  direction. 

The  olfactory  apparatus  also  becomes  habituated  to  odors,  whether 
agreeable  or  disagreeable  in  their  nature,  in  the  confined  air  of  a  close 

1  Brown-Sequard,  Physiology  and  Pathology  of  the  Central  Nervous  System. 
Philadelphia,  1860,  pp.  97,  126.  Hammond,  Diseases  of  the  Nervous  System. 
New  York,  1871,  p.  82. 


GENERAL    SENSIBILITY.  599 

apartment ;  although,  on  first  entering  from  without,  the  attention  may 
have  been  attracted  by  them  in  a  decided  manner.  A  continuous  and 
uniform  sound,  like  the  steady  rumbling  of  carriages,  or  the  monotonous 
hissing  of  boiling  water,  becomes  after  a  time  inaudible  ;  but  as  soon  as 
the  sound  ceases,  we  notice  the  alteration,  and  our  attention  is  at  once 
excited.  The  senses,  accordingly,  receive  their  stimulus  more  from  the 
variation  and  contrast  of  external  impressions,  than  from  these  impres- 
sions themselves. 

Another  important  particular,  in  regard  to  the  senses,  is  their  capacity 
for  education.  The  touch  can  be  so  trained  that  the  blind  may  read 
words  and  sentences  by  its  aid,  in  raised  letters,  where  an  ordinary 
observer  would  hardly  detect  more  than  a  slight  inequality  of  surface. 
The  educated  eye  of  the  artist  or  the  naturalist  will  distinguish  varia- 
tions of  color,  size,  and  outline,  quite  inappreciable  to  ordinary  vision ; 
and  the  senses  of  taste  and  smell,  in  those  who  are  in  the  habit  of 
examining  wines  and  perfumes,  acquire  a  similar  superiority  of  discrimi- 
nating power. 

In  these  instances,  it  is  not  the  organ  of  sense  itself  which  becomes 
more  perfect  in  organization,  or  more  susceptible  to  sensitive  impres- 
sions. The  functional  power,  developed  by  cultivation,  depends  upon 
the  increased  delicacy  of  the  perceptive  and  discriminating  faculties. 
It  is  a  mental  and  not  a  physical  superiority  which  gives  the  painter  or 
the  naturalist  a  greater  facility  for  distinguishing  colors  and  outlines, 
and  which  enables  the  medical  observer  to  detect  nice  variations  in  the 
sounds  of  the  heart  or  the  respiratory  murmur  of  the  lungs.  The 
impressions  of  external  objects,  to  produce  their  complete  effect,  must 
first  be  received  by  a  sensitive  apparatus,  which  is  perfect  in  organiza- 
tion and  functional  activity  ;  and,  secondly,  they  must  be  subjected  to 
the  action  of  an  intelligent  perception,  by  which  their  nature,  source, 
and  relations  are  fully  appreciated. 

Beside  the  endowment  of  general  sensibility  distributed  over  the 
integument,  there  are  other  faculties  by  which  we  appreciate  particular 
physical  qualities  or  phenomena,  namely,  those  of  taste,  odor,  light,  and 
sound,  the  exercise  of  which  is  confined  to  special  organs,  having  a  struc- 
ture adapted  to  that  purpose  alone.  These  are  called  the  special  senses. 
Their  organs  differ  from  the  general  integument  in  their  more  compli- 
cated structure  and  in  the  delicate  and  varied  character  of  the  functions 
which  they  perform.  They  are  incapable  of  feeling  pain,  similar  to  that 
perceived  by  the  nerves  of  general  sensibilit}',  though  they  may  com- 
municate disagreeable  as  well  as  pleasing  impressions.  The  light,  how- 
ever intense,  has  no  perceptible  effect  when  allowed  to  fall  upon  the 
skin,  and  causes  a  sensation  only  when  admitted  to  the  eye.  The  impres- 
sion of  sound  is  appreciated  only  by  the  ear,  and  that  of  odors  only  by 
the  olfactory  membrane.  These  different  sensations,  therefore,  are  not 
merely  exaggerations  of  ordinary  sensibility,  but  are  peculiar  in  their 
nature,  and  are  in  relation  with  distinct  properties  of  external  objects. 


600  THE    SENSES. 

Each  organ  of  special  sense  consists — First,  of  a  nerve,  endowed  with 
the  special  sensibilitj'  required  for  its  peculiar  function ;  and,  Secondly, 
of  certain  accessory  parts,  forming  an  apparatus  adapted  to  aid  in  the 
performance  of  this  function,  and  render  it  more  delicate  and  complete. 

Sense  of  Taste. 

The  sense  of  taste  is,  in  some  measure,  intermediate  in  character 
between  the  functions  of  general  and  special  sensibility.  First,  the 
organ  by  which  it  is  exercised  forms  a  part  of  the  mucous  membrane 
lining  the  commencement  of  the  alimentary  canal,  furnished  with  vas- 
cular and  nervous  papillae  analogous  in  structure  to  those  of  the  general 
integument.  Secondly,  this  mucous  membrane  is  also  endowed  with 
general  sensibility.  Although  it  is  highly  probable  that  certain  minute 
formations  in  its  epithelial  layer,  known  as  "  taste  buds,"  may  be  espe- 
cially connected  with  the  perception  of  savors,  there  is  thus  far  no  cer- 
tainty in  this  respect ;  and  in  any  case  the  tactile  and  gustatory  sensi- 
bilities are  closely  intermingled  in  the  substance  of  the  mucous  mem- 
brane. Thirdly,  the  sensibility  of  taste  is  not  confined  to  the  fibres  of 
one  special  and  distinct  nerve,  but  resides  in  portions  of  two,  namely, 
the  lingual  branch  of  the  fifth  pair  and  the  glossopharyngeal  nerve, 
which  also  supply  general  sensibility  to  the  corresponding  parts. 
Fourthly,  this  sense  gives  rise  to  impressions  only  from  the  actual  con- 
tact of  sapid  substances  with  the  mucous  membrane,  and  can  establish 
no  communication  with  objects  at  a  distance ;  and  Fifthly,  though  some 
of  the  impressions  derived  from  this  source  are  of  a  distinct  and  special 
character,  others,  like  the  taste  of  oily  or  mucilaginous  substances,  differ 
but  little  in  kind  from  those  of  tactile  sensibility. 

The  sense  of  taste  is  localized  in  the  mucous  membrane  of  the  tongue, 
the  soft  palate,  and  the  pillars  of  the  fauces.  The  tongue,  which  is  more 
particularly  the  seat  of  this  sense,  is  a  flattened,  leaf-like  muscular  organ, 
attached  to  the  inner  surface  of  the  symphysis  of  the  lower  jaw  in  front, 
and  to  the  os  hyoides  behind.  It  has  a  vertical  sheet  or  lamina  of  fibrous 
tissue  in  the  median  line  which  serves  as  its  framework,  and  is  provided 
with  longitudinal,  transverse,  and  radiating  muscular  fibres,  by  which  it 
can  be  elongated,  retracted,  and  moved  in  every  direction. 

The  mucous  membrane  of  the  fauces  and  posterior  third  of  the  tongue, 
like  that  lining  the  cavity  of  the  mouth,  is  covered  with  vascular  papillae, 
analogous  in  structure  to  those  of  the  skin,  but  imbedded  and  concealed 
in  the  smooth  layer  of  epithelium  forming  the  surface  of  the  organ. 
Upon  the  dorsum  of  the  tongue,  about  the  junction  of  its  posterior  and 
middle  thirds,  there  is  a  double  row  of  rounded  eminences,  arranged  in 
a  V-shaped  figure,  running  forward  and  outward,  on  each  side,  from  the 
situation  of  the  foramen  caecum ;  and  from  this  point  forward,  the 
mucous  membrane  is  covered  with  thickly-set  papillae,  containing  nerves 
and  bloodvessels,  and  giving  a  soft  velvety  texture  to  the  surface  of  the 
organ. 

The  lingual  papillae  are  of  three  different  kinds.     First  i\\Q  filiform 


SENSE    OF    TASTE.  601 

papillae,  which  are  the  most  numerous,  and  which  cover  most  uniformly 
the  upper  surface  of  the  tongue.  They  are  long  and  slender,  and  are 
covered  with  horny  epithelium,  usually  prolonged  into  filamentous  tufts. 
At  the  edges  of  the  tongue  they  are  often  united  into  parallel  ranges 
or  ridges  of  the  mucous  membrane.  Secondly,  the  fungiform  papillae. 
These  are  thicker  and  larger  than  the  foregoing,  of  a  club-shaped 
figure,  and  covered  with  soft  epithelium.  They  are  most  abundant 
at  the  tip  of  the  tongue,  but  may  be  seen  elsewhere  on  the  surface  of 
the  organ,  scattered  among  the  filiform  papillae.  Thirdly,  the  circum- 
vallate  papillae.  These  are  the  rounded  eminences,  eight  or  ten  in 
number,  which  form  the  V-shaped  figure  near  the  situation  of  the  fora- 
men caecum.  Each  consists  of  a  central  eminence,  surrounded  by  a  wall 
or  circumvallation,  from  which  they  derive  their  name.  The  circum. 
vallation,  as  well  as  the  central  eminence,  has  a  structure  similar  to  that 
of  the  fungiform  papillae. 

The  sensitive  nerves  of  the  tongue,  as  above  mentioned,  are  two  in 
number,  namely,  the  lingual  branch  of  the  fifth  pair,  and  the  lingual 
portion  of  the  glossopharyngeal.  The  lingual  branch  of  the  fifth  pair 
enters  the  tongue  at  the  anterior  border  of  the  hyoglossal  muscle.  Its 
branches  pass  from  below  upward  and  from  behind  forward,  between  the 

Fig.  187. 


DIAGRAM  OP  THE  TONGUE,  with  its  sensitive  nerves  and  papillae. — 1.  Lingual  branch 
of  the  fifth  pair.    2.  Glossopharyngeal  nerve. 

muscular  bundles  of  the  organ,  until  they  reach  its  mucous  membrane. 
The  nerve  fibres  then  penetrate  the  lingual  papillae,  where  they  termi- 
nate, partly  in  the  "  terminal  bulbs"  already  described  (p.  594),  and 
partly  in  a  manner  not  yet  distinctly  ascertained. 

The  lingual  portion  of  the  glossopharyngeal  nerve  passes  into  the 
tongue  below  the  posterior  border  of  the  hyoglossus  muscle.  It  then 
divides  into  various  branches,  which  pass  through  the  muscular  tissue, 
and  are  distributed  to  the  mucous  membrane  of  the  base  and  sides  of 
the  organ. 

The  mucous  membrane  of  the  base  of  the  tongue,  of  its  edges,  and 
of  its  under  surface  near  the  tip,  as  well  as  that  of  the  mouth  and  fauces 
generally,  is  also  supplied  with  mucous  follicles  furnishing  a  viscid 
39 


602  THE    SENSES. 

secretion  by  which  its  free  surface  is  lubricated.  The  muscles  of  the 
tongue  are  animated  exclusive^  by  filaments  of  the  hypoglossal  nerve. 

The  exact  seat  of  the  sense  of  taste  has  been  determined  by  placing  in 
contact  with  different  parts  of  the  mucous  membrane  a  small  sponge, 
moistened  with  a  solution  of  some  sweet  or  bitter  substance.  The  ex- 
periments of  Duges,  Verniere,  and  Longet,  have  shown  that  taste  resides 
in  the  whole  superior  surface,  the  point  and  edges  of  the  tongue,  the  soft 
palate,  fauces,  and  part  of  the  pharynx.  The  base,  tip,  and  edges  of 
the  tongue  possess  the  greatest  amount  of  sensibility  to  savors,  the 
middle  portion  of  its  dorsum  less,  and  its  inferior  surface  little  or  none. 
As  the  whole  anterior  part  of  the  organ  is  supplied  by  the  lingual  branch 
of  the  fifth  pair  alone,  and  the  whole  of  its  posterior  portion  by  the 
glossopharyngeal,  it  follows  that  the  sense  of  taste  is  derived  from  both 
these  nerves. 

Furthermore,  the  tongue  is  supplied,  at  the  same  time  and  by  the  same 
nerves,  with  general  sensibility  and  with  the  special  sensibility  of  taste. 
The  general  sensibility  of  the  anterior  portion  of  the  tongue,  and  that 
of  the  branch  of  the  fifth  pair  with  which  it  is  supplied,  are  sufficiently 
well  known.  Section  of  the  fifth  pair  destroys  the  sensibility  of  this 
part  of  the  tongue  as  well  as  that  of  the  rest  of  the  face.  Longet  found 
that  after  division  of  the  lingual  branch  of  this  nerve,  the  mucous  mem- 
brane of  the  anterior  two-thirds  of  the  tongue  might  be  cauterized  with 
a  hot  iron  or  with  potassium  hydrate  in  the  living  animal,  without  pro- 
ducing any  sign  of  pain.  Reid,  on  the  other  hand,  determined  that 
ordinary  sensibility  exists  in  a  marked  degree  in  the  glossopharyngeal 
nerve,  and  is  supplied  by  it  to  the  parts  in  which  its  branches  are  dis- 
tributed. 

A  distinction  is  to  be  made,  in  the  action  of  foreign  substances  taken 
into  the  mouth,  between  the  special  impressions  derived  from  their  sapid 
qualities,  and  the  general  sensations  produced  by  their  ordinary  physical 
properties.  As  the  same  substance  is  often  capable  of  exciting  both 
tactile  and  gustatory  impressions,  the  two  are  sometimes  liable  to  be 
confounded  with  each  other  The  truly  sapid  qualities,  which  we  per- 
ceive by  the  special  sense  of  taste,  are  savors,  designated  by  the  terms 
sweet,  bitter,  salt,  sour,  alkaline,  and  the  like.  Beside  these,  however, 
there  are  other  characters,  belonging  to  various  articles  of  food,  which 
partake  largely  of  the  nature  of  ordinary  physical  properties,  appreci- 
able by  means  of  general  sensibility.  A  starchy,  oily,  or  mucilaginous 
taste,  when  uncomplicated  with  additional  savors,  is  but  little  different 
in  kind  from  the  tactile  impressions  produced  by  the  same  substances. 
The  quality  of  pungency,  communicated  to  the  food  by  the  use  of  con- 
diments, as  pepper  or  mustard,  is  one  which  is  appreciated  altogether 
by  the  general  sensibility.  The  styptic  taste  seems  to  be  a  combination 
of  an  ordinary  astringent  effect  with  a  peculiar  excitement  of  the  gus- 
tatory nerves,  analogous  to  that  caused  by  the  galvanic  stimulus. 

Furthermore,  the  taste  or  savor  of  a  substance  is  to  be  distinguished 
from  its  odoriferous  properties  or  flavor.  In  most  aromatic  articles  of 


SENSE    OF    TASTE.  603 

food,  such  as  tea  and  coffee,  and  the  various  kinds  of  wine,  a  great  part 
of  the  effect  produced  is  due  to  the  aroma  or  smell  which  reaches  the 
nares  during  the  act  of  swallowing.  Even  in  many  kinds  of  solid  food, 
such  as  freshly  cooked  meats,  their  odor  takes  a  very  important  share  in 
producing  the  impression  on  the  senses.  If,  during  the  deglutition  of 
such  substances,  the  nares  be  compressed  so  as  to  suspend  in  great 
measure  the  sense  of  smell,  their  ordinary  flavor  becomes  nearly  imper- 
ceptible ;  and  a  similar  effect  is  produced  by  catarrhal  inflammation  of 
the  nasal  passages,  which  suspends  more  or  less  completely  the  sensi- 
bility of  the  olfactory  membrane. 

Necessary  Conditions  of  the  Sense  of  Taste. — There  are  certain  con- 
ditions requisite  for  the  production  of  gustatory  impressions,  beside  the 
integrity  of  the  organ  by  which  they  are  received. 

In  the  first  place,  the  sapid  substance,  in  order  that  its  taste  may  be 
perceived,  must  be  brought  in  contact  with  the  mucous  membrane  in  a 
state  of  solution.  So  long  as  it  remains  solid,  however  marked  a  savor 
it  may  possess,  it  gives  no  other  impression  than  that  of  a  foreign  body 
in  contact  with  the  tongue.  But  if  applied  in  a  liquid  form,  it  spreads 
over  the  surface  of  the  mucous  membrane,  and  its  taste  is  perceived. 
Thus  it  is  only  the  liquid  and  soluble  portions  of  the  food  which  are 
tasted,  such  as  the  animal  and  vegetable  juices  and  the  soluble  salts. 
Saline  substances  which  are  insoluble,  such  as  calomel  or  lead  carbonate, 
when  applied  to  the  tongue,  produce  no  gustatory  sensation. 

The  mechanism  of  the  sense  of  taste  is,  in  all  probability,  a  direct 
and  simple  one.  The  sapid  substances  in  solution  penetrate  the  lingual 
papillae  by  endosmosis,  and,  coming  in  contact  with  the  terminal  nervous 
filaments,  excite  their  sensibility  by  uniting  with  the  substance  of  which 
they  are  composed.  The  rapidity  with  which  endosmosis  will  take 
place  under  certain  conditions  is  sufficient  to  account  for  the  instanta- 
neous perception  of  sapid  substances  when  introduced  into  the  cavity 
of  the  mouth. 

It  is  on  this  account  that  a  free  secretion  of  the  salivary  fluids  is 
essential  to  the  full  performance  of  the  gustatory  function.  If  the 
mouth  be  dry  and  parched,  the  food  seems  to  have  but  little  taste. 
When  the  saliva,  on  the  other  hand,  is  freely  secreted,  it  mixes  readily 
with  the  food  in  mastication,  and  assists  the  solution  of  its  sapid  ingre- 
dients; and  the  fluids  of  the  mouth,  impregnated  with  the  savory  sub- 
stances, are  absorbed  by  the  mucous  membrane,  and  excite  the  gusta- 
tory nerves. 

An  important  part  is  also  taken  in  this  process  by  the  movements  of 
the  tongue.  By  these  movements  the  food  is  carried  from  one  part  of 
the  mouth  to  another,  pressed  against  the  hard  palate,  the  gums,  and 
the  cheeks,  its  solution  assisted,  and  the  penetration  of  fluids  into  the 
papillae  more  rapidly  accomplished.  If  powdered  sugar,  or  a  bitter 
extract,  be  simply  placed  upon  the  dorsum  of  the  tongue,  little  or  no 
effect  is  produced  ;  but  when  pressed  by  the  tongue  against  the  roof  of 
the  moutli,  as  in  eating  or  drinking,  its  taste  is  immediately  perceived. 


604:  THE    SENSES. 

This  effect  is  easily  explained  ;  since  it  is  well  known  bow  readily  move- 
ment over  a  free  surface,  combined  with  slight  friction,  will  facilitate 
the  solution  and  imbibition  of  solid  substances.  The  nervous  papillae 
of  the  tongue  may  therefore  be  regarded  as  the  essential  organs  of  taste, 
and  the  lingual  muscles  as  its  accessory  organs. 

Impressions  of  taste  made  upon  the  tongue  remain  for  a  certain  time 
afterward.  When  a  very  sweet  or  a  very  bitter  substance  is  taken  into 
the  mouth,  its  taste  is  retained  for  several  seconds  after  it  has  been 
ejected  or  swallowed.  Consequently,  if  several  different  savors  be  pre- 
sented to  the  tongue  in  rapid  succession,  we  become  unable  to  distinguish 
them,  and  they  produce  only  a  confused  impression,  made  up  of  the 
union  of  various  different  sensations.  The  taste  of  the  first,  remaining 
in  the  mouth,  is  mingled  with  that  of  the  second,  the  taste  of  both  with 
that  of  the  third,  and  so  on,  until  neither  one  can  be  distinguished.  It 
is  notoriously  impossible  to  recognize  several  different  kinds  of  wine 
with  the  eyes  closed,  if  they  be  repeatedly  tasted  in  quick  succession. 

If  the  substance  first  tasted  have  a  particularly  marked  savor,  its 
impression  will  preponderate  over  that  of  the  others.  This  effect  is 
especially  produced  by  substances  which  excite  the  general  sensibility 
of  the  tongue,  such  as  acrid  or  stimulating  powders;  and  it  belongs, 
in  the  greatest  degree,  to  substances  which  are  at  the  same  time  sapid, 
pungent,  and  aromatic,  like  sweetmeats  flavored  with  the  volatile  oils. 
Advantage  is  sometimes  taken  of  this  in  the  administration  of  disagree- 
able medicines.  By  first  taking  into  the  mouth  some  highly  flavored 
and  pungent  substance,  nauseous  drugs  may  be  swallowed  immediately 
afterward  with  but  little  perception  of  their  disagreeable  qualities. 

Sense  of  Smell. 

The  distinguishing  character  of  the  sense  of  smell  is  that  it  gives  us 
intelligence  of  the  physical  quality  of  bodies  in  a  gaseous  or  vaporous 
condition.  Thus  by  its  aid  it  is  possible  to  detect  the  existence  of  an 
odoriferous  substance  at  a  distance,  and  although  it  may  be  concealed 
from  sight.  The  minute  quantity  of  volatile  material  emanating  from 
it,  and  pervading  the  atmosphere,  produces,  by  contact  with  the  olfactory 
membrane,  the  special  sensation  of  smell.  The  sense  of  smell  differs, 
furthermore,  from  that  of  taste  in  being  more  distinctly  localized.  While 
the  gustatory  sensibility  is  distributed  over  the  whole  mucous  mem- 
brane covering  the  dorsum  and  base  of  the  tongue,  and  is  supplied  to 
its  various  parts  by  two  different  sensitive  nerves,  that  of  smell  is  con- 
fined to  the  upper  portion  of  the  nasal  passages  and  is  dependent  on 
the  filaments  of  a  single  special  nerve. 

The  mucous  membrane  covering  the  superior  and  middle  turbinated 
bones  and  the  upper  part  of  the  septum  nasi,  which  is  alone  capable  of 
receiving  odorous  impressions,  and  is  limited  by  a  tolerably  well-defined 
outline,  is  known  as  the  olfactory  membrane.  It  is  easily  distinguish- 
able from  that  of  the  rest  of  the  nasal  passages:  1st,  by  its  color,  which 
in  man,  the  sheep,  and  the  calf  is  yellow,  but  in  most  of  the  other  mam- 


SENSE    OF    SMELL. 


605 


Fig.  188. 


malia  has  a  brownish  tinge;  2dly,  in  its  softer  and  more  succulent 
consistenc}7^ ;  and  3dly,  in  the  greater  thickness,  not  only  of  the  whole 
membrane  but  also  of  its  epithelial  layer.  According  to  Kolliker,  the 
epithelium  of  the  olfactory  membrane,  in  the  sheep  and  the  rabbit,  is 
from  60  to  66  per  cent,  thicker  than  that  of  the  remaining  nasal  mucous 
membrane.  It  also  differs,  according  to  the  same  observer,  in  the 
character  of  its  surface.  In  most  of  the  quadrupeds  the  epithelium  of 
the  Schneiderian  mucous  membrane  generally  is  covered  with  vibrating 
cilia,  which  are  absent  in  the  olfactory  portion  ;  though  in  man  the  vibrat- 
ing cilia  may  also  be  found  in  the  epithelium  of  the  olfactory  portion 
itself.  This  difference  of  structure  is  probably  connected  with  the 
inferior  acuteness  of  the  sense  of  smell  in  man,  as  compared  with  many 
of  the  lower  animals. 

The  nasal  passages  are  provided   with    nerves  •  from  three  different 
sources. 

I.  The  first  and  most  important  of  these  are  the  filaments  of  the 
olfactory  nerve  (Fig.  188,  i).  They  are  derived  immediately  from  the 
olfactory  bulb,  which  rests  upon  the  cribriform  plate  of  the  ethmoid 
bone,  and  from  which  they  penetrate  the  nasal  passages  through  the 
perforations  in  this  bony 
lamina.  An  important  pecu- 
liarity, however,  shows  itself 
in  the  nerve  fibres  of  this 
region.  While  the  substance 
of  the  so-called  olfactory 
nerves  within  the  cranial 
cavity,  as  well  as  that  of  the 
olfactory  bulb,  contains  dark 
bordered  medullated  nerve 
fibres,  like  those  in  other 
parts  of  the  white  substance 
of  the  brain,  the  filaments 
which  are  given  off  from  the 
under  side  of  the  olfactory 
bulb,  and  are  distributed  to 
the  Olfactory  membrane,  Con-  DISTRIBUTION  OF  NEBVES  i*  THE  NASAL 
tain  Only  pale,  flattened,  PASSAGES.— 1.  Olfactory  bulb,  with  its  nerves.  2. 

nucleated   nerve-fibres  with-     ™™ ^JiT™11  °f  the  fifth  pair<  3<  sPhen°-Palatine 
out  a  medullary  layer.     The 

main  question  of  interest  in  regard  to  them  is  that  of  their  final  mode 
of  termination;  but  this,  as  in  so  many  other  similar  cases,  has  thus  far 
escaped  absolute  demonstration.  The  branches  of  the  olfactory  nerves 
frequently  divide  and  subdivide,  forming  microscopic  plexuses  in  the 
substance  of  the  olfactory  membrane ;  and  the  finest  nervous  ramifica- 
tions are  to  be  followed  without  doubt  nearly  to  the  epithelial  surface 
f  the  membrane  itself.  According  to  the  researches  of  Schultze,  con- 
firmed by  these  of  Kolliker  and  Babuchin,  the  epitheMum  of  this  part 


THE    SENSES. 

consists  of  two  different  kinds  of  elongated  cells,  both  standing  verti- 
cally upon  the  mucous  membrane,  and  closely  adherent  to  each  other  by 
their  lateral  surfaces.  One  portion  are  analogous  in  form  to  ordinary 
nucleated  columnar  epithelium  cells  ;  the  remainder  are  very  slender  and 
filamentous,  except  in  their  middle  portion,  at  the  situation  of  their  oval 
nucleus.  The  deeper  portion  of  these  cells,  which  is  also  more  slender 
than  the  rest,  has  been  found  to  resemble  the  material  of  the  nerve  fibres 
in  its  reaction  with  solutions  of  gold  chloride ;  but  a  direct  continuity 
of  substance  between  the  fibres  and  the  cells  has  not  been  shown  in  an 
unequivocal  manner. 

There  is  no  doubt  that  the  nerve  filaments  given  off  from  the  olfac- 
tory bulb  are  the  special  agents  for  communicating  impressions  of  smell, 
and  that  they  are  the  only  ones  endowed  with  olfactory  sensibility. 
This  follows  from  their  exclusive  and  abundant  distribution  to  the  olfac- 
tory portion  of  the  nasal  membrane,  from  their  comparatively  large 
development  in  animals  of  acute  smell,  from  the  absence  of  this  sense 
in  cases  of  congenital  absence  of  the  olfactory  bulbs,  and  from  its  loss 
in  animals  after  their  destruction  (p.  515).  So  far  as  we  can  judge 
from  the  results  of  experiment,  they  are  not  capable  of  receiving  or 
transmitting  any  other  kind  of  sensibility  than  that  excited  by  odor- 
iferous substances. 

II.  The  second  set  of  nerves  distributed  to  the  nasal  passages  con- 
sists of  the  nasal  branch  of  the  fifth  pair,  and  its  ramifications  (Fig. 
188,  2).     This  nerve,  after  entering  the  cavity  of  the  nose  just  in  advance 
of  the  cribriform  plate  of  the  ethmoid  bone,  sends  its  filaments  mainly 
to  the  mucous  membrane  covering  the  inferior  turbinated  bone  and  the 
walls  of  the  inferior  meatus,  which  are  thus  supplied  with  general  sen- 
sibility, though  they  are  destitute  of  the  power  of  smell.     JSome  filaments 
from  this  nerve,  however,  are  also  continued  into  the  mucous  membrane 
of  the  olfactory  region,  where  they  run  in  proximity  to  those  of  the 
olfactory  nerves;   and  this  region,  according  to  the  observations  of 
Babuchin,1  possesses  consequently  a  certain  amount  of  general  sensi- 
bility, though  much  less  than  the  remainder  of  the  nasal  passages. 

III.  The  third  set  are  those  derived  from  the  spheno-palat ine  gan- 
glion of  the  sympathetic  (Fig.  188,  3)  which  supply  the  mucous  mem- 
brane of  the  posterior  part  of  the  nasal  passages  and  the  muscles  aiding 
in  the  closure  of  the  posterior  nares.     Finally,  the  muscles  which  regu- 
late the  expansion  of  the  anterior  nares  are  supplied  by  filaments  of  the 
facial  nerve. 

Necessary  Conditions  of  the  Sense  of  Smell In  order  to  produce 

an  olfactory  impression,  the  emanations  of  the  odoriferous  body  must 
be  drawn  freely  through  the  nasal  passages.  As  the  sense  of  smell  is 
situated  only  in  the  upper  part  of  these  passages,  whenever  an  unusu- 
ally faint  or  delicate  odor  is  to  be  perceived,  the  air  is  forcibly  directed 
toward  the  superior  turbinated  bones,  by  a  peculiar  inspiratory  move- 
In  Strieker's  Manual  of  Histology,  Buck's  Edition.  New  York,  1872,  p.  799. 


SENSE    OF    SIGHT.  607 

ment  of  the  nostrils,  a  movement  which  is  very  marked  in  many  of  the 
lower  animals.  As  the  odoriferous  vapors  arrive  in  the  upper  part  of 
the  nasal  passages,  they  are  probably  dissolved  in  the  secretions  of  the 
olfactory  membrane,  and  thus  brought  into  relation  with  its  nerves. 
Inflammatory  disorders  consequently  interfere  with  the  sense  of  smell, 
both  by  altering  the  secretions  of  the  part,  and  by  producing  a  tume- 
faction of  the  mucous  membrane,  which  prevents  the  free  passage  of 
air  through  the  nasal  fossae. 

A  distinction  is  also  to  be  made  between  the  perception  of  true  odors. 
and  the  excitement  of  the  general  sensibility  of  the  Schneiderian  mu- 
cous membrane  by  irritating  substances.  Some  of  the  true  odors  are 
similar  in  their  nature  to  impressions  perceived  by  the  sense  of  taste. 
Thus  we  have  sweet  and  sour  smells,  though  none  corresponding  to  the 
alkaline  or  the  bitter  tastes.  Most  of  the  odors,  however,  are  of  a  pe- 
culiar nature  and  are  difficult  to  describe ;  but  they  are  always  distinct 
from  the  simply  irritating  properties  which  may  belong  to  vapors  as 
well  as  to  liquids.  Thus,  pure  alcohol  has  little  or  no  odor,  and  is  only 
stimulating  to  the  mucous  membrane  ;  while  the  odor  of  wines,  cordials, 
and  perfumes,  is  communicated  to  them  by  other  ingredients  of  a  vege- 
table origin.  The  vapor  of  pure  acetic  acid  is  simply  irritating ;  while 
vinegar  has  also  a  peculiar  odor,  derived  from  its  vegetable  constituents. 
Ammonia  is  an  irritating  gas,  but  contains  no  proper  odoriferous  prin- 
ciple. 

The  sensations  of  smell,  like  those  of  taste,  remain  for  a  certain  time 
after  they  have  been  produced,  and  modify  in  this  way  other  less  strongly 
marked  odors  presented  afterward.  Asa  general  rule,  the  longer  the 
olfactory  membrane  is  exposed  to  a  particular  odor,  the  longer  its 
effect  continues ;  and  in  some  cases  it  may  be  perceived  for  many  hours 
after  the  odoriferous  substance  has  been  removed.  Odors,  however,  are 
particularly  apt  to  remain  after  the  removal  or  destruction  of  the  source 
from  which  they  were  derived,  owing  to  the  facility  with  which  the}'  are 
entangled  by  porous  substances,  such  as  plastered  walls,  carpets,  hang- 
ings, and  woollen  clothes. 

The  sense  of  smell,  which  is  only  moderately  developed  in  the  human 
species,  is  excessively  acute  in  some  of  the  lower  animals.  Thus,  the 
clog  will  not  only  discover  game  and  follow  it  by  the  scent,  but  will  dis- 
tinguish particular  individuals  by  their  odor,  or  recognize  articles  of 
dress  belonging  to  them  by  the  minute  quantity  of  odoriferous  vapor 
adhering  to  their  substance. 

Sense  of  Sight. 

This  is  the  most  remarkable  of  all  the  senses,  both  for  the  special 
nature  of  the  impressions  which  it  receives,  the  complicated  structure 
of  its  apparatus,  and  the  variety  and  value  of  the  information  which  it 
affords  with  regard  to  external  objects.  It  is  by  this  sense  that  we 
receive  the  impressions  of  light  and  color,  with  all  their  modifications 
of  intensity  and  combination,  and  acquire  our  principal  ideas  of  form, 


608 


THE    SENSES. 


space,  and  movement.  The  organs  of  touch,  taste,  and  smell,  in  order 
to  perform  their  functions,  must  be  placed  in  actual  contact  with  the 
foreign  substances  which  excite  their  activity  ;  and  even  that  of  hearing 
is  affected  only  by  the  sonorous  vibrations  of  the  atmosphere,  or  of  some 
other  solid  or  fluid  medium.  But  the  eye  is  equally  sensitive  to  the 
impressions  of  light,  whether  it  come  from  near  or  remote  objects,  or 
even  from  the  immeasurable  distances  of  the  fixed  stars.  It  is  also 
superior  to  the  other  organs  of  special  sense  in  the  rapidity  of  its  action, 
and  in  the  delicacy  of  the  distinctions  which  it  is  capable  of  making 
in  the  physical  qualities  of  external  objects  ;  and  it  affords  the  most 
continuous  and  indispensable  aid  for  all  the  ordinary  occupations  of 
life. 

Organ  of  Vision. — The  eyeball  consists  of  a  spheroidal  fibrous  sac, 
the  sclerotic  coat  (Fig.  189,  2),  filled  with  fluid  and  gelatinous  material, 

Fig.  189. 


HORIZONTAL  SECTION  OF  THE  RIGHT  EYEBALL.—!.  Optic  nerve.  2.  Sclerotic 
coat.  3.  Cornea.  4.  Canal  of  Schlemm.  5.  Choroid  coat.  6.  Ciliary  muscle.  7.  Iris.  8. 
Crystalline  lens.  9.  Retina.  10.  Hyaloid  membrane.  11.  Canal  of  Petit.  12.  Vitreous 
body. 

provided  anteriorly  with  a  transparent  portion,  the  cornea  (s),  and 
lined  at  its  posterior  part  with  a  nervous  expansion,  the  retina  (s), 
which  is  sensitive  to  light,  and  which  receives  the  luminous  rays  admit- 
ted through  the  cornea.  The  cavity  of  the  eyeball  is  therefore  like  that 
of  a  room  with  but  one  window,  where  all  the  light  which  enters  from  the 
front  necessarily  strikes  the  back  wall  of  the  apartment.  There  are,  in 
addition  to  the  above-mentioned  parts,  a  transparent  refracting  body 
with  convex  surfaces,  the  crystalline  lens  (s),  by  which  the  light  is 


SENSE    OF    SIGHT.  609 

concentrated  at  the  level  of  the  retina ;  a  perforated  muscular  curtain 
or  diaphragm,  the  iris  (7),  placed  in  front  of  the  lens,' which  regulates 
the  quantity  of  light  admitted  through  its  central  orifice,  the  pupil ;  and 
finally  a  vascular  membrane  with  an  opaque  layer  of  blackish-brown 
pigment,  the  choroid  (s),  which  lines  the  whole  inner  surface  of  the 
sclerotic  and  the  posterior  surface  of  the  iris,  thus  preventing  reflec- 
tions within  the  eye,  and  absorbing  all  the  light  which  has  once  passed 
through  the  substance  of  the  retina.  The  construction  of  the  eyeball, 
in  its  general  arrangement  as  an  organ  of  vision,  is  not  unlike  that  of 
a  photographic  camera;  where  the  sensitized  plate  at  the  back  part 
represents  the  retina,  the  blackened  inner  surface  of  the  box  the  choroid, 
wrhile  the  lenses  of  the  tube  in  front  perform  the  office  of  the  crystalline 
lens  and  cornea  of  the  eyeball. 

Sclerotic  Coat. — The  sclerotic,  so  named  from  its  toughness  and  re- 
sistance, is  the  external  coat  and  protective  membrane  of  the  eyeball.  It 
is  composed  of  condensed  layers  of  connective  tissue,  similar  to  those 
of  the  fasciae  and  membranous  tendons  in  general ;  and  toward  its  an- 
terior third  it  receives  the  tendons  of  the  external  muscles  of  the  eyeball, 
which  become  fused  with  its  substance.  Posteriorly  it  is  continuous 
with  the  neurilemma  of  the  optic  nerve  (Fig,  189,  i),  which  penetrates  it 
from  behind  at  its  point  of  entrance  into  the  eyeball.  A  portion  of  the 
sclerotic  is  visible  anteriorly  through  the  conjunctiva,  forming  the  so- 
called  "white"  of  the  eye. 

Cornea. — The  cornea,  which  derivesMts  name  from  its  firm  consistencjr 
and  homogeneous  appearance,  resembling  that  of  horn,  forms  the  anterior 
part  of  the  wall  of  the  eyeball.  It  is  inserted  into  the  nearly  circular 
space  left  at  this  situation  by  the  deficiency  of  the  sclerotic,  with  the 
texture  of  which  it  is  continuous  at  its  edges  ;  the  difference  in  the  phy- 
sical appearance  of  the  two  being  that  the  sclerotic  is  white  and  opaque, 
while  the  cornea  is  colorless  and  transparent,  so  that  the  colored  iris 
and  dark  pupil  are  visible  through  its  substance.  The  surface  of  the 
cornea  has  a  sharper  curvature  than  that  of  the  sclerotic,  so  that  it  pro- 
jects from  the  front  of  the  eyeball,  like  a  smaller  dome  set  upon  a  larger 
one.  Its  outline,  where  it  joins  the  edge  of  the  sclerotic,  is  a  little  oval 
in  form,  the  transverse  diameter  of  the  cornea,  in  man,  being  slightly 
longer  than  the  vertical.  At  its  centre,  it  is  about  0.8  millimetre  in 
thickness,  becoming  a  little  thicker  at  its  edges.  Its  anterior  surface  is 
kept  polished  and  brilliant  by  the  watery  secretion  of  the  lachrymal 
glands,  distributed  over  it  by  the  frequent  movements  of  the  eyeball 
and  the  lids. 

At  the  outer  border  of  the  cornea,  where  it  joins  the  sclerotic,  and 
where  the  tissues  of  the  two  membranes  pass  into  each  other,  there  is  a 
small  cavit}',  running,  in  the  form  of  a  circular  canal,  the  canal  of 
Schlemm  (Fig.  189,  4),  through  the  thickness  of  this  part  of  the  wall 
of  the  eyeball.  The  inner  wall  of  the  canal  of  Schlemm  is  composed  of 
elastic  and  tendinous  tissue,  and  gives  attachment  to  the  fibres  of  the 
ciliary  muscle  on  the  one  hand,  and  on  the  other  to  the  outer  border  of 


610  THE    SENSES. 

the  iris.  The  canal  itself  is  regarded  by  most  anatomists  as  occupied 
by  a  venous  plexus,  which  receives  veins  from  the  ciliary  muscle  and 
from  the  anterior  part  of  the  sclerotic. 

Choroid. The  choroid  coat  is  a  vascular  and  pigmentary  membrane, 

lining  the  inner  surface  of  the  sclerotic,  and  presenting  anteriorly  a  thick- 
ened portion,  the  "  ciliary  body."  The  inner  part  of  the  ciliary  body 
is  thrown  into  a  series  of  radiating  folds,  the  "  ciliary  processes,"  which 
surround  the  borders  of  the  crystalline  lens.  The  internal  surface  of  the 
choroid  is  occupied  by  a  layer  of  hexagonal  nucleated  cells,  closely  packed 
side  by  side,  and  filled  with  granules  of  blackish-brown  pigment.  Similar 
pigment  is  also  deposited,  though  less  abundantly,  in  the  substance  and 
near  the  external  surface  of  the  choroid.  At  its  anterior  part,  the  cho- 
roid is  separated  from  the  internal  surface  of  the  sclerotic  by  the  ciliary 
muscle  (Fig.  189,  e).  This  muscle  is  composed  of  unstriped  fibres,  which 
arise  from  the  inner  wall  of  the  canal  of  Schlemm,  at  the  junction  of 
the  sclerotic  and  cornea,  and  thence  diverge  in  a  radiating  direction, 
outward  and  backward,  to  be  inserted  into  the  external  surface  of  the 
choroid,  at  the  point  where  it  begins  to  pass  into  the  folds  of  the  ciliary 
processes.  At  the  anterior  and  inner  part  of  the  muscle  there  are  also 
bundles  of  circular  fibres,  running  parallel  with  the  margin  of  the  cornea. 
The  whole  muscle  is  thus  composed  of  two  parts ;  namely,  an  internal 
circular,  and  an  external  radiating  portion,  the  fibres  of  which  are  more  or 
less  interwoven  with  each  other  at  the  inner  edge  of  the  muscular  layer. 

Iris. — The  iris  is  a  variously  colored  membrane,  extending  across 
the  antero-posterior  axis  of  the  eyeball,  attached  by  its  external  border 
to  the  inner  wall  of  the  canal  of  Schlemm,  and  presenting  at  its  centre 
the  nearly  circular  orifice  of  the  pupil.  It  consists  of  connective  and 
muscular  tissue,  with  an  abundant  supply  of  bloodvessels,  and  is  covered 
on  its  posterior  surface  by  a  layer  of  blackish-brown  pigment  cells,  con- 
tinuous with  that  of  the  choroid.  The  color  of  the  iris,  which  appears, 
in  different  individuals,  blue,  gray,  brown,  or  black,  depends  upon  the 
abundance  and  disposition  of  its  pigmentary  elements.  In  gray  and  blue 
eyes,  the  visible  hue  of  the  iris  depends  upon  the  diffused  light  of  its 
semi-transparent  tissues,  seen  against  the  dark  back-ground  of  the  pig- 
ment layer  upon  its  posterior  surface.  In  brown  and  black  eyes,  the 
pigment  is  more  abundant,  and  is  deposited,  according  to  Kolliker  and 
Cruveilhier,  not  only  upon  the  posterior  aspect  of  the  iris,  but  also  in 
its  stroma,  between  its  fibres,  and  to  some  extent  even  upon  its  anterior 
surface.  It  thus  predominates,  and  extinguishes  more  or  less  com- 
pletely the  reflected  and  diffused  light  of  the  remaining  elements  of  the 
tissue. 

The  position  of  the  iris  is  such  that  while  its  outer  border  is  attached 
to  the  junction  of  the  cornea  and  sclerotic,  its  central  portion  lies  in 
contact  with  the  anterior  surface  of  the  crystalline  lens.  According  to 
the  observations  of  Helmholtz,1  the  iris  in  myopic  eyes  is  sometimes  so 

1  Optique  Physiologique,  traduit  par  Javal  et  Klein.     Paris,  1867,  p.  20. 


SENSE    OF    SIGHT.  611 

nearly  flat  that  it  throws  no  perceptible  shadow  under  an  extreme  late- 
ral illumination ;  but  in  normal  eyes,  as  a  rule,  the  portion  immediately 
surrounding  the  pupil  is  sufficiently  prominent  to  throw  a  distinct 
shadow ;  and  if  the  source  of  illumination  be  not  more  than  one  milli- 
metre in  advance  of  the  edge  of  the  cornea,  this  shadow  may  extend 
even  to  the  opposite  border  of  the  iris. 

When  the  pupil  dilates,  the  central  prominence  of  the  iris  of  course 
diminishes,  or  even  disappears  altogether;  but, according  to  Helmholtz, 
the  pupillary  border  of  the  iris  hardly  separates  from  the  anterior  face 
of  the  lens,  even  in  the  most  complete  dilatation  obtainable  by  bella- 
donna. 

An  important  portion  of  the  structure  of  the  iris  is  formed  by  its 
muscular  fibres.  These  are  arranged  in  two  sets,  both  of  which  consist 
of  unstriped  fibres,  namely,  the  sphincter  and  the  dilator  muscles  of  the 
pupil. 

The  sphincter  pupillse  is  composed  of  bundles  of  muscular  fibres, 
situated  at  the  pupillary  margin  of  the  iris,  and  circularly  disposed,  in 
such  a  manner  that  their  contraction  has  the  effect  of  diminishing  the 
orifice  of  the  pupil,  while  their  relaxation  allows  of  its  enlargement. 
When  the  sphincter  is  in  a  state  of  moderate  contraction,  the  remaining 
non-contractile  portions  of  the  iris  are  thrown  into  radiating  folds, 
which  can  be  readily  seen,  under  the  influence  of  ordinary  daylight, 
extending  from  the  pupillary  margin  for  one-third  or  one-half  the  dis- 
tance toward  its  outer  border. 

The  dilator  pitpillde,  which  consists  of  radiating  muscular  fibres,  is 
much  more  difficult  of  demonstration,  and  its  existence  in  man  con- 
tinued to  be  a  matter  of  uncertainty,  even  after  it  was  known  to  be 
present  in  the  lower  animals.  It  has,  however,  been  described  by  so 
many  independent  observers,  that  there  can  be  no  doubt  of  its  forming 
a  normal  part  of  the  muscular  apparatus  of  the  iris.  Its  fibres  are 
interwoven  with  those  of  the  sphincter  at  the  pupillary  margin,  and 
extend  thence  in  a  diverging  direction  toward  the  attached  border ; 
either  as  isolated  bundles  running  between  the  bloodvessels  (Briicke, 
Kolliker),  or  as  a  very  thin,  continuous  sheet  of  fibres,  covering  the 
whole  posterior  surface  of  the  iris,  immediately  underneath  its  pig- 
mentary layer  (Henle,  Iwanoff).  According  to  Kolliker,  the  iris  also 
contains  elements  analogous  to  the  fibres  of  elastic  tissue,  which  may 
thus  assist  the  action  of  the  dilator. 

Notwithstanding  the  acknowledged  existence  of  both  these  muscles, 
and  their  evident  physiological  association  with  each  other,  the  action 
of  the  sphincter  is  much  the  most  prominent  and  the  most  clearly 
understood.  It  is  this  muscle  which  contracts  under  the  influence  of 
light  falling  upon  the  retina,  causing  contraction  of  the  pupil,  and  which 
relaxes  when  the  stimulus  is  withdrawn,  causing  dilatation.  The  con- 
traction of  the  pupil  is  therefore,  for  the  most  part,  an  active  movement; 
its  dilatation  a  passive  one.  Division  of  the  oculomotorius  nerve,  loss 
of  sensibility  in  the  retina,  opacity  of  the  crystalline  lens,  or  insensi- 


612  THE    SENSES. 

bility  from  cerebral  compression,  are  all  followed  by  dilatation  of  the 
pupil ;  and  the  same  thing  takes  place  immediately  after  death.  In  the 
normal  reflex  actions  of  expansion  and  contraction  of  the  pupil,  under 
the  varying  intensity  of  illumination,  the  fibres  of  the  sphincter  are 
those  which  alternately  contract  and  relax  in  a  manner  analogous  to 
that  of  the  voluntary  muscles  ;  while  those  of  the  dilator  are  more  con- 
tinuous in  their  operation,  and  are  under  the  control  of  different  nervous 
influences. 

The  pigmentary  layer  which  is  continued  uninterruptedly,  except  at 
the  entrance  of  the  optic  nerve,  over  the  internal  surface  of  the  choroid, 
the  ciliary  processes,  and  the  posterior  surface  of  the  iris,  is  called  the 
system  of  the  uvea,  from  its  resemblance  to  the  skin  of  a  purple  grape 
separated  from  its  stem ;  the  opening  of  the  membranous  sac  at  the 
point  of  detachment  representing  the  orifice  of  the  pupil.  Owing  to  the 
existence  of  this  continuous  pigmentary  layer,  no  light  can  penetrate 
the  eyeball  excepting  that  which  enters  through  the  pupil;  and  the 
rays,  furthermore,  which  reach  the  retina  at  any  point  are  arrested 
there,  and  prevented  from  being  dispersed  by  reflection  over  other  parts 
of  the  membrane. 

Aqueous  Humor  and  Vitreous  Body. — By  the  transverse  partition  of 
the  iris,  the  cavity  of  the  eyeball  is  divided  into  two  portions,  an  anterior 
and  posterior.  The  portion  situated  in  front  of  the  iris,  called  the  "an- 
terior chamber,"  is  filled  with  a  colorless,  transparent  fluid,  of  watery 
consistency,  the  aqueous  humor.  This  fluid  is  to  be  regarded  as  an 
extremely  dilute  exudation  from  the  bloodvessels  of  the  surrounding 
parts,  especially  from  those  of  the  iris  ;  since  it  consists  mainly  of  water, 
holding  in  solution  less  than  two  per  cent,  of  solid  ingredients,  namely, 
sodium  chloride  and  other  inorganic  salts  derived  from  the  blood,  with 
a  trace  of  albuminous  matter.  It  is  faintly  alkaline  in  reaction,  and 
has  a  refractive  power  but  slightly  different  from  that  of  water.  It 
is  rapidly  reproduced  after  evacuation  by  puncture  of  the  cornea.  It 
serves  to  maintain  the  internal  tension  of  the  anterior  parts  of  the  eye- 
ball, and  to  allow  of  the  changes  of  figure  of  the  iris  and  crystalline 
lens,  without  affecting  the  external  configuration  of  the  cornea.  The 
posterior  and  larger  portion  of  the  cavity  of  the  eyeball  is  filled  mainly 
by  a  semifluid  substance,  the  vitreous  body,  so  called  from  its  trans- 
parent and  glassy  appearance.  Its  composition  is  similar  to  that  of  the 
aqueous  humor,  excepting  for  the  larger  proportion  of  albuminous 
matter,  which  gives  it  more  or  less  of  a  gelatinous  consistency.  Its 
refractive  power,  according  to  Helmholtz,  though  slightly  greater  than 
that  of  the  aqueous  humor,  does  not  differ  much  from  that  of  water. 
It  distends  the  principal  part  of  the  cavity  of  the  sclerotic,  supports  the 
retina  which  is  extended  over  its  surface,  and  preserves  the  general 
spheroidal  form  of  the  eyeball. 

The  vitreous  bocty  is  enveloped  by  an  exceedingly  thin,  colorless 
membrane,  for  the  most  part  without  definite  structure,  and  measuring, 
according  to  Kolliker,  not  more  than  4  mmni.  in  thickness.  This  is  the 


SENSE    OF    SIGHT.  613 

"  hyaloid  membrane"  (Fig.  189, 10).  Its  inner  surface  is  in  contact  with 
the  vitreous  body,  its  outer  surface  with  the  retina.  It  extends  unin- 
terruptedly over  the  posterior  and  middle  portions  of  the  vitreous  body 
until  it  reaches  a  point  anteriorly  corresponding  with  the  ciliary  body 
of  the  choroid.  Here  it  becomes  thicker  and  divides  into  two  layers. 
The  anterior  layer,  which  is  the  stronger  of  the  two,  the  zone  of  Zinn, 
extends  forward  and  inward,  remaining  adherent  to  the  folds  of  the 
ciliary  body,  and  terminates  in  the  capsule  of  the  crystalline  lens,  just 
in  front  of  its  lateral  border.  The  posterior  layer  of  the  hyaloid  mem- 
brane, after  separating  from  the  anterior,  passes  inward  and  a  little 
backward,  and  terminates  also  in  the  capsule  of  the  lens,  but  a  little 
behind  its  lateral  border.  The  triangular  canal  left  between  the  two 
separated  layers  of  the  hyaloid  membrane  and  the  lateral  border  of  the 
lens  is  the  canal  of  Petit  (Fig.  189,  n),  and  is  filled  with  a  little  trans- 
parent serosity.  The  lens  is  thus  suspended  on  all  sides  by  a  double 
layer  derived  from  the  hyaloid  membrane.  The  anterior  portion  of 
this  double  layer,  or  the  zone  of  Zinn,  being  the  stronger  of  the  two, 
and  presenting  a  distinctly  fibrillated  texture,  is  regarded  as  more 
especially  fulfilling  the  part  of  a  suspensory  ligament  of  the  crystalline 
lens. 

Crystalline  Lens — The  lens  is  a  transparent,  refractive  body,  of  cir- 
cular form,  with  convex  anterior  and  posterior  surfaces,  placed  directly 
behind  the  pupil,  and  retained  in  its  position  by  the  counterbalancing 
pressure  of  the  aqueous  humor  and  the  vitreous  body,  and  by  the  two 
layers  of  the  hyaloid  membrane  attached  to  its  capsule  round  its  circular 
border.  It  is  composed  of  flattened  fibres,  adherent  to  each  other  by 
their  adjacent  surfaces  and  edges,  and  so  arranged  as  to  pass  in  a 
curvilinear  direction,  parallel  to  the  surface  of  the  lens,  from  one  of  its 
two  opposite  poles  to  the  other.  Notwithstanding  the  fibrous  structure 
of  the  lens,  the  ribbon-shaped  elements  of  which  it  is  composed  being 
united  by  simple  juxtaposition,  without  the  intervention  of  any  different 
material,  the  entire  body  is  transparent,  and  allows  the  passage  of  the 
light  without  perceptible  absorption  or  irregular  dispersion. 

As  the  refractive  power  of  the  substance  of  the  crystalline  is  greater 
than  that  of  the  cornea  or  the  aqueous  humor,  it  acts,  by  virtue  of  its 
double-convex  form,  as  a  converging  lens,  to  change  the  direction  of 
the  luminous  rays  passing  through  it,  and  bring  them  to  a  focus  at 
some  point  situated  behind  its  posterior  surface.  The  amount  of  con- 
vergence thus  effected  by  a  refractive  lens  depends  both  upon  the  index 
of  refraction  of  the  substance  of  which  it  is  composed  and  the  greater 
or  less  curvature  of  its  surfaces.  The  stronger  the  curvatures,  for 
lenses  composed  of  the  same  material,  the  greater  the  amount  of  con- 
vergence impressed  upon  luminous  rays  passing  through  them.  In  the 
case  of  the  crystalline  lens  of  the  human  eye,  the  two  surfaces  are  dif- 
ferent in  curvature ;  the  anterior  surface  being  comparatively  flat,  the 
posterior  much  more  convex.  According  to  the  estimates  of  Listing, 
based  upon  a  variety  of  measurements,  and  adopted  by  Helmholtz,  the 


614  THE    SENSES. 

radius  of  curvature  for  the  anterior  surface  is,  on  the  average,  10  milli- 
metres, that  for  the  posterior  surface  6  millimetres. 

This  makes  the  crystalline  lens  the  most  powerfully  refracting  body  in 
the  eyeball,  and  by  it  said  parallel  or  diverging  luminous  rays,  after  pass- 
ing through  the  pupil,  are  brought  to  a  focus  at  the  situation  of  the 
retina.  This  effect  is  not  due  entirely  to  the  lens,  since  the  convex  form 
of  the  cornea  and  the  more  or  less  spheroidal  figure  of  the  whole  eye- 
ball necessarily  have  in  some  degree  a  similar  action  upon  rays  enter- 
ing from  the  front.  According  to  Helmholtz,  parallel  rays  would  be 
brought  to  a  focus  "by  the  cornea  alone,  if  they  were  sufficiently  pro- 
longed, at  a  point  situated  10  millimetres  behind  the  retina.  But  on 
passing  through  the  lens,  their  convergence  is  increased  to  such  a  degree 
that  they  are  concentrated  at  the  situation  of  the  retina  itself. 

The  function  of  the  crystalline  lens  is  to  produce  distinct  perception 
of  form  and  outline.  If  the  eye  consisted  merely  of  a  sensitive  retina, 
covered  with  transparent  integument,  although  the  impressions  of  light 
would  be  received  by  such  a  retina,  they  could  give  no  idea  of  the  form 
of  particular  objects,  but  would  only  produce  the  sensation  of  a  confused 
luminosity.  This  condition  is  illustrated  in  Fig.  190,  where  the  arrow, 
a,  6,  represents  the  luminous  object,  and  the  vertical  dotted  line,  at  the 
right  of  the  diagram,  represents  the  retina.  The  rays,  diverging  from 
every  point  of  the  object  in  every  direction,  will  thus  reach  every  part 
of  the  retina.  The  different  parts  of  the  retina,  consequently,  1,  2,  3,  4, 
will  each  receive  rays  coming  both  from  the  point  of  the  arrow,  a,  and 
from  its  butt,  b.  There  will,  therefore,  be  no  distinction,  upon  the  retina, 
between  the  different  parts  of  the  object,  and  no  definite  perception  of 
its  figure.  But  if,  between  the  object  and  the  retina,  there  be  inserted  a 
double  convex  refracting  lens,  with  the  proper  curvatures  and  density, 
as  in  Fig.  191,  the  effect  will  be  different.  All  the  rays  emanating  from 

Fig.  190.  Fig.  191. 


VISION  WITHOUT  A  LENS.  VISION  WITH  A  LENS. 

a  will  then  be  concentrated  at  a?,  and  all  those  emanating  from  ~b  will  be 
concentrated  at  y.  Thus  the  retina  will  receive  the  impression  of  the 
point  of  the  arrow  separate  from  that  of  its  butt ;  and  all  parts  of  the 
object,  in  like  manner,  will  be  distinctly  and  accurately  perceived. 

The  action  of  a  refractive  body  with  convex  surfaces,  in  thus  focussing 
luminous  rays  at  a  particular  point,  may  be  readily  illustrated  in  the 
following  manner.  If  a  sheet  of  white  paper  be  held  at  a  short  distance 
from  a  candle  flame,  in  a  room  where  there  is  no  other  source  of  light, 


SENSE    OF    SIGHT.  615 

the  whole  of  the  paper  will  be  moderately  and  uniformly  illuminated  by 
the  diverging  rays.  But  if  a  double  convex  glass  lens,  with  suitable 
curvatures,  be  interposed  between  the  paper  and  the  light,  the  outer 
portions  of  the  paper  will  become  darker  and  its  central  portion  brighter, 
because  a  portion  of  the  rays  are  diverted  from  their  original  course  and 
bent  inward  toward  each  other.  By  varying  the  position  of  the  lens 
and  its  distance  from  the  paper,  a  point  will  at  last  be  found,  where 
none  of  the  light  reaches  the  external  parts  of  the  sheet,  but  all  of  it  is 
concentrated  upon  a  single  spot ;  and  at  this  spot  will  be  seen  a  distinct 
inverted  image  of  the  end  of  the  candle  and  its  flame. 

Distinct  perception  of  the  figure  of  external  objects  thus  depends 
upon  the  action  of  the  crystalline  lens  in  converging  all  the  rays  of 
light,  emanating  from  a  given  point,  to  an  accurate  focus  at  the  retina. 
For  this  purpose,  the  density  of  the  lens,  the  curvature  of  its  surfaces, 
and  its  distance  from  the  retina,  must  all  be  properly  adapted  to  each 
other.  If  the  lens  were  too  convex,  and  its  refractive  power  excessive, 
or  if  its  distance  from  the  retina  were  too  great,  the  rays  would  con- 
verge to  a  focus  too  soon,  and  would  not  reach  the  retina  until  after 
they  had  crossed  each  other  and  become  partially  dispersed,  as  in  Fig. 
192.  The  visual  impression,  therefore,  coming  from  any  particular  point 
in  the  object,  would  not  be  concentrated  and  distinct,  but  diffused  and 
dim,  from  being  dispersed  more  or  less  over  the  retina,  and  interfering 
with  the  impressions  from  other  parts.  On  the  other  hand,  if  the  lens 
were  too  flat,  as  in  Fig.  193,  or  placed  too  near  the  retina,  the  rays 

Fig.  192.  Fig.  193. 


INDISTINCT  IMAGE  from  excessive  INDISTINCT  IMAGE  from  deficient 

refraction.  refraction. 

would  fail  to  come  together  at  all,  and  would  strike  the  retina  sepa- 
rately, producing  a  confused  image,  as  before.  In  both  these  cases,  the 
immediate  cause  of  the  confusion  of  sight  is  the  same,  namely,  that 
rays  coming  from  the  same  point  of  the  object  strike  different  points  of 
the  retina ;  but  in  the  first  instance,  this  is  because  the  rays  have  actually 
converged  and  crossed  each  other ;  in  the  second,  it  is  because  they  have 
only  approximated,  but  have  never  converged  to  a  focus. 

The  proof  that  the  rays  emanating  from  luminous  objects  are  ac- 
tually thus  concentrated,  in  the  interior  of  the  living  eye,  upon  the 
retina,  is  furnished  by  the  use  of  the  ophthalmoscope.  This  instrument 
consists  essentially  of  a  mirror,  so  placed  as  to  illuminate  by  reflected 
light,  through  the  pupil,  the  bottom  of  the  eye  which  is  under  observa- 


616  THE    SENSES. 

tion,  and  perforated  at  its  centre  by  a  small  opening  through  which  the 
observer  looks.  By  this  means  the  retina  and  its  vessels,  as  well  as 
the  images  delineated  upon  it,  may  be  distinctly  seen.  According  to 
the  observations  of  Helmholtz,  objects  at  a  certain  distance,  which  are 
perceived  with  distinctness,  present  to  the  eye  of  the  observer,  if  suffi- 
ciently illuminated,  perfectly  well-defined  inverted  images  upon  the  ret- 
ina, like  those  which  would  be  thrown  upon  a  screen  by  a  system  of  glass 
lenses  properly  arranged.  If  the  eyeball  furthermore  be  taken  out  from 
a  recently  killed  animal,  and  a  circular  portion  of  the  sclerotic  and  ch.oroid 
removed  from  its  posterior  part,  similar  inverted  images  of  illuminated 
objects  in  front  of  the  cornea  may  be  seen  by  transparency  upon  the 
exposed  portion  of  the  retina. 

It  is  accordingly  certain  that  luminous  rays  in  passing  through  the 
eyeball  are  brought  to  a  focus  at  the  retina,  principally  by  means  of  the 
crystalline  lens.  The  formation  of  a  visible  image  at  this-  spot  does 
not  by  itself  explain  all  the  phenomena  of  vision,  since  these  images 
are  not  seen  by  the  individual,  and  we  should  not  even  know  of  their 
existence  except  for  the  results  of  physiological  experiment  and  obser- 
vation. But  the  formation  of  such  an  image  shows  that  all  the  light 
coming  from  each  different  part  of  the  object  is  made  to  fall  upon  a 
separate  and  distinct  point  of  the  retina ;  and  it  thus  becomes  possible 
to  perceive  the  figure  and  extension  of  an  object,  as  well  as  its  luminosity. 

Retina. — The  retina  is  the  most  essential  part  of  the  organ  of  vision, 
since  it  is  the  only  one  of  its  tissues  directly  sensitive  to  light.  It 
forms  a  delicate,  colorless,  nearly  transparent  membrane,  composed 
of  nervous  elements,  situated  between  the  inner  surface  of  the  choroid 
and  the  outer  surface  of  the  hyaloid  membrane,  and  extending  from  the 
entrance  of  the  optic  nerve  outward  and  forward  to  the  commencement 
of  the  ciliary  body.  Here  it  terminates  by  an  indented  border,  termed 
the  or  a  serrata,  which  is  situated  nearly  at  the  plane  of  the  posterior 
surface  of  the  crystalline  lens.  In  front  of  this  region  it  is  replaced  by 
an  attenuated  layer,  which  remains  in  contact  with  the  surface  of  the 
ciliary  body,  but  which  contains  no  nervous  elements.  The  retina 
proper  has,  accordingly,  the  form  of  a  thin  membrane  moulded  upon  a 
nearly  hemispherical  surface,  the  concavity  of  which  is  directed  for- 
ward, and  which  receives  the  luminous  rays  admitted  through  the  pupil, 
and  traversing  the  transparent  and  refracting  media  of  the  ej^eball.  Its 
greatest  thickness  is  in  the  immediate  vicinity  of  the  entrance  of  the 
optic  nerve,  where  it  measures,  according  to  Kolliker,  0.40  millimetre. 
At  a  short  distance  from  this  point  it  is  reduced  to  0.20,  and  thence 
becomes  gradually  thinner  in  its  middle  and  anterior  portions.  At  its 
terminal  border,  at  the  ora  serrata,  it  is  only  0.09  millimetre  in  thickness. 

The  retina  consists  of  a  variety  of  superimposed  Ia3'ers,  in  which 
many  different  microscopic  elements  alternate  with  each  other.  In  re- 
gard to  its  physiological  properties,  so  far  as  these  have  been  deter- 
mined with  a  sufficient  degree  of  certainty,  four  of  these  layers  may  be 
distinguished  as  representing  the  essential  constituent  parts  of  the 


SENSE    OF    SIGHT.  617 

membrane.  These  layers,  counting  from  the  internal  to  the  external 
surface  of  the  retina,  are  as  follows:  1.  The  layer  of  nerve  fibres,  de- 
rived from  the  expansion  of  the  optic  nerve;  2.  The  ganglionic  layer 
of  nerve  cells;  3.  The  layer  of  nuclei;  4.  The  layer  of  rods  and 
cones. 

1.  Layer  of  Nerve  Fibres. — The  optic  nerve  joins  the  posterior  part 
of  the  eyeball  at  a  point  about  2  millimetres  inside  its  longitudinal  axis, 
and  slightly  below  the  horizontal  plane  of  this  axis.     The  neurilemma 
of  the  nerve  at  once  becomes  continuous  with  the  sclerotic  coat  of  the 
e}*eball,  while  the  nerve  fibres  alone  penetrate  into  its  cavity.     Up  to 
this  point  the  fibres  of  the  optic  nerve  present  the  usual  dark-bordered 
appearance  of  medullated  nervfc  fibres,  and  have,  according  to  Kolliker, 
a  diameter  of  from  1  to  4.5  mmm.     But  at  their  entrance  into  the  cavity 
of  the  eyeball  the  nerve  fibres  not  only  lose  the  prolongations  of  con- 
nective tissue  which  previously  surrounded  their  different  bundles,  but 
also  become  much  smaller  in  size,  being  reduced,  on  the  average,  to 
less  than  2  mmm.,  and  many  of  them  to  less  than  1  mmm.  in  diameter. 
Owing  to  these  changes,  the  nerve  appears  suddenly  diminished  in  size 
at  its  passage  through  the  sclerotic  and  choroid  membranes.     Internally 
it  forms  a  slight  prominence  on  the  inner  surface  of  the  wall  of  the  eye- 
ball, the  so-called  papilla  ;  and  from  a  depression  at  its  middle  part,  the 
central  artery  and  vein  of  the  retina  send  out  their  branches  to  supply  the 
retinal  capillary  plexus.     From  the  papilla  as  a  centre  the  optic  nerve 
fibres,  which  have  thus  reached  the  inner  surface  of  the  retina,  diverge 
in  every  direction  under  the  form  of  a  closely  set  layer.     This  layer 
diminishes  gradually  in  thickness  from  within  outward,  and  from  behind 
forward,  owing  to  the  fact  that  the  nerve  fibres  of  which  it  is  composed 
terminate  successively  in  the  deeper  parts  of  the  membrane,  thus  estab- 
lishing a  connection  between  every  point  of  the  retina  and  the  nervous 
centres  in  the  brain.     The  longest  fibres  continue  their  course  until  they 
reach  the  ora  serrata  at  the  anterior  limit  of  the  retina,  beyond  which 
none  are  visible. 

2.  Ganglionic  Layer  of  Nerve  Cells. — This  layer  is  situated  imme- 
diately outside  the  former,  and  contains,  as  its  special  distinguishing 
element,  multipolar  nerve  cells,  similar  to  those  of  the  gray  matter  of 
the  brain.     According  to  Kolliker,  they  vary  in  size  from  9  to  36  mmm. 
in  diameter,  and  are  provided  with  a  number  of  pale,  ramified  prolonga- 
tions.    Some  of  these  prolongations  are  directed  outward,  penetrating 
into  the  more  external  portions  of  the  retina;  others  pass  in  a  horizon- 
tal direction,  and,  according  to  some  observers  (Kolliker,  Miiller,  Corti), 
become  connected  with  optic  nerve  fibres.     For  the  most  part,  however, 
it  is  only  the  identity  in  appearance  between  some  of  the  prolongations 
of  these  nerve  cells  and  the  more  slender  optic  nerve  fibres,  which  leads 
to  the  presumption  of  their  direct  terminal  continuity.     It  is,  in  any 
case,  possible  that  some  of  the  fibres  of  expansion  of  the  optic  nerve 
are  connected  with  prolongations  of  the  nerve  cells,  while  others  con- 
tinue their  course  to  the  deeper  layers  of  the  retinal  tissue. 

40 


618 


THE    SENSES. 


Fig.  194. 


3.  Layer  of  Nuclei. — The  layer  of  nuclei  is  so  called  because  its  most 
characteristic  elements  have,  in  the  main,  the  aspect  of  nuclei ;  although 
by  some  observers  (Kolliker,  Schultze),  they  are  regarded   as  having 
rather  the  signification  of  nucleated  cells,  in  which  the  enveloping  cell- 
substance  is  in  small  quantity  as  compared  with  the  size  of  the  nucleus. 
The  nuclei  themselves,  sometimes  called  "grains"  or  "granules,"  are 
oval  bodies,  placed  with  their  long  axes  perpendicular  to  the  surface 
of  the  retina.     There  are  two  varieties  of  them  mingled  together,  which 
differ  mainly  in  size ;  the  larger  being  from  9  to  13  mmm.  in  length,  the 
smaller  one-half  or  two-thirds  as  long.     They  are  all  contained  in  the 
interior  of  varicose  enlargements  of  slender  fibres,  which  are  also  di- 
rected perpendicularly  to  the  surface  of  Jthe  retina,  and  extend  uninter- 
ruptedly through  the  whole  thickness  of  the  layer.     These  fibres  are 
presumed  to  be  of  the  nature  of  modified  nerve  fibres,  and  to  represent, 
either  directly  or  indirectly,  the  continuations  of  those  derived  from 
the  expansion  of  the  optic  nerve.     At  their  outer  extremities  they  are 
immediately  continuous  with  the  elements  of  the  following  layer. 

4.  Layer  of  Rod*  and  Cones — This  is  undoubtedly  the  most  remark- 
able of  the  retinal  layers,  since  it  consists  of  elements  which  are  more 
peculiarly  constituted  than  those  found  elsewhere,  and  which  are  most 

immediately  connected  with  the  physiology 
of  luminous  impressions.  As  the  name 
indicates,  these  elements  are  of  two  kinds; 
distinguished,  according  to  their  shape,  by 
the  name  of  "rods"  and  "cones."  There 
is  reason  to  believe  that  their  offices  are 
essentially  similar,  and  that  they  are  to  be 
regarded  as  modifications  of  each  other. 

The  rods  (Fig.  194)  are  straight,  elon- 
gated, cylindrical  bodies,  composed  of  a 
transparent,  homogeneous  substance,  re-' 
markable  for  its  highly  refractive  power. 
They  are  about  50  mmm.  in  length  by  a  lit- 
tle less  than  2  mmm.  in  diameter.  They  are- 
all  placed  parallel  with  each  other,  closely 
packed  side  by  side,  standing  perpendicu- 
larly to  the  surface  of  the  retina,  and  ex- 
tending through  the  whole  thickness  of 
the  layer.  At  its  outer  extremity  each 
rod  terminates  by  a  plane  perpendicular 
to  its  axis ;  at  its  inner  extremity  it  tapers 
/  ^A  A  I  \  h  '  )  suddenly  to  a  point  and  is  continuous 

wifch  a  fibre  of  the  Preceding  Kver,  and 
thus  with  one  of  its  nucleated  enlarge- 
ments or  grains.  According  to  Schultze, 
the  internal  half  of  each  rod  is  slightly 
thicker,  and  exhibits  rather  less  refractive 
power  than  its  external  half. 


DIAGRAMMATIC  SECTION, 
from  the  posterior  portion  of  the 
human  retina. — 1.  Layer  of  rods 
and  cones.  2.  Layer  of  nuclei. 
(Schultze.} 


SENSE    OF    SIGHT,  619 

•  The  con es  differ  from  the  rods  mainly  in  their  tapering  form  and  the 
greater  diameter  of  their  internal  portion,  which,  as  a  general  rule,  is 
from  two  to  three  times  as  thick  as  that  of  the  rods.  They  have  the 
same  transparent,  highly  refractive  appearance,  and  are  intercalated 
among  the  rods  in  the  same  position,  that  is,  perpendicularly  to  the 
surface  of  the  retina.  Their  outer  extremities,  in  some  regions,  stop 
short  of  the  external  surface  of  the  retina,  while  in  others,  particularly 
in  that  of  most  perfect  vision,  they  reach  the  same  level  with  the  ends 
of  the  rods.  Each  cone  is  connected  at  its  inner  extremity  with  a  nu- 
cleated fibre  belonging  to  the  preceding  layer,  the  only  difference  in  this 
respect  being  that  both  the  fibres  and  the  nuclei  connected  with  the 
cones  are  larger  than  those  connected  with  the  rods. 

Over  the  greater  part  of  the  retina  the  rods  are  more  abundant  than 
the  cones.  When  viewed  from  the  external  surface  (Fig.  195,  J),  their 
closely  packed  extremities  present  the  appearance  of  a  fine  mosaic  pat- 
tern, while  the  cones  are  interspersed  among  them  in  smaller  numbers. 
At  the  borders  of  the  macula  lutea  (p.  623),  on  the  other  hand,  the 
cones  are  more  abundant,  being  only  separated  from  each  other  by  single 
ranges  of  rods  (-S);  and  at  its  central  portion  (G)  there  are  only  cones, 
the  rods  being  entirely  absent.  The  cones  at  this  point  are  also  longer 
and  more  slender  than  elsewhere.  The  following  figure  indicates  the 
appearance  of  the  rods  and  cones,  as  shown  in  an  external  view  of 
different  parts  of  the  retina.  The  smaller  circles  represent  the  rods, 
the  larger  circles  the  cones.  In  the  interior  of  each  cone  is  seen  the 
section  of  its  conical  extremity. 


OUTER  SURFACE  OF  THE  RETINA,  showing  the  ends  of  the  rods  and  cones. — A.  From 
the  lateral  portion  of  the  eyeball.  B.  From  the  posterior  portion,  at  the  edge  of  the  macula 
lutea.  C.  From  the  macula  lutea.  (Helmholtz.) 

Beside  the  distinctly  marked  layers  above  described,  there  are  vari- 
ous others  of  less  certain  signification  and  less  uniformity  of  extent, 
which  are  found  in  different  parts  of  the  retina.  Throughout  the  mem- 
brane there  also  exists  a  certain  proportion  of  delicate  connective  tissue, 
which  serves  for  the  support  and  attachment  of  its  remaining  anatomi- 
cal elements. 

Perception  of  Luminous  Impressions  by  the  Retina. — It  appears, 
from  the  description  given  above,  that  the  retina  is  not  simply  an  ex- 
pansion of  the  fibres  of  the  optic  nerve.  It  is  a  membrane  of  special 
structure,  connected  with  the  extremities  of  the  optic  nerve  fibres,  but 
containing  also  many  additional  anatomical  elements.  It  is  accordingly 
a  peculiar  nervous  apparatus,  adapted  to  receive  the  impression  of  lumi- 
nous rays,  and  connected,  by  means  of  the  optic  nerve,  witli  the  central 


620  THE    SENSES. 

gray  matter  of  the  brain.  An  examination  of  the  manner  in  which  the 
impressions  of  light  are  perceived  brings  into  view  the  following  facts. 

The  optic  nerve  and  its  fibres  are  insensible  to  light.  Notwith- 
standing that  this  nerve  is  capable  of  transmitting  luminous  impressions 
from  the  retina  to  the  brain,  yet  in  order  to  do  this,  it  must  first  receive 
its  own  stimulus  from  the  retina.  The  optic  nerve  fibres  themselves, 
though  sensitive  to  mechanical  or  galvanic  irritation,  cannot  be  called 
into  activity  by  the  direct  influence  of  luminous  rays.  This  is  shown 
by  the  experiment  of  Bonders,  in  which,  by  aid  of  the  ophthalmoscope, 
a  light  of  a  certain  degree  of  intensity  is  concentrated  upon  the  optic 
nerve,  without  being  allowed  to  reach  the  tissue  of  the  retina.  When 
the  bottom  of  the  eye  is  illuminated  by  the  ophthalmoscope,  the  ob- 
server sees  the  general  surface  of  the  retina  of  a  red  or  brownish  color, 
while  the  papilla,  which  corresponds  to  the  entrance  of  the  optic  nerve, 
presents  itself  as  a  white  circular  spot.  This  spot  is  occupied  entirely 
by  optic  nerve  fibres,  while  the  elements  of  the  retina  commence  only 
beyond  its  borders.  If  the  minute  image  of  a  candle  flame  at  some  dis- 
tance be  thrown  by  reflection  upon  the  retina,  its  light  is  perceived  by 
the  person  under  observation,  as  well  as  its  image  by  the  observer.  If 
the  eye  however  be  turned  in  such  a  direction  as  to  bring  the  image  of 
the  flame  upon  the  white  circle  of  the  optic  nerve,  this  circle,  and  the 
nerve  fibres  of  which  it  is  composed,  are  visibly  illuminated  to  a  certain 
depth,  owing  to  the  translucency  of  their  substance ;  but  the  light  of 
the  candle  flame  is  no  longer  perceived  by  the  person  under  examina- 
tion. The  moment,  on  the  other  hand,  the  image  of  the  flame  is  allowed 
to  pass  beyond  the  limits  of  the  white  spot,  and  to  touch  the  retina,  its 
light  becomes  perceptible. 

The  Blind  Spot. — The  region,  accordingly,  occupied  by  the  entrance  of 
the  optic  nerve,  and  in  which  the  elements  of  the  retina  proper  are  ab- 
sent, is  a  blind  spot,  where  luminous  rays  make  no  perceptible  impres- 
sion. The  real  diameter  of  this  spot,  according  to  the  average  measure- 
ments obtained  by  Listing,  Hannover,  and  Helmholtz,is  1.G5  millimetre, 
and  it  covers  in  the  field  of  vision  a  space  equivalent  to  about  6  degrees. 
Notwithstanding  the  existence  of  this  insensible  part  at  the  bottom 
of  the  eye,  no  dark  point  is  usually  observed  in  the  field  of  vision,  for 
the  following  reasons.  The  blind  spot  is  not  situated  in  the  visual  axis 
of  the  eye,  but  is  placed,  corresponding  with  the  entrance  of  the  optic 
nerve,  nearer  the  median  line  (Fig.  189).  Consequently  the  image  of 
an  object  which  is  directly  examined  in  the  normal  line  of  vision  can- 
not fall  upon  this  spot,  but  is  always  outside  of  it,  at  the  end  of  the 
visual  axis.  Even  an  object  which  is  perceived  in  the  field  of  vision  out- 
side the  direct  line  of  sight,  can  never  reach  the  blind  spot  of  both  eyes 
at  the  same  time.  If  it  happen  to  be  so  placed  that  its  image  falls  upon 
the  blind  spot  of  one  eye,  it  will  necessarily  reach  the  retina  of  the  other 
eye  at  a  different  point,  and  is  accordingly  perceived.  If,  on  the  other 
hand,  one  eye  alone  be  employed,  there  is  always  a  small  portion  of  the 
field  of  vision  which  is  imperceptible.  This  deficiency  is  not  generally 


SENSE    OF    SIGHT.  621 

noticeable,  because  it  is  located  in  a  part  of  the  field  to  which  our  at- 
tention is  not  directed,  and  where  the  distinction  of  various  objects, 
under  moderate  illumination,  is  so  imperfect,  that  the  momentary  ab- 
sence of  one  of  them  is  not  regarded.  It  may,  however,  be  readily  made 
apparent  by  using  for  the  test  a  single  strongly  defined  object,  like  a 
white  spot  on  a  black  ground,  the  presence  or  absence  of  which  may  be 
noticed  without  difficulty,  even  in  indirect  vision. 

If  the  left  eye  be  covered  and  the  right  eye  directed  steadily  at  the 
white  cross  in  figure  196,  the  circular  spot  will  also  be  visible,  though 

Fi>.  196. 


DIAGRAM,  for  observing  the  situation  of  the  blind  spot.     (Helmholtz.) 

less  distinctly,  since  it  will  be  out  of  the  direct  line  of  sight.  Let  the 
page  be  held  vertically  at  the  height  of  the  eyes,  and  at  a  convenient 
distance  for  seeing  both  objects  in  the  above  manner.  If  it  be  now 
moved  slowly  backward  and  forward,  a  point  will  be  found  where  the 
circular  spot  disappears  from  sight,  because  its  image  has  fallen  upon 
the  blind  spot ;  while  both  within  and  beyond  this  distance  it  again  be- 
comes visible.  It  may  also  be  made  to  reappear,  even  at  the  same  dis- 
tance, by  inclining  the  page  laterally  to  the  right  or  left ;  since  this 
brings  the  white  circle  either  above  or  below  the  level  of  the  blind  spot. 

The  experiment  may  be  varied  by  fixing  two  cards,  at  the  height  of 
the  eyes,  upon  a  dark  wall,  two  feet  apart  from  each  other.  If  the  left 
eye  be  covered,  and  the  right  eye  fixed  upon  the  left-hand  card,  the 
other  one  will  disappear  from  view  at  a  distance  of  about  eight  feet 
from  the  wall. 

It  is  evident,  furthermore,  that  the  optic  nerve  fibres  are  not  directly 
sensitive  to  light,  even  outside  the  blind  spot,  and  where  they  form 
part  of  the  retina.  These  fibres  radiate  from  the  point  of  entrance  of 
the  optic  nerve,  forming  a  continuous  sheet  on  the  inner  surface  of  the 
retina ;  some  of  them  terminating  at  successive  points  in  the  retinal 
membrane,  others  extending  to  its  extreme  border  at  the  ora  serrata. 
A  luminous  ray  striking  the  retina  near  the  fundus  of  the  eye  must, 
therefore,  traverse  a  considerable  number  of  nerve  fibres,  which  are  con- 
nected at  their  peripheral  extremities  with  different  parts  of  the  retina ; 
and  such  a  ray,  coming  from  a  single  point,  would  necessarily  cause  the 
sensation  of  multiplied  luminous  points  or  even  of  a  more  or  less  con- 


622  THE    SENSES. 

tinuous  bright  line.  As  distinct  points  are  actually  perceived  as  such 
by  the  retina,  although  the  luminous  ray  emanating  from  each  one  has 
passed  through  the  whole  layer  of  nerve  fibres  on  its  internal  surface,  it 
follows  that  the  sensibility  of  these  fibres  is  not  affected  by  the  direct 
action  of  light. 

The  sensitive  elements  of  the  retina  are  in  its  posterior  or  external 
layers.  This  fact  is  deduced  partly  from  the  phenomena  manifested 
when  the  retinal  bloodvessels  are  made  visible  in  the  interior  of  the  eye. 
These  bloodvessels  and  their  branches  radiate  from  the  central  trunk 
which  enters  with  the  optic  nerve.  Their  ramifications,  down  to  a  cer- 
tain size,  are  all  situated  in  the  nerve  fibre  layer  of  the  retina,  and  it  is 
only  the  finest  subdivisions  which  pass  into  the  next  layer  of  ganglionic 
nerve  cells.  The  two  outer  layers,  namely,  the  layer  of  nuclei,  and  that 
of  the  rods  and  cones,  are  completely  destitute  of  bloodvessels.  Owing 
to  this  anatomical  arrangement,  the  posterior  or  external  layers  of  the 
retina,  situated  behind  the  main  branches  of  the  retinal  bloodvessels, 
must  lie  m  the  shadow  of  these  branches,  the  light  coming  directly  from 
the  front  through  the  pupil.  The  shadows  thus  thrown  are  not  habitu- 
ally perceived  by  any  diminution  of  the  light,  because  the  portions  of 
the  retina  covered  by  them  are  always  in  shadow  at  the  same  points, 
and  its  sensibility  to  light  is  greater,  in  proportion  as  the  quantity  of 
light  reaching  it  is  less.  But  the  shadows  may  be  rendered  perceptible 
by  a  lateral  or  oblique  illumination,  thus  causing  them  to  be  thrown 
upon  points  of  the  retina  unaccustomed  to  their  presence. 

Let  a  lighted  candle  be  held,  in  a  dark  room,  about  three  inches 
distant  from  the  external  angle  of  either  eye,  and  about  45  degrees  in 
advance  of  the  plane  of  the  iris.  On  moving  the  candle  alternately 
upward  and  downward,  the  field  of  vision  becomes  filled  with  an  abun- 
dant and  elegant  tracery  of  aborescent  bloodvessels,  the  exact  counter- 
part of  those  of  the  retina.  The  form  of  the  vessels  is  distinctly  marked 
in  purpl.e-black,  upon  a  finely  granular  grayish-red  ground.  The  point 
of  entrance  of  the  vascular  trunks  may  even  be  seen,  witli  their  division 
into  two  principal  branches  passing  respectively  upward  and  downward, 
and  then  breaking  up  into  ramifications  of  various  curvilinear  form.  Jf 
the  candle  be  held  immovable,  the  appearances  rapidly  fade,  since  the 
shadows  in  reality  are  quite  faint,  and  are  only  made  visible  from  the 
sudden  contrast  produced  by  throwing  them  successively  upon  different 
parts  of  the  retina. 

As  the  bloodvessels  which  throw  these  shadows  are  at  or  near  the 
anterior  surface  of  the  retina,  the  extent  of  their  apparent  movement 
on  varying  the  position  of  the  light,  gives  a  means  of  ascertaining  how 
far  behind  the  anterior  surface  of  the  retina  its  sensitive  elements  arc 
situated.  According  to  the  measurements  of  Miiller,1  this  distance  must 
be,  in  various  cases,  from  0.17  to  0.36  millimetre;  and  the  same  ob- 
server finds  the  posterior  layers  of  the  retina  to  be  separated  from  its 

1  Cited  in  Helmholtz,  Optique  Physiologique.     Paris,  1867,  p.  289. 


SENSE    OF    SIGHT.  623 

anterior  surface  by  from  0.20  to  0.30  millimetre's  distance.  It  is,  there- 
fore, one  or  both  of  the  posterior  layers,  namely,  that  of  the  rods  and 
cones,  and  that  of  the  nuclei  immediately  within  it,  which  contain  the 
sensitive  elements  of  the  retina,  and  in  which  the  luminous  rays  produce 
their  effect.  This  conclusion  is  rendered  still  more  certain  by  the  fact 
that  in  the  fovea  central  is,  the  point  of  most  distinct  vision,  hereafter 
to  be  described,  the  two  external  layers  of  the  retina  are  the  only  ones 
present. 

Macula  Lutea  and  Point  of  Distinct  Vision. — The  macula  lutea,  or 
yellow  spot  of  the  retina,  is  an  oval  spot,  measuring  about  2  millimetres 
in  its  horizontal  diameter,  situated  between  2  and  2.5  millimetres  out- 
side the  entrance  of  the  optic  nerve.  According  to  Helmholtz,  it  is 
placed  a  very  little  beyond  the  middle  of  the  fundus  of  the  eyeball, 
toward  the  temporal  side.  It  is  distinguished  from  the  remainder  of 
the  retina  by  its  yellow  tinge,  which  depends  upon  the  presence  of  a 
peculiar  organic  pigment.  This  pigment  is  not  deposited  in  grains,  but 
is  completely  hyaline,  and  imbibes  the  whole  tissue  of  the  retina  at  this 
spot,  with  the  exception,  according  to  Schultze,  of  the  two  external 
layers,  which  remain  colorless. 

At  its  centre  is  a  minute  depression,  the  fovea  centralis,  where, 
owing  to  its  steeply  sloping  sides,  the  retina  is  reduced,  at  the  bottom 
of  the  fovea,  to  less  than  one-half  its  usual  thickness.  The  macula 
lutea  becomes  perceptible,  in  ophthalmoscopic  examination  of  the  eye 
with  a  moderate  illumination,  as  a  yellowish  spot,  less  brilliant  than  the 
rest,  in  wThich  the  position  of  the  fovea  centralis  is  marked  by  a  peculiar 
colorless  reflection.  The  macula  lutea,  and  especially  the  fovea  cen- 
tralis, is  the  point  of  most  distinct  vision,  where  the  image  of  an  object, 
fixed  by  the  eye  in  the  direct  line  of  sight,  falls  upon  the  retina.  It  is 
well  known  that  external  objects  are  seen  with  perfect  distinctness  only 
when  their  images  fall  in  the  immediate  neighborhood  of  the  optical 
axis  at  the  fundus  of  the  eyeball.  Outside  this  region,  the  perception 
of  their  figure  is  more  or  less  imperfect.  According  to  the  observations 
of  Donders,  confirmed  by  Helmholtz,  if,  while  the  retina  is  illuminated 
by  the  ophthalmoscope,  the  person  under  observation  fixes  the  eye  in 
succession  upon  several  different  objects,  or  upon  different  points  of  the 
same  object,  the  minute  reflection  which  marks  the  fovea  centralis 
always  places  itself  upon  the  part  of  the  optical  image  fixed  by  the  eye ; 
and  this  appearance  is  so  constant  that  the  observer  can  tell  with  cer- 
tainty, from  the  place  occupied  by  the  reflection,  what  point  of  the 
object  has  been  fixed  in  the  direct  line  of  sight. 

The  evident  importance  of  the  macula  lutea  and  the  fovea  centralis, 
in  the  exercise  of  vision,  gives  a  special  interest  to  the  anatomical 
structure  of  this  part  of  the  retina ;  and  the  researches  of  microscopic 
anatomists  have  shown  that  its  structure  presents  peculiarities  fully 
corresponding  with  its  physiological  endowments. 

The  macula  lutea  is  distinguished,  in  the  first  place,  by  the  fact  that 
the  superficial  layer  of  optic  nerve  fibres  is  absent.  Those  fibres,  ac- 


624 


THE    SENSES. 


cording  to  Kolliker,  which,  in  radiating  from  the  entrance  of  the  optic 
nerve,  pass  directly  to  the  edges  of  the  macula,  lose  themselves  among 
the  nerve  cells  of  its  ganglionic  layer.  The  others  curve  round  the 
borders  of  the  macula  on  each  side,  to  resume  their  peripheral  direction 
beyond  its  limit ;  so  that  the  yellow  spot  itself  is  not  covered,  like  the 
rest  of  the  retina,  by  a  continuous  superficial  layer  of  nerve  fibres. 

Secondly,  the  nerve  cells  of  the  ganglionic  layer  are  more  abundant 
in  the  macula  lutea  than  elsewhere.  Over  the  greater  portion  of  the 
retina,  according  to  Schultze,  these  cells  exist,  in  the  ganglionic  layer, 
only  in  a  single  plane ;  that  is,  they  are  arranged  side  by  side,  and 
neither  above  nor  below  each  other.  But  in  the  yellow  spot  they  form 
several  ranges  of  superimposed  cells.  On  the  other  hand,  toward  the 
centre  of  the  yellow  spot  the  cells  diminish  in  number,  and  are  entirely 
absent  at  the  fovea  centralis.  Various  other  layers,  which  exist  more 
or  less  distinctly  in  surrounding  regions  of  the  retina,  also  diminish  in 
thickness,  and  disappear  toward  the  centre  of  the  macula  lutea. 

Fig.  197. 


DIAGRAMMATIC  SECTION  OF  HITMAN  RKTIWA,  through  the  macula  lutea  and  foveu 
centralis. — 1.  Internal  surface  of  the  retina,  in  contact  with  the  vitreous  body.  2.  Gan- 
glionic layer  of  nerve  cells.  3.  Intermediate  layers  of  the  retina,  disappearing  at  the  centre 
of  the  macula  lutea.  4.  Layer  of  nuclei,  showing  the  oblique  course  of  the  fibres  in  this 
region.  5.  Layer  of  rods  and  cones  ;  consisting  at  its  central  portion  exclusively  of  attenu- 
ated and  elongated  cones.  C.  External  surface  of  the  retina,  in  contact  with  the  choroid. 
In  the  middle  of  the  diagram  is  the  depression  of  the  fovea  centralis.  (Schultze.) 

Thirdly,  owing  to  the  modifications  described  above,  the  retina,  at 
the  situation  of  the  fovea  centralis,  consists  only  of  its  two  external 
layers,  namely  the  layer  of  nuclei  and  the  layer  of  rods*  and  cones. 
Even  these  two  layers  exhibit,  at  this  point,  certain  important  peculiari- 
ties in  the  form  and  arrangement  of  their  elements. 

In  the  layer  of  nuclei,  the  nuclei  themselves  are  present  in  nearly 
their  usual  numbers  and  position ;  but  the  fibres  with  which  they  are 
connected,  instead  of  passing  through  the  layer  in  a  direction  perpen- 
dicular to  the  surface  of  the  retina,  bend  obliquely  outward,  to  reach 
the  more  superficial  layers  of  the  retina  in  the  external  portions,  or 
even  beyond  the  borders,  of  the  yellow  spot.  Thus  this  layer  is  very 
much  diminished  in  thickness,  although  it  still  contains  its  cell  nuclei, 


SENSE    OF    SIGHT.  625 

and  although  these  are  still  connected,  by  their  fibrous  extensions,  with 
the  other  parts  of  the  retinal  tissue. 

Finally  the  layer  of  rods  and  cones,  at  the  situation  of  the  macula  lutea 
and  fovea,  though  preserving  its  general  character,  shows  special  features 
by  which  it  is  readily  distinguished  from  the  corresponding  parts  else- 
where. In  this  la^'er,  over  the  greater  portion  of  the  retina,  the  rods 
are  the  most  abundant  element,  the  cones  being  distributed  among  them 
in  smaller  numbers.  In  the  borders  of  the  macula  lutea  (Fig.  195,  B), 
the  cones  become  more  numerous  in  proportion  to  the  rods,  and  in  the 
fovea  centralis  (Fig.  195,  (7)  the  layer  is  composed  exclusively  of  cones. 
At  this  part,  the  cones  are  longer  than  elsewhere,  and  more  slender,  so 
that  a  larger  number  are  comprised  within  an  equal  space ;  and  the 
layer  itself,  consisting  of  elongated  cones  standing  perpendicularly,  is 
increased  in  thickness,  in  proportion  to  the  greater  length  of  its  con- 
stituent elements.  The  thickness  of  the  cones  at  their  base,  over  the 
retina  generally,  according  to  the  measurements  of  Schultze,  is  a  little 
over  6  mmm.,  and  their  length  less  than  50  mmm. ;  but  at  the  fovea  cen- 
tralis their  thickness  is  reduced  to  3  or  3.5  mmm.,  while  their  length, 
in  the  same  situation,  may  reach  100  mmm.  Each  cone  is  connected, 
here  as  elsewhere,  through  the  nucleus  and  nucleus  fibre  of  the  pre- 
ceding layer,  with  the  other  portions  of  the  retina,  and  beyond  doubt, 
in  some  direct  or  indirect  way,  with  the  optic  nerve  fibres  of  its  internal 
layer. 

Thus  the  perception  of  light,  in  the  act  of  vision,  is  a  process  con- 
sisting of  several  successive  acts.  The  luminous  ray  passes  through 
the  transparent  internal  or  superficial  layers  of  the  retina,  until  it 
reaches  the  situation  of  the  two  outer  layers.  Here  it  produces  a 
change  in  the  condition  of  the  nervous  elements,  of  whose  nature  we 
are  entirely  ignorant.  It  might  be  compared  with  that  which  is  caused 
by  the  same  agent  in  the  sensitive  film  of  a  photographic  camera ;  but 
this  comparison  would  be  only  one  of  analogy,  and  would  not  imply 
any  identity  of  the  ph3rsical  or  chemical  change  produced  in  the  two 
cases.  It  would  simply  express  the  fact,  which  is  undoubtedly  estab- 
lished, that  the  luminous  ray,  after  traversing  all  the  other  transparent 
and  refracting  media  of  the  eye  without  leaving  any  trace  of  its  passage, 
on  arriving  at  the  two  outer  layers  of  the  retina,  excites  in  one  or  both 
of  them  a  kind  of  action  which  is  the  first  step  in  the  visual  process. 
This  condition  of  the  retinal  elements  then  calls  into  activity  the  fibres 
of  the  optic  nerve,  which  in  turn  transmit  the  stimulus  to  their  point  of 
origin  in  the  brain.  Thus  far,  there  is  no  conscious  perception,  nor 
even  any  nervous  effect  resembling  in  itself  our  idea  of  lurninositj^. 
The  retina  itself  is  distinguished  from  other  nervous  tissues  by  being 
sensitive  to  light ;  that  is,  it  may  be  thrown  into  a  state  of  activity 
under  the  influence  of  a  luminous  ray.  But  it  has  no  other  perception 
of  light  than  this,  any  more  than  the  silvered  film  of  a  photographic 
plate ;  and,  if  the  optic  nerve  be  severed,  blindness  results,  however  per- 
fect may  be  the  condition  of  the  retina. 


626  THE    SENSES. 

On  the  other  hand,  the  optic  nerve  fibres,  which  are  insensible  to  light 
itself,  are  thrown  into  excitement  by  the  changed  condition  of  the  retinal 
tissue.  There  is  no  reason  for  believing  that  the  action  of  the  fibres 
of  the  optic  nerve  is  different  in  kind  from  that  of  other  sensitive  nerve 
fibres.  Their  office  is  simply  that  of  receiving  and  communicating  a 
stimulus  from  and  to  certain  special  structures  containing  nerve  cells. 
In  the  case  of  the  optic  nerve,  the  stimulus  is  received  from  the  retina 
and  communicated  to  the  nervous  centres  of  the  brain.  These  nervous 
centres,  when  excited  by  the  stimulus  thus  received,  first  produce  the 
phenomenon  of  the  perception  of  light.  The  preceding  nervous  actions, 
in  the  retina  and  optic  nerve,  though  necessary  to  the  final  result,  have 
no  direct  connection  with  consciousness.  The  conscious  perception  of 
light  and  of  luminous  objects  is  the  last  step  in  the  process  of  vision, 
and  is  effected  by  a  special  act  of  the  gray  matter  of  the  brain. 

Acuteness  of  Vision  in  the  Retina. — The  acuteness  of  vision,  so  far 
as  it  is  connected  with  the  sensibility  of  the  retina,  depends  upon  the 
minimum  distance  from  each  other  of  two  visual  rays,  at  which  they 
can  still  be  perceived  as  distinct  points.  If  the  luminous  rays,  coming 
respectively  from  the  top  and  bottom  of  an  object,  are  so  closely  ap- 
proximated, where  they  strike  the  retina,  that  the  two  impressions  are 
confounded,  there  can  be  no  distinct  perception  of  its  figure  or  dimen- 
sions. On  the  other  hand,  if  the  sensibility  of  the  retina  be  such  that 
the  two  impressions  are  still  perceived  as  separate  from  each  other,  the 
form  of  the  object  will  be  recognized  as  well  as  its  luminosity,  notwith- 
standing the  small  size  of  its  retinal  image.  The  figure  of  a  man,  six 
feet  high,  seen  at  the  distance  of  ten  yards,  makes  at  the  cornea  a  visual 
angle  of  11°  30',  and  forms  upon  the  retina  an  image  which  is  less  than 
half  a  millimetre  (^  of  an  inch)  in  length  ;  and  yet  an  abundance  of 
details  are  distinctly  perceptible  within  this  space.  The  extreme  limit 
of  approximation  at  which  two  points  may  be  distinguished  from  each 
other  has  been  examined  by  the  observation  of  fixed  stars,  and  by  that 
of  parallel  threads  of  the  spider's  web,  or  of  fine  metallic  wires,  placed 
at  known  distances  from  each  other.1  The  general  result  of  these 
examinations  has  shown  that,  for  the  average  of  well-formed  eyes,  the 
smallest  visual  angle,  at  which  two  adjacent  points  or  lines  can  be  dis- 
tinguished, is  from  60  to  13  seconds ;  corresponding  to  a  distance  upon 
the  retina  of  from  4  to  5  rnmm.  According  to  the  measurements  of 
Schultze,  the  diameter  of  the  retinal  cones,  at  the  fovea  centralis,  is 
from  3  to  3.5  mmm.  ;  and  if  two  points  of  light  were  separated  at  the 
retina  by  a  less  distance  than  this,  they  would  often  fall  upon  the  same 
cone,  and  consequently  excite  the  same  nucleus  and  fibre  in  the  adjacent 
layer.  If  the  diameter  of  the  cones  be  the  element  which  determines 
the  limit  of  acuteness  of  vision,  two  luminous  points,  to  be  distinctly 
perceptible,  must  be  separated  upon  the  retina  by  a  distance  of  at  least 
3  mmm.,  and  must  have  a  visual  angle  with  each  other  of  at  least  42 

1  Helmholtz,  Optique  Physiologique.     Paris,  1867,  p.  292. 


SENSE    OF    SIGHT.  627 

seconds.  In  the  observations  made  upon  fixed  stars,  it  is  found  that 
two  stars  can  never  be  separately  distinguished  by  the  eye  unless  their 
angular  distance  from  each  other  is  equal  to  30  seconds  ;  and  very 
seldom,  unless  it  be  as  great  as  60  seconds.  These  measurements 
correspond  with  each  other  only  in  an  approximative  manner ;  perhaps 
because  there  has  never  been  an  opportunity  of  examining  the  retinal 
elements  in  an  eye,  of  which  the  acuteness  of  vision  has  been  tested 
beforehand.  But  they  are  sufficient  to  indicate  a  probable  connection 
between  the  minute  structure  of  the  retina  and  the  possible  limit  of  its 
sensibility  to  separate  impressions. 

Physiological  Conditions  of  the  Sense  of  Sight. — The  apparatus  of 
vision,  as  above  described,  consists  of  various  parts,  each  of  which  has 
its  appropriate  share  in  producing  the  final  result  of  visual  perceptions. 
The  eye,  so  far  as  regards  its  physical  structure,  is  an  optical  instrument, 
composed  of  transparent  and  refracting  media,  a  perforated  diaphragm, 
and  a  dark  chamber  lined  with  a  blackened  membrane,  all  of  which  act 
upon  the  luminous  rays  according  to  the  same  laws  as  the  corresponding 
parts  in  a  telescope  or  a  camera  ;  and  the  accuracy  of  their  adjustment 
is  one  of  the  first  requisites  for  the  exercise  of  sight.  The  organ, 
furthermore,  is  movable  as  a  whole;  and  certain  of  its  internal  parts 
are  also  under  the  control  of  muscular  tissues,  whose  alternate  con- 
traction and  dilatation  contribute  to  determine  its  mode  of  action.  It 
is,  in  addition,  a  double  organ  ;  and  impressions  may  be  derived  from 
the  simultaneous  employment  of  both  eyes,  which  cannot  be  acquired 
by  the  use  of  one  alone.  Finally,  the  special  sensibility  of  its  nervous 
elements  is  liable  to  modifications  of  various  kinds,  which  have  an  in- 
fluence upon  the  nature  and  intensity  of  the  sensations  produced.  The 
principal  conditions  regulating  the  physiological  exercise  of  the  sense 
of  sight  are  the  following : 

Field  of  Vision. — As  the  eyeball  is  placed  in  the  orbit  with  the 
cornea  and  the  pupil  directed  forward,  there  is,  in  front  of  each  eye,  a 
circular  space  within  which  luminous  objects  are  perceptible ;  while 
beyond  its  borders,  laterally  and  posteriori}^,  nothing  can  be  seen. 
This  space  is  the  "field  of  vision."  Its  extreme  limit,  in  man,  reaches 
nearly  to  180  degrees  of  angular  distance  ;  that  is  to  say,  with  the  eye 
directed  straight  forward,  the  light  from  a  brilliant  object  may  be  per- 
ceived, when  the  object  itself  is  placed  laterally  almost  as  far  back  as 
the  plane  of  the  iris.  The  possibilit}r,  for  light  which  has  come  from 
this  direction,  of  penetrating  the  pupil  and  finally  reaching  a  sensitive 
part  of  the  retina,  depends  upon  the  refractive  power  of  the  cornea 
and  the  curvature  of  its  anterior  surface,  by  which  the  luminous  ray 
is  bent  inward  and  thus  enabled  to  enter  obliquely  the  orifice  of  the 
pupil.  In  many  of  the  lower  animals,  where  the  eyes  are  more  promi- 
nent than  in  man,  and  the  curvatures  of  the  cornea  and  crystalline  lens 
more  pronounced,  the  field  of  vision  is  enlarged  in  a  corresponding 
degree.  In  birds  and  fishes,  it  is  still  further  modified  by  the  lateral 


628  THE    SENSES. 

position  of  the  two  eyes.  The  ostrich,  with  the  head  directed  forward, 
can  easily  see  objects  placed  a  few  yards  behind  its  back ;  and  in  many 
fish,  when  examined  from  different  points  in  an  aquarium,  it  is  impossi- 
ble for  the  observer  to  place  himself  in  any  position,  above,  behind,  or 
on  either  side,  where  he  cannot  see  one  or  both  of  the  pupils  of  the 
animal.  The  field  of  vision  consequently,  for  the  animal,  is  a  complete 
sphere ;  the  light  being  perceptible  from  every  point  of  the  surrounding 
space.  In  man,  the  external  borders  of  the  field  of  vision  are  very  ill 
defined ;  and  objects  placed  at  a  lateral  distance  of  90  degrees  must  be 
very  brilliant  to  attract  attention.  For  practical  purposes,  the  space 
within  which  objects  are  perceptible  is  one  of  not  more  than  75  degrees 
on  each  side,  or  150  degrees  for  the  entire  field  of  vision. 

Line  of  Direct  Vision. — Within  the  field  of  vision,  however,  there  is 
onlyjone  point,  at  its  centre,  where  the  form  of  objects  can  be  perceived 
with  distinctness  ;  and  the  prolongation  of  this  point,  in  the  visual  axis 
of  the  eye,  from  the  pupil  forward,  is  called  the  "line  of  direct  vision." 
Objects  met  with  upon  this  line  can  be  distinctly  seen ;  all  others,  situ- 
ated upon  either  side,  above  or  below  it,  are  perceived  only  in  an  imper- 
fect manner.  If  the  observer  place  himself  in  front  of  a  row  of  vertical 
stakes  or  palisades,  he  can  see  those  placed  directly  in  front  of  the  e3'e 
with  perfect  distinctness ;  but  those  on  each  side  appear  as  uncertain 
and  confused  images.  On  looking  at  the  middle  of  a  printed  page,  in 
the  line  of  direct  vision,  we  see  the  distinct  outlines  of  the  letters; 
while  at  successive  distances  from  this  point,  the  eye  remaining  fixed, 
we  distinguish  first  only  the  separate  letters  with  confused  outlines, 
then  only  the  words,  and  lastly  only  the  lines  and  spaces. 

This  limitation  of  serviceable  sight  to  the  line  of  direct  vision  is 
practically  compensated  by  the  great  mobility  of  the  eyeball,  which 
turns  successively  in  different  directions  ;  thus  shifting  the  field  of  vision 
and  examining  in  turn  every  part  of  the  space  attainable  by  the  eye. 
In  reading  a  printed  page,  the  eye  follows  the  lines  from  left  to  right, 
seeing  each  letter  and  word  distinctly  in  succession.  At  the  end  of 
each  line,  it  returns  suddenly  to  the  commencement  of  the  next,  repeat- 
ing the  same  movement  from  the  top  to  the  bottom  of  the  page. 

The  deficiency  of  distinctness  outside  the  line  of  direct  vision  depends 
upon  two  causes,  which  are  both  present,  although  either  separately 
would  tend  to  produce  a  similar  result ;  namely,  1st,  inaccurate  focus- 
ing of  the  luminous  rays ;  and  2d,  diminished  acuteness  of  the  retinal 
sensibility. 

Rays  of  light  entering  the  eye  from  the  front,  in  the  line  of  direct 
vision,  may  be  brought  to  an  accurate  focus  at  the  situation  of  the 
retina.  But  those  which  enter  at  a  certain  degree  of  obliquity,  whether 
from  above,  from  below,  or  from  one  side,  suffer  a  more  rapid  conver- 
gence and  are  accordingly  brought  to  a  focus  and  again  dispersed,  before 
reaching  the  retina.  Thus  rays  diverging  from  the  point  a  (Fig.  198), 
in  the  line  of  direct  vision,  are  again  concentrated  at  x,  and  form  a  dis- 
tinct image  upon  the  retina  at  that  point.  But  those  coming  from  6, 


SENSE    OF    SIGHT.  629 

situated  considerably  on  one  side,  under  a  similar  degree  of  divergence, 
fall  upon  the  cornea  and  the  crystalline  lens  in  such  a  way  that  there  is 
more  difference  in  their  angles  of  incidence,  and  consequently  more  dif- 
ference in  the  amount  of  their  refraction.  They  are  therefore  brought 
together  too  rapidly,  and  are  dispersed  upon  the  retina  over  the  space 
?/,  z,  forming  an  imperfect  image.  Ophthalmoscopic  examination  of  the 
retina  shows  that,  in  point  of  fact,  the  images  formed  at  the  fundus  of 

Fig.  198. 


DIAGRAMMATIC  SECTION  OF  THE  EYEBALL,  showing  difference  of  refraction  for 
direct  and  indirect  vision.— a,  x.  Rays  from  a  point  in  the  line  of  direct  vision,  focussed  at 
the  retina.  6,  y,  z.  Rays  from  a  point  outside  the  line  of  direct  vision,  brought  to  a  focus 
and  dispersed  before  reaching  the  retina. 

the  eye,  from  luminous  objects  in  the  line  of  direct  vision,  present  per- 
fectly distinct  outlines  ;  while  those  at  a  certain  distance  from  this  point, 
toward  the  lateral  parts  of  the  retina,  are  comparatively  ill-defined. 

Secondly,  there  is  reason  to  believe  that  the  sensibility  of  the  retina 
is  also  less  acute  in  its  lateral  regions  than  at  the  fundus,  and  particu- 
larly at  the  macula  lutea  and  fovea  centralis;  since,  according  to  Helm- 
holtz,  the  sharpness  of  sight  for  objects  at  a  little  distance  from  the 
line  of  direct  vision  diminishes  in  greater  proportion  than  the  dis- 
tinctness of  their  images  formed  upon  the  retina.  The  fovea  centralis, 
according^,  is  the  spot  where  the  retina  possesses  the  most  acute  sensi- 
bility, and  it  is  also  situated  at  the  extremity  of  the  visual  axis,  where 
the  refraction  and  covergence  of  the  luminous  rays  are  effected  with  the 
greatest  accuracy.  Objects  situated  upon  the  line  of  this  axis  are  seen 
by  direct  vision,  and  are  distinctly  perceived;  those  situated  in  the 
field  of  view,  outside  this  line,  are  seen  by  indirect  vision,  and  their 
outlines  appear  more  or  less  confused  and  uncertain. 

Point  of  distinct  vision,  and  Accommodation  of  the  eye  for  different 
distances.  •  An  optical  instrument,  composed  of  refracting  lenses,  can- 
not be  made  to  serve  at  the  same  time  for  near  and  remote  objects.  In 
a  refracting  telescope  or  spy-glass,  if  the  instrument  be  directed  toward 


630  THE    SENSES. 

any  part  of  the  landscape,  objects  at  a  certain  distance  only  are  dis- 
tinctly seen ;  all  others,  situated  within  or  beyond  this  distance,  are 
obscure  or  imperceptible.  This  is  necessarily  the  case,  since  a  lens  or 
system  of  lenses  can  bring  to  a  focus  at  one  spot  only  those  rays  which 
strike  its  anterior  surface  within  a  certain  degree  of  divergence.  The 
formation  of  a  visible  image  at  the  desired  spot  depends  entirely  upon 
the  refracting  power  of  the  lenses  being  such,  that  all  the  rays  diverg- 
ing from  a  particular  point  of  the  object  shall  be  again  brought  to  an 
exact  focus  at  the  plane  where  the  image  is  to  be  perceived.  If  the  object 
be  placed  at  an  indefinite  distance  near  the  horizon,  or  if  it  be  one  of 
the  heavenly  bodies,  the  rays  emanating  from  any  one  point  of  such  an 
object  reach  the  telescope  under  so  slight  a  degree  of  divergence  that 
they  are  nearly  parallel;  and,  on  suffering  refraction,  they  will  be 
brought  to  a  focus  at  a  short  distance  behind  the  lens.  But  if  the 
object  be  less  remote,  the  rays  emanating  from  it  strike  the  lens  under 
a  higher  degree  of  divergence.  The  same  amount  of  refractive  power, 
therefore,  produces  a  less  rapid  convergence  than  in  the  former  case, 
the  rays  are  consequently  brought  to  a  focus  only  at  a  greater  distance 
behind  the  lens.  To  provide  for  this  difficulty,  the  spy-glass  is  pro- 
vided with  a  sliding  tube,  by  which  the  distance  of  the  eye-piece  from 
the  object-glass  may  be  shifted  at  will.  For  the  examination  of  remote 
objects,  the  eye-piece  is  pushed  forward,  so  as  to  bring  into  view  the 
image  formed  at  a  short  distance  behind  the  lens ;  for  the  examination 
of  near  objects  it  is  drawn  backward,  to  receive  the  image  placed 
farther  to  the  rear.  This  is  the  accommodation  of  the  spy-glass  for 
yision  at  different  distances. 

A  similar  necessity  exists  in  the  optical  apparatus  of  the  eye.  If 
one  eye  be  covered,  and  two  long  needles  placed  vertically  in  front  of 
the  other,  in  nearly  the  same  linear  range,  but  at  different  distances- 
one,  for  example,  at  eight,  and  the  other  at  twenty  inches  from  the 
eye — it  will  be  found  that  they  cannot  both  be  seen  distinctly  at  the 
same  time.  When  we  look  at  the  one  nearer  the  eye,  so  as  to  perceive 
its  form  distinctly,  the  image  of  the  more  remote  one  becomes  con- 
fused; and  when  we  see  the  more  distant  object  in  perfection,  that 
which  is  nearer  loses  its  sharpness  of  outline. 

The  same  thing  may  be  made  evident  by  stretching  in  front  of  the 
eye,  at  the  distance  of  seven  or  eight  inches,  a  plain  gauze  veil,  or  other 
woven  fabric  formed  of  fine  threads,  with  tolerably  open  meshes,  so 
that  objects  beyond  may  be  readily  visible  through  its  tissue.  The  ob- 
server, in  using  a  single  eye,  may  fix  at  will  either  the  threads  of  the 
veil,  or  the  more  distant  objects  placed  beyond  it ;  but  they  alternate 
with  each  other  in  distinctness,  like  the  two  needles  in  the  experiment 
described  above.  At  the  time  when  the  threads  are  sharply  defined, 
other  objects  are  indistinct ;  and  when  the  eye  is  fixed  upon  the  more 
distant  objects,  so  that  they  are  perfectly  delineated  in  the  field  of 
vision,  the  threads  of  the  veil  become  almost  imperceptible,  and  hardly 
interfere  by  their  presence  with  the  images  seen  beyond. 


SENSE    OF    SIGHT.  631 

;  It  is  evident,  therefore,  that  the  eye  cannot  perceive  distinctly,  at  the 
same  time,  objects  which  are  placed  at  different  distances,  but  it  must 
fix  alternately  the  nearer  and  the  more  remote,  and  examine  each  in 
turn.  It  is  also  evident  that,  in  thus  bringing  alternately  the  one  or 
the  other  into  distinct  view,  there  is  a  change  of  some  kind  in  the  con- 
dition of  the  eye,  by  which  it  adapts  itself  to  the  distance  or  nearness 
of  the  object  under  examination.  The  observer  himself,  at  the  moment 
of  transferring  the  sight  from  one  object  to  another,  is  conscious  of  a 
certain  effort,  by  means  of  which  the  eye  assumes  its  new  condition ; 
and  the  alteration  thus  produced  is  not  quite  instantaneous,  but  re- 
quires a  certain  interval  for  its  completion.  The  process  which  takes 
place  at  this  time  is  the  accommodation  of  the  eye  for  vision  at  different 
distances. 

The  method  by  which  the  accommodation  of  the  eye  is  effected  forms 
one  of  the  most  important  parts  of  the  physiology  of  sight.  The  facts 
which  have  been  established  by  observation  in  regard  to  it  are  as 
follows : 

I.  The  change  in  ocular  accommodation  for  different  distances  is 
accompanied  by  an  alteration  in  distinctness  of  the  images  formed  upon 
the  retina. 

This  is  demonstrated  by  the  observations  of  Helrnholtz  with  the  aid 
Of  the  ophthalmoscope.  When  the  retina  is  brought  into  view  by  this 
instrument,  if  the  person  under  examination  fix  his  attention  upon  a 
distant  object,  its  image  is  shown  upon  the  retina  with  distinct  outlines; 
but  on  changing  the  point  of  vision  for  a  near  object,  the  image  of  the 
latter  becomes  distinct,  while  that  of  the  former  loses  its  sharpness. 
This  indicates  that  the  result  in  question  is  not  produced  simply  by  the 
mental  effort  of  the  individual,  but  depends  upon  a  physical  change  in 
the  refractive  condition  of  the  eye. 

II.  Accommodation  for  distant  objects  is  a  passive  condition  of  the 
eye;  that  for  near  objects  is  the  result  of  muscular  activity. 

This  fact  is  in  some  degree  made  apparent  by  the  nature  of  the  sen- 
sations accompanying  the  change.  The  eye  rests  without  fatigue  for 
an  indefinite  time  upon  remote  objects;  but  for  the  examination  of 
those  in  close  proximity,  especially  if  it  be  prolonged,  a  certain  effort  is 
necessary,  which,  after  a  time,  amounts  to  the  sense  of  fatigue.  It  is 
also  remarked  that  solutions  of  atropine,  which,  when  applied  to  the 
eye,  cause  temporary  paralysis  of  the  sphincter  muscle  of  the  iris  and 
consequent  dilatation  of  the  pupil,  suspend,  more  or  less  completely, 
the  power  of  accommodation  for  near  objects,  while  that  for  remote 
objects  remains  perfect.  If  both  these  changes  were  due  to  muscular 
action,  it  would  be  necessary  to  assume  that  the  same  substance  could 
paralyze  one  of  the  internal  muscles  of  the  eyeball,  and  at  the  same 
time  leave  the  other  intact,  or  throw  it  into  a  state  of  permanent  rigid- 
ity;  and  there  is  nothing  known  which  would  justify  such  an  assump- 
tion. Furthermore,  there  are  certain  cases  of  paralysis -of  the  oculo- 
motorius  nerve,  where  not  only  the  corresponding  external  muscles  of 


632  THE    SENSES. 

the  eyeball  and  the  sphincter  pupillae  are  relaxed,  but  the  changes  of 
accommodation  are  also  interfered  with  ;  and  in  these  instances,  accord- 
ing to  Helinholtz,  the  eye  invariably  remains  adapted  for  long  distances, 
and  cannot  be  brought  to  a  state  of  distinct  vision  for  near  objects. 
The  evidence  in  this  direction  is  completed  by  the  well-known  facts 
which  accompany  the  usual  diminution  or  loss  of  accommodative  power 
with  advancing  years.  In  old  persons,  where  this  change  has  taken 
place,  it  is  the  accommodation  for  near  objects  which  is  deficient,  while 
that  for  distant  objects  remains  perfect. 

III.  In  accommodation  for  near  cbjects,  the  crystalline  lens  becomes 
more  convex,  thus  increasing  its  refractive  power.  This  is  the  essential 
change  upon  which  all  the  results  of  accommodation  are  directly  de- 
pendent. Its  existence  was  demonstrated  by  Cramer  and  Donders,1  by 
the  aid  of  what  are  called  the  "catoptric 
images,"  or  images  of  reflection  in  the  eye. 
If  a  brilliant  candle  flame  be  so  disposed,  in  a 
room  with  dark  walls,  that  its  rays  fall  some- 
what obliquely  upon  the  cornea  of  the  eye 
tinder  observation,  and  at  an  angle  of  about 
30  degrees  with  its  line  of  sight,  and  if  the 
observer  place  himself  on  the  opposite  side,  at 
an  equal  angle  with  the  line  of  sight,  three 
^fleeted  images  of  the  flame  will  become  visi- 
of  reflection,  from  the  surface  ble,  as  in  the  accompanying  figure. 

The   first    left-hand   image    (Fig.    199,   a) 
face  of  the  lens.    c.  inverted     which  is  brightest  of  all,  and  upright,  is  that 
ie'n.?08  !ri°r  8Ur"     reflected  from  the  surface  of  the  cornea.     The 


second,  6,  which  is  also  upright,  but  much 
fainter,  is  the  reflection  from  the  convex  anterior  surface  of  the  lens; 
and  the  third,  c,  which  is  tolerably  distinct,  but  inverted,  is  thrown 
back  from  the  posterior  surface  of  the  lens,  acting  as  a  concave  mirror. 
If  the  person  under  observation  now  changes  his  point  of  sight,  from  a 
distant  to  a  near  object,  the  position  of  the  eyeball  remaining  fixed,  the 
second  image,  6,  becomes  smaller,  and  places  itself  nearer  the  first. 
This  indicates  that  the  anterior  surface  of  the  lens,  from  which  this 
image  is  reflected,  becomes  more  bulging,  and  approaches  the  cornea: 
at  the  same  time  no  change  is  observable  in  the  other  two  images, 
showing  that  the  curvatures,  both  of  the  cornea  and  of  the  posterior 
surface  of  the  lens,  remain  unaltered. 

Helmholtz  has  made  the  phenomenon  above  described  much  more 
apparent  by  employing,  instead  of  a  single  light,  two  similar  sources  of 
illumination  placed  in  the  same  vertical  line.  There  are  thus  produced 
two  catoptric  images,  one  above  the  other,  from  each  surface  of  reflec- 
tion ;  and  an  increase  or  diminution  in  convexity  of  either  of  these  sur- 

1  DONDERS,  Accommodation  and  Kefraction  of  the  Eye,  Sydenham  edition. 
London,  1864,  p.  10. 


SENSE    OF    SIGHT. 


633 


faces  would  be  readily  manifested  by  an  approach  or  recession  of  the 
two  images  belonging  to  it.  In  accommodation  for  remote  objects  (Fig. 
200,  A),  the  two  images  from  the  anterior  surface  of  the  lens  are  of 
considerable  size  and  somewhat  widely  separated  ;  in  accommodation 
for  near  objects  (#),  they  diminish  in  size  and  approach  each  other. 
The  double  reflections  from  the  cornea  and  the  posterior  surface  of  the 
lens,  remain  at  sensibly  the  same 

distance  from  each  other  in  both  Fig.  200. 

states  of  accommodation. 

The  advance  of  the  iris  and  pu- 
pil, in  consequence  of  the  protru- 
sion of  the  anterior  face  of  the  lens, 
as  remarked  by  Helmholtz,can  also 
be  observed  directly,  by  looking 
into  the  eye  from  the  side.  If  the 
observer  look  from  this  direction 
so  as  to  obtain  a  profile  view  of  the 
cornea  and  part  of  the  sclerotic  be- 
tween the  opening  of  the  e3^elids,  he 
will  see  the  dark  pupil  in  perspec- 
tive under  the  form  of  an  upright 
elongated  oval,  a  little  in  front  of 

the  edge  of  the  sclerotic.  The  person  under  observation  fixes  his  sight 
upon  a  distant  object,  and  the  observer  places  himself  steadily  in  such 
a  position  that  the  hither  edge  of  the  iris  is  just  concealed  by  the  ante- 
rior border  of  the  sclerotic.  If  the  sight  be  now  shifted  from  the  dis- 
tant to  a  near  object,  in  the  same  linear  range,  the  pupil  visibly  ad- 
vances toward  the  cornea,  and  the  edge  of  the  iris  shows  itself  a  little 
from  behind  the  edge  of  the  sclerotic.  If  the  sight  be  again  directed  to 
the  distant  object,  the  pupil  recedes  and  the  edge  of  the  iris,  disappears, 
as  before,  behind  the  sclerotic. 

The  accommodation  of  the  eye  for  near  objects  is  therefore  produced 
by  an  increased  refractive  power  of  the  lens,  from  the  greater  bulging 


CHANGE  OF  POSITION  IN  DOUBLE 
CATOPTRIC  IMAGES  during  accommoda- 
tion.—  A.  Position  of  the  images  in  accom- 
modation for  distant  objects.  B.  Position 
of  the  images  in  accommodation  for  near  ob- 
jects, a.  Corneal  image,  b.  Image  from  an- 
terior surface  of  lens.  c.  Image  from  poste- 
rior surface  of  lens. 


Fig.  201. 


Fig.  202. 


VISION    FOR    DISTANT    OBJECTS. 


VISION    FOR    NEAR    OBJECTS. 


of  its  anterior  face.  This  has  the  effect  of  increasing  the  rapidity  of 
convergence  of  rays  passing  through  it,  and  consequently  compensates 
for  their  greater  divergence  before  entering  its  substance.  In  the  ordi- 
nary condition  of  ocular  repose,  when  the  eye  is  directed  to  distant  ob- 
41 


634  THE    SENSES. 

jects,  the  rays  coming  from  any  point  of  such  an  object  arrive  at  the 
cornea  in  a  nearly  parallel  position,  and  are  then  refracted  to  such  a  de- 
gree that  they  meet  in  a  focus  at  the  retina  (Fig.  201).  When  the  eye 
is  directed  to  a  nearer  point  (Fig.  202),  the  lens  increases  its  anterior 
convexity ;  and  the  divergent  rays,  being  more  strongly  refracted,  are 
still  brought  to  a  focus  at  the  retina,  as  before.  It  thus  becomes  possi- 
ble to  fix  alternately,  in  distinct  vision,  objects  at  various  distances  in 
front  of  the  eye. 

Mechanism  of  the  Change  in  Figure  of  the  Lens  in  Accommodation. — 
The  mechanism  by  which  the  lens  is  rendered  more  convex,  in  vision 
for  near  objects,  is  far  from  being  completely  demonstrated.  The  rea- 
sons have  already  been  given  which  lead  to  the  conclusion  that  it  is 
accomplished,  in  some  way,  by  muscular  action ;  and  the  two  muscles 
which,  separately  or  together,  undoubtedly  produce  this  change,  are  the 
iris  and  the  ciliary  muscle. 

The  iris  certainly  contracts  in  accommodation  for  near  objects.  This 
is  easily  observed  on  examining  by  daylight  the  pupil  of  an  eye  which 
is  alternately  directed  to  near  and  remote  objects.  The  pupil  visibly 
diminishes  in  size  when  the  eye  is  fixed  upon  a  point  near  by,  and  again 
enlarges  when  the  sight  is  accommodated  for  the  distance.  The  move- 
ments of  the  ciliary  muscle,  on  the  other  hand,  are  not  subject  to  ob- 
servation ;  but  the  attachments  and  position  of  this  muscle  have  led 
many  writers  to  attribute  to  it  an  important,  if  not  the  principal,  part 
in  causing  a  change  of  form  in  the  crystalline  lens. 

So  far  as  we  are  at  present  able  to  form  a  judgment  on  this  question, 
it  may  be  said  that  the  diminution  in  size  of  the  pupil  is  not  by  itself 
an  efficient  cause  of  accommodation ;  since,  according  to  Helmholtz,  if 
the  observer  look  through  a  perforated  card,  the  orifice  of  which  is 
smaller  than  the  pupil,  near  objects  still  appear  indistinct  when  the 
sight  is  directed  to  the  distance,  and  vice  versa,  notwithstanding  the 
invariable  dimensions  of  the  artificial  pupil  thus  employed.  The  con- 
traction of  the  circular  fibres  of  the  sphincter  papillae  must,  therefore, 
have  for  its  probable  object  to  fix  the  inner  border  of  the  iris,  thus 
affording  an  internal  point  of  attachment  for  the  radiating  fibres  of  the 
same  muscle.  These  fibres  have  for  their  external  attachment  the 
elastic  tissue  at  the  inner  wall  of  the  canal  of  Schlemm  (Fig.  189);  and 
from  this  circle  also  arise  the  fibres  of  the  ciliary  muscle,  which  radiate 
outward  and  backward  to  their  final  attachment  at  the  surface  of  the 
choroid  membrane.  If  the  circular  and  radiating  fibres  of  both  these 
muscles  contract  together,  they  will  form  a  connected  system,  which 
may  exert  a  pressure  upon  the  borders  of  the  lens,  sufficient  to  cause 
the  protrusion  of  its  anterior  face  at  the  pupil,  where  alone  its  advance 
is  not  resisted.  The  aqueous  humor,  displaced  by  the  protrusion  of  the 
lens,  may  find  room  in  the  external  parts  of  the  anterior  chamber,  where 
the  outer  border  of  the  iris  recedes,  under  the  traction  of  the  ciliary 
muscle.  These  are  the  general  features  of  the  mechanical  action  in 
accommodation,  as  it  is  generally  supposed  to  take  place.  At  the  same 


SENSE    OF    SIGHT.  635 

time,  its  details  are  by  no  means  clearly  understood ;  and  explanations, 
varying  more  or  less  from  that  given  above,  have  been  proposed  by 
observers  of  very  high  authority.  The  direction  and  degree  in  which 
pressure  would  be  exerted,  by  muscular  fibres  attached  like  those  in  the 
interior  of  the  eye,  are  too  imperfectly  known  to  warrant  a  positive 
statement  in  this  respect. 

Limits  of  Accommodation  for  the  Normal  Eye. — The  normal  eye  is 
so  constructed  that  rays  emanating  from  a  single  point,  though  coming 
from  an  indefinite  distance,  and  therefore  sensibly  parallel  to  each  other, 
are  brought  to  a  focus  at  the  retina  (Fig.  203).  Vision  is  accordingly 
distinct,  even  for  the  heavenly  bodies,  provided  their  light  be  neither  too 
dim  nor  too  excessive  in  brillianc3T.  For  bodies  situated  nearer  to  the 
eye,  the  convexity  of  the  lens  increases  with  the  diminution  of  the  dis- 
tance, and  vision  still  remains  perfect.  But  there  is  a  limit  to  the  change 
of  shape  which  the  lens  is  capable  of  assuming ;  and  when  this  limit  is 
reached,  a  closer  approximation  of  the  object  necessarily  destroys  the 
accuracy  of  its  image.  For  ordinary  normal  eyes,  in  the  early  or  middle 
periods  of  life,  accommodation  fails  and  vision  becomes  indistinct,  when 
the  object  is  placed  at  less  than  15  centimetres  (6  inches)  from  the  eye- 
Between  these  two  limits,  of  15  centimetres  and  infinity,  the  amount 
of  accommodation  required  is  by  no  means  in  simple  proportion  to  the 
variation  of  the  distance.  The  change  of  accommodation  necessary  for 
objects  situated  respectively  at  15  and  30  centimetres  from  the  eye  (6 
inches  and  12  inches),  is  much  greater  than  that  corresponding  to  the 
distances  of  one  yard  and  two  yards.  The  farther  the  object  recedes 
from  the  eye,  the  less  diiference  is  produced,  in  the  sensible  divergence 
of  the  rays,  by  any  additional  increase  of  distance ;  and  consequently 
less  variation  is  required  in  the  refractive  condition  of  the  eye  to  pre- 
serve the  accuracy  of  its  image.  It  is  generally  found  that  no  sensible 
effort  of  accommodation  is  required  for  objects  situated  at  any  distance 
beyond  fifty  feet  from  the  observer ;  while  within  this  limit  the  amount 
of  accommodation  necessary  for  distinct  vision  increases  rapidly  with 
the  diminution  of  the  distance. 

An  eye  which  is  capable  of  accommodating  for  distinct  vision,  through- 
out the  whole  range  included  between  15  centimetres  and  an  indefinite 
distance,  is,  in  this  respect,  a  normal  eye,  and  is  said  to  be  emmetropic ; 
that  is,  its  powers  of  accommodation  are  placed  within  the  natural  limits 
or  measurements  of  this  function. 

Presbyopia  Eye. — The  power  of  accommodation  diminishes  naturally 
with  the  advance  of  age ;  and  observation  shows  that  this  diminution 
dates  from  the  earliest  period  of  life.  Infants  often  examine  minute  ob- 
jects at  very  short  distances,  in  a  manner  which  would  be  quite  imprac- 
ticable for  the  healthy  adult  eye ;  and  the  minimum  distance  of  distinct 
vision  at  twenty  years  of  age  is  placed  by  some  writers  at  ten  centi- 
metres instead  of  fifteen.  The  power  of  increasing  the  convex^  of  the 
lens  to  this  extent  is  soon  lost ;  and,  as  it  continues  to  diminish,  a  time 
arrives,  usually  between  the  ages  of  40  and  50  years,  when  the  incapacity 


636 


THE    SENSES. 


of  accommodation  for  near  objects  begins  to  interfere  with  the  ordinary 
occupations  of  life.  When  this  condition  is  established  the  eye  is  said 
to  be  presbyopia.  Its  vision  is  still  perfect  for  distant  objects,  but  it 
can  no  longer  adapt  itself  for  the  examination  of  those  in  close  prox- 
imity to  the  eye.  To  remedy  this  'defect  the  patient  employs  a  convex 
eye-glass,  which  replaces  for  him  the  increased  convexity  of  the  crys- 
talline lens,  in  accommodation  for  near  objects  ;  and  by  the  aid  of  such 
a  glass  he  is  able  to  read  or  write  at  ordinary  distances  and  in  characters 
of  the  ordinary  size. 

The  use  of  a  convex  eye-glass  does  not  restore  the  perfection  of  sight 
as  it  existed  beforehand.  In  the  normal  eye,  the  degree  of  accommoda- 
tion varies  for  every  change  of  distance  within  fifty  feet ;  and  the  organ 
is  thus  adjusted,  by  an  instantaneous  and  unconscious  movement,  for 
the  most  delicate  variations  of  refractive  power.  But  an  eye-glass,  the 
curvatures  of  which  are  invariable,  can  give  perfect  correction  only  for 
a  single  distance.  A  glass  is,  therefore,  usually  selected  of  such  a 
strength  as  to  serve  for  the  most  convenient  distance  in  the  ordinary 
manipulation  of  near  objects. 

Fig.  203. 


EMMETEOPIC  EYE,  iii  vision  at  long  distances.     (Wundt.) 
Fig.  204. 


MYOPIC  EYE,  in  vision  at  long  distances.    (Wundt.) 

Myopic  Eye. — In  many  instances,  where  the  eye  is  otherwise  of  nor- 
mal configuration,  its  antero-posterior  diameter  is  longer  than  usual, 
thus  placing  the  retina  at  a  greater  distance  behind  the  lens.  The  con- 
sequence of  this  peculiarity  is  that  while  the  luminous  ra}^s  are  brought 
to  a  focus  at  the  usual  distance  from  their  point  of  entrance  into  the  eye, 
this  focus  is  situated  within  the  vitreous  body;  and  the  rays  reach  the 
retina  only  after  they  have  crossed  and  suffered  a  partial  dispersion. 


SENSE    OF    SIGHT.  637 

(Fig.  204.)  This  produces  an  indistinct  image  for  all  remote  objects. 
Within,  however,  a  certain  distance  from  the  eye,  the  rays  enter  the 
pupil  under  such  a  degree  of  divergence,  that  their  focus  behind  the  lens 
falls  at  the  situation  of  the  retina,  and  the  object  is  distinctly  seen. 
Such  an  eye  is  said  to  be  myopic,  or,  in  ordinary  language,  "near 
sighted,"  because  its  range  of  distinct  vision  is  confined  to  objects 
situated  comparatively  near  the  eye.  The  flexibility  of  the  lens,  and  its 
capacity  for  increasing  its  convexity,  may  be,  in  the  myopic  eye,  fully  up 
to  the  normal  standard,  and  consequently  its  power  of  accommodation 
may  be  as  great  in  reality,  though  not  in  distance,  as  that  of  the  normal 
eye.  In  the  ernmetropic.  condition,  a  certain  degree  of  variation  in  the 
curvature  of  the  lens  produces  the  necessary  change  of  accommodation 
for  any  distance  between  15  centimetres  and  infintty.  In  the  myopic 
eye  the  same  amount  of  accommodating  power  may  be  present,  though 
perfectly  distinct  vision  be  confined  between  the  distances  of  8  and  20 
centimetres.  The  myopic  eye  consequently  has  distinct  vision  at  shorter 
distances  than  a  natural  one,  but  gives  an  imperfect  image  for  remote 
objects. 

The  remedy  adopted  for  the  myopic  eye  is  to  employ  a  concave  eye- 
glass, which  increases  the  divergence  of  the  incident  rays.  This  enables 
the  eye  to  bring  parallel  or  nearly  parallel  rays  to  a  focus  situated 
farther  back  than  it  would  otherwise  fall,  and  at  the  actual  position  of 
the  retina ;  thus  giving  distinct  vision  for  remote  objects.  As  the 
accommodative  power  is  normal  in  amount,  this  contrivance  restores 
completely  the  perfection  of  sight,  in  a  myopic  eye  which  is  otherwise 
well-formed  ;  and  the  patient  can  then  accommodate  accurately  for  all 
distances  within  the  natural  limits  of  distinct  vision. 

Apparent  Position  of  Objects,  and  Binocular  Vision. — The  apparent 
position  of  an  object  is  determined  by  the  direction  in  which  the  lumi- 
nous rays  pass  from  it  to  the  interior  of  the  eye.  The  perception  of 
the  light  itself  necessarily  marks  the  direction  from  which  it  has  arrived, 
and  therefore  the  apparent  position  of  its  source.  It  is  difficult  to  under- 
stand fully  the  precise  physiological  conditions  which  cause  this  appreci- 
ation of  the  path  followed  by  a  luminous  beam ;  although  there  seems 
reason  for  the  belief  that  it  is  in  some  way  connected  with  the  posi- 
tion of  the  rods  and  cones  which  stand  perpendicularly  to  the  curved 
surface  of  the  retina,  and  thus  receive  the  impression  of  a  ray,  if  at  all, 
in  the  direction  of  their  longitudinal  axes.  But  whatever  may  be  the 
optical  or  physiological  mechanism  of  the  process,  its  plain  result  is  that 
a  ray  coming  from  below  attracts  attention  to  the  inferior  part  of  the 
field  of  vision ;  and  one  coining  from  above  is  referred  to  its  point  of 
origin  in  the  upper  part  of  the  same  field.  Thus  if  two  luminous  points 
appear  simultaneously  in  the  field  of  vision,  they  present  themselves  in  a 
certain  position  with  regard  to  each  other,  above  or  below,  to  the  right 
or  the  left,  according  to  the  direction  in  which  their  light  has  reached 
the  eye. 


638  THE    SENSES. 

This  fact  is  fully  demonstrated  by  the  phenomena  of  angular  reflec- 
tion and  refraction.  If  a  candle  be  held  behind  the  back,  in  such  a  posi- 
tion as  to  be  reflected  in  a  mirror  placed  at  the  front,  the  light  presents 
itself  to  the  eye  as  if  it  were  really  in  front,  because  it  is  from  this 
direction  that  the  luminous  rays  finally  come.  If  we  observe  the  reflec- 
tion of  objects  in  a  mirror  held  horizontally,  or  in  a  smooth  sheet  of 
water,  the  objects  seem  to  be  placed  below  the  reflecting  surface,  although 
they  are  really  above  it ;  since  the  rays  which  make  their  impression 
upon  the  eye  actually  come  from  below.  A  stick  or  pebble,  seen  ob- 
liquely at  the  bottom  of  a  transparent  pool,  appears  nearer  the  surface 
than  it  really?  is,  because  the  rays  which  reach  the  visual  organ  have 
been  bent  from  their  course,  in  passing  from  the  water  into  the  atmos- 
phere, and  have  consequently  assumed  a  more  oblique  direction. 

Erect  Vision,  with  Inverted  Retinal  Image. — Since  it  is  the  direction 
of  the  visual  rays,  rather  than  the  point  of  their  impact  upon  the  retina, 
which  determines  the  apparent  relative  position  of  luminous  objects, 
such  objects  appear  erect  although  their  images  upon  the  retina  are 
inverted.  The  retinal  image  is  not  the  form  which  is  seen  by  the  eye 
itself,  but  is  only  a  phenomenon  visible  to  the  inspection  of  another 
eye.  It  is  an  appearance  which  is  incidental  to  the  mode  of  refraction 
of  the  visual  rays ;  and  its  position  is  quite  a  distinct  matter  from  that 
of  the  luminous  impressions  perceived  by  the  retina.  Its  relation  to 
the  picture  really  presented  to  the  sensitive  membrane,  is  like  that  of 
the  reversed  engraving  upon  a  wood-cut  to  the  printed  impression  of 
the  same  design ;  or  like  that  of  the  elevations  and  depressions  of  a 
mould  to  the  depressions  and  elevations  of  the  cast  taken  from  it.  In 
the  field  of  sight,  therefore,  for  each  eye,  every  object  appears  above  or 
below,  to  the  right  or  left,  according  to  the  position  which  it  really 
occupies  in  regard  to  the  centre  of  the  field  and  the  line  of  direct  vision. 

Point  of  Fixation,  in  Vision  with  Two  Eyes. — For  each  eye,  distinct 
perception  is  possible,  as  shown  above  (p.  628),  only  for  objects  situated 
in  a  single  range,  which  is  known  as  the  "  line  of  direct  vision."  Since 
the  eyes  are  placed  in  their  orbits  at  a  lateral  distance  from  each  other 
of  about  six  centimetres,  when  they  are  both  directed  at  the  same  object, 
within  a  moderate  distance,  their  lines  of  direct  vision  have  a  sensible 
convergence,  and,  of  course,  cross  each  other  only  at  a  single  point. 
At  this  point  of  intersection  of  the  two  lines  of  direct  vision,  an  object 
may  be  seen  distinctly  by  both  eyes  at  the  same  time.  But  at  every 
other  point,  it  must  appear  indistinct  to  one  of  them ;  because  if  it  be 
in  the  line  of  direct  vision  for  the  right  eye  it  will  be  out  of  that  line 
for  the  left,  and  vice  versa.  There  is,  accordingly,  only  a  certain  dis- 
tance, directly  in  front,  at  which  an  object  can  be  distinctly  seen  sim- 
ultaneously by  both  eyes ;  namely,  that  at  which  the  two  lines  of  direct 
vision  cross  each  other.  This  point  is  called  the  point  of  fixation,  for 
the  two  eyes.  In  fixing  any  object,  for  binocular  vision,  the  accommo- 
dation in  each  eye  is  at  the  same  time  adjusted  for  the  required  distance ; 


SENSE    OF    SIGHT. 


639 


Fig.  205. 


and  thus  the  entire  accuracy  of  both  organs  is  concentrated  upon  a  single 
point. 

Since  it  is  the  position  of  the  two  eyes  in  their  respective  orbits  which 
determines  the  point  of  fixation,  the  observer  can  form  a  tolerably  accu- 
rate judgment,  as  to  whether  another  person  within  a  moderate  distance 
be  looking  at  him,  or  at  some  other  object  farther  removed  in  the  same 
direction.  For  more  considerable  distances  the  estimate  fails,  because 
the  obliquity  of  the  two  eyes,  which  varies  perceptibly  within  moderate 
distances,  diminishes  so  much  in  looking  afc  remote  objects,  that  the 
slight  differences  which  exist  are  no  longer  appreciable  by  the  observer. 

Single  and  Distinct  Vision  with  both  Eyes. — From  the  preceding 
facts  it  is  evident  that  only  one  point  can  be  found  in  the  line  of  direct 
vision,  for  both  eyes  at  the  same  time. 
When  an  object  occupies  this  situation, 
namely,  the  point  of  fixation,  it  is  distinctly 
perceived  by  both  eyes  in  the  centre  of  the 
field  of  vision ;  thus  its  two  visual  images 
exactly  cover  each  other  in  their  apparent 
position  and  so  form  but  one.  Consequently, 
the  object  appears  single,  though  seen  simul- 
taneously by  both  eyes  (Fig.  205).  But  if 
placed  either  within  or  bej'ond  the  point  of 
fixation,  an  object  appears  indistinct  and  at 
the  same  time  double.  If  the  observer  hold 
a  slender  rod  in  the  vertical  position  at  a 
distance  of  one  or  two  feet  before  the  face, 
and  in  the  same  range  with  any  small  object, 
such  as  a  door-knob,  on  the  opposite  side  of 
the  room,  it  will  be  found  that  when  both 
eyes  are  directed  at  the  rod,  it  is  seen  single 
and  distinctly,  but  the  door-knob  appears 
double  one  of  its  images  falling  upon  each 
side.  If  the  eyes  be  now  directed  at  the  door- 
knob, that  in  turn  becomes  distinct  and  single, 
•while  the  rod  appears  double,  one  indistinct 
image  being  placed  on  each  side,  as  before. 

These  phenomena  depend  upon  the  different  directions  of  the  two 
lines  of  direct  vision.  When  the  eyes  are  so  directed  that  the  nearer 
object  (Fig.  205,  i)  occupies  the  point  of  fixation,  the  farther  object  (a) 
will  also  be  seen,  because  it  is  still  included  in  the  visual  field ;  although 
it  will  be  seen  indistinctly,  because  the  accommodation  of  the  eye  is  no 
longer  adjusted  to  its  distance,  and  because  it  is  not  in  the  line  of  direct 
vision.  But  for  the  right  eye  (a)  it  will  be  placed  to  the  right  of  this 
line,  and  for  the  left  eye  (b)  to  the  left  of  it.  Its  two  images  do  not  cor- 
respond with  each  other  in  situation,  and  the  object  accordingly  appears 
double. 

If  the  eyes,  on  the  other  hand,  be  directed  at  the  more  distant  object, 


b 

SlTTGLE    ATTD    DOTTBLE    Vl- 

SION,  at  different  distances.— a. 
Right  eye.  b.  Left  eye.  1.  Ob- 
ject at  the  point  of  fixation,  seen 
single.  2.  Object  beyond  the 
point  of  fixation,  seen  double. 


64:0  THE    SENSES. 

the  nearer  one  is  no  longer  in  the  point  of  fixation.  For  the  right  eye, 
its  image  will  appear  to  the  left  of  the  line  of  direct  vision,  and  for  the 
left  eye  to  the  right  of  this  line.  It  therefore  appears  double  and  in- 
distinct. 

Thus,  in  the  ordinary  use  of  binocular  vision  every  object  but  one 
appears  double  and  at  the  same  time  imperfectly  delineated.  This  cir- 
cumstance is  so  little  noticed  that  it  is  never  a  source  of  confusion  for 
the  sight,  and  even  requires  a  special  experiment  to  demonstrate  its 
existence.  The  reason  for  its  passing,  as  a  general  rule,  unobserved  is 
twofold.  First,  the  attention  is  naturally  concentrated  upon  the  object 
which  is  placed,  for  the  moment,  at  the  point  of  fixation.  When  this 
point  is  shifted,  the  new  object  upon  which  it  falls  also  appears  single ; 
and  thus  the  idea  of  a  double  image,  even  if  indistinctly  suggested  at 
any  time,  is  at  once  dispelled  by  the  movement  of  the  eyes  in  that 
direction.  Secondly,  an  object  which  is  really  placed  in  any  degree 
toward  the  right  hand  or  the  left  will  form  an  indistinct  double  image, 
since  it  occupies  a  different  apparent  position  for  the  two  eyes.  But 
the  obliquity  of  its  rays,  and  consequently  the  indistinctness  of  its 
image,  will  be  greater  for  the  right  eye  than  for  the  left,  or  vice  versa; 
and  the  notice  of  the  observer,  if  drawn  to  it  at  all,  is  occupied  with 
the  more  distinct  of  the  two  images,  to  the  exclusion  of  the  other. 
The  fact  becomes  palpable  only  in  such  an  experiment  as  that  detailed 
above ;  where  two  bodies  are  examined  in  the  same  linear  range,  so  that 
the  double  images  produced  are  equal  in  intensity,  and  sufficiently  de- 
tached by  contrast  from  surrounding  objects  to  force  themselves  upon 
the  attention. 

Double  vision  may  also  be  produced  at  any  time  by  pressure  with 
the  finger  at  the  external  angle  of  one  of  the  eyes,  so  as  to  alter  its  posi- 
tion in  the  orbit,  the  other  eye  remaining  untouched.  But  in  this  case 
it  is  the  whole  field  of  vision  which  is  displaced,  and  all  objects  are 
doubled  indiscriminately ;  their  images  being  separated  to  the  same 
degree  and  in  the  same  direction,  whatever  may  be  their  distance  from 
the  eye.  It  is  this  form  of  double  vision  which  is  produced,  in  vertigo 
or  intoxication,  by  irregular  action  of  the  muscles  of  the  eyeball. 

Appreciation  of  Solidity  and  Projection. — When  both  eyes  are  direct- 
ed simultaneously  at  a  single  point,  the  distance  of  the  object  may  be 
estimated  with  considerable  accuracy  by  the  degree  of  convergence  of 
the  visual  axes  required  for  its  fixation.  Since  this  convergence  is 
in  proportion  to  the  proximity  to  the  observer  of  the  point  of  fixation, 
another  impression,  of  different  kind  but  of  equal  importance,  is  also 
produced  by  binocular  vision,  when  the  object  has  an  appreciable  volume 
and  thickness,  and  when  it  is  placed  within  a  moderate  distance.  Owing 
to  the  lateral  separation  of  the  two  eyes,  and  the  convergent  direction 
of  their  visual  axes,  they  do  not  both  receive  from  such  an  object  pre- 
cisely the  same  image.  Both  e}res  will  see  the  front  of  the  object  in 
nearly  the  same  manner ;  but  in  addition  the  right  eye  will  see  a  little 
of  its  right  side,  and  the  left  eye  will  see  a  little  of  its  left  side.  This 


SENSE    OF    SIGHT. 

is  illustrated  in  Figs.  206  and  20T,  which  represent  a  skull  as  seen  by 
the  two  eyes,  when  placed  exactly  in  front  of  the  observer  at  a  distance 
of  eighteen  inches  or  two  feet ;  rather  more  of  the  details  on  one  side 
being  visible  to  the  left  eye,  and  rather  more  of  those  on  the  other 

Fig.  206.  Fig.  207. 


AS    SEEN    BY    THE    LEFT    EYE.  AS    SEEN    BY    THE    RIGHT    EYE. 

being  visible  to  the  right  eye.  As  the  central  part  of  the  mass  is  in  the 
point  of  fixation,  at  the  junction  of  the  two  visual  axes,  the  object 
appears  single.  But  the  images  which  it  presents  to  the  two  eyes  are 
not  precisely  identical  in  form ;  and  it  is  the  combination  of  these  dif- 
ferent images  into  one  which  gives  rise  to  the  impression  of  solidity  or 
projection. 

But  this  effect  is  complete  only  when  the  object  is  situated  within  a 
moderately  short  distance.  For  those  which  are  comparatively  remote, 
the  convergence  of  the  visual  axes,  and  consequently  the  difference  in 
the  apparent  configuration  of  the  two  images,  become  inappreciable, 
and  the  optical  impression  of  solidity  disappears.  At  a  distance  of 
some  miles  even  a  large  object,  like  a  mountain,  loses  its  projection, 
and  presents  the  form  of  a  flattened  mass  against  the  horizon.  It  is  on 
this  account  that  pictorial  representations  of  distant  views  are  often 
extremely  effective ;  the  idea  of  successive  remoteness  in  different  parts 
of  the  landscape  being  conveyed  by  appropriate  intersection  of  the  out- 
lines and  by  variations  in  tone,  color,  and  distinctness,  like  those  due 
to  the  interposition  of  the  atmosphere.  On  the  other  hand,  a  picture 
of  near  objects,  which  aims  to  represent  their  solidity,  can  never  de- 
ceive us  in  this  respect,  however  elaborate  may  be  the  details  of  surface, 
shadow,  and  color ;  since  the  flat  surface  of  the  picture  presents  the 
same  image  to  both  eyes,  and  it  is  consequently  evident  that  the  ob- 
jects delineated  have  no  real  projection.  But  if  two  pictures  of  the 
same  object,  taken  in  two  different  positions,  be  presented  in  such  a 
way  that  only  one  of  them  is  seen  by  the  right  eye,  and  only  the  other 
by  the  left,  the  same  optical  effect  may  be  produced  as  by  the  object 
itself,  and  the  appearance  of  solidity  and  projection  may  be  perfectly 


642  THE    SENSES. 

imitated.  Such  is  the. principle  of  the  instrument  known  as  the  stereo- 
scope. This  is  simply  a  box  or  framework,  holding  two  photographic 
pictures  of  the  same  object,  which  have  been  taken  from  two  different 
points  of  view,  corresponding  to  the  different  positions  of  the  two  eyes. 
Thus  one  of  the  pictures  represents  the  object  as  it  would  in  reality  be 
seen  by  the  right  eye,  and  the  other  represents  it  as  it  would  be  seen 
by  the  left.  When  these  pictures  are  so  placed  in  the  stereoscope  that 
each  eye  has  presented  to  it  the  appropriate  view,  the  two  images,  occu- 
pying the  point  of  fixation,  are  fused  upon  the  retina,  and  produce  an 
extremely  deceptive  resemblance  to  the  projection  and  stolidity  of  the 
real  object. 

The  acuteness  of  perception,  by  which  the  eyes  appreciate  a  slight 
difference  in  the  two  retinal  images,  is  the  measure  of  what  may  be 
called  their  stereoscopic  sensibility.  It  has  been  observed  that  two 
coins,  composed  of  different  metals,  but  struck  from  the  same  die,  are 
slightly  different  in  volume,  owing  to  the  unequal  dilatation  of  the 
metals  after  receiving  the  impression  of  the  die.  This  difference  may  be 
quite  inappreciable  to  the  eye  in  ordinary  examination,  even  when  the 
coins  are  placed  in  contact  with  each  other ;  but  if  they  be  made  to  take 
the  place  of  the  two  pictures  in  a  stereoscope  box  and  viewed  together, 
the  resulting  image,  instead  of  presenting  a  plane  surface,  appears  ob- 
lique and  convex. 

The  degree  of  stereoscopic  sensibility  was  tested  by  Helmholtz  in  the 
following  manner:  Three  metallic  pins  were  fixed  upright  in  small 
movable  blocks  of  wood,  placed  side  by  side,  so  that  the  pins  sh6uld  be 
about  12  millimetres  distant  from  each  other,  and  nearly  in  the  same 
vertical  plane.  The  observer  then,  using  both  eyes  simultaneously, 
examined  the  appearance  of  the  objects  from  a  distance  of  340  milli- 
metres, the  pins  being  arranged  at  right  angles  across  the  line  of  view. 
The  immediate  object  of  the  examination  was  to  determine,  from  the 
stereoscopic  effect,  whether  the  three  pins  were  placed  exactly  in  the 
same  plane,  or  whether  either  of  them  were  in  advance  of  or  behind  the 
others.  It  was  found  possible  to  detect  in  this  way  a  deviation  in  posi- 
tion of  one  of  the  pins  equal  to  one-half  its  own  thickness,  that  is, 
0.25  mm. ;  and  the  deviation  was  recognized  with  absolute  certainty 
when  it  amounted  to  the  entire  thickness  of  the  pin,  that  is,  0.50  milli- 
metre. 

General  Laws  of  Visual  Perception. — Beside  the  laws  regulating  the 
formation  and  combination  of  optical  images,  there  are  certain  pheno- 
mena connected  with  visual  perceptions  in  general,  which  are  of  con- 
siderable importance  in  the  physiology  of  sight.  Some  of  these  phe- 
nomena require  for  their  study  special  modes  of  investigation,  while 
others  are  made  evident  by  comparatively  simple  means,  and  are  often 
of  consequence  in  their  hygienic  relations. 

Luminous  impressions  upon  the  eye  remain  for  a  certain  time 
after  the  cessation  of  the  light.  The  persistence  of  luminous  impres- 
sions thus  left  upon  the  eye  is  very  short,  and  is  not  usually  noticeable, 


SENSE    OF    SIGHT.  643 

because  these  impressions  are,  under  all  ordinary  conditions,  immediately 
followed  by  others  upon  the  same  part  of  the  retina,  and  the  new 
sensation  practically  obliterates  the  old  one.  But,  if  the  instantaneous 
impression  be  not  followed  by  a  different  one,  or  if  it  be  sufficiently 
vivid  to  be  perceived,  notwithstanding  the  presence  of  others,  its  con- 
tinuance may  be  made  evident  to  observation.  Thus,  in  a  dark  room, 
if  a  bright  point,  like  the  heated  end  of  a  wire,  be  carried  round  in  a 
circle  with  moderate  rapidity,  the  eye  follows  its  movement,  as  it  presents 
itself  successively  in  different  parts  of  the  circle ;  the  light  always  ap- 
pearing at  one  point  only,  the  rest  of  the  space  remaining  dark.  But 
if  the  rapidity  of  the  circular  movement  be  greatly  increased,  the  bright 
point  seems  to  be  drawn  out  more  or  less  into  a  curved  line;  and,  when 
the  rate  of  revolution  has  attained  a  very  high  degree  of  velocity,  it 
becomes  transformed  into  a  continuous  circle  of  light,  since  the 
impression  made  upon  the  retina,  when  the  end  of  the  wire  is  at  one 
part  of  the  circle,  lasts  until  it  has  completed  a  revolution  and  again  re- 
turned to  the  same  point.  The  succession  of  sparks  thrown  off  rapidly 
from  a  knife-grinder's  wheel  often  produce  the  effect,  even  by  daylight, 
of  an  unbroken  stream  of  fire.  A  circular  saw  with  large  teeth,  driven 
by  machinery  under  a  high  rate  of  speed,  presents  apparently  a  perfectly 
smooth  edge,  the  outline  of  which  is  formed  by  the  moving  points  of  the 
teeth ;  and  the  revolving  spokes  of  a  carriage  wheel,  in  rapid  motion, 
become  confused  upon  the  retina  with  each  other  and  with  the  interven- 
ing spaces,  and  assume  the  appearance  of  a  uniform  glimmering  disk. 

The  absolute  duration  of  visual  impressions  upon  the  retina  has  been 
the  subject  of  various  researches,  but  it  is  found  that  its  length  cannot 
be  expressed  by  any  single  number  which  would  be  correct  for  all  cases. 
A  brilliant  light  leaves,  on  the  whole,  an  impression  which  lasts  longer 
than  that  from  a  feeble  one  ;  but,  on  the  other  hand,  its  relative  intensity 
to  the  light  of  surrounding  objects  diminishes  more  rapidly,  and  con- 
sequently, when  it  is  in  motion,  a  higher  degree  of  velocity  is  required 
to  produce  the  appearance  of  a  uniformly  bright  line.  The  experiments 
employed  to  determine  the  length  of  time,  during  which  a  luminous 
impression  remains  upon  the  eye  without  appreciable  diminution  of 
its  intensity,  have  been  usually  those  with  revolving  disks,  the  surface 
of  which  is  variegated  in  sectors  of  black  and  white.  The  rate  of  revo- 
lution of  the  disk  being  known,  as  well  as  the  width  of  the  different  sec- 
tors, when  the  revolving  surface  presents  to  the  eye  the  appearance  of 
an  absolutely  uniform  gray  tint,  the  time  during  which  the  black  or  white 
impressions  remain  undiininished  in  strength  is  readily  ascertained.  The 
result  obtained,  from  experiments  conducted  in  this  manner,  under 
moderate  illumination,  gives  the  duration  of  perfect  visual  impressions  as 
one  twenty-fourth  of  a  second,  and,  for  the  oscillation  of  a  very  luminous 
point  following  the  vibrations  of  a  tuning  fork,  one-thirtieth  of  a  second. 

The  persistence  and  apparent  continuity  of  successive  visual  images, 
appearing  at  the  same  spot,  is  illustrated  in  the  optical  contrivance 
known  as  the  Thaumatrope,  or  magic  wheel.  It  consists  of  an  opaque 


644:  THE    SENSES. 

disk,  with  a  perforation  at  one  spot  near  its  edge,  through  which  another 
disk  is  visible,  placed  immediately  behind  the  first,  and  capable  of  re- 
volving rapidly  while  the  first  remains  stationary.  Upon  the  second  disk 
is  a  circle  of  pictures  representing  the  same  figure  in  different  positions ; 
and  when,  by  its  revolution,  these  pictures  are  made  to  pass  in  quick 
succession  across  the  opening  of  the  disk  in  front,  they  present  the  ar> 
pearance  of  a  single  figure  in  rapid  motion.  The  interval  between  the 
perception  by  the  eye  of  successive  pictures  is  too  short  to  be  observed, 
and  the  same  object  appears  to  take  successively  the  different  positions 
in  which  it  is  represented. 

Duration  of  a  Luminous  Impulse  required  for  the  Perception  of 
Visual  Impressions. — This  point  has  been  investigated  by  Rood1  by 
means  of  the  light  of  an  electric  spark  obtained  from  an  induction  coil 
connected  by  its  terminal  wires  with  the  inner  and  outer  surfaces  of  a 
Leyden  jar.  On  breaking  the  primary  current  a  discharge  takes  place 
between  the  electrodes,  which  is  of  exceedingly  short  duration.  This 
duration  was  measured  by  Prof.  Rood  with  the  aid  of  a  mirror  revolv- 
ing upon  its  transverse  axis,  by  which  the  light  of  the  electric  spark 
was  thrown  upon  a  plate  of  glass,  where  it  could  be  examined  by  the 
naked  eye,  or  with  a  magnifying  eye-piece,  as  in  Fig.  208. 

The  light  emanating  from  the  spark  S,  was  received  by  an  achromatic 
lens  L,  of  nine  inches  focal  length.  It  then  fell  upon  a  plane  mirror 
revolving  with  a  uniform  velocity  of  340  times  per  second,  and,  after 
reflection  by  the  mirror,  was  brought  to  a  focus  upon  a  glass  plate  G, 
where  it  could  be  examined  by  the  telescope  eye-piece  E,  magnifying 

ten  diameters.  From  the  known 
rate  of  revolution  of  the  mirror,  and 
its  distance  from  the  glass  plate  G, 
the  necessary  rate  of  movement  of  a 
reflected  beam  upon  the  plate  was 
determined.  If  the  spark,  used  in 
these  experiments,  lasted  long 
enough  for  its  reflected  image  to 
move  over  an  appreciable  distance, 
this  image  would  appear  to  the  eye 
to  be  drawn  out  in  the  direction  of 
the  movement,  owing  to  the  persist- 
ence of  its  visual  impression  as  de- 
Apr  AR  A  TUB  for  measuring  the  dura-  scribed  above.  But  with  the  mirror 

tion  of  an  electric  spark  -S    Position   of  revolving    at   this  Speed   no  SUCh  de- 
the  spark.     L.    Achromatic  lens.     M.    Re- 
volving mirror.   G.  Glass  plate  for  receiv-  formation  was  perceptible,  the  spark 
ing  the  image  of  the  spark.    E.  Telescope  image    appearing    of    precisely    the 

same   form    as   if  the   mirror  were 

stationary;  showing  that  the  duration  of  the  light  could  not  be  greater 
than  .000002  (500'ooo)  of  a  second. 

1  The  American  Journal  of  Science  and  Arts.     New  Haven,  September,  1871. 


SENSE    OF' SIGHT.  645 

In  a  continuation  of  the  experiments,  there  was  interposed  between 
the  spark  and  the  mirror  a  blackened  glass  plate,  ruled  with  parallel 
transparent  lines  j%  of  a  millimetre  in  width,  and  separated  from  each 
other  by  the  same  distance.  The  image  of  this  plate,  when  illuminated 
by  the  spark,  would  appear  upon  the  glass  G,  so  long  as  the  mirror 
were  stationary,  as  a  series  of  equal  alternating  black  and  white  lines. 
With  the  mirror  in  motion,  if  the  illumination  lasted  long  enough  for 
the  image  to  be  shifted  a  distance  equal  to  the  combined  width  of  a 
black  and  white  line,  these  lines  would  become  undistinguishable  from 
each  other,  as  in  the  case  of  the  revolving  disk  with  black  and  white 
sectors.  Thus  the  continuance  of  the  visible  lines,  under  a  given  rate 
of  motion,  proved  that  the  duration  of  the  electric  spark  was  less  than 
a  certain  calculable  period.  Their  disappearance  as  distinct  objects 
indicated  that  the  limits  of  this  duration  had  been  reached  ;  and  that 
it  was  long  enough  to  allow  of  the  shifting  of  two  adjacent  lines.  The 
result  showed  that  the  duration  of  the  shortest  measurable  spark  was 
but  little  over  .00000004  (^ooWo)  of  a  second. 

With  a  spark  of  this  duration,  distinct  vision  of  motionless  objects 
was  perfectly  possible.  The  letters  on  a  printed  page  were  plainly  to  be 
seen,  and  even  the  phenomena  of  polarization  of  light  distinctly  observ- 
able. It  is  accordingly  sufficient  to  produce  a  complete  retinal  impres- 
sion. 

These  experiments  do  not  indicate  the  time  required  for  the  necessary 
nervous  action  in  the  perception  of  light.  They  only  show  that  a  lumi- 
nous impulse  having  the  above  duration  is  sufficient  to  cause  a  distinct 
sensation.  But  the  time  which  is  requisite  for  the  sensation  to  be  per- 
ceived is  very  much  longer.  From  the  results  given  in  a  preceding 
chapter  (p.  431)  it  appears  that  the  transmission  of  a  luminous  impres- 
sion through  the  optic  nerve,  would  undoubtedly  require  at  least  j^^ 
of  a  second,  and  its  perception  in  the  brain  considerably  more.  It  fol- 
lows from  this  that,  at  the  instant  when  the  image  of  the  electric  spark 
is  seen,  in  the  experiment  of  Prof.  Rood,  it  has,  in  fact,  already  disap- 
peared ;  the  interval  which  elapses  between  its  actual  occurrence  and  its 
perception  by  the  observer  being  very  much  greater  than  the  duration 
of  the  spark  itself. 

The  facts  detailed  above  explain  the  cause  of  a  peculiar  optical  effect, 
which  has  often  been  observed  under  the  use  of  the  electric  spark ; 
namely,  that  bodies  in  rapid  motion,  if  illuminated  by  an  instantaneous 
discharge,  appear  to  the  observer  as  if  at  rest.  A  disk,  painted  with 
black  and  white  sectors,  if  set  in  revolution  under  continuous  light, 
appears  of  a  uniform  gray;  or,  if  the  sectors  be  painted  of  the  rainbow 
colors,  their  tints  are  mingled  and  the  disk  appears  white.  But  if  such 
a  disk,  revolving  in  a  dark  room,  be  illuminated  by  the  electric  spark, 
it  becomes  visible  for  an  instant,  with  its  different  sectors  as  distinct 
from  each  other  as  if  they  were  at  rest.  A  jet  of  water  discharged  from 
an  orifice  at  the  bottom  of  a  vessel,  though  transparent  in  the  imme- 
diate neighborhood  of  the  orifice,  is  turbid  lower  down;  and  by  instan- 


646  THE    -SENSES. 

taneous  illumination  the  turbid  portion  is  seen  to  be  composed  of 
separate  drops,  which  appear  to  be  motionless.  A  flash  of  lightning  has 
a  similar  effect  in  exhibiting  objects  which  are  in  motion  as  if  they  were 
quiescent.  The  passage  of  a  cannon  ball  or  a  rifle  bullet  by  daylight 
is  imperceptible  ;  because,  as  an  opaque  object,  it  does  not  remain  long 
enough  at  any  one  point  to  efface  the  persistent  impression  of  the  objects 
visible  behind  it,  and  the  sight  of  these  objects  accordingly  does  not 
appear  to  have  suffered  any  interruption.  But  if  such  a  missile  should 
happen  to  be  passing  in  front  of  the  observer  in  the  night  time  during 
a  thunder  storm,  at  the  moment  of  a  flash,  it  would  be  visible  equally 
with  the  other  parts  of  the  landscape,  and  would  appear  as  a  motionless 
object  suspended  in  the  air. 

The  momentary  closure  of  the  eyes  in  winking,  for  the  same  reason, 
does  not  cause  any  noticeable  interference  with  sight,  and  is  not  even 
observed  by  the  individual ;  since  the  visual  impression  of  external 
objects  appears  to  be  continuous  during  the  short  interval  occupied  by 
the  movement  of  the  lids. 

The  local  sensibility  of  the  retina  is  diminished  by  continued  visual 
impressions.  This  diminution  of  the  retinal  sensibility  appears  to  be 
continuous  from  the  very  commencement  of  a  visual  impression,  so  that 
it  may  be  made  perceptible  within  a  few  seconds.  In  the  experiment  of 
exhibiting  the  image  of  the  retinal  bloodvessels  by  changing  the  posi- 
tion of  their  shadows  (page  622)  these  shadows  are  visible  for  an  instant 
with  extreme  sharpness.  But  they  begin  to  fade  almost  at  once  and 
after  a  short  interval  become  imperceptible.  They  can  only  be  seen  for 
a  considerable  time,  by  keeping  the  light  in  motion,  so  that  the  shadows 
fall  alternately  upon  different  parts  of  the  retina.  The  portions  of  the 
retina  which  are  in  full  illumination  have  their  sensibility  so  rapidly 
diminished,  that  the  shadow,  if  motionless,  is  no  longer  visible  by  con- 
trast. Those  which  are  in  shadow,  on  the  other  hand,  become  compara- 
tively more  sensitive  by  repose ;  and  when  the  shifting  of  the  light 
brings  them  again  into  illumination,  they  not  only  receive  more  stimulus 
than  the  adjacent  parts,  but  are  also  more  impressible  to  its  influence. 

If  one  eye  be  covered  by  a  dark  glass,  and  the  other  be  used  ex- 
clusively, for  an  hour  or  two,  in  reading  or  writing,  at  the  end  of  that 
time  the  difference  in  retinal  sensibility  of  the  two  eyes  will  be  very 
apparent.  A  single  faintly  luminous  object  in  a  dark  room  may  then 
be  almost  imperceptible  to  the  eye  which  has  been  in  use,  while  it  will 
appear  to  the  other  quite  brilliant.  If  the  application  of  the  eye  have 
not  been  carried  beyond  the  bounds  of  moderation,  this  difference  is 
transitory ;  and  by  reversing  the  conditions,  that  is,  covering  the  eye 
previously  in  use,  and  reading  or  writing  by  aid  of  the  other,  that  which 
was  before  the  most  sensitive  to  light  becomes  less  so,  and  that  which 
was  previously  fatigued  recovers  its  sensibility. 

The  alternate  diminution  and  recovery  of  the  retinal  sensibility,  by 
excitement  and  repose,  is  directly  connected  with  the  phenomena  of 
negative  images.  If  the  eye  be  steadily  fixed  for  a  short  time  upon  a 


SENSE    OF    SIGHT.  647 

white  spot  in  the  middle  of  a  black  ground,  and  then  suddenly  directed 
toward  a  blank  wall  of  a  uniform  white  or  light  gray  color,  a  dark  spot 
will  appear  at  its  centre,  of  the  same  apparent  size  and  figure  with  the 
white  one  previously  observed.  This  is  the  "  negative  image"  of  the 
retinal  impression.  That  part  of  the  retina  which  was  first  impressed 
by  the  rays  from  the  white  spot  becomes  less  sensitive  to  light ;  and 
another  white  surface,  looked  at  immediately  afterward,  appears  darker 
than  usual.  On  the  other  hand,  those  parts  which  were  exposed  only 
to  the  dark  ground,  that  is,  to  the  comparative  absence  of  light,  are 
more  sensitive  than  before ;  and  the  surface  of  the  white  wall,  outside 
the  central  spot,  appears  brighter  than  usual.  It  is  not  necessary  that 
the  contrast  in  hue  between  the  different  parts  of  a  retinal  image  should 
be  as  strong  as  that  of  black  and  white,  in  order  to  produce  this  effect. 
Any  decided  difference  in  illumination  will  be  sufficient.  It  is  not  even 
essential  to  look  at  a  different  background,  to  observe  the  appearance 
in  question.  If  a  piece  of  furniture  of  dark  wood  be  placed  against  a 
blank  wall  of  white  or  gray  surface,  and  looked  at  steadily  for  a  short 
time,  on  shifting  the  eyes  to  a  different  part  of  the  same  wall,  the  figure 
of  the  chair  or  table  will  appear,  with  all  its  details  of  outline,  expressed 
in  a  lighter  tint  than  that  of  the  surrounding  parts. 

The  above  effect  may  be  also  produced  in  a  still  more  simple  man- 
ner. Let  a  black  ruler,  about  one  inch  wide,  be  laid  upon  a  sheet  of 
white  paper,  and  looked  at  steadily  for  thirty  or  forty  seconds.  If  the 
ruler  be  now  removed  by  a  sudden  motion,  the  eye  remaining  fixed,  its 
image  will  appear  as  a  bright  band  upon  the  paper,  fading  gradually  as 
the  sensibilitjr  of  the  retina  becomes  equalized  in  its  different  parts. 

If  the  figure  which  is  thus  examined  be  a  colored  one,  its  negative 
image,  subsequently  produced,  will  present  a  complementary  hue  to  that 
of  the  original  object.  A  strip  of  red  paper  placed  upon  the  white 
sheet,  and  then  suddenly  removed,  leaves  a  negative  image  which  is 
bluish-green ;  and  a  green  one  leaves  an  image  which  has  a  decided 
tinge  of  red.  This  shows  that  the  sensibility  of  the  retina  may  be  in- 
creased or  diminished  separately  for  the  different  colored  rays  of  the 
luminous  beam.  While  looking  at  a  red  object,  the  retina  becomes  less 
sensitive  to  the  red  rays,  but  more  so  for  those  at  the  opposite  end  of 
the  spectrum,  and  vice  versa ;  so  that,  on  looking  subsequently  at  a 
white  object,  the  negative  image  exhibits  a  tint  corresponding  to  the 
rays  for  which  the  retina  has  remained  most  sensitive.  That  this  is  the 
mechanism  of  the  production  of  complementary  colors  in  negative 
images  becomes  evident  on  simplifying  the  experiment.  If  the  black 
ruler  be  laid  upon  a  book  bound  in  blue  cloth,  on  taking  it  away  the 
band  which  remains  in  its  place  is  of  a  more  intense  blue  than  the  rest. 
If  a  red  book  be  used  for  the  same  purpose,  the  negative  image  of  the 
ruler  presents  a  remarkably  pure  red  color,  while  the  remainder  of  the 
surface  appears  of  a  dull  brown. 

The  variable  sensibility  of  the  retina,  according  to  its  exposure, 
affords  an  explanation  of  the  well-known  fact,  that  under  some  condi- 


648  THE    SENSES. 

tions  an  object  may  be  most  easily  perceived  by  indirect  vision.  It 
often  happens  that  in  searching  for  a  star  of  very  small  magnitude  and 
feeble  light,  it  may  be  momentarily  perceived  by  looking  not  directly 
at  it,  but  at  a  point  in  its  immediate  neighborhood,  at  a  small  angular 
distance  from  its  real  position.  The  star  is  not  seen  distinctly  under 
these  circumstances,  because  it  is  out  of  the  line  of  direct  vision.  But 
its  light  falls  upon  a  part  of  the  retina  near  the  fovea  centralis,  the  sen- 
sibility of  which  is  more  acute  than  usual,  owing  to  its  continued 
exposure  only  to  the  dark  sky ;  while  the  fovea  itself,  which  has  been 
receiving  in  succession  the  images  of  particular  stars,  is  comparatively 
deficient  in  impressibility  to  light.  When  the  visual  axis  is  turned 
directly  upon  the  fainter  star,  for  the  purpose  of  getting  a  distinct 
image,  its  light  disappears ;  and  thus  it  can  only  be  seen  as  an  evanes- 
cent object  by  indirect  vision. 

If  the  eye  be  fixed  immovably  for  too  long  a  time  upon  the  same 
luminous  object,  the  local  diminution  of  retinal  sensibility  may  amount 
to  fatigue  ;  and  a  persistence  in  its  continuous  application  may  produce 
permanent  injury  of  the  visual  organ.  After  steadily  examining  a 
single  object  for  even  a  short  time,  it  becomes  difficult  to  resist  the 
tendency  to  turn  the  sight  in  another  direction  by  the  automatic  move- 
ment of  the  muscles  of  the  eyeball.  Naturally,  the  eye  never  rests  for 
more  than  a  few  seconds  upon  an}r  one  point  in  the  field  of  view ;  but 
is  directed  in  succession  at  different  objects,  fixing  each  one  in  turn  at 
the  point  of  distinct  vision,  and  immediately  passing  to  another  more 
or  less  remote.  Thus  the  fatigue  of  the  retina  is  avoided,  since  those 
parts  which  at  one  instant  have  a  stronger  illumination,  at  the  next 
receive  the  impression  of  a  shadow  ;  and  no  portion  of  the  membrane 
is  .exposed  sufficiently  long  to  any  single  object  to  become  insensible  to 
its  grade  of  light  or  color. 

There  is  also  reason  to  believe  that  the  eye  requires,  for  its  safety, 
the  periodical  suspension  of  all  visual  impressions  which  is  obtainable 
in  sleep.  It  is  not  essentially  different  in  this  respect  from  other  parts 
of  the  nervous  apparatus  of  animal  life ;  but  the  delicacy  of  its  sensi- 
bility, which  is  requisite  for  the  due  performance  of  its  function,  and  the 
complication  of  its  structure,  which  includes  so  many  parts  adjusted  to 
each  other  with  mathematical  accuracy,  indicate  that  it  is  one  of  the 
organs  most  liable  to  derangement  if  deprived  of  its  natural  interval 
of  restoration  and  repose. 

Sense  of  Hearing. 

By  the  sense  of  hearing  we  receive  the  impressions  of  sound,  and 
appreciate  their  intensity,  their  tone  or  pitch,  with  all  the  variations 
of  higher  or  lower  notes,  as  well  as  their  quality,  that  is,  the  different 
character  of  sounds  of  the  same  tone  and  intensity,  but  produced  by 
different  methods,  as  by  reeds,  strings,  or  wind  instruments,  or  by  the 
concussion  of  solid  bodies.  Our  idea  of  time,  or  the  succession  of 
events,  seems  also  to  be  connected  more  especially  with  auditory  sensa- 


SENSE    OF    HEARING.  649 

tions.  The  impressions  received  in  this  way  depend  upon  the  vibrations 
excited  in  the  atmosphere  by  sonorous  bodies,  which  are  themselves 
thrown  into  vibration  by  various  causes,  and  which  then  communi- 
cate similar  undulations  to  the  surrounding  air.  These  undulations 
are  of  such  a  kind  that  they  cannot  be  directly  appreciated  by  the 
organs  of  general  sensibility ;  but  when  communicated  to  the  auditory 
apparatus  they  produce,  through  it,  the  sensation  of  sound. 

Organ  of  Hearing. — The  organ  of  hearing  consist  of,  first,  the  ex- 
ternal ear,  a  conch  or  trumpet-shaped  expansion,  destined  to  collect  the 
sonorous  impulses  coming  from  various  quarters,  and  to  conduct  them 
into  its  tubular  continuation,  the  external  auditory  meatus ;  secondly, 
a  membranous  sheet  or  drum-head,  the  membrana  tympani,  stretched 
across  the  bottom  of  the  external  auditory  meatus,  by  which  the  sono- 
rous vibrations  are  received  and  transmitted,  through  the  chain  of  bones 
or  auditory  ossicles,  across  the  cavity  of  the  tympanum  or  middle  ear, 
to  the  third  portion  of  the  auditory  apparatus,  namely,  the  labyrinth, 
or  internal  ear ;  a  cavity  excavated  in  the  petrous  portion  of  the  tem- 
poral bone,  filled  with  fluid,  and  containing  various  membranous  sacs 
and  canals,  upon  which  are  distributed  the  filaments  of  the  auditory 
nerve. 

Thus  the  delicate  terminal  expansions  of  the  auditory  nerve,  deeply 
concealed  in  their  bony  cavities,  and  sustained  by  the  surrounding  fluid, 
are  protected  from  all  other  mechanical  impressions,  but  are  so  placed 
as  to  receive  the  impulse  of  sonorous  vibrations. 

External  Ear. — The  external  ear  consists  of  a  cartilaginous  frame- 
work, covered  with  integument,  loosely  attached  to  the  bones  of  the 
head,  and  more  or  less  movable  by  means  of  various  muscles,  which, 
by  their  contractions,  tend  to  turn  its  concavity  in  various  directions. 
In  man,  notwithstanding  the  existence  of  these  muscles,  their  functional 
activity  is  nearly  imperceptible ;  and  it  is  only  in  exceptional  cases  that 
thej7  are  capable  of  producing  a  partial  sliding  or  rotatory  movement  of 
the  external  ear.  In  most  of  the  quadrupeds,  on  the  other  hand,  these 
movements  are  vigorous  and  extensive,  and  play  an  important  part,  not 
only  in  the  changes  of  expression  by  varying  the  attitude  of  the  ex- 
ternal ear,  but  also  in  aid  of  the  sense  of  hearing,  by  enabling  the 
animal  to  catch  distinctly  the  sonorous  vibrations,  from  whatever  quarter 
they  may  come.  By  their  assistance  the  direction  of  a  sound  is  also 
appreciated,  since  the  animal  ascertains,  in  placing  the  ear  in  different 
positions,  the  region  from  which  it  is  received  with  the  greatest  distinct- 
ness. 

Membrana  Tympani  and  the  Chain  of  Bones — The  membrana  tym- 
pani  is  a  fibrous  sheet  of  circular  form,  composed  of  a  principal  la}^er 
not  more  than  0.05  millimetre  in  thickness,  but  quite  strong,  and  con- 
sisting of  circular  and  radiating  tendinous  fibres  with  a  trace  of  inter- 
mingled elastic  fibres.  Its  external  and  internal  surfaces  respectively 
are  covered  by  thin  continuations  of  the  integument  of  the  external 
auditory  meatus  on  the  one  hand,  and  of  the  mucous  membrane  of  the 
42 


650  THE    SENSES. 

tj'mpanic  cavity  on  the  other ;  and  all  three  layers  together  form  a  mem- 
brane which  is  about  0.10  millimetre  thick. 

In  its  natural  condition  the  membrane  is  drawn  inward,  by  its  attach- 
ment to  the  handle  of  the  malleus,  in  such  a  way  that  its  external  sur- 
face •  exhibits  a  funnel-shaped  depression,  the  deepest  point  or  bottom 
of  which  corresponds  to  the  situation  of  the  end  of  the  handle  of  the 
malleus.  According  to  the  observations  of  Helmholtz,1  the  sides  of  this 
funnel-shaped  depression  are  not  plane  but  convex,  somewhat  like  the 
inner  surface  of  the  blossom  of  a  morning-glory.  It  is  only  along  a 
single  line,  corresponding  to  the  attachment  of  the  handle  of  the  malleus, 
that  the  meridian  of  the  funnel  would  be  a  nearly  straight  line ;  else- 
where the  radial  fibres  of  the  membrana  tympani  are  curved,  with  their 
convexities  looking  toward  the  external  auditory  meatus. 

As  the  only  attachment  of  the  membrana  tympani,  except  at  its  cir- 
cular border  where  it  adheres  to  the  bony  walls  of  the  meatus,  is  to 
the  movable  handle  of  the  malleus,  any  movement  of  the  handle  of  the 
malleus  inward  will  draw  the  membrana  tympani  in  the  same  direction, 
deepen  the  funnel-shaped  depression  at  its  centre,  and  put  its  fibres 
more  upon  the  stretch.  On  the  other  hand,  a  movement  of  the  mem- 
brana tympani  outward  will  draw  the  handle  of  the  malleus  outward ; 
and,  finally,  if  the  malleus  be  held  in  a  position  of  equilibrium,  by  its 
elastic  and  muscular  attachments  internally  to  the  membrana  tympani, 
any  movement  of  this  membrane,  either  outward  or  inward,  will  be 
followed  \)y  a  corresponding  change  of  position  in  the  malleus  itself. 

This  is  the  physiological  action  of  the  membrana  tympani.  From  its 
thinness  and  tension  and  from  its  position  at  the  bottom  of  the  external 
auditory  meatus,  it  enters  into  vibration,  under  the  impulse  of  sound 
coming  from  the  exterior,  and  communicates  similar  movements  to  the 
handle  of  the  malleus  attached  to  its  internal  surface. 

The  chain  of  bones  consists  of  three  ossicles,  articulated  with  each 
other  by  their  corresponding  extremities,  and  forming  a  zigzag  line 
of  jointed  levers,  extending  from  without  in- 
_*g'  209>  ward,    across    the    cavity    of   the   tympanum. 

They  are  known  respectively,  from  the  resem- 
blances of  their  configuration,  as  the  "  malleus," 
"incus,"  and  "stapes,"  or  the  hammer,  the 
anvil,  and  the  stirrup.  The  malleus  is  about 
OSSICLES  of  the  human  nine  millimetres  in  length,  of  which  a  little 

stags'  M(Rfldin  er  I™"*'  3'  more  tna"  one-third  is  occupied  by  the  rounded 
head  and  the  neck,  and  a  little  less  than  two- 
thirds  by  the  comparatively  straight  and  tapering  handle.  The  very 
slender  long  process  projects  laterally  in  a  nearly  horizontal  direction 
from  behind  forward  in  the  natural  position  of  the  bone.  The  handle 
is  the  only  part  of  the  malleus  which  is  adherent  to  the  membrana 

1  Mechanism  of  the  Ossicles  of  the  Ear.  Translated  by  Albert  H.  Buck,  M.D., 
and  Normand  Smith,  M.D.  New  York,  1873,  p.  20. 


SENSE    OF    HEARING.  651 

tympani,  the  neck  corresponding  to  the  upper  border  of  this  membrane, 
while  the  head  projects  above  it,  lying  comparatively  free  in  the  cavity 
of  the  tympanum.  It  is,  however,  maintained  more  or  less  closely  in 
its  position  by  thin  ligamentous  bands  arising  from  the  bony  wall  of  the 
tympanic  cavity  and  inserted  into  its  head  and  neck,  and  by  the  tendon 
of  the  internal  muscle  of  the  malleus  or  "  tensor  tympani,"  which,  com- 
ing from  a  direction  anterior  and  internal  to  the  bone,  is  inserted  into 
the  upper  extremity  of  its  handle.  The  action  of  this  muscle  is  to 
draw  the  handle  of  the  malleus  inward,  tightening  the  membrana  tym- 
pani, and  rotating  the  head  of  the  malleus  slightly  outward.  The  prin- 
cipal movement  of  the  malleus  is  therefore  a  rocking,  to  and  fro  move- 
ment, about  a  nearly  horizontal  axis  situated  at  the  junction  of  the 
handle  and  the  neck. 

The  head  of  the  malleus  is  articulated  with  the  body  of  the  incus  by 
acapsular  joint  with  double-inclined  surfaces.  As  Helmholtz  has  shown, 
the  surfaces  are  so  different  in  their  inclination,  one  being  very  steep, 
the  other  but  slightly  oblique,  that  when  the  handle  of  the  malleus  is 
drawn  inward,  the  two  articular  surfaces  lock  together,  and  the  incus 
follows  the  movement  of  the  malleus  ;  but  when  the  latter  bone  is 
drawn  outward,  the  surfaces  may  glide  upon  each  other,  without  the 
incus  necessarily  moving  at  the  same  time. 

The  third  bone  of  the  middle  ear,  the  stapes,  has  in  its  form  the  most 
exact  resemblance  to  its  namesake,  an  ordinary  metallic  stirrup.  It  is 
articulated  by  its  angular  extremity  to  the  lower  end  of  the  long  arm 
of  the  incus  in  such  a  manner  as  to  be  nearly  horizontal  in  position,  its 

Fig.  210. 


RIGHT  TEMPORAL  BONE  of  the  new-born  infant,  seen  from  its  inner  side;  showing 
the  internal  surface  of  the  membrana  tympani  and  the  chain  of  bones  in  their  natural  posi- 
tion. (Riidinger.) 

two  arms  being  placed,  one  anteriorly  the  other  posteriorly.  Its  oval 
base  corresponds  in  form,  and  nearly  in  size,  with  the  fenestra  ovalis 
of  the  bony  labyrinth,  in  which  it  is  inserted;  being  adherent  by  its 
surface  and  its  edges  to  the  internal  periosteum  of  the  labyrinth. 


652  THE    SENSES. 

The  stapes  accordingly  forms  a  kind  of  movable  lid  or  piston-head 
occupying  the  orifice  of  the  fenestra  ovalis,  and  capable  of  transmitting 
directly  to  the  fluid  of  the  labyrinth  the  impulses  received  from  the 
membrana  tympani.  The  extent  of  inward  and  outward  movement  of 
the  base  or  footpiece  of  the  stapes  has  been  determined  by  Helmholtz 
in  the  following  manner.  The  cavity  of  the  tympanum  and  that  of  the 
vestibule  having  both  been  opened  from  above,  the  point  of  a  line  sewing 
needle  was  inserted  into  the  fibrous  covering  of  the  base  of  the  stapes 
from  the  side  of  the  vestibule,  and  the  needle  allowed  to  rest,  near  the 
point  of  its'insertion,  upon  an  adjacent  edge  of  bone.  It  thus  formed  a 
kind  of  index-lever,  which  would  indicate  by  the  displacements  of  its 
long  arm,  very  slight  movements  of  the  stapes.  The  stapes  was  then 
pressed  inward  and  outward,  as  freely  as  its  attachments  would  allow, 
either  by  means  of  a  needle  applied  to  the  bone  itself,  or  by  alternately 
condensing  and  rarefying  the  air  in  the  external  auditory  meatus ;  the 
force,  in  the  latter  case,  being  transmitted  through  the  membrana  t3'm- 
pani  and  chain  of  bones.  The  same  observer  estimated  these  movements 
according  to  another  plan,  by  opening  the  superior  semicircular  canal 
of  the  labyrinth,  and  inserting  into  it  a  slender  glass  tube  of  known 
calibre,  a  portion  of  which,  as  well  as  the  cavity  of  the  vestibule,  was 
filled  with  water.  Any  inward  pressure  upon  the  stapes  would  accord- 
ingly be  indicated  by  a  corresponding  rise  of  the  level  of  water  in  the 
tube.  The  movement  of  the  stapes,  in  these  experiments,  varied,  accord- 
ing to  circumstances,  from  .025  to  .072  millimetre. 

The  change  of  position  of  the  stapes  in  the  fenestra  ovalis,  due  to  the 
impulses  received  through  the  chain  of  bones,  is  not  a  simple  sliding 
movement  of  advance  and  recession,  but  a  rocking  motion,  in  which  its 
upper  border  is  tilted  over  toward  the  cavity  of  the  vestibule  and  back 
again,  and  its  anterior  end  moves  more  freely  than  its  posterior.  This 
feature  of  the  action  of  the  stapes,  which  has  been  described  by  several 
observers,  is  shown  by  Helmholtz  to  depend  upon  the  varying  compact- 
ness of  its  fibrous  attachments ;  these  attachments  being  closer  along 
its  inferior  border  and  at  its  posterior  end,  thus  allowing  more  freedom 
of  movement  above  and  in  front  than  below  and  behind. 

The  position  of  the  stapes  is  also  regulated  by  the  action  of  the 
stapedius  muscle.  This  muscle,  the  smallest  in  the  body,  arises  from  a 
bony  canal  behind  the  cavity  of  the  tympanum ;  and  its  slender  tendon, 
after  entering  this  cavity,  passes  almost  directly  forward  and  is  inserted 
into  the  posterior  side  of  the  neck  of  the  stapes,  near  its  articulation 
with  the  incus.  Its  contraction  will,  therefore,  draw  the  angle  of  the 
stapes  backward  and  its  anterior  extremity  outward  from  the  fenestra 
ovalis. 

Physiological  Action  of  the  Chain  of  Bones  and  the  Muscles  of  the 
Middle  Ear. — The  cavity  of  the  tympanum  is  an  irregularly  shaped 
space,  inside  the  membrana  tympani,  filled  with  air,  across  which  the 
vibrations  received  by  the  membrane  from  without  are  transmitted  by 
the  chain  of  bones.  In  their  natural  position  and  with  their  natural 


SENSE    OF    HEARING.  653 

tendinous  connections  undisturbed,  these  bones  are  held  in  such  close 
connection  with  each  other  that  they  vibrate  as  a  single  solid  body. 

The  vibratory  movement  of  the  ossicles  of  the  ear  has  no  immediate 
dependence  upon  the  action  of  the  muscles  attached  to  them,  but  results 
from  the  shocks  received  by  the  tympanic  membrane.  The  influence  of 
the  muscles  is  to  increase  or  diminish  the  tension  of  this  membrane, 
and  thus  to  influence  the  mode  of  transmission  of  the  sound. 

The  action  of  the  internal  muscle  of  the  malleus,  or  tensor  tympani, 
is  beyond  doubt,  as  its  name  indicates,  to  increase  the  tension  of  the 
membrana  tympani.  It  has  long  been  known  that,  on  opening  the  canal 
in  which  this  muscle  is  lodged,  as  well  as  the  cavity  of  the  tympanum,  by 
drawing  upon  its  tendon  within  the  canal,  the  membrana  tympani  may 
be  manifestly  rendered  more  tense ;  and  according  to  Helmholtz,  all  the 
ligaments  holding  the  ossicles  in  place  are  at  the  same  time  put  upon 
the  stretch. 

The  effect  produced  upon  the  act  of  hearing  by  increased  tension  of  the 
membrana  tympani  has  been  interpreted  in  a  different  sense  by  different 
observers.  Savart,1  who  first  studied  systematically  the  vibrations 
induced  in  stretched  membranes  by  the  proximity  of  sounding  bodies, 
estimated  the  extent  of  these  vibrations  by  the  agitation  of  particles  of 
fine  sand  spinkled  on  the  surface  of  the  membranes ;  and  he  found  the 
vibrations  more  difficult  of  production,  other  things  being  equal,  when 
the  tension  of  the  membrane  was  increased.  He  applied  the  same  mode 
of  experimentation  to  the  membrani  tympani  in  the  ear  of  man  and 
animals,  and  found  not  only  that  sand,  sprinkled  on  its  surface,  would 
be  thrown  into  agitation  by  holding  near  it  a  sounding  body,  but  that 
also,  as  in  the  former  case,  these  appearances  were  less  easy  of  produc- 
tion when  the  membrane  was  rendered  more  tense  by  traction  upon  the 
tensor  tympani  muscle.  He  concluded  from  that,  that  during  life  the 
ear  is  more  susceptible  to  sounds  of  a  given  intensity  when  the  mem- 
brana tympani  is  relaxed,  and  less  so  when  it  is  put  upon  the  stretch ; 
the  tensor  tympani,  accordingly,  exerting  a  protective  action  by  lessen- 
ing the  apparent  intensity  of  very  loud  sounds. 

This  view  has  been  adopted  by  many  eminent  authors,  owing  in  great 
measure  to  the  valuable  experiments  of  Savart.  But  this  observer  was 
not  aware  of  an  important  fact  which  has  been  established  by  subse- 
quent investigations,  namely,  that  stretched  membranes,  like  cords,  can- 
not respond  indiscriminately  to  sounds  of  every  grade  of  tone,  but  only 
to  a  certain  number  of  these  tones,  which  are  separated  from  each  other 
by  definite  intervals  ;*  and  they  will  respond  to  a  different  set  of  tones 
only  after  their  tension  has  been  increased  or  diminished.  In  order, 
therefore,  that  a  membrane  may  be  easily  thrown  into  induced  vibra- 
tion, its  tension  must  correspond  in  a  certain  ratio  with  the  tone  of  the 
sound  produced. 

1  Journal  de  Physiologic.     Paris,  1825,  tome  iv.  p.  2^5. 

2  Daguiu,  Traite  elementaire  de  Physique.     Paris,  1867,  tome  i.  p.  596. 


654:  THE    SENSES. 

These  considerations  have  induced  a  different  view  of  the  action  of 
the  tensor  tympani  in  modifying  the  sensations  of  sound.  With  the 
membrane  in  a  state  of  moderate  tension,  a  certain  proportion  of  tones 
only  are  distinctly  appreciated,  while  the  remainder  are  either  inaudible 
or  imperfectly  transmitted  to  the  internal  ear.  This  is  the  state  in 
which  sounds  generally  are  received  by  the  organ  of  hearing,  without 
exact  appreciation  of  their  relative  pitch.  But  when  the  ear  follows 
distinctly  successive  tones  of  varying  pitch,  or  when  it  listens  intently 
for  a  particular  note,  the  tension  of  the  membrana  tympani  is  increased 
or  diminished  to  such  a  degree  as  will  enable  the  vibration  to  be  trans- 
mitted with  the  most  complete  distinctness  by  the  chain  of  bones  to  the 
fluid  of  the  labyrinth.  With  regard  to  the  modifications  induced  in  the 
apparent  intensity  of  sound,  it  is  probable  that  Savart's  explanation 
holds  good ;  and  that  a  diminished  tension  of  the  membrane  enables 
the  ear  to  catch  more  readily  sounds  which  are  faint  or  distant.  This 
partial  relaxation  is  accomplished  by  the  action  of  the  stapedius  muscle, 
which  is  animated  directly  by  a  filament  of  the  facial  nerve ;  while  the 
tensor  tympani  is  supplied  only  from  the  otic  ganglion  of  the  sympa- 
thetic. 

The  cavity  of  the  tympanum  is  not  hermetically  closed,  but  commu- 
nicates with  the  pharynx  by  means  of  the  Eustachian  tube.  The  exist- 
ence of  this  opening  secures  the  equality  of  atmospheric  pressure  within 
and  without  the  membrana  tympani,  a  condition  which  is  essential  to  its 
proper  vibration  under  the  influence  of  sonorous  impulses.  The  ex- 
ternal barometric  pressure  varies  from  day  to  day,  and  even  for  dif- 
ferent periods  of  the  same  day ;  and  if  the  middle  ear  were  a  closed 
cavity,  this  variation  would  of  itself  change  the  tension  of  the  mem- 
brana tympani,  independently  of  the  action  of  the  muscles.  Although 
the  mucous  surfaces  of  the  Eustachian  tube  are  habitually  in  contact 
with  each  other,  the}^  readily  yield  to  a  preponderance  of  atmospheric 
pressure  in  either  direction,  and  thus  the  equilibrium  is  maintained 
between  the  air  inside  and  outside  the  cavity  of  the  tympanum. 

Labyrinth. — The  internal  ear,  or  labyrinth,  so  called  from  the  compli- 
cated extension  and  windings  of  its  various  cavities  and  passages,  is 
situated  in  the  petrous  portion  of  the  temporal  bone.  Its  external  wall 
consists  of  a  thin  lamina  of  compact  osseous  tissue,  which  is  readily 
isolated  in  the  foetus  and  in  newly  born  infants,  owing  to  its  being  im- 
mediately surrounded  by  spongy  tissue;  while  in  the  adult  it  is  more  or 
less  completely  consolidated  with  the  adjacent  bony  parts.  It  may  be 
divided  physiologically  into:  1.  The  vestibule  and  semicircular  canals, 
which  constitute  its  most  essential  parts  and  are  present  in  all  verte- 
brate animals  ;  and  2.  The  cochlea,  which,  in  man  and  the  mammalia,  is 
a  more  highly  developed  portion,  of  complicated  structure,  but  which 
is  absent  in  the  fishes  and  naked  reptiles,  and  only  partially  developed 
in  the  scaly  reptiles  and  in  birds. 

The  vestibule  (Fig.  211,i)  is  so  called  because  its  cavity  is  that  into 
which  the  fenestra  ovalis  immediately  opens,  and  from  which  those  of 


SENSE    OF    HEARING.  655 

the  semicircular  canals  and  cochlea  Fig.  211. 

diverge  in  various  directions.  It  is 
of  a  more  or  less  ovoid  form,  and 
presents,  toward  the  cavity  of  the 
tympanum,  two  openings,  namely : 
1.  The  fenestra  ovalis  (5),  corre- 
sponding in  form  to  the  base  of  the 
stapes,  which  nearly  fills  it,  and 
which  is  •  adherent  to  the  internal 
periosteum  of  the  labyrinth  stretch- 
ed across  the  opening ;  and  2.  The 
fenestra  rotunda  (e)  of  smaller  size  BoNY  LABYKINTH  OF  THE  HUMAN 

EAR,  twice  the  natural  size.— 1.  Vestibule. 

and    Closed   Only   by  a   fibrOUfl    mem-      2   Superior  vertical  semicircular  canal.    3. 
brane.      The  posterior  portion  of  the      Inferior    vertical    semicircular   canal.      4. 
..  .    .  Horizontal  semicircular  canal.    5.  Fenestra 

Vestibule   gives    origin   to    the    three      Ovalis.    6.  Fenestra  rotunda.    7.  Cochlea. 

semicircular  canals,  which  commu- 
nicate with  its  cavity  at  each  extremity,  namely:  1.  The  superior  ver- 
tical canal  ( 2 )  the  plane  "of  which  is  directed  across  the  longitudinal 
axis  of  the  petrous  bone.  2.  The  inferior  vertical  canal  ( 3 )  the  plane 
of  which  is  parallel  with  the  internal  surface  of  the  petrous  bone ;  and 
3.  The  horizontal  canal  (4)  which  is  directed  across  the  axis  of  the 
petrous  bone,  but  lies,  as  its  name  indicates,  in  a  horizontal  plane.  Each 
semicircular  canal  opens  into  the  vestibule  by  two  orifices,  one  at  each 
end ;  except  that  the  two  vertical  canals  unite  at  one  of  their  extremi- 
ties into  a  branch  and  orifice  common  to  both.  Thus  there  are  five 
orifices  leading  from  the  vestibule  into  the  three  semicircular  canals ; 
and  each  canal  has  free  communication  at  each  end,  directly  or  indi- 
rectly with  the  interior  of  the  vestibule.  Each  canal  is  enlarged  at  one 
of  its  extremities  where  it  joins  the  vestibule,  into  a  slightly  rounded 
dilatation. 

The  common  cavity  of  this  part  of  the  bony  labyrinth  contains  a 
limpid,  colorless  fluid,  the  perilymph,  and,  in  addition,  a  closed  mem- 
branous sac,  also  filled  with  fluid,  which,  by  its  various  prolongations, 
presents  a  repetition  of  the  form  of  the  vestibule  and  semicircular  canals. 
This,  together  with  its  extension  in  the  cochlea  hereafter  to  be  described, 
constitutes  the  membranous  labyrinth.  It  forms  the  most  important 
part  of  the  internal  ear,  since  in  its  walls  the  filaments  of  the  auditory 
nerve  have  their  terminal  distribution. 

The  cavity  of  the  vestibule  contains  two  membranous  sacs,  lying  in 
contact  with  each  other,  but  separated  by  a  transverse  partition.  One 
of  these,  the  smaller  of  the  two,  is  the  sacculus,  a  spherical  vesicle,  a 
little  over  1.5  millimetre  in  diameter,  occupying  the  anterior  and  inferior 
portion  of  the  vestibule,  and  communicating  by  a  narrow  canal  with  the 
ductus  cochlearis  of  the  cochlea.  The  other,  or  larger  sac,  is  the  utricle, 
of  ellipsoid  form,  measuring  3.5  millimetres  in  its  long  diameter.  The 
utricle  nnd  the  three  membranous  semicircular  canals  communicate  with 
each  other  in  the  same  way  as  the  corresponding  bony  cavities  in  which 


656  THE    SENSES. 

they  are  lodged.  Each  membranous  semicircular  canal  presents  at  one 
of  its  extremities,  at  the  expanded  part  of  its  bony  canal,  a  similar 
rounded  dilatation,  known  as  the  "  ampulla." 

The  membranous  sacs  and  semicircular  canals  are  considerably 
smaller  than  the  osseous  cavities  which  contain  them,  and  occupy 
nearly  everywhere  an  eccentric  position  ;  being,  at  certain  points,  in 
contact  with  and  adherent  to  the  internal  periosteum,  while  at  others 
they  are  surrounded  by  the  perilymph.  The  sacculus  and  utricle 
together  occupy  about  two-thirds  of  the  cavity  of  the  vestibule;  and, 
according  to  Riidinger,  are  so  placed  that  neither  of  them  touches  the 
base  of  the  stapes  at  the  fenestra  ovalis,  but  are  separated  from  it  by 
an  appreciable  layer  of  fluid.  Thus  the  sonorous  impulses  which  reach 
the  membranous  labyrinth  come  to  it,  not  directly  from  the  stapes,  but 
through  the  intermediate  vibration  of  the  perilymph. 

The  sacculus  and  the  utricle  are  adherent  to  the  internal  periosteum 
of  the  vestibule  at  the  points  of  entrance  of  their  corresponding  branches 
of  the  auditory  nerve.  The  ampullae  of  the  semicircular  canals  fill 
almost  completely  the  bony  cavities  in  which  they  rest,  their  outer 
surface  lying  for  the  most  part  in  contact  with  the  periosteum.  On 
the  other  hand,  the  membranous  semicircular  canals  are  very  much 
smaller  in  calibre  than  the  osseous  excavations  which  contain  them, 
and  lie  in  contact  with  the  periosteum  only  along  the  inner  or  smaller 
curvature  of  the  bony  canals ;  so  that  they  are  surrounded  externally 
by  a  comparatively  large  quantity  of  perilymph.  They  are,  however, 
attached  and  held  in  place,  as  shown  by  Riidinger,  by  slender,  scattered, 
fibrous  bands  and  partitions,  which  traverse  at  various  points  the  peri- 
lymphic  space. 

The  main  point  of  interest  in  regard  to  the  membranous  labyrinth 
relates  to  the  mode  of  distribution  and  termination  of  the  auditory 
nerve. 

The  auditory  nerve  sends  to  the  vestibule  two  branches;  one  of 
which  is  distributed  to  the  sacculus,  the  other  to  the  utricle  and 
ampulla?.  The  mode  of  termination  of  the  nerve  fibres  in  both  these 
divisions  is  essentially  the  same.  They  are  not  distributed  generally 
over  the  membrane,  but  terminate  only  in  particular  well-defined  spots, 
characterized  by  a  thickening  or  prominence  of  the  membranous  wall, 
and  by  the  presence  of  a  peculiar  form  of  epithelium  provided  with  stiff, 
pointed  cilia,  the  so-called  auditory  hairs. 

In  the  sacculus  and  in  the  utricle,  the  terminal  nerve  spot,  or  "  macula 
auditiva,"  is  in  the  form  of  an  oval  plate,  or  lamina,  3  millimetres  by 
1.5  in  the  sacculus,  and  3  millimetres  by  2  in  the  utricle.  In  the  am- 
pullae, it  forms  a  transverse  ridge  or  fold  of  the  membranous  wall,  pro- 
jecting inward  after  the  manner  of  the  valvnlae  conniventes  of  the  small 
intestine,  but  occupying  only  about  one-third  of  the  circumference  of 
the  ampulla.  Elsewhere,  the  membranous  sacs  of  the  labyrinth  are 
lined,  according  to  Kolliker,  by  a  single  layer  of  pavement  epithelium 
cells.  But  at  the  spots  in  question  the  epithelium  is  twice  or  three 


SENSE    OF    HEARING.  657 

times  as  thick  as  in  the  remaining  portions,  and  consists  of  elongated 
cells  of  two  different  forms,  namely,  cylindrical  and  fusiform.  It  also 
presents,  standing  upright  upon  its  free  surface,  the  pointed  cilia  above 
mentioned,  or  auditory  hairs,  which  in  man  are  about  25  mmm.  in 
length.  The  terminal  nerve  fibres  of  the  auditory  nerve,  which  pass 
up  toward  these  thickened  spots  of  epithelium,  may  be  traced,  accord- 
ing to  the  testimony  of  all  recent  observers,  into  the  epithelial  layer 
itself;  and  certain  appearances  give  rise  to  the  supposition  that  the 
ultimate  axis-cylinder  of  each  nerve  fibre  is  prolonged  through  the  sub- 
stance of  a  fusiform  epithelium  cell,  and  finally  becomes  the  cilium  or 
auditory  hair  projecting  from  its  free  extremity.  These  appearances 
are,  1st,  the  similarity  in  size  and  aspect  between  the  axis-cylinder  of 
the  nerve  fibres  and  the  slender  downward  prolongations  of  the  fusiform 
cells;  and,  2d,  the  fact  that  both  these  structures  become  stained  more 
or  less  deeply  of  a  blackish  or  brown  color  by  the  action  of  osmic  acid 
(Riidinger).  Whatever  the  precise  relations  of  the  terminal  nerve 
fibres  to  the  other  elements  of  the  epithelial  layer  may  be,  there  is  no 
doubt  that  the  projecting  cilia  act  either  mechanically,  or  by  virtue  of 
a  real  nervous  sensibility  belonging  to  them,  and  are  the  immediate 
recipients  of  the  sonorous  vibrations  communicated  by  the  surrounding 
fluid. 

A  remarkable  secondary  feature  connected  with  the  auditory  spots  of 
the  sacculus  and  utricle  is  the  existence,  at  each,  of  a  deposit  of  minute 
solid  calcareous  grains,  the  so-called  otoconia,  or  ear  sand.  These  grains 
are  embedded  in  a  homogenous  gelatinous  material,  and  form  a  white 
chalky-looking  \ayer  immediately  over  the  auditory  spot,  by  which  the 
situation  of  this  spot  is  easily  recognized.  The  grains  are  composed 
almost  exclusively  of  lime  carbonate.  They  are  rounded,  elongated, 
or  distinctly  prismatic  and  crystalline  in  form  ;  the  largest  measuring, 
according  to  Kolliker,  about  10  mmm.  in  length.  The  exact  office  per- 
formed by  these  calcareous  deposits  is  unknown,  but  it  is  evident  from 
their  constant  existence  in  the  same  situation  in  different  animals,  that 
they  have  some  important  relation  to  the  sense  of  hearing.  In  mam- 
malians and  birds  they  are  pulverulent,  as  in  man.  In  reptiles  and  fish 
they  assume  the  form,  sometimes,  of  friable  chalk}7  concretions,  some- 
times of  rounded  masses  of  considerable  size,  hard  and  dense  as  por- 
celain. According  to  Wagner,  they  are  completely  absent  only  in  the 
cyclostomi,  or  lowest  order  of  true  fishes,  including  the  lamprey  and 
the  hag. 

Physiological  Action  of  the  Membranous  Labyrinth. — The  sacculus 
and  utricle,  contained  in  the  cavity  of  the  vestibule,  are  membranous 
formations,  to  which  the  fibres  of  the  auditory  nerve  are  distributed,  and 
in  which  they  terminate.  These  membranous  expansions  are  supported 
by  the  contact  of  fluid  on  each  side,  and  are  held  in  place  by  the  partial 
fibrous  attachments  which  connect  them  with  the  wall  of  the  vestibule. 
They  are  the  structures  upon  which  the  impressions  of  sound  are  finally 
received,  and  correspond,  in  this  respect,  to  the  retina  in  the  organ  of 


658  THE    SENSES. 

vision.  The  sonorous  impulses,  first  communicated  by  the  atmosphere 
to  the  membrana  tympaui,  are  thence  transmitted  through  the  bony 
tissue  of  the  malleus,  incus,  and  stapes.  From  the  base  of  the  stapes 
they  pass  to  the  perilymph  of  the  vestibular  cavity  ;  from  that,  through 
the  floating  wall  of  the  membranous  sac,  to  the  endolymph  or  the  fluid 
contained  in  its  interior  ;  and  it  is  the  vibration  of  this  internal  fluid 
which  finally  acts  upon  the  sensitive  nervous  terminations  in  the  audi- 
tory spot.  It  is  thus  through  a  series  of  intermediate  vibrations,  that 
sounds  coming  from  the  exterior  produce  their  impression  upon  the 
internal  ear. 

Office  of  the  Semicircular  Canals. — These  singular  appendages  of 
the  bony  and  membranous  labyrinth  have  attracted  attention,  especially 
on  account  of  the  constancy  of  their  occurrence  and  the  peculiarity  of 
their  position.  The  principal  features  of  their  anatomical  history  are 
the  following : 

1.  They  are  universally  present,  as  portions  of  the  internal  ear,  in 
mammalians,  birds,  and  reptiles,  and  nearly  always  in  fish  ;  being  entirely 
absent  only  in  amphioxus,  where  there  is  no  organ  of  hearing  whatever. 

2.  They  are  always  three  in  number.    The  only  exception  to  this  rule 
is  found  among  fishes,  in  the  lamprey  and  the  hag ;  where  the  entire  struc- 
tural development,  especially  in  the  organs  of  sense,  is  very  incomplete.1 
In  the  lamprey  there  are  two,  and  in  the  hag  one  only,  the  cavity  of 
which  is  confounded  with  that  of  the  utricle ;  the  whole  forming  a  mem- 
branous canal  bent  upon  itself  like  a  ring. 

3.  The  three  canals  stand  in  three  different  planes,  which  are  all  per- 
pendicular to  each  other.     Thus  one  is  vertical   and  longitudinal,  in 
respect  to  the  axis  of  the  petrous  bone  ;  another  vertical  and  transverse; 
and  the  third  transverse  and  horizontal.     They  represent  accordingly, 
by  their  position,  the  three  dimensions  of  space ;  and  from  this  circum- 
stance the  idea  was  earty  suggested  that  they  might  serve  in  some  way 
to  indicate   the   direction  in  which   sounds  arrive  from  the  exterior. 
But  subsequent  researches  have  yielded  nothing  to  corroborate  this 
assumption  ;  and  it  is  evident,  furthermore,  that,  from  whatever  quarter 
sonorous  impulses  originally  come,  they  must  traverse  the  membrana 
tympani  and  chain  of  bones,  and  finally  reach  the  internal  ear  by  the 
same   course.      This  view  of  the   office  of  the  semicircular  canals  is 
therefore  no  longer  entertained. 

Lastly,  an  essential  point  in  their  anatomical  structure  is  that  they 
are  destitute  of  nerve  fibres,  and  consequently  are  wranting  in  sensi- 
bility. The  only  nervous  distribution  connected  with  them  is  that  to 
the  ampullae  situated  at  one  of  their  extremities,  but  no  nerve  fibres 
extend  to  the  semicircular  canals  themselves.  The  function  which  they 
perform  must  therefore  in  all  probability  be  one  of  a  mechanical  or 
physical  kind. 

1  Owen,  Anatomy  of  the  Vertebrates.  London,  1868,  vol.  iii.  p.  222.  Wagrner, 
Comparative  Anatomy  of  the  Vertebrate  Animals,  Tulk's  translation.  New  York, 
1845,  p.  227. 


SENSE    OF    HEARING.  659 

In  experimenting  upon  the  internal  ear  in  the  lower  animals,  it  has 
been  remarked  that  division  or  injury  of  the  semicircular  canals  is  fol- 
lowed by  a  singular  alteration  in  the  position  and  movements  of  the 
animal,  indicating  a  disturbance  of  equilibrium.  These  phenomena  were 
first  made  known  by  Flourens  in  1825,1  and  have  been  corroborated  by 
many  subsequent  observations,  the  most  recent  being  those  of  Cyon, 
Curschman,  Boettcher,  and  Berthold,  in  18t4.  The  results  met  with  are 
not  explained  in  the  same  way  by  all  experimenters,  but  there  is  little 
discrepancy  in  regard  to  the  phenomena  actually  presented.  The  opera- 
tion of  exposing  the  semicircular  canals  during  life  is  impracticable,  as 
a  general  rule,  in  the  mammalia,  owing  to  the  density  of  the  petrous 
bone  in  which  they  are  imbedded  ;  but  it  can  be  done  without  much 
difficulty  in  birds,  where  they  are  surrounded  only  by  a  loose  and 
spongy  osseous  tissue.  The  pigeon  is  the  species  which  has  been  most 
frequently  used  for  this  purpose. 

The  most  striking  and  constant  effect  produced  by  injury  of  the  semi- 
circular canals  consists  of  abnormal  oscillatory  movements  of  the  head, 
together  with  an  imperfect  balancing  of  the  whole  body  These  phe- 
nomena vary  according  to  the  particular  canal  which  has  been  divided. 
If  a  vertical  canal  be  the  one  injured,  the  oscillation  of  the  head  is  up- 
ward and  downward;  if  it  be  a  horizontal  canal,  the  oscillations  are 
lateral,  from  left  to  right,  and  vice  versa.  If  the  two  corresponding 
canals  on  both  sides  be  divided,  the  abnormal  movements  are  much 
more  rapid  and  continuous  than  if  the  injury  be  inflicted  on  one  alone. 
The  animal  is  still  capable  of  preserving  the  equilibrium  of  the  body,  so 
long  as  he  remains  at  rest ;  but  any  attempt  at  movement  brings  on  a 
disorder  of  muscular  action  which  makes  walking,  running,  or  flying- 
difficult  or  impossible.  The  most  simple  interpretation  of  these  results 
is  that  the  animal  can  no  longer  appreciate  the  direction  or  extent  of 
the  changes  in  position  of  the  head,  and  that  the  sense  of  equilibrium 
is  consequently  impaired  for  movements  of  the  body  and  limbs. 

The  manner  in  which  the  semicircular  canals,  in  their  natural  condi- 
tion, may  be  regarded  as  contributing  to  the  sense  of  equilibrium,  is  as 
follows :  If  a  glass  goblet,  filled  with  water,  be  turned  round  its  vertical 
axis,  it  will  be  seen  that  the  water  does  not  readily  turn  with  it;  and 
any  small  objects  suspended  in  it,  or  floating  upon  its  surface,  will 
remain  in  nearly  the  same  position,  while  the  goblet  revolves  through 
an  entire  circle.  The  adhesion  of  the  fluid  to  the  sides  of  the  glass 
vessel  is  not  sufficient  to  communicate  to  it  at  once  the  circular  motion 
of  the  parts  with  which  it  is  in  contact.  Consequently  the  water  lags 
behind  the  glass;  and  if  any  flat  object  were  cemented  perpendicularly 
to  the  inside  of  the  goblet,  so  as  to  turn  with  it,  it  would  be  subjected 
to  a  backward  pressure  from  the  water,  whenever  the  goblet  were  put 
in  rotation. 

1  Recherches  Exp6rimentales  sur  les  Propri£t6s  et  les  Fonctions  du  Systfeme 
Nerveux,  2me  Edition.  Paris,  1842,  pp.  452,  454. 


660  THE    SENSES. 

Somewhat  similar  conditions  are  present  in  the  semicircular  canals. 
Whenever  the  head  is  rotated  from  side  to  side  in  a  horizontal  plane,  a 
momentary  increase  of  pressure  must  take  place  in  the  fluid  of  the 
horizontal  semicircular  canal  (Fig.  211,  *),  either  toward  or  from  the 
ampulla  at  one  end;  and  this  increase  or  diminution  of  pressure  may  be 
preceptible  by  the  nervous  expansions  which  are  situated  there.  If  the 
head  be  moved  upward  or  downward,  a  similar  variation  of  pressure 
will  take  place  in  the  inferior  vertical  canal  (Fig.  211,  a) ;  and  if  it  be 
inclined  laterally,  toward  the  right  or  left  shoulder,  the  superior  vertical 
canal  (Fig.  211,  2),  will  experience  a  variation  of  the  same  kind.  Thus, 
although  the  membranous  semicircular  canals  be  not  themselves  sensi- 
tive to  pressure,  they  may  serve  as  channels  for  conducting  an  impulse 
to  the  sensitive  organs  in  their  ampullae.  Even  the  peculiar  configura- 
tion of  the  nervous  expansions  in  the  ampullae  seems  especially  adapted 
for  this  purpose;  since  they  are  arranged  in  the  form  of  transverse 
crescentic  folds,  while  in  the  sacculus  and  utricle  they  are  simply  flat- 
tened prominences  on  the  inner  surface  of  these  cavities. 

If  the  question  be  asked,  why  an  apparatus  for  appreciating  changes 
of  equilibrium  should  be  especially  associated  with  the  organ  of  hearing, 
it  may  be  remarked  that  in  the  auditory  labyrinth  alone  there  is  to  be 
found  a  terminal  distribution  of  sensitive  nerve  fibres  in  an  epithelium 
provided  with  hair  cells,  and  surrounded  by  a  fluid  of  watery  consis- 
tency ;  all  of  which  conditions  are  suitable  for  the  perception  both  of 
sonorous  vibrations  and  of  the  variation  in  pressure  due  to  changes  of 
position. 

Cochlea. — The  cochlea,  named  from  its  external  resemblance  to  a 
snail-shell,  is  a  bony  canal  rolled  spirally  about  a  central  axis,  and 

Fig.  212. 


BONY   COCHLEA    OF  THB  HUMAN   EAR,  right  side  ;  opened  from  its  anterior  face. 

(Cruveilhier.) 

making  between  two  and  three  turns  upon  itself.  Owing  to  the  gradual 
rise  of  the  turns,  it  has  a  slightly  conoidal  form,  the  extremity  of  which, 
or  cupola,  is  directed  forward,  downward,  and  outward.  The  canal  of 


SENSE    OF    HEARING.  66i 

the  cochlea  is  divided  longitudinally  into  two  parts  by  a  thin,  bony  par- 
tition, the  spiral  lamina,  which  winds  round  its  bony  axis,  following 
its  spiral  turns,  but  limited  externally  by  a  free  border. 

From  the  free  border  of  the  bony  spiral  lamina  a  fibrous  membrane, 
the  membrana  basilaris,  extends  outwardly  quite  to  the  external  wall 
of  the  cavity,  to  which  it  is  attached.  The  common  canal  of  the  cochlea 
is  thus  divided  into  two  parallel  passages  or  stairways,  one  above  the 
other.  The  superior  of  these  passages  communicates  freely  at  its  base 
with  the  cavity  of  the  vestibule,  and  is  the  scala  vestibuli.  The  inferior 
reaches  to  the  fenestra  rotunda,  and  is  terminated  by  the  membrane 
stretched  across  this  opening,  which  alone  divides  its  cavity  from  that 
of  the  tympanum ;  it  is  accordingly  known  as  the  scala  tympani.  Both 
these  canals  extend,  in  their  spiral  course,  to  the  summit  or  cupola  of 
the  cochlea.  At  this  point  a  minute  orifice  of  communication  between 
the  two  has  been  described  by  some  writers,  and  doubted  by  others. 
According  to  the  observations  of  Buck,1  it  is  probable  that  no  such 
opening  exists  in  the  natural  condition  of  the  parts,  unless  it  be  micro- 
scopic in  size.  But  whether  the  two  canals  communicate  or  not,  at  the 
summit  of  the  cochlea,  the  partition  between  them,  throughout  their 
parallel  course,  is  partly  membranous ;  and  by  this  means  an  increase 
or  diminution  of  pressure  upon  the  fluid  of  the  vestibule  at  the  fenestra 
ovalis  will  be  at  once  transmitted,  through  that  of  the  scala  vestibuli 
and  the  scala  tympani,  to  the  membrane  of  the  fenestra  rotunda.  Not- 
withstanding, therefore,  the  incompressible  character  of  the  fluid  of  the 
labyrinth,  provision  is  made,  to  a  certain  extent,  for  the  movement  of 
the  stapes,  according  to  the  contraction  or  relaxation  of  the  muscles  of 
the  middle  ear. 

But  the  septum  above  described,  formed  by  the  spiral  lamina  and  the 
membrana  basilaris,  is  not  the  only  longitudinal  partition  in  the  cavity 
of  the  cochlea.  The  scala  vestibuli  is  also  divided  into  two  parallel 
canals,  an  internal  and  an  external,  by  a  thin  membranous  sheet  which 
starts  from  the  upper  surface  of  the  spiral  lamina  near  its  outer  border, 
and  extends  upward  and  outward  to  reach  the  external  wall  of  the  coch- 
lear  cavity.  As  this  membrane  leaves  the  plane  of  the  spiral  lamina 
and  membrana  basilaris  at  an  angle  of  about  45  or  50  degrees,  it  shuts 
off  from  the  scala  vestibuli  a  separate  canal  of  prismatic  form,  having 
for  its  floor  the  membrana  basilaris,  for  its  outer  wall  the  wall  of  the 
cochlea,  and  for  its  upper  boundary  the  oblique  membranous  partition 
between  it  and  the  scala  vestibuli.  This  canal  contains  the  auditory 
epithelium  cells  and  the  termination  of  the  fibres  of  the  auditory  nerve. 
It  is  therefore  the  essential  part  of  the  cochlea,  and  is  termed  accord- 
ingly the  ductus  cochlearis, 

The  ductus  cochlearis  terminates  at  the  summit  of  the  cochlea  by  a 

1  On  the  Mechanism  of  Hearing,  Prize  Essay  of  the  Alumni  Association  of  the 
College  of  Physicians  and  Surgeons,  New  York.  Published  in  the  New  York 
Medical  Journal,  March,  1874. 


662  THE    SENSES. 

blind  extremity ;  but  at  its  base  it  communicates,  by  a  narrow  channel, 
with  the  cavity  of  tlie  sacculus.  It  is  consequently  an  extension  of  the 
sacculus,  and  a  part  of  the  membranous  labyrinth ;  while  the  scala  ves- 
tibuli  is  only  an  extension  of  the  general  cavity  of  the  vestibule.  The 
ductus  cochlearis  may  be  considered  as  a  tubular  prolongation  of  the 
sacculus,  rolled  upon  itself  in  a  spiral  form,  and  maintained  in  position 
by  the  bony  and  membranous  partitions  of  the  cochlea  by  which  it  is 
enveloped.  Like  the  rest  of  the  membranous  labyrinth,  it  is  filled  with 
a  watery  fluid,  and  is  bathed  externally  on  both  sides  by  the  perilymph, 
except  where  it  is  adherent  to  the  wails  of  its  bony  cavity. 

Organ  of  Corti. — The  inner  surface  of  the  ductus  cochlearis  is  lined 
for  the  most  part  with  a  thin  layer  of  pavement  epithelium,  except  along 
a  longitudinal  line  situated  at  about  the  middle  of  the  membrana  basi- 
laris.  Here  there  is  a  continuous  elevated  ridge,  four  or  five  times 
thicker  than  the  epithelium  elsewhere,  following  a  spiral  course,  like 
the  rest  of  the  cochlear  structures,  and  consisting  of  enlarged  and  modi- 
fied epithelium  cells,  with  the  terminal  fibres  of  the  auditory  nerve. 
This  body  is  termed  the  organ  of  Corti,  from  the  name  of  the  observer 
who  first  described  it  in  185 1.1  It  is  justly  considered  as  the  most 
remarkable  and  complicated  structure  in  the  internal  ear,  although  in 
its  essential  features  it  is  analogous  to  the  auditory  spots  in  the  sac- 
culus and  utricle. 

Fig.  213. 


DIAGRAMMATIC  SECTION  OP  THE  ORGAN  OF  CORTI,  in  profile;  from  the  descrip- 
tions of  various  authorities. — 1.  Membrana  basilaris.  2,3.  Internal  and  external  fibres  of  the 
arch.  4.  Epithelium  cells  r.ear  its  inner  and  outer  borders.  6,  5,  5,  5  Hair  cells  lying  in  con- 
tact with  the  arch.  Magnified  500  diameters. 

The  organ  of  Corti  rests  upon  the  upper  surface  of  the  membrana 
basilaris.  Its  framework  consists  of  a  series  of  elongated,  rafter-like 
bodies,  arranged  in  two  rows,  internal  and  external.  These  bodies, 
the  internal  and  external  "fibres  of  Corti,"  are  separated  from  each  other 
at  their  base,  where  they  rest  upon  the  membrana  basilaris,  by  a  consid- 
erable interval ;  but  they  lean  toward  each  other  and  lie  in  contact  by 
their  upper  extremities  or  heads,  thus  forming  a  roof-like  or  arched  con- 
nection, the  "  arch  of  Corti."  Near  the  situation  of  the  arch  of  Corti,  the 
epithelium  cells  lining  the  ductus  cochlearis  become  modified  in  form, 
gradually  increasing  in  size  and  length.  At  the  inner  border  of  the 
arch  there  is  a  single  row  of  epithelium  cells  which  are  nearly  as  long 

Zeitschrift  fur  Wissenschaftliche  Zoologie.     Leipzig,  1851,  Band  III.  p.  109. 


SENSE    OF    HEARING.  663 

as  the  internal  fibres  of  Corti,  and  which  lie  immediately  next  to  them 
in  a  similar  leaning  position.  The  upper  extremity  of  each  of  these 
cells  bears  a  tuft  of  rigid  hairs  or  cilia,  which  are  analogous  to  those  of 
the  hair  cells  of  the  sacculus  and  utricle.  On  the  outside  of  the  arch 
there  are  three  such  rows  of  hair  cells,  and  in  every  instance  the  tufts  of 
cilia  project  through  openings  in  a  sort  of  fenestrated  cuticle  which  lies 
above  the  cells,  and  extends  over  them,  inward  and  outward,  from  the 
heads  of  the  two  bodies  forming  the  arch  of  Corti. 

The  terminal  fibres  of  the  cochlear  branch  of  the  auditory  nerve  are 
distributed  to  the  organ  of  Corti.  The  bundles  of  nerve  fibres  forming 
this  branch  penetrate  the  cochlea  at  the  base  of  its  central  axis,  and 
pass  from  below  upward  through  its  interior,  diverging  successively 
from  writhin  outward,  to  continue  their  course  in  a  horizontal  direction 
between  the  two  layers  of  the  spiral  lamina.  At  the  level  of  the  at- 
tached border  of  the  spiral  lamina  there  is  situated,  within  the  cavity 
of  the  osseous  canal,  a  linear  collection  of  bipolar  nerve  cells,  in  and 
among  which  the  nerve-fibres  pass,  and  with  many,  if  not  all,  of  which 
the  nerve  fibres  are  directly  connected.  This  forms  the  "spiral  gan- 
glion'- of  the  cochlear  nerve.  After  the  bundles  of  nerve  fibres  have 
passed  through  the  ganglion,  and  while  they  are  contained  in  the  thick- 
ness of  the  spiral  lamina,  they  form,  by  repeated  subdivision  and  re- 
union, a  complicated  plexus,  the  filaments  of  which  continue  however 
to  follow  a  general  diverging  course  toward  the  outer  border  of  the  spi- 
ral lamina  and  the  attached  edge  of  the  membrana  basilaris.  Arrived 
at  this  point,  the  nerve  fibres  diminish  in  diameter  and  lose  their  me- 
dullary layer  ;  and,  in  this  form,  penetrate  into  the  ductus  cochlearis, 
where  they  continue  to  radiate  toward  the  organ  of  Corti.  It  is  at  this 
situation  that  the  final  termination  of  the  slender  and  pale  nerve  fibres 
in  the  substance  of  the  epithelial  hair  cells  has  been  most  positively  de- 
scribed and  figured  by  Waldeyer.1  There  can  be  no  doubt  that  this 
structure  represents,  in  the  ductus  cochlearis,  the  especial  organ  of  au- 
ditory sensibility. 

Physiological  Action  of  the  Cochlea. — The  cochlea  is  undoubtedly  that 
part  of  the  internal  ear,  which,  as  compared  with  the  remainder,  serves 
for  the  more  precise  discrimination  of  minute  variations  in  sound.  Its 
elongated  and  spiral  form,  the  two  membranes  of  uniform  tension  which 
inclose  the  ductus  cochlearis  above  and  below,  and  the  remarkable  com- 
plication of  structure,  with  the  multiple  rows  of  hair  cells  belonging  to 
the  organ  of  Corti,  all  indicate  that  it  is  adapted  for  the  distinct  percep- 
tion of  particular  sonorous  impulses.  The  analogy  of  its  construction 
in  some  respects  with  the  mechanism  of  a  musical  stringed  instrument, 
the  fibres  of  the  membrana  basilaris  representing  its  vibrating  strings, 
has  induced  the  belief,  in  the  minds  of  many  eminent  physiologists,  that 
it  is  the  organ  by  which  we  appreciate  the  difference  in  tone  or  pitch 
between  different  sounds.  According  to  this  view,  the  radiating  fibres 

1  In  Strieker's  Manual  of  Histology,  Buck's  edition.     New  York,  1872,  p.  1040. 


664  THE    SENSES. 

in  successive  portions  of  the  membrana  basilaris  are  attuned,  by  their 
length  or  tension,  to  vibrate  in  response  to  different  notes  of  the  musical 
scale  ;  and  the  vibration  of  each  set,  when  excited,  is  communicated 
to  the  corresponding  hair  cells  of  the  organ  of  Corti,  and  thus  reaches 
the  auditory  nerve  fibres  terminating  in  their  substance.  Thus  for  every 
note  sounded  in  the  atmosphere  which  gains  admission  to  the  internal 
ear,  only  certain  fibres  and  hair  cells  of  the  ductus  cochlearis  will  be 
thrown  into  vibration,  and  only  certain  terminal  fibres  of  the  codilear 
nerve  will  receive  a  sonorous  impression.  Some  writers  have  even  found 
in  certain  parts  of  the  organ  of  Corti,  an  apparatus  for  damping  the 
vibration  of  the  fibres  after  the  cessation  of  the  sound,  and  thus  prevent- 
ing the  confused  intermingling  of  separate  impressions.  There  is  cer- 
tainly a  suggestive  appearance  of  similarity  between  the  long  row  of 
fibrous  and  cellular  elements  m  the  organ  of  Corti,  with  their  various 
appendages,  and  the  ranges  of  strings,  capable  of  vibrating  to  different 
notes,  in  a  harp  or  piano  forte ;  and  the  similarity  is  sufficient  to  suggest 
a  certain  correspondence  of  mechanical  and  physiological  action  between 
the  two. 

But  the  main  difficult}^  in  attributing  to  the  cochlea,  as  its  function, 
the  discrimination  of  musical  notes,  lies  in  the  fact  that  its  development 
in  different  animals  does  not  correspond  with  their  capacity  for  the  pro- 
duction and  perception  of  musical  sounds.  The  cochlea,  under  the  form 
which  it  presents  in  man,  is  confined  to  the  mammalia.  In  birds  this 
part  of  the  auditory  apparatus  has  not  the  form  of  a  coiled  spiral,  but 
is  an  obtusely  conical  eminence,1  containing  two  small  cartilaginous 
cylinders  united  by  a  membrane  which  represents  the  membrana  basi- 
laris ;  and  the  part  corresponding  to  the  organ  of  Corti  contains  only 
nerve  terminations  and  hair  cells  somewhat  resembling  those  of  the 
inner  row  in  mammalia  ;  the  arch  of  Corti,  and  the  three  outer  rows  of 
hair  cells,  with  their  cuticular  covering,  being  absent.  In  serpents  and 
lizards,  the  cochlea  is  similar  to  that  of  birds ;  while  in  the  naked  rep- 
tiles and  in  fishes  it  is  completely  undeveloped. 

Thus,  in  all  the  mammalia,  the  cochlea  is  an  important  part  of  the 
internal  ear,  apparently  but  little,  if  at  all,  inferior  to  the  same  organ  in 
man.  But  in  the  singing  birds  it  is  comparatively  a  rudimentary  struc- 
ture. Some  of  these  birds  may  be  taught  artificially  to  repeat  par- 
ticular melodies,  showing  conclusively  that  their  capacity  of  percep- 
tion for  musical  notes  is  equal  to  their  power  of  producing  them  by  the 
vocal  organs.  And  yet  that  part  of  the  auditory  apparatus  which 
should  be  most  highly  developed  in  these  animals,  according  to  the  view 
in  question,  is  in  reality  the  least  so.  If  we  compare,  for  example,  a 
horse  or  a  pig  with  a  thrush  or  a  mocking-bird,  it  is  evident  that  the 
grade  of  musical  sensibility  in  these  animals  is  in  no  relation  with  the 

s  Owen,  Anatomy  of  the  Vertebrates.  London,  1866,  vol.  ii.  p.  134.  Wagner, 
Comparative  Anatomy  of  the  Vertebrate  Animals,  Tulk's  Translation.  New 
York,  1845,  p.  95.  Waldeyer,  in  Strieker's  Manual  of  Histology,  Buck's  Edition. 
New  York,  1872,  p.  1046. 


SENSE    OP    HEARING.  665 

development  of  the  cochlea.  In  fact,  the  cochlea  of  a  singing  bird 
resembles  that  of  a  crocodile  or  a  serpent  more  closely  than  that  of  a 
quadruped  or  a  man.  At  the  same  time,  the  other  parts  of  the  internal 
and  middle  ear  in  birds,  the  double  sac  of  the  vestibular  cavity,  the 
membranous  semicircular  canals  and  ampullae,  the  fenestra  ovalis  and 
rotunda,  the  chain  of  bones  and  the  ineinbrana  tympani,  are  all  highly 
developed ;  some  of  them  nearly  or  quite  as  much  so  as  in  the  mamma- 
lian class.  These  facts  throw  a  certain  degree  of  doubt  upon  the  special 
office  of  the  cochlea  in  the  perception  of  auditory  sensations. 

Persistence  of  Auditory  Impressions  and  the  Production  of  Musical 
Notes. — The  sensation  excited  by  a  sonorous  vibration  continues  for  a 
short  time  after  the  cessation  of  its  cause.  Usually  the  interval  be- 
tween successive  impulses  is  more  than  sufficient  to  allow  the  continued 
impression  to  disappear,  and  the  ear  distinguishes  without  difficulty  the 
succession  of  sounds.  But  if  the  impulses  follow  each  other  at  equal 
intervals,  and  with  a  certain  degree  of  rapidity,  they  produce  upon  the 
ear  the  impression  of  a  continuous  sound,  and  this  sound  has  a  higher 
or  lower  pitch  according  to  the  rapidity  with  which  the  vibrations  are 
repeated.  The  numerical  relation  of  different  musical  notes  thus  pro- 
duced has  been  studied  by  means  of  various  instruments.  One  of  these 
is  the  siren  of  Savart,  in  which  successive  puffs  of  air  are  emitted  from 
the  body  of  the  machine  through  small  openings,  with  a  degree  of 
rapidity  which  can  be  varied  at  will  and  registered  by  an  index  attached 
to  the  moving  parts.  Another  method  is  that  in  which  the  shocks  are 
given  by  the  points  of  a  toothed  wheel  turning  with  known  velocity, 
and  striking,  in  their  passage,  against  the  projecting  edge  of  a  card. 
In  another  modification  of  the  same  plan,  the  revolving  wheel  carries 
one  or  more  projecting  rods,  which  pass,  in  succession,  through  a  cor- 
responding slit  in  a  stiff  board ;  making  at  each  transit  an  atmospheric 
concussion,  owing  to  the  instantaneous  displacement  and  rebound  of 
the  air  at  the  opening.  Finally,  the  number  of  vibrations  correspond- 
ing to  a  particular  note  may  be  registered  by  attaching  to  the  extremity 
of  a  diapason,  or  tuning-fork,  a  light  stilet  which  traces  upon  the 
blackened  surface  of  a  cylinder,  revolving  at  a  known  rate,  an  undu- 
lating line  (Fig.  146,  a) ;  the  number  of  undulations  within  a  given 
space  indicating  the  frequency  of  the  vibrations  of  the  tuning-fork.  A 
simple  vibration  represents  the  single  oscillation  of  a  solid  body,  or  the 
particles  of  a  fluid,  in  one  direction ;  a  double  vibration  is  the  complete 
to-and-fro  movement  of  a  particle,  which  brings  it  back  to  its  original 
position. 

By  this  means  it  is  found  that  sonorous  impulses,  which  follow  each 
other  with  a  rapidity  of  less  than  sixteen  times  per  second,  are  readily 
distinguishable  as  separate  shocks  ;  but  above  that  degree  of  frequency 
they  become  merged  into  each  other,  and  produce  the  sensation  of  a 
continuous  sound.  In  case  the  repetition  of  the  shocks  takes  place 
at  irregular  or  unequal  intervals,  the  only  characters  perceptible  in 
the  sound  are  its  intensity  and  the  peculiarities  due  to  the  special 
43 


THE    SENSES. 

mechanism  of  its  production.  But  if  the  shocks  succeed  each  other  at 
regular  intervals,  the  sound  has  then  a  definite  position  in  the  musical 
scale,  and  is  appreciated  by  the  ear  as  a  high  or  low  note.  The  more 
frequent  the  repetitions  in  a  given  time,  the  higher  is  the  note  produced, 
until  a  limit  is  reached  at  which  the  ear  fails  to  perceive  a  sound  at  all. 
The  physical  reason  why  excessively  high  notes  become  inaudible  is 
probably  this:  In  the  special  arrangement. of  the  auditory  apparatus,  a 
vibration,  in  order  to  be  perceptible,  must  have  a  certain  degree  of 
extent  or  amplitude;  that  is,  the  particles  of  the  vibrating  body  must 
move  to  and  fro,  at  each  impulse,  for  a  certain  distance  in  space.  The 
intensity  of  a  sonorous  impression,  accordingly,  depends  upon  the  am- 
plitude of  the  vibrations,  while  its  pitch  or  tone  depends  upon  their 
frequency.  But  the  more  frequently  a  body  vibrates  in  a  single  second, 
the  less  extensive  must  be  its  movements,  if  their  velocity  remain  the 
same.  Consequently,  when  these  vibrations  arrive  at  a  certain  high 
degree  of  frequency,  unless  the  velocity  of  movement  can  be  increased 
in  proportion,  their  amplitude  becomes  so  small  that  they  can  make  no 
impression  upon  the  ear,  and  the  sound  becomes  inaudible. 

It  is  evident,  however,  that  such  a  sound  would  be  perceptible  if  the 
sensibility  of  the  auditory  apparatus  were  increased  to  the  requisite 
degree;  and  it  has  been  suspected  by  some  naturalists  that  certain 
insects  may  be  capable  of  perceiving  sounds  of  so  high  a  pitch  as  to  be 
inaudible  for  the  human  ear  ;  while,  on  the  other  hand,  for  them,  a  very 
low  note  would  appear  as  a  succession  of  distinct  impulses. 

The  limits  of  frequency,  within  which  sonorous  vibrations  are  percep- 
tible to  man  as  continuous  musical  sounds,  are  16  double  vibrations 
per  second  for  the  lowest  notes,  and  38,000  for  the  highest.  But, 
according  to  Wundt,  the  exact  discrimination  of  the  pitch  of  musical 
sounds  is  confined  within  much  narrower  limits,  especially  for  the  higher 
notes. 

Duration  of  a  Sound  required  for  the  perception  of  Sonorous  Impres- 
sions.— This  point  has  been  investigated  by  Savart1  in  the  following 
manner.  He  ascertained,  by  experiment,  that  the  ear  could  appreciate 
the  pitch  of  a  sound  made  by  a  toothed  wheel  revolving  at  such  a  rate 
as  to  cause  10,000  shocks  per  second.  By  removing  successively  the 
teeth  from  larger  portions  of  the  circumference,  he  diminished  in  a 
corresponding  degree  the  time  during  which  the  shocks  were  produced ; 
and  he  found  that  such  a  wheel  would  give  a  sound  of  definite  pitch 
with  only  two  adjacent  teeth  remaining.  The  double  shocks  thus  pro- 
duced would  occupy  only  -g-^y  of  a  second ;  and  this  duration  of  the 
impulses  was  sufficient  to  make  upon  the  ear  a  distinct  musical  impres- 
sion. 

1  Daguin,  TraitS  ElSmentaire  de  Physique.     Paris,  1869,  tome  i.  p.  517. 


SECTION  III. 
REPRODUCTION. 


CHAPTEE  I. 

THE  NATURE  OF  REPRODUCTION,  AND  THE 
ORIGIN  OF  PLANTS  AND  ANIMALS. 

REPRODUCTION  is  the  process  by  which  the  different  kinds  of  organized 
bodies  are  perpetuated  in  continuous  series,  notwithstanding  the  limited 
term  of  existence  allotted  to  each  individual.  It  includes  the  phe- 
nomena of  the  production,  growth,  and  development  of  new  germs,  as 
well  as  the  whole  history  of  the  successive  changes  in  the  organs  and 
functions,  and  the  consequent  modifications  of  external  bodily  form  pre- 
sented at  different  periods  of  life. 

All  organized  bodies  pass  through  certain  successive  stages  of  de- 
velopment, in  which  their  structure  and  functions  undergo  corresponding 
alterations.  The  living  animal  or  plant  is  mainly  distinguished  from 
inanimate  substances  by  the  continuous  changes  of  nutrition  and  growth 
which  take  place  in  its  tissues.  These  nutritive  changes  correspond  in 
activity  with  the  other  vital  phenomena ;  since  the  production  of  these 
phenomena  depends  upon  the  regular  and  normal  continuance  of  the 
nutritive  process.  Thus  the  organs  and  tissues,  which  are  the  seat  of 
a  double  change  of  renovation  and  decay,  retain  nevertheless  their 
original  constitution,  and  continue  capable  of  exhibiting  the  vital  phe- 
nomena. 

These  changes,  however,  are  not  the  only  ones  which  take  place. 
Although  the  structure  of  the  body  appears  to  be  maintained  in  an 
unaltered  condition  by  the  nutritive  process  from  one  moment  to  an- 
other, or  from  day  to  day,  yet  a  comparative  examination  at  greater 
intervals  of  time  will  show  that  this  is  not  precisely  the  case;  but  that 
the  changes  of  nutrition  are,  in  point  of  fact,  progressive  as  well  as  mo- 
mentary. The  composition  and  properties  of  the  skeleton  are  not  the 
same  at  the  age  of  twenty-five  years  that  they  were  at  fifteen.  At  the 
later  period  the  bones  contain  more  calcareous  and  less  organic  matter 
than  before  ;  and  their  solidity  is  increased,  while  their  elasticity  is  di- 
minished. Even  the  anatomy  of  the  bones  alters  in  an  equally  gradual 
manner;  the  medullary  cavities  enlarging  with  the  progress  of  growth, 

(  667  ) 


NATURE    OF    REPRODUCTION. 

and  the  cancellated  tissue  becoming  more  open  in  texture.  There  is  a 
notable  difference  in  the  quantities  of  oxygen  and  carbonic  acid  inspired 
and  exhaled  at  different  ages.  The  muscles,  also,  if  examined  after  the 
lapse  of  some  years,  are  found  to  be  less  irritable  than  formerly,  owing 
to  a  slow,  but  steady  and  permanent  deviation  in  their  intimate  con- 
stitution. 

The  vital  properties  of  the  organs,  therefore,  change  with  their  vary- 
ing structure ;  and  a  time  comes  at  last  when  they  are  perceptibly  less 
capable  of  performing  their  original  functions  than  before.  The  very 
exercise  of  the  vital  powers  is  inseparably  connected  with  the  subse- 
quent alteration  of  the  organs  employed  in  them  ;  and  the  functions  of 
life,  instead  of  remaining  indefinitely  the  same,  pass  through  a  series 
of  successive  changes,  which  finally  terminate  in  their  complete  cessa- 
tion. 

The  history  of  a  living  animal  or  plant  is,  therefore,  a  history  of  suc- 
cessive epochs  or  phases  of  existence,  in  each  of  which  the  structure 
and  functions  of  the  body  differ  more  or  less  from  those  in  every  other. 
The  organized  being  has  a  definite  term  of  life,  through  which  it  passes 
by  the  operation  of  an  invariable  law,  and  which,  at  some  regularly 
appointed  time,  comes  to  an  end.  The  plant  germinates,  grows,  blos- 
soms, bears  fruit,  withers,  and  decays.  The  animal  is  born,  nourished, 
and  brought  to  maturity,  after  which  he  retrogrades  and  dies.  The 
very  commencement  of  existence,  by  leading  through  its  successive 
intermediate  stages,  conducts  at  last  necessarily  to  its  own  termination. 

But  while  individual  organisms  are  constantly  perishing  and  disap- 
pearing from  the  stage,  the  particular  kind,  or  species,  remains  in  exist- 
ence, without  any  important  change  in  the  appearance  of  the  organized 
forms  belonging  to  it.  The  horse  and  the  ox,  the  oak  and  the  pine,  the 
different  kinds  of  wild  and  domesticated  animals,  even  the  different 
races  of  man  himself,  have  remained  without  any  essential  alteration 
since  the  earliest  historical  epochs.  Yet  during  this  period  innumer- 
able individuals,  belonging  to  each  species  or  race,  have  lived  through 
their  natural  term  and  successively  passed  out  of  existence.  A  species 
may  therefore  be  regarded  as  a  type  or  class  of  organized  beings,  in 
which  the  particular  forms  composing  it  die  off  and  disappear,  but  which 
nevertheless  repeats  itself  from  year  to  year,  and  maintains  its  ranks 
constantly  full  by  the  regular  accession  of  new  individuals.  This  pro- 
cess, by  which  new  organisms  make  their  appearance,  to  take  the  place 
of  those  which  are  destroyed,  is  known  as  the  process  of  reproduction. 
The  first  important  topic,  in  the  study  of  reproduction,  is  that  of  the 
conditions  necessary  for  its  accomplishment. 

Reproduction  by  Generation. — It  is  well  known  that,  as  a  rule,  in 
the  reproduction  of  any  particular  kind  of  living  organism,  the  young 
animals  or  plants  are  produced,  directly  or  indirectly,  from  the  bodies 
of  the  elder.  The  relation  between  the  two  is  that  of  parents  and 
progeny.  The  progeny,  accordingly,  owes  its  existence  to  an  act  of 
generation;  and  the  new  organisms,  thus  generated,  become  in  turn  the 


NATURE    OF    REPRODUCTION.  669 

parents  of  others  which  succeed  them.  For  this  reason,  wherever  such 
plants  or  animals  exist,  they  indicate  the  preceding  existence  of  others 
belonging  to  the  same  species ;  and  if  by  any  accident  the  whole  species 
should  be  destroyed  in  any  particular  locality,  no  new  individuals  could 
be  produced  there,  unless  by  the  previous  importation  of  others  of  the 
same  kind. 

The  most  prominent  feature  of  generation,  as  a  natural  phenomenon, 
is  that  the  young  animals  or  plants  thus  formed  are  of  the  same  kind 
with  their  parents.  They  reproduce  all  the  essential  specific  characters 
by  which  their  predecessors  were  distinguished  ;  and  this  takes  place 
by  a  law  so  universal  that  it  seems  almost  a  truism  to  state  it.  But 
this  is  only  because  it  has  been  so  constantly  a  matter  of  observation, 
that  in  popular  experience  it  appears  as  a  natural  necessity.  In  reality 
it  is  one  of  the  most  remarkable  phenomena  connected  with  the  genera- 
tive process ;  and  it  indicates  an  unbroken  connection  of  physiological 
acts,  extending  through  the  entire  lives  of  many  different  individuals. 
Thus  we  know  that  the  progeny  of  a  fox  will  always  be  foxes ;  and  that 
if  we  sow  oats,  it  will  be  a  crop  of  oats  tiiat  is  produced  in  consequence. 
Generation,  accordingly,  not  only  gives  rise  to  new  animals  and  plants, 
or  increases  their  number,  but  it  also  serves  to  continue  indefinitely  the 
existence  of  the  particular  species,  with  all  its  characteristic  marks  and 
qualities. 

Our  idea,  therefore,  of  a  species,  whether  animal  or  vegetable,  includes 
two  different  elements,  one  of  which  is  anatomical,  the  other  physiologi- 
cal. The  anatomical  character  of  a  species  consicts  in  the  similarity  of 
form,  size,  and  structure  existing  between  all  the  individuals  belonging 
to  it,  and  which  we  recognize  at  a  glance  j  its  physiological  character 
depends  upon  the  fact,  which  has  been  learned  by  experience,  that  it 
will  reproduce  itself,  and  that  the  different  species  in  existence  at  any 
one  time  remain  distinct  through  an  indefinite  series  of  successive  gene- 
rations. 

It  is  not  possible  to  say  that  the  anatomical  characters  of  species 
have  remained  absolutely  the  same  throughout  all  previous  time,  or 
that  they  will  continue  to  do  so  without  limit  in  the  future.  The 
existence  of  many  fossil  remains  of  animals  and  plants,  different  from 
those  which  are  known  at  the  present  day,  shows  that  species  are  not 
invariable  and  persistent  through  very  long  periods  of  time ;  and  that 
they  may  either  very  gradually  become  so  modified  as  to  present  a 
different  appearance,  or  else  that  they  may  entirely  come  to  an  end, 
like  the  extinct  mastodons  and  fossil  horses  of  the  United  States,  and 
be  replaced  by  others  from  a  different  localit}'.  But  in  whatever  way 
the  succession  of  species  in  different  geological  epochs  be  explained,  it 
is  certain  that  at  any  one  period  their  essential  physiological  characters 
are  those  above  described ;  and  that  each  species,  by  the  process  of 
generative  reproduction,  remains  distinct  from  the  others  which  are 
contemporary  with  it. 

But  the  production  of  young  animals,  similar  in  every  respect  to  their 


670  NATURE    OF    REPRODUCTION. 

parents,  although  in  all  cases  the  final  result  of  the  generative  process, 
is  never  immediate.  The  young  progeny  when  first  produced  is  different 
from  its  parents,  and  only  reaches  a  condition  of  resemblance  to  them 
through  a  series  of  changes,  often  of  a  very  extraordinary  kind.  In 
the  vertebrate  animals  generally,  the  embryo,  though  quite  incomplete 
in  structure,  yet  presents  a  certain  analogy  of  form  with  the  adult  con- 
dition. But  in  many  of  the  invertebrate  animals  the  young,  even  after 
hatching,  and  when  capable  of  active  locomotion,  are  so  different  in 
appearance  from  their  parents  that  they  would  never  be  supposed  to 
belong  to  the  same  species,  unless  their  identity  were  demonstrated  by 
their  subsequent  development.  Thus  the  young  mosquito  is  a  wingless 
creature  living  beneath  the  surface  of  the  water  in  stagnant  pools  j  and 
the  eggs  of  the  butterfly,  when  hatched,  give  birth  not  to  butterflies  but 
to  caterpillars.  These  caterpillars,  however,  are  not  creatures  of  a 
different  species,  but  only  young  butterflies ;  and  they  become  fully 
developed  and  similar  to  their  parents  after  certain  changes,  which  take 
place  at  definite  periods  of  their  development. 

The  reproduction  or  repetition,  therefore,  of  the  form  which  distin- 
guishes a  particular  species  is  accomplished  by  a  series  of  changes  which 
follow  each  other  in  regular  order;  and  this  series,  taken  together,  may 
be  represented  by  a  circuit,  which  starts  from  the  egg,  is  continued 
through  the  different  phases  of  growth,  transformation  and  maturity  of 
the  animal,  and  terminates  again  with  the  production  of  an  egg.  As 
this  egg  is  similar  to  the  first,  the  changes  repeat  themselves  in  their 
previous  order,  and  the  indefinite  continuance  of  the  species  is  thus 
established. 

Spontaneous  Generation The  commonest  observation  shows  that 

the  facts  detailed  above  hold  good  in  regard  to  all  animals  and  plants 
with  whose  history  we  are  familiarly  acquainted.  An  opinion,  however, 
has  sometimes  been  entertained  that  there  may  be  exceptions  to  this 
rule;  and  that  living  beings  can,  under  certain  circumstances,  be  pro- 
duced from  inanimate  materials ;  presenting,  accordingly,  the  singular 
phenomenon  of  a  progeny  without  parents.  Such  a  production  of 
organized  bodies  is  known  by  the  name  of  spontaneous  generation  Its 
existence  is  doubted  by  most  physiologists  at  the  present  time,  and  has 
never  been  positively  established  for  any  particular  organized  species; 
but  it  has  been  at  various  periods  the  subject  of  active  discussion, 
forming  a  somewhat  remarkable  chapter  in  the  history  of  general 
physiology. 

It  may  be  remarked  in  general  terms  that  the  organisms,  in  regard 
to  which  the  idea  of  the  possibility  of  spontaneous  generation  has  been 
entertained,  have  been  always  those  whose  natural  history  was  imper- 
fect or  obscure,  owing  either  to  their  minute  size  or  to  certain  of  their 
physiological  peculiarities.  Wherever  animals  or  plants  appeared  in 
considerable  abundance  without  exhibiting  any  evidence  of  the  source 
from  which  they  came,  it  was  formerly  conjectured,  from  that  fact  alone, 
that  their  production  was  a  spontaneous  one.  The  ancient  naturalists 


NATURE    OF    REPRODUCTION.  671 

supposed  that  all  species  of  animals,  excepting  those  which  visibly  either 
laid  eggs  or  produced  living  young,  were  formed  spontaneously  from 
the  combination  of  their  organic  ingredients.  Maggots,  shell  fish,  grubs, 
worms,  and  even  some  fishes  were  thought  to  be  produced  in  this  way, 
simply  because  they  had  no  apparent  specific  origin. 

But  continued  observation  in  natural  history  showed  that  in  these 
cases  the  animals  were  really  produced  by  generation  from  parents ; 
their  secret  methods  of  propagation  being  discovered,  and  their  specific 
identity  being  established  by  successive  changes  in  development  of  the 
young.  The  difficulty  of  doing  this  in  any  particular  case  is  often  in- 
creased by  the  interval  which  elapses  between  the  deposit  of  eggs  by 
the  parents  and  the  subsequent  hatching  of  the  young ;  the  new  genera- 
tion not  showing  itself  until  after  the  former  has  disappeared.  A  similar 
instance  is  that  of  the  American  seventeen-year  locust  (  Cicada  xepten- 
decim),  where  a  period  of  seventeen  years  intervenes  between  the  hatch- 
ing of  the  larva  and  the  appearance  of  the  perfect  insect ;  the  larva  all 
this  time  remaining  buried  in  the  ground,  while  the  life  of  the  perfect 
insect  does  not  last  over  six  weeks.  But  notwithstanding  this  difficulty, 
all  such  doubtful  cases  were  gradually  traced  to  the  usual  method  of 
generation  from  parents. 

Another  source  of  error  was  the  great  dissimilarity  in  the  figure  some- 
times existing  between  the  parents  and  their  young,  especially  as  this  is 
accompanied  by  an  equal  dissimilarity  in  their  habits  of  life.  Until 
about  the  middle  of  the  seventeenth  century  there  was  supposed  to  be 
no  more  undoubted  instance  of  spontaneous  generation  than  the  appear- 
ance of  maggots  in  putrefying  meat.  These  creatures  always  show 
themselves  in  meat  at  a  certain  stage  of  its  decomposition  ;  they  never 
appear  elsewhere  ;  and  they  do  not  themselves  manifest  the  power  of 
producing  young:  and  for  these  reasons  they  were  believed  to  originate 
from  the  dead  flesh  and  to  die  themselves  without  leaving  a  progeny. 
But  the  simple  experiments  of  Francisco  Redi  in  1668,  demonstrated 
the  source  of  fallacy  in  this  opinion  and  the  true  origin  of  the  maggots. 
He  took,  in  the  month  of  July,  eight  wide-mouthed  glass  bottles  and 
placed  in  them  various  pieces  of  dead  flesh.  Four  of  these  bottles  were 
left  open  to  the  atmosphere,  while  the  remaining  four*  were  closed  by 
pieces  of  paper  carefully  adjusted  over  the  mouth  of  each  and  fastened 
by  a  cord  round  its  neck.  A  short  time  afterward  the  flesh  in  the  un- 
covered bottles  was  filled  with  maggots,  a  peculiar  kind  of  fly  meanwhile 
passing  in  and  out  by  the  open  mouth ;  but  in  the  closed  bottles  not  a 
single  maggot  was  visible,  even  after  the  lapse  of  several  months. 

Thus  it  was  evident  that  the  maggots  were  not  formed  from  the  dead 
flesh,  but  that  their  germs  came  in  some  way  from  without ;  and  con- 
tinued observation  showed  that  they  were  hatched  from  eggs  deposited 
by  the  flies,  and  that  after  a  time  they  became  developed  into  perfect 
insects  similar  to  their  parents.  An  extension  of  these  observations  to 
other  species  of  invertebrate  animals  made  known  a  great  variety  of 
instances  in  which  the  connection  of  parents  and  progeny  might  be  traced 


672  NATURE    OF    REPRODUCTION. 

through  several  intermediate  conditions ;  so  that  the  apparent  difference 
between  them  in  configuration  and  structure  no  longer  offered  a  serious 
difficulty  to  the  investigator.  As  a  general  rule,  since  that  time,  when- 
ever a  rare  or  comparatively  unknown  animal  or  plant  has  been  suspected 
to  originate  by  spontaneous  generation,  it  has  only  been  necessary  to 
examine  thoroughly  its  habits  and  functions,  to  discover  its  real  methods 
of  propagation,  and  to  show  that  they  correspond,  in  all  essential  par- 
ticulars, with  the  ordinary  laws  of  reproduction.  The  limits  within 
which  it  is  possible  for  the  doctrine  of  spontaneous  generation  to  be 
applied  have  been  successively  narrowed,  in  the  same  degree  that  the 
study  of  natural  history  has  advanced  ;  the  presumption  of  its  existence 
always  hanging  upon  the  outskirts  of  definite  knowledge,  and  being 
connected  only  with  those  animal  or  vegetable  organisms  which  are  for 
the  time  imperfectly  understood.  The  two  groups  from  which  it  has 
been  most  recently  excluded  by  the  progress  of  discovery  are,  1.  The 
Entozoa,  or  internal  parasites ;  and  2.  The  Infusoria. 

I.  Entozoa. — These  are  organisms  which  live  within  the  bodies  of 
other  living  animals,  from  whose  organic  juices  they  derive  their  nourish- 
ment. 

There  are  many  different  kinds  of  entozoa,  all  of  which  are  confined, 
more  or  less  strictly,  to  certain  parts  of  the  body  which  they  inhabit. 
Some  of  them  are  found  in  the  intestines,  others  in  the  liver,  the  kidneys, 
the  lungs,  or  the  heart  and  bloodvessels ;  others  on  the  surface  of  the 
brain ;  others  even  in  the  muscles  or  in  the  interior  of  the  eyeball. 
Each  particular  kind  of  parasite,  as  a  rule,  is  peculiar  to  the  species  of 
animal  which  it  inhabits,  and  even  to  a  particular  part  of  the  body,  often 
to  a  particular  part  of  one  organ.  Thus,  Ascaris  lumbricoides  is  found 
in  the  small  intestine,  Oxyuris  vermicularis  in  the  rectum,  Trichoce- 
phalus  dispar  in  the  cteciun.  One  kind  of  Distoma  has  its  place  in 
the  lungs  of  the  green  frog,  another  in  those  of  the  brown  frog.  Cysti- 
cercus  cellulosae  is  found  in  the  connective  tissue ;  Trichina  spiralis  in 
the  substance  of  the  muscles. 

With  regard  to  many  of  these  parasites  the  only  difficulty  in  account- 
ing for  their  existence,  except  on  the  presumption  of  their  spontaneous 
generation,  lay  in  their  being  confined  to  such  narrow  limits  and  their 
never  being  met  with  elsewhere.  It  seemed  probable  that  some  local 
combination  of  conditions  was  necessary  to  the  production  of  a  para- 
site, which  was  never  to  be  found  except  in  the  biliary  passages,  the 
kidneys,  or  the  lungs  of  a  living  animal.  A  little  consideration,  how- 
ever, makes  it  evident  that  these  conditions  are  in  reality  neither  neces- 
sary nor  sufficient  for  the  production,  but  only  for  the  development  of 
the  parasites  in  question.  Most  of  the  internal  parasites  evidently 
reproduce  their  species  by  generation.  They  have  male  and  female 
organs,  and  produce  fertile  eggs,  often  in  great  abundance.  The  eggs 
contained  in  a  single  female  Ascaris  are  to  be  counted  by  thousands ; 
and  in  a  tapeworm  even  by  millions.  These  eggs,  in  order  that  they 
may  be  hatched,  and  produce  new  individuals,  require  certain  special 


NATURE    OF    REPRODUCTION.  673 

conditions  which  are  favorable  for  their  development ;  in  the  same  man- 
ner as  the  seeds  of  plants  require,  for  their  germination  and  growth,  a 
certain  kind  of  soil  and  a  certain  supply  of  warmth  and  moisture.  It  is 
accordingly  no  more  remarkable  that  Oxyuris  vermicularis  should  in- 
habit the  rectum,  and  Ascaris  lumbricoides  the  ileum,  than  that  Lobelia 
inflata  should  grow  only  in  dry  pastures,  and  Lobelia  cardinally  by  the 
side  of  running  brooks.  The  lichens  flourish  on  the  exposed  surfaces 
of  rocks  and  stone  walls  ;  while  the  fungi  vegetate  in  darkness  and 
moisture,  on  the  decaying  trunks  of  dead  trees.  Yet  both  these  classes 
of  vegetables  are  well  known  to  be  reproduced  by  generation,  from 
germs  which  require  special  conditions  for  their  growth  and  develop- 
ment. If  the  germ  of  any  species,  whether  animal  or  vegetable,  be  de- 
posited in  a  locality  where  these  requisite  conditions  are  present,  it  is 
developed  and  comes  to  maturity ;  otherwise  not.  This  accounts  fully 
for  the  fact  that  internal  parasites,  like  other  living  organisms,  are  con- 
fined to  certain  situations  by  the  requirements  of  their  nourishment  and 
growth. 

But  in  regard  to  a  few  of  the  internal  parasites  a  further  difficulty 
existed,  owing  to  the  presence  of  two  peculiaries  :  first,  these  particular 
kinds  do  not  inhabit  the  open  passages  or  canals  of  the  body,  but  lie 
encysted,  in  the  solid  substance  of  the  tissues,  where  there  are  no  visible 
means  of  access  from  without ;  and  secondly,  they  are  sexless,  perform- 
ing no  generative  function,  and  having  no  progeny  of  their  own ;  so  that 
it  does  not  readily  appear  how  they  can  themselves  have  been  derived 
from  parents.  The  two  kinds  of  entozoa  which  have  presented  this 
difficulty  in  the  most  marked  manner,  and  in  which  it  has  been  most 
fully  explained  by  the  results  of  observation  and  experiment,  are  those 
known  as  Cysticercus  cellulose  and  Trichina  spiralis. 

1.  Cysticercus  celluloses. — This  is  a  bladder-shaped  parasite  of  some- 
what flattened  form,  about  10  millimetres  in  diameter,  found  in  the  sub- 
cutaneous and  intermuscular  connective 

tissue  of  the  pig,  where  it  appears  under  Fig-  214. 

the  form  of  whitish  specks,  giving  to 
the  flesh  the  appearance  known  as  that 
of  "measly  pork."  Each  parasite  is 
enveloped  in  a  perfectly  closed  c}Tst,  but 
the  bladder-like  body,  when  extracted, 
exhibits  at  one  spot  a  minute  depression 

Or    involution    of  its    wall.      From    this        CYSTICBRCTTS  CELLULOSE,  from 

point    a    slender    neck,    ending    in    a    ^yS^.iSJ^SSSS 

rounded  head,  may  be  extruded  by  and  neck  extruded.  2,  a.  The  same, 
pressure ;  after  which  the  animal  is  seen 
to  consist  of  a  head  and  neck,  termi- 
nated posteriorly  by  a  dilated,  sac-like  tail,  whence  its  generic  name  of 
cysticercus.  Its  specific  name  was  derived  from  its  inhabiting  the  con- 
nective tissue,  formerly  known  as  the  "  cellular  tissue."  The  head  of 
the  parasite,  when  magnified,  shows  upon  its  surface  four  sucking  disks, 


674 


NATURE    OF    REPRODUCTION. 


.  215. 


and  near  its  extremity  a  double  crown  of  curved  calcareous  processes  or 
hooks,  implanted  in  its  substance.  There  are  no  distinguishable  internal 
organs,  and  the  caudal  vesicle  is  filled  simply  with  an  albuminous 
watery  fluid.  Thus  there  is  no  apparent  source  from  which  these  or- 
ganisms can  have  come,  other  than  the  tissues  which  they  inhabit,  nor 
any  visible  mode  of  continuing  the  species  by  generation. 

But  it  has  been  shown  by  the  investigations  of  Van  Beneden,  Leuck- 
art,  Haubner,  and  Kiichenmeister,1  that  Cysticercus  celluloste  is  only 
the  embryonic  progeny  of  Tsenia  soliuin,  or  the  solitary  tapeworm,  found 
in  the  small  intestine  of  the  human  subject.  The  specific  identity  of 
the  two  was  first  suspected  from  the  exact  simi- 
larity in  the  form  and  structure  of  the  head  and 
narrow  neck,  which  presents  the  same  sucking 
disks  and  double  crown  of  hooks  in  Tsenia  as  in 
Cysticercus.  But  in  Taenia  this  neck,  instead  of 
terminating  in  a  vesicular  appendage,  is  elongated 
and  transversely  .  wrinkled.  The  wrinkles,  after  a 
certain  distance,  become  deepened  into  superficial 
furrows,  marking  off  the  body  of  the  animal  into 
oblong  divisions  or  articulations,  each  articulation 
showing  a  double  system  of  communicating  vascu- 
lar canals,  and  also  distinctly  marked  generative 
organs  of  both  sexes.  As  they  recede,  by  succes- 
sive growth,  farther  and  farther  from  the  head,  the 
generative  organs  contained  in  the  articulations 
become  more  completely  formed,  and  are  at  last 
filled  with  mature  fecundated  eggs,  in  which  the 
embryos  have  begun  to  be  developed.  The  entire 
tapeworm  then  forms  a  continuous  chain  or  colony 
of  articulations,  sometimes  from  six  to  eight  metres 
in  length,  and  attached  to  the  mucous  membrane  of 
the  intestine  only  by  the  minute  head  at  its  ante- 
rior extremity. 

By  the   experiments    above   mentioned   it  was 
found,    1st.  That   mature    articulations   from    the 
tsenia  solium  of  the  human  subject,  if  administered 
to  young  pigs  with  their  food,  produce  an  abundance 
of  Cysticercus  cellulosse  in  the  flesh  of  these  ani- 
mals ;    and,    2d.  That   cysticercus    cellulosse    from 
measly  pork,  if  swallowed  by  man,  becomes  developed  in  the  intestine 
within  a  few  days,  into  ribbon-like  worms,  distinctly  recognizable  as 
young  specimens  of  tsenia  solium. 

The  manner  in  which  the  pig  becomes  infested  with  cysticercus  is  as 
follows  :  In  the  fully-formed  tapeworm,  in  the  human  intestine,  the  last 


1  Kiichenmeister,  Animal  and  Vegetable  Parasites.     Sydenham  edition,  Lon- 
don, 1857,  pp.  115,  120. 


NATURE    OF    REPRODUCTION.  675 

and  most  mature  articulations  separate  spontaneously  from  the  rest  of 
the  colony,  and  either  find  their  way  out  by  the  anus  singly,  or  are  dis- 
charged with  the  evacuations.  They  have,  while  still  living,  a  con- 
siderable degree  of  contractility  and  power  of  locomotion ;  and  thus 
become  accidentally  transferred  to  the  surface  of  neighboring  vegetable 
matters,  and  are  devoured  by  the  pig  with  his  food.  In  the  stomach 
and  intestine,  the  substance  of  the  articulation  is  digested  and  dissolved ; 
but  the  embryos,  which  are  33  mmm.  in  diameter,  and  armed  with  three 
pairs  of  calcareous  spines,  make  their  way  through  the  intestinal  walls, 
and  thence  are  dispersed,  either  by  a  continuance  of  the  same  movement 
or  by  the  bloodvessels,  throughout  the  connective  tissue,  where  they 
are  afterward  found.  Here  they  become  encysted,  and  go  through  with 
a  partial  development,  remaining  in  the  condition  of  C}Tsticer«us  in  the 
flesh  of  the  pig  until  this  flesh  is  used  for  food,  when  they  finally  be- 
come converted  into  tsenia  solium.  Thus  the  entire  round  of  generation 
and  development  is  completed,  and  the  original  form  of  the  parasite 
reproduced.  A  similar  relation  has  been  shown  by  Kiichenmeister 
and  Siebold1  to  exist  between  certain  other  species  of  taenia  and  cysti- 
cercus. 

2.  Trichina  spiralis — This  is  a  sexless,  encysted,  worm-like  para- 
site, found  in  the  muscular  tissue  of  the  pig,  and  sometimes  in  that  of 
the  rat,  the  cat,  and  the  human  species.  Each  worm  lies  closely  coiled, 
in  a  spiral  form,  in  the  interior  of  its 

enveloping  cyst.      It  is  about   0.75  Fig.  216. 

millimetre  in  length,  of  a  tapering 
form,  with  a  slender  anterior  and 
rounded  posterior  extremity.  It  pre- 
sents a  nearly  straight  intestine  ex- 
tending through  its  whole  length, 
and  rudimentary  sexual  organs  which 
are  entirely  inactive.  The  worm  has  TRICHINA  SPIRALIS,  encysted, 

from  muscular  tissue  of  a  trichinous  cat. 
been  known  Since    1835,  as    Occasion-      Magnified  76  diameters. 

ally  found  in  the  human  muscular 

tissue  in  the  encysted  form;  but  it  is  only  since  1860,  principally  from 
the  investigations  of  Leuckart,2  that  the  different  stages  of  its  growth 
and  development  have  been  made  known.  If  muscular  flesh  containing 
encysted  trichinae  be  administered  with  the  food  to  a  rabbit,  cat,  rat, 
mouse,  or  pig,  the  cysts  become  digested  and  the  worms  liberated  in 
the  small  intestine.  Here  they  rapidly  increase  in  size  and  develop- 
ment, the  females  becoming  impregnated  and  filled  with  living  young, 
and  attaining,  at  the  end  of  a  fortnight,  three  or  four  times  their  pre- 
vious size.  The  young  emb^os  are  now  discharged  from  the  body  of 
the  parent,  make  their  way  through  the  walls  of  the  intestine,  and  are 

1  Yon  Siebold,  On  Tape  and  Cystic  Worms.      Sydenham  edition.     London, 
1857,  p.  57. 

2  Untersuclmngen  liber  Trichina  spiralis.     Leipzig  und  Heidelberg,  1860. 


676 


NATURE    OF    REPRODUCTION. 


dispersed  throughout  the  body.  They  thus  reach  the  muscular  tissue, 
where  they  become  encysted,  and  remain  quiescent  until  again  intro- 
duced into  the  intestine  of  another  animal  or  of  man.  In  this  way  the 
existence  of  sexless  and  encysted  parasites  is  seen  to  be  entirely  analo- 
gous to  that  of  the  caterpillar  or  the  maggot.  They  are  sexless, 
because  they  are  still  in  the  embryonic  or  incomplete  stage  of  develop- 
ment. But  they  have  been  produced  by  the  regular  mode  of  generation 
from  parents  ;  and  they  will,  at  a  subsequent  period,  themselves  produce 
young  by  the  same  process. 

II.  Infusoria. — These  are  microscopic  organisms,  first  discovered  by 
Leeuwenhoek,  in  1675,  in  rain-water  which  had  been  kept  in  standing 
vases.  On  account  of  their  active  movement  and  minute  size  he  called 
them  ''animalcules ;"  but  as  they  were  soon  afterward  discovered  to 

Fig.  217. 


INFUSORIA,  of  various  kinds.— 1.  Urostyla  grandis,  from  decaying  sedge-grass  2. 
Paramecium  aurelia,  from  vegetable  infusions.  3.  Chlamydodon  mnemosyne,  Baltic  Sea 
water.  4.  Kerona  polyporum,  on  the  fresh-water  polype.  6.  Oxytricha  caudata,  open 
stagnant  waters.  6.  Ervilia  fluviatilis,  clear  brook  water.  7.  Heteromita  ovata,  on  aquatic 
river-plants.  Magnified  325  diameters.  (Ehrenberg  and  Stein.) 

make  their  appearance  in  great  numbers  and  with  remarkable  rapidity 
in  watery  infusions  of  organic  matter  exposed  to  the  air,  they  received 
the  general  name  of  "infusoria."  They  present  themselves  in  great 
variety,  and  under  rapidly  changing  forms;  so  much  so  that  Ehrenberg 


NATURE    OF    REPRODUCTION.  677 

in  18381  described  more  than  700  different  kinds.  They  are  generally 
provided  with  cilia  attached  to  the  exterior  of  their  bodies,  and  are,  for 
the  most  part,  in  constant  and  rapid  motion  in  the  fluid  which  they 
inhabit. 

In  consequence  of  the  numerous  different  forms  of  the  infusoria,  their 
frequent  changeability  of  figure,  and  their  want  of  resemblance  to  any 
previously  known  class  of  animal  organisms,  they  were  thought,  by 
some  of  the  earlier  observers,  to  have  no  regular  mode  of  generation, 
but  to  arise  indiscriminately  from  the  organic  materials  of  the  infusion ; 
the  particular  form  which  they  might  assume  being  determined  by  the 
special  conditions  of  each  case.  Their  inevitable  appearance  in  organic 
infusions,  at  all  ordinary  temperatures  and  exposures,  contributed  to 
sustain  this  belief.  The  substance  of  the  infusion  might  be  previously 
baked  or  boiled ;  the  water  in  which  it  was  infused  might  be  distilled,  and 
thus  freed  from  all  organic  contamination ;  and  yet  the  infusoria  would 
make  their  appearance  at  the  usual  time  and  in  the  usual  abundance, 
provided  only  that  the  infusion  were  exposed  to  moderate  warmth  and 
to  the  access  of  atmospheric  air.  But  these  conditions  are  essential  to 
maintaining  the  life  of  all  organized  creatures,  from  whatever  source 
they  may  come,  and  are  not,  therefore,  more  necessary  to  the  infusoria 
than  to  others. 

Therefore  the  infusoria  must  either  have  been  spontaneously  gene- 
rated from  the  materials  of  the  infusion,  or  else  they  must  have  been 
produced  from  germs  introduced  from  the  atmosphere.  In  the  latter 
case  these  germs  must  be  wafted  about,  in  a  comparatively  dry  state 
and  in  an  inactive  condition,  by  the  atmospheric  currents,  to  resume 
their  activity  and  development  when  brought  in  contact  with  sufficient 
moisture  and  with  the  organic  material  requisite  for  their  nutrition. 

The  researches  relating  to  this  question  continued  with  the  most  extra- 
ordinary persistence,  and  with  various  interruptions  and  revivals,  from 
1775,  when  they  were  carried  on  by  Needham  and  Spallanzani,  through- 
out the  greater  part  of  the  present  century,  in  the  hands  of  Cuvier, 
Schultze,  Helmholtz,  Milne-Edwards,  Longet,  Pouchet,  Pasteur,  Wy- 
man,  and  Bastian.  The  main  object  of  investigation  was  to  discover 
whether,  if  all  previous  living  germs  were  destroyed  by  heat,  and  the 
access  of  others  prevented  by  hermetically  sealing  the  vessels,  or 
thoroughly  purifying  the  air  which  was  introduced,  infusorial  life 
would,  under  such  circumstances,  be  developed. 

The  general  result  of  these  experiments  was  that  such  precautions 
diminished  and  often  entirely  prevented  the  production  of  infusoria. 
Spallanzani2  had  already  shown  in  1776  that  organic  infusions  in  her- 
metically sealed  glass  flasks,  if  boiled  for  two  minutes,  failed  to  produce 
any  of  the  larger  and  more  highly  organized  animalcules;  and  that 
boiling  for  three-quarters  of  an  hour  prevented  the  appearance  of  the 
more  minute  and  simpler  kinds. 

1  Die  Inftisionsthierchen  als  vollkommene  Organismen.     Leipzig,  1838. 

2  Opuscoli  de  Fisica  animale  e  vegetabile.     Modena.  1776,  vol.  i.  p.  10. 


673  NATURE    OF    REPRODUCTION. 

Schultze1  performed  similar  experiments,  with  the  additional  advan- 
tage of  admitting  to  the  organic  infusion  fresh  air  purified  from  germs. 
He  placed  his  infusion  in  a  glass  flask,  the  stopper  of  which  was  pro- 
vided with  two  narrow  tubes,  bent  at  right  angles.  When  the  infusion 
had  been  thoroughly  boiled,  and  all  the  air  contained  in  the  flask  ex- 
pelled, he  fastened  to  each  of  the  projecting  tubes  a  series  of  bulbs 
containing  on  the  one  side  sulphuric  acid,  and  on  the  other  a  solution 
of  potassium  hydrate ;  so  that  the  air  which  re-entered  the  flask  while 
it  was  cooling  must  pass  through  these  fluids,  and  thus  be  cleansed  of 
all  living  organic  matter.  The  apparatus  was  then  kept  in  a  warm 
place  for  two  months,  the  air  being  renewed  daily  by  suction  through 
the  tubes,  without  any  infusoria  being  detected  in  its  contents.  But 
they  showed  themselves  in  great  abundance  after  it  had  been  taken 
apart,  and  the  infusion  exposed  for  a  few  days  directly  to  the  atmo- 
sphere. 

Pasteur'2  found  that  if  a  flask  containing  an  organic  liquid  were  boiled 
upon  a  high  mountain,  where  the  air  is  of  unusual  purity,  allowed  to 
fill  itself  with  this  air  while  cooling,  and  then  hermetically  sealed,  it 
would  often  remain  free  from  infusorial  growth.  He  kept  several  such 
flasks,  boiled  and  filled  with  air  upon  the  Montanvert  in  Switzerland, 
for  four  years,  without  the  liquids  which  they  contained  undergoing  any 
perceptible  change.  But  on  making,  at  the  end  of  that  time,  a  minute 
opening  in  the  neck  of  one  of  these  flasks,  it  exhibited  after  three  days 
a  perceptible  growth  of  cryptogamic  vegetation. 

These  results  did  not  absolutely  exclude  the  possibility  of  spontane- 
ous generation,  which  was  still  maintained  by  Pouchet  and  a  number 
of  other  observers ;  but  they  indicated  in  a  very  decisive  manner  that 
the  atmosphere  might  contain  the  inactive  germs  of  infusoria,  which 
were  capable  of  being  developed  on  meeting  with  a  suitable  organic 
infusion. 

But  in  the  mean  time  the  study  of  the  infusoria  themselves  had  been 
going  on  independently  of  the  question  of  spontaneous  generation,  and 
this  alone  has  been  sufficient  to  demonstrate  that  they  are  reproduced 
in  the  usual  way,  like  other  animal  species,  by  means  of  fertilized  eggs 
and  embryonic  development. 

The  apparent  confusion  and  variability  in  form  of  the  infusoria,  at 
the  time  of  their  first  discovery,  depended  only  upon  their  great  num- 
bers and  upon  the  want  of  sufficient  knowledge  in  regard  to  them.  Sub- 
sequent observation  has  shown  that  their  organization  is  as  definite  as 
that  of  other  classes  of  the  animal  kingdom ;  and  they  have  now  been 
arranged,  by  the  labors  of  Claparede  and  Lachmann,3  Stein,4  and  Bal- 
biani,5  into  orders,  families,  genera,  and  species,  which  may  be  recog- 

Poggendorf  s  Annalen,  1836.     Band  xxxix.  p.  487. 

Comptes  Rendus  de  I'Academie  des  Sciences.     Paris,  Fevrier  20,  1865. 

Etudes  sur  les  Infusoires  et  les  Rhizopodes.     Geneve,  1856-1861. 

Organismus  der  Infusionsthiere.     Leipzig,  1859. 

Journal  de  la  Physiologic  de  PHomme  et  des  Animaux.     Paris,  1861. 


NATURE    OF    REPRODUCTION. 


679 


nized  with  certainty  by  their  distinctive  marks.  They  are  not  confined 
to  infusions  of  decaying  material  artificially  or  accidentally  prepared  ; 
but  many  of  them  have  their  natural  habitation  in  the  clearest  waters 
of  lakes,  pools,  marshes,  running  brooks,  or  the  open  sea.  Certain  forms, 
originally  included  in  this  class,  such  as  Rotifer,  Stephanoceros,  and 
Floscularia,  have  been  found  to  possess  a  more  complicated  structure 
than  the  rest,  and  to  belong  properly  to  the  class  of  worms;  while  their 
mode  of  reproduction  is  sufficiently  manifest  from  the  fact  that  living 
embryos,  in  process  of  development,  are  often  to  be  seen  in  their  interior. 

Fig.  218. 


RTYLONTCHIA  MYTILITS;  a  fresh-water  infusorium.— 1.  Unimpregnated.  2.  Impreg- 
nated, and  containing  mature  eggs  and  two  embryos.  3.  Showing  the  form  of  the  embryo. 
Magnified  375  diameters.  (Stein.) 

Finally,  the  ciliated  infusoria  themselves  have  been  shown  to  repro- 
duce their  species  by  means  of  eggs,  formed  in  special  generative  organs 
and  fecundated  by  union  of  the  sexes  (Fig.  218).  This  fact,  first  demon 
strated  by  Balbiani,  has  been  since  confirmed,  in  many  instances,  by 
Stein,  Engelmann,1  and  Cohn  ;2  Balbiani  and  Stein  together  having 


Zeitsehrift  fur  Wissenschaftliche  Zoologie. 
Ditto.     Band  xii.  p.  197. 


Leipzig,  1862,  Band  xi.  p.  347. 


680 


NATURE    OF    REPRODUCTION. 


Fig.  219. 


observed  the  occurrence  of  sexual  generation  in  47  different  genera 
and  66  different  species. 

Thus  the  infusoria  proper  are  in  their  turn  excluded  from  the  field 
of  spontaneous  generation.  But,  on  the  other  hand,  a  considerable 
group  of  organisms,  formerly  referred  to  the  class  of  infusoria,  are  now 
known  to  be  of  a  different  character.  These  are  the  forms  included 
under  the  general  term  of  Bacteria,  and  comprising  the  special  varieties 
of  bacterium,  vibrio,  spirillum,  and  micrococcus.  They  are  demon- 
strated to  be  of  a  vegetable  nature,  notwithstanding  their  frequent 
exhibition  of  rapid  and  continuous  movement;  and  they  consist  of  cells, 
which  multiply,  often  in  great  abundance,  by  a  process  of  repeated  sub- 
division. Whether  they  are  also  reproduced  by  means  of  spores  or 
germs,  has  not  been  determined  ;  but  their  minute  size  and  their  imper- 
fect classification  have  thus  far  proved  ^obstacles  to  the  complete  study 
of  their  physiological  characters. 

The  representative  of  this  group  may  be  considered  to  be  the  species 
known  as  Bacterium  termo,  already  described  (page  83),  in  connection 

with  the  phenomena  of  pu- 
trefaction. It  consists  of 
elongated  or  rod-like  cells, 
averaging  3  mmm.  in  length 
by  0.6  mmm.  in  thickness, 
sometimes  single,  often 
double,  two  of  them  being 
attached,  more  or  less  firmly, 
end  to  end.  The  latter  ap- 
pearance is  due  to  the  pro- 
gressive multiplication  of 
the  cells,  which  takes  place 
by  a  transverse  division  at 
the  middle  of  their  length. 
The  two  new  cells  thus  pro- 
duced remain  for  a  time  in 
connection  with  each  other, 
and  afterward  separate,  to 
repeat  the  process  indepen- 
dently of  each  other.  The  final  separation  of  two  cells  may  often  be 
seen  to  occur  under  the  microscope.  The  bacterium  cells,  during  a 
considerable  part  of  their  existence,  are  in  rapid  vibratory  and  progres- 
sive movement.  The  vibrations  take  place  in  a  circular  manner,  about 
some  point  situated  either  at  or  near  one  of  the  extremities ;  so  that  the 
rest  of  the  cell  performs  a  conical  movement  around  this  point,  present- 
ing, on  superficial  examination,  the  appearance  of  a  lateral  oscillation. 
The  mechanism  by  which  this  vibration  is  accomplished  is  unknown; 
but  it  is  no  doubt  analogous  to  the  slower  spiral  undulations  of  the 
Oscillatorise,  among  fresh-water  algae ;  and  its  effect  is  to  propel  the 


Cells  of  BACTERIUM  TERMO;  from  a  putrefying 
infusion. 


NATURE    OF    REPRODUCTION.  681 

bacterium  cells,  often  with  extreme  velocity,  through  the  fluid  in  which 
they  are  immersed. 

Of  later  years,  the  investigations  in  regard  to  spontaneous  generation 
have  been  almost  exclusively  confined  to  the  bacteria  and  their  allies, 
since  they  now  form  the  only  group  of  organisms  in  which  reproduction 
by  generation  has  not  been  fully  established.  Even  for  them,  the  rapid 
multiplication  by  cell  division,  which  takes  place  under  favorable  con- 
ditions, indicates  the  usual  mode  of  their  increase  in  numbers;  but  in 
order  to  establish  an  entire  similarity  between  them  and  other  living 
organisms,  they  must  also  be  shown  to  reproduce  themselves  by  spores 
or  germs,  which  has  not  thus  far  been  done.  The  experiments  with 
boiled  infusions  in  sealed  flasks  have  led  to  results  which  are  not  inter- 
preted in  the  same  manner  by  all  writers ;  but  it  is  evident  that  for 
bacteria,  as  well  as  for  other  organic  forms,  the  application  of  heat 
exerts  in  various  degrees  a  preventive  action  on  their  subsequent  appear 
ance. 

Among  the  most  careful  and  satisfactory  experiments  on  this  part  of 
the  subject  are  those  of  Prof.  Wyman,1  who  operated  with  infusions  of 
both  animal  and  vegetable  matters.  The  infusions,  placed  in  sealed 
flasks,  with  abundance  of  atmospheric  air,  were  submerged  in  boiling 
water  for  periods  varying  from  thirty  minutes  to  five  hours,  and  after- 
ward kept  under  observation  at  the  ordinary  temperatures  requisite  for 
the  development  of  bacteria.  The  result  showed  that  the  appearance 
of  these  organisms  was  always  delayed  by  the  previous  application  of 
heat,  and  that  this  dela}^  in  different  series  of  observations,  was  often  in 
direct  proportion  to  the  length  of  time  during  which  the  boiling  had 
been  continued.  Furthermore,  in  certain  cases  the  bacteria  failed  to  be 
produced  at  all,  and  tlu;  chances  of  their  production  decreased  in  pro- 
portion to  the  length  of  time  during  which  the  liquid  had  been  boiled. 
Thus,  of  four  series  of  flasks,  each  containing  the  same  infusion,  and 
boiled  respectively  during  one,  two,  three,  and  four  hours,  all  of  the  first 
and  second  series  afterward  produced  bacteria,  only  one  of  the  third, 
and  none  of  the  fourth.  Finally,  in  no  instance,  among  numerous  trials, 
did  they  appear  in  any  infusion  which  had  been  boiled  for  a  period  ex- 
ceeding five  hours.  Thus  a  limit  was  reached  to  the  production  of  bac- 
teria, in  fluids  previously  subjected  to  the  action  of  heat. 

There  can  be  no  doubt  as  to  the  scientific  bearing  of  these  and  similar 
experiments.  Spontaneous  generation  is  inadmissible  at  the  present 
day  for  everything  except  bacteria ;  and  with  regard  to  them  there  is 
no  sufficient  proof  that  they  are  ever  generated  without  the  concurrence 
of  previously  existing  germs. 

1  American  Journal  of  Science  and  Arts.  New  Haven,  vol.  xliv.,  September, 
1867. 

44 


CHAPTEE  II. 


Fig.  220. 


SEXUAL  GENERATION,  AND  THE  MODE  OF  ITS 
ACCOMPLISHMENT: 

SEXUAL  generation  is  performed  by  two  sets  of  organs,  each  of  which 
gives  origin  to  a  peculiar  product,  capable  of  uniting  with  the  other, 
to  produce  a  new  individual.  These  organs,  belonging  to  the  two  dif- 
ferent sexes,  are  called  the  male  and 
female  organs  of  generation.  The  female 
organs  produce  a  globular  body  called 
the  egg  or  germ,  which  is  capable  of  be- 
ing developed  into  the  body  of  the  young 
animal  or  plant ;  the  male  organs  produce 
a  substance  which  is  necessary  to  fecun- 
date the  germ,  and  enable  it  to  go  througli 
with  the  process  of  growth  and  develop- 
ment. 

Such  are  the  essential  and  universal 
characters  of  the  organs  of  generation. 
These  organs,  however,  while  exhibiting 
everywhere  the  same  principal  features, 
present  certain  modifications  of  structure 
and  arrangement  in  different  classes  of 
organized  beings. 

In  the  flowering  plants,  the  blossom, 
which  is  the  generative  apparatus  (Fig. 
220),  consists  first  of  a  female  organ  con- 
taining the  germ  (a),  situated  usually 
upon  the  highest  part  of  the  leaf-bearing 
stalk.  This  is  surmounted  by  a  nearly 
straight  column,  termed  the  pistil  (6),  dilated  at  its  summit  into  a 
globular  expansion,  and  occupying  the  centre  of  the  flower.  Around  it 
are  arranged  several  slender  filaments,  or  stamens,  bearing  upon  their 
extremities  the  male  organs,  or  anthers  (c,  c).  The  whole  is  surrounded 
by  a  circle  or  crown  of  delicate  colored  leaves,  termed  the  corolla  (d), 
which  is  frequently  provided  with  a  smaller  sheath  of  green  leaves  out- 
side, called  the  calyx  (e).  The  anthers,  when  arrived  at  maturity,  dis- 
charge a  fine  organic  dust,  called  the  pollen,  the  grains  of  which  are 
caught  upon  the  extremity  of  the  pistil.  Each  pollen-grain  then  absorbs 
the  nutritious  juices  with  which  it  is  in  contact,  and  develops  from  its 
substance  a  tubular  prolongation,  the  pollen-tube,  which,  by  its  con- 
(  682  ) 


BLOSSOM  OP  IPOM<EA  PUK- 
PTJREA.  (Morning-glory.) — a.  Germ. 
6.  Pistil,  c.  c.  Stamens,  with  anthers. 
d.  Corolla,  e.  Calyx. 


SEXUAL    GENERATION. 


683 


Fig.  221. 


tinued  growth,  penetrates  downward  through  the  tissues  of  the  pistil 
until  it  comes  in  contact  with  the  germ  below.  The  germ  thus  fecun- 
dated, the  process  of  generation  is  accomplished.  The  pistil,  anthers, 
and  corolla  wither  and  fall  off,  while  the  germ  increases  in  size,  and 
changes  in  form  and  texture,  until  it  ripens  into  the  mature  fruit  or 
seed.  It  is  then  ready  to  be  separated  from  the  parent  stem  ;  and,  if 
placed  in  the  proper  soil,  will  germinate  and  produce  a  new  plant  similar 
to  the  old. 

In  many  species  of  plants,  the  male  and  female  organs,  as  above 
described,  are  both  situated  upon  the  same  flower ;  as  in  the  lily,  the 
violet,  the  convolvulus.  In  other  instances,  there  are  separate  male 
and  female  flowers  upon  the  same  plant,  of  which  the  male  flowers  pro- 
duce only  the  pollen,  the  female, 
the  germ  and  fruit.  In  others  still, 
the  male  and  female  flowers  are 
situated  upon  different  plants, 
which  otherwise  resemble  each 
other,  as  in  the  willow,  the  poplar, 
the  sassafras. 

In  animals,  the  female  organs 
of  generation  are  called  ovaries, 
since  it  is  in  them  that  the  egg,  or 
"  ovum,"  is  produced.  The  male 
organs  are  the  testicles,  which 
give  origin  to  the  fecundating  pro- 
duct, the  "sperm"  or  "seminal 
fluid,"  by  which  the  egg  is  fer- 
tilized. In  the  taenia  or  tapeworm, 
already  described  (page  674),  each 
articulation  contains  both  ovary 
•and  testicle.  The  ovary  (Fig.  221, 
G,  a,  a)  is  a  series  of  branching 
tubes  ending  in  rounded  follicles, 
and  communicating  with  a  central 
canal.  The  testicle  (6)  is  a  narrower  convoluted  tube,  closely  folded 
upon  itself,  and  opening  by  an  external  orifice  (c)  upon  the  lateral 
border  of  the  articulation.  The  seminal  fluid  produced  in  the  testicle 
is  introduced  into  the  female  generative  passage,  which  opens  at  the 
same  spot,  and,  penetrating  into  the  interior,  comes  in  contact  with  the 
eggs,  which  are  thereby  fecundated.  Each  egg  then  produces  a  young 
embryo,  which  is  capable  of  being  afterward  developed  into  a  full-grown 
tsenia. 

In  various  other  families  of  invertebrate  animals,  as  the  snail,  the 
slug,  the  leech  and  the  earth  worm,  an  ovary  and  a  testicle  are  both 
present  in  the  body  of  the  same  individual.  But  in  these  instances 
impregnation  is  effected  only  by  the  concurrent  action  of  two  different 
organisms ;  and  when  sexual  union  takes  place,  the  eggs  produced  by 


SINGLE  ARTICULATION  OF  T.ENIA 
CRASSICOLLIS,  from  the  cat. — a,  a,  a. 
Ovary  filled  with  eggs,  6.  Testicle,  c.  Genital 
orifice. 


684  SEXUAL    GENERATION. 

one  animal  are  fecundated  by  the  seminal  fluid  of  another,  and  vice 
versa. 

In  all  the  vertebrate  animals,  on  the  other  hand,  the  two  sets  of 
generative  organs  are  located  in  separate  individuals ;  and  the  species 
is  divided  into  two  sexes,  male  and  female.  Beside  this,  there  are,  in 
most  instances,  certain  secondary  or  accessory  organs  of  generation, 
which  assist  in  the  accomplishment  of  the  process,  and  which  occasion 
a  corresponding  difference  in  the  anatomy  of  the  two  sexes.  In  some 
cases  this  difference  is  so  great  that  the  male  and  female  would  never 
be  recognized  as  belonging  to  the  same  species,  unless  they  were  seen 
in  company  with  each  other,  and  were  known  to  reproduce  the  species 
by  sexual  congress.  Not  to  mention  some  extreme  instances  of  this 
among  insects  and  other  invertebrate  animals,  it  is  sufficient  to  refer  to 
the  well-known  examples  of  the  cock  and  the  hen,  the  lion  and  lioness, 
the  buck  and  the  doe.  In  the  human  species,  the  distinction  between 
the  sexes  shows  itself  in  the  mental  constitution,  the  disposition,  habits, 
and  pursuits,  as  well  as  in  the  general  conformation  of  the  body,  and 
the  external  appearance. 

The  special  details  of  the  generative  process  depend  upon  the  struc- 
ture of  the  male  and  female  organs,  the  manner  in  which  their  products 
are  formed  and  discharged,  the  union  of  the  two  in  the  act  of  fecunda- 
tion, and  the  changes  which  take  place  in  the  development  of  the 
embryo. 


CHAPTER  III. 

THE  EGG,  AND  THE  FEMALE  ORGANS  OF 
GENERATION. 

THE  egg,  in  man  and  in  all  species  of  mammalians,  presents  an  essen- 
tial similarity  of  form,  size,  and  structure.  It  is  a  globular  body,  about 
0.25  millimetre  in  diameter,  and  consists  of  two  parts,  namely,  first, 
an  external  closed  sac,  the  vitelline  membrane  ;  and,  secondly,  a  sphe- 
rical mass  contained  in  its  interior,  the  vitellus.  Of  these  two,  the 
vitellus  is  the  essential  constituent  part  of  the  egg,  since  it  is  from  its 
substance  that  the  rudiments  of  the  embryo  are  formed.  The  vitelline 
membrane  is  a  protective  envelope,  destined 
to  maintain  the  form  and  integrity  of  the 
vitellus. 

Vitelline  Membrane. — The  vitelline  mem- 
brane is  a  smooth,  transparent,  colorless 
layer,  about  .01  millimetre  in  thickness. 
When  viewed  with  magnifying  powers  suffi- 
ciently moderate  to  include  the  view  of  the 
whole  egg,  the  membrane  presents  a  perfectly 
homogeneous  aspect;  although  with  higher 
powers,  according  to  Klein,  it  exhibits  an  HUMAN  OVUM,  magnified  75 

diameters.— a,  Vitelline   mem- 

appearance  of  vertical  striations.  Notwith-  brane.  &.  Vitellus.  c.  Germi- 
standing  its  delicacy  and  transparency,  it  is  ™ £jve  vesicle-  *.  Germinative 
very  elastic,  and  has  a  considerable  degree 

of  retistance.  If  the  egg  of  the  human  species,  or  of  any  of  the  mam- 
malians, be  placed  under  the  microscope,  surrounded  by  fluid  and 
covered  with  a  thin  slip  of  glass,  it  may  be  perceptibly  flattened  out 
by  pressing  upon  the  cover-glass  with  the  point  of  a  steel  needle ;  and 
when  the  pressure  is  removed  it  readily  resumes  its  globular  form. 
When  the  egg  is  partially  flattened  in  this  way,  by  the  pressure  of  a 
needle  or  by  the  weight  of  the  cover-glass,  the  apparent  thickness  of  the 
vitelline  membrane  is  increased,  giving  it  the  appearance  of  a  rather 
wide,  pellucid  border  or  zone,  surrounding  the  granular  and  compara- 
tively opaque  vitellus.  From  this  circumstance  it  has  sometimes  re- 
ceived the  name  of  the  "  zona  pellucida." 

In  the  vitelline  membrane  of  many  invertebrates,  and  also  in  that  of 
fishes,  a  minute  opening  has  been  discovered,  termed  the  "  micropyle," 
leading  into  the  interior  of  the  vitelline  cavity ;  and  it  is  through  this 
opening  that  the  filaments  of  the  male  seminal  fluid  penetrate,  to  reach 
the  vitellus.  It  is  very  possible  that  such  an  opening  may  also  exist 

(  685) 


686    EGG  AND  FEMALE  ORGANS  OF  GENERATION. 

in  the  vitelline  membrane  of  man  and  the  other  vertebrate  animals  ;  but 
the  globular  form  of  the  egg,  the  transparent  and  homogeneous  texture 
of  the  vitelline  membrane,  and  the  absence  of  any  other  material,  of  dif- 
ferent refractive  power,  in  the  canal  or  orifice  of  the  micropyle  itself, 
prevent  its  being  detected  in  microscopic  examination. 

Vitellus. — The  vitellus  is  a  globular  mass,  of  semifluid,  tenacious  con- 
sistency, composed  of  a  transparent  and  colorless  albuminous  material, 
with  oleaginous  looking  granules  thickly  disseminated  throughout  its 
substance.  Owing  to  the  physical  admixture  of  these  two  constituents, 
it  has  a  distinctly  granular  aspect,  and  a  considerable  degree  of  opacity. 
Imbedded  in  the  vitellus,  at  a  point  near  its  surface,  and  consequently 
almost  immediately  beneath  the  vitelline  membrane,  is  a  clear,  colorless, 
transparent  vesicle,  of  a  rounded  form,  the  germinative  vesicle.  In  the 
mammalian  egg,  this  vesicle  measures  about  .04  millimetre  in  diameter. 
It  presents  upon  its  surface  a  nucleus-like  spot,  known  by  the  name  of 
the  germinative  spot.  Both  the  germinative  vesicle  and  germinate  spot 
are  partially  concealed,  in  the  uninjured  condition  of  the  egg,  by  the 
granules  of  the  surrounding  vitellus. 

If  the  egg,  while  under  the  microscope,  be  ruptured  by  continued 
pressure  upon  the  covering  glass,  the  semifluid  vitellus  is  gradually 

expelled  by  the  elasticity  of  the  vitelline  mem- 
Fig-.  223.  brane.  It  retains  the  granules  imbedded  in 
its  substance,  but  often  allows  the  germina- 
tive vesicle  to  become  detached,  and  therefore 
more  distinctly  visible. 

In  man  and  the   mammalians,  the  simple 
form  of  egg  above  described,  consisting  mainly 
of  a  vitellus  of  minute  size,  is  sufficient  for  the 
production  of  the  embryo,  since  it  is  retained, 
HUMAN  OVUM,  ruptured    after  fecundation,  in  the  interior  of  the  gene- 
by  pressure,  showing  the  vi-     rative    passages,  and  absorbs   the  nutritious 

tellus   partially   expelled,   the  .    t  &.^  ' 

germinative  vesicle,  with  its    materials  for  its  subsequent  growth  from  the 


t.ata  and  the    tissues  of  the  female  parent.      In  the  naked 

smooth  fracture  of  the  vitel- 
line membrane.  reptiles  and  in  most  fish,  where  the  eggs  are 

deposited  and  hatched  in  the  water,  the  vitel- 
lus is  also  of  small  size  ;  since  the  hatching  takes  place  at  a  compara- 
tively early  period  of  development,  and  the  requisite  additional  fluid 
is  supplied  from  the  surrounding  medium.  But  in  birds,  and  in  most 
of  the  scaly  reptiles,  as  serpents,  turtles,  and  lizards,  the  eggs  are  de- 
posited in  a  nest  or  in  the  ground,  and  there  is  consequently  no  external 
source  of  nutrition  for  the  support  and  growth  of  the  embryo  during 
its  development.  In  these  instances  the  vitellus,  or  "  yolk,"  is  of  large 
size ;  and  the  bulk  of  the  egg  is  still  further  increased  by  the  addition, 
within  the  female  generative  passages,  of  layers  of  albumen  and  various 
external  fibrous  and  calcareous  envelopes.  The  essential  constituents 
of  the  egg,  nevertheless,  still  remain  the  same  in  character,  and  the 
process  of  embryonic  development  follows  its  usual  course. 


EGG  AND  FEMALE  ORGANS  OF  GENERATION.    687 


Ovaries  and  Oviducts. — The  eggs  are  produced  in  the  interior  of 
certain  organs,  situated  in  the  abdominal  cavity,  called  the  ovaries. 
These  organs  consist  of  a  mass  of  vascular  connective  tissue,  inclosing 
a  number  of  globular  sacs  or  follicles,  the  "  Graafian  follicles ;"  so 
called  from  the  name  of  the  anatomist  who  first  fully  described  them1 
as  constituent  parts  of  the  ovary.  Each  Graafian  follicle  contains  an 
egg,  which  varies  more  or  less  in  size  and  appearance  in  different  classes 
of  animals,  but  which  has  always  the  same  essential  characters,  and 
is  produced  in  the  same  way. 

The  egg  thus  grows  in  the  interior  of  the  ovarian  sac,  like  a  tooth  in 
its  follicle  ;  and  forms,  accordingly,  a  constituent  part  of  the  body  of 
the  female.  It  is  destined  to  be  subsequently  separated  from  its  at- 
tachments, and  thrown  off ;  but  until  that  time,  it  is  one  of  the  elements 
of  the  tissue  of  the  ovary,  and  is  nourished  like  any  other  portion  of  the 
female  organism. 

Since  the  ovaries  are  the. organs  directly  concerned  in  the  production 
of  the  egg,  they  form  the  most  essential  part  of  the  female  generative 
apparatus.  Beside  them,  there  are  usually  present  certain  other  organs, 
which  play  a  secondary  part  in  the  process  of  generation.  The  most 
important  of  these  accessory  organs  are  two  symmetrical  tubes,  or 
oviducts,  destined  to  receive  the  eggs  at  their  inner  extremity  and  con- 
vey them  to  the  external  generative  orifice.  The  mucous  membrane 
lining  the  oviducts  is  also  adapted  by  its  structure  to  supply  certain 
secretions  during  the  passage  of  the  egg, 
which  are  requisite,  either  to  complete  it§ 
formation,  or  to  provide  for  the  nutrition 
of  the  embryo. 

In  the  frog,  the  oviduct  commences  at 
the  upper  part  of  the  abdomen,  by  a  rather 
wide  orifice,  communicating  directly  with 
the  peritoneal  cavity.  It  soon  afterward 
contracts  to  a  narrow  tube,  and  pursues  a 
zigzag  course  down  the  side  of  the  abdo- 
men (Fig.  224),  folded  upon  itself  in  nume- 
rous convolutions,  until  it  opens,  near  its 
fellow  of  the  opposite  side,  into  the  "  clo- 
aca" or  lower  part  of  the  intestinal  canal. 
The  oviducts  present  the  general  charac- 
ters described  above  in  nearly  all  species 
of  reptiles  and  birds. 

The  ovaries,  as  well  as  the  eggs  which 

they  contain,   undergo   at   particular   sea- 

FEMALE   GENERATIVE    OR- 

sons  a  periodical  development  or  increase     GANS  OF  FRoo.-a,  a    Ovaries. 
in  growth.     In  the  female  fros,  during  the     6» b  Oviducts,   c,  c.  Their  internal 

orifices,    d.  Cloaca,  showing  inle- 

latter  part  of  summer  or  the  fall,  the  ova-     ri0r  orifices  of  oviducts. 


Fig.  224. 


Regner  de  Graaf,  Opera  Omnia.     Arastelaedami,  1705,  p.  228. 


688    EGG  AND  FEMALE  ORGANS  OF  GENERATION. 

ries  appear  like  small  clusters  of  minute  and  nearly  colorless  eggs,  the 
smaller  of  which  are  perfectly  transparent  and  less  than  0.18  millimetre 
in  diameter.  But  in  the  early  spring,  when  the  season  of  reproduction 
approaches,  the  ovaries  increase  to  four  or  five  times  their  former  size, 
forming  large  lobulated  masses,  crowded  with  dark-colored  opaque 
eggs,  each  2  millimetres  in  diameter.  At  the  generative  season,  in  all 
the  lower  animals,  a  certain  number  of  eggs,  which  were  previously  in 
an  imperfect  condition,  increase  in  size  and  become  altered  in  structure. 
The  vitellus  especially,  which  was  before  colorless  and  transparent,  be- 
comes granular  and  increased  in  volume ;  and  it  assumes  at  the  same 
time  a  black,  brown,  yellow,  or  orange  color.  In  the  mammalian  egg 
the  change  consists  only  in  an  increase  of  size  arid  granulation,  without 
any  remarkable  alteration  of  color. 

The  eggs,  as  they  ripen  in  this  way,  gradually  distend  the  Graafian 
follicles  and  project  from  the  surface  of  the  ovary.  When  fully  ripe, 
they  are  discharged  by  a  rupture  of  the  follicles,  and,  passing  into  the 
oviducts,  are  conveyed  to  the  external  generative  orifice,  and  there  ex- 
pelled. In  successive  seasons,  successive  crops  of  eggs  enlarge,  ripen, 
leave  the  ovaries,  and  are  discharged.  Those  which  are  to  be  expelled 
at  the  next  generative  epoch  may  be  recognized  by  their  greater  degree 
of  development ;  and  in  this  way,  in  many  animals,  the  eggs  of  no  less 
than  three  different  crops  may  be  distinguished  in  the  ovary  at  once, 
namely,  1st,  those  which  are  perfectly  mature  and  ready  to  be  dis- 
charged ;  2d,  those  which  are  to  ripen  in  the  following  season  ;  and  3d, 
those  which  are  as  yet  inactive  and  undeveloped.  In  most  fish  and 
reptiles,  as  well  as  in  birds,  this  regular  process  of  the  ripening  and 
discharge  of  eggs  takes  place  but  once  a  year.  In  different  species  of 
quadrupeds  it  may  occur  annually,  semi-annually,  bi-monthly,  or  even 
monthly ;  but  in  every  instance  it  returns  at  regular  intervals,  and 
exhibits,  therefore,  a  well-marked  periodical  character. 

Action  of  the  Oviducts  and  Female  -Generative  Passages. — In  the 
frog,  after  the  ripening  of  the  eggs  and  their  discharge  from  the  ovarian 
follicles,  they  receive  an  additional  investment  while  passing  through 
the  oviducts.  At  the  time  of  leaving  the  ovary,  the  eggs  consist  simply 

of  the  dark-colored  and  granular  vitellus, 
225<  inclosed  in  the  vitelline  membrane.    They 

are  received  by  the  inner  extremity  of 
the  oviducts,  and  carried  downward  by 
the  peristaltic  movement  of  these  canals, 
aided  by  the  contraction  of  the  abdominal 
muscles.  During  their  passage,  the  mu- 
cous membrane  of  the  oviduct  secretes 

MATUKE    FKOGS'    EGGS.-  a.      an    albuminous    substance,    which    is    de- 
While  still  in  the  ovary,     b.   After  . 

passing  through  the  oviduct.  posited    m    successive    layers,    forming 

round  each  egg  a  thick  coating  or  en- 
velope (Fig.  225).  When  the  eggs  are  discharged,  this  envelope 
absorbs  moisture  from  the  water  in  which  the  spawn  is  deposited,  and 


EGG  AND  FEMALE  ORGANS  OF  GENERATION.    689 

swells  into  a  transparent  gelatinous  mass,  in  which  the  eggs  are  sepa- 
rately imbedded.  Jt  supplies,  by  its  subsequent  liquefaction  and  ab- 
sorption, a  certain  amount  of  nutritious  material,  for  the  development 
and  growth  of  the  embryo. 

In  the  scaly  reptiles  and  in  birds,  the  oviducts  perform  a  more  im- 
portant function.  In  the  common  fowl,  the  ovary  consists,  as  in  the 
frog,  of  follicles,  loosely  united  by  connective  tissue,  and  containing  eggs 
in  different  stages  of  development  (Fig.  226,  «).  As  the  egg  which  is 
approaching  maturity  enlarges,  it  distends  the  cavity  of  its  follicle,  and 
projects  farther  from  the  general  surface  of  the  ovary ;  so  that  it  hangs 
at  last  into  the  peritoneal  cavity,  retained  only  by  the  attenuated  waM 
of  the  follicle,  and  a  slender  pedicle  through  which  run  the  bloodvessels 
by  which  its  circulation  is  supplied.  A  rupture  of  the  follicle  then 
occurs  at  its  most  prominent  part,  and  the  egg  is  discharged  from  the 
lacerated  opening. 

At  the  time  of  leaving  the  ovary,  the  egg  of  the  fowl  consists  of  a 
large,  globular,  orange-colored  vitellus,  or  "  yolk,"  inclosed  in  a  thin 
and  transparent  vitelline  membrane.  Immediately  underneath  the 
vitelline  membrane,  at  one  point  upon  the  surface  of  the  vitellus,  is  a 
round  white  spot,  consisting  of  a  la}'er  of  minute  granules,  termed  the 
"  cicatricula,"  in  which  the  germinative  vesicle  is  imbedded  at  an  early 
stage  of  the  development  of  the  egg.  At  the  time  of  its  discharge  from 
the  ovary,  the  germinative  vesicle  has  usually  disappeared;  but  the 
cicatricula  is  still  an  important  part  of  the  vitellus,  and  it  is  from  this 
spot  that  the  body  of  the  chick  begins  afterward  to  be  developed. 

As  the  egg  protrudes  from  the  surface  of  the  ovary,  it  projects  into 
the  inner  orifice  of  the  oviduct ;  so  that,  when  discharged  from  its 
follicle,  it  is  embraced  by  the  upper  expanded  extremity  of  this  tube, 
and  commences  its  passage  downward.  In  the  fowl,  the  muscular  coat 
of  the  oviduct  is  highly  developed,  and  its  peristaltic  contractions  urge 
the  egg  from  above  downward,  somewhat  in  the  same  manner  as  the 
oesophagus  or  the  intestines  transport  the  food  in  a  similar  direction. 
While  passing  through  the  first  five  or  six  centimetres  of  the  oviduct 
(c,  d),  where  the  mucous  membrane  is  smooth  and  transparent,  the 
yolk  absorbs  a  certain  quantity  of  fluid,  becoming  consequently  rather 
more  flexible  and  yielding  in  consistency.  It  then  passes  into  a  second 
division  of  the  generative  canal,  in  which  the  mucous  membrane  is 
thicker  and  more  glandular,  and  is  thrown  into  longitudinal  folds. 
This  portion  of  the  oviduct  (d,  e)  extends  over  about  22  centimetres, 
or  more  than  one-half  its  entire  length.  In  its  upper  part,  the  mucous 
membrane  secretes  a  viscid  material,  by  which  the  yolk  is  incased, 
and  which  soon  consolidates  into  a  gelatinous  deposit,  thus  forming  a 
second  envelope,  outside  the  vitelline  meihbrane. 

The  peristaltic  movements  of  this  part  of  the  oviduct  are  such  as  to 
give  a  rotary,  as  well  as  a  progressive  motion  to  the  egg ;  and  by  this 
means  the  two  extremities  of  the  gelatinous  envelope  become  twisted 
in  opposite  directions;  forming  two  whitish  looking  cords,  attached 


690 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


Fig.  226. 


to  the  opposite  poles  of  the  egg.  These  cords  are  termed  the  "  chalazse," 
and  the  membrane  with  which  they  are  connected,  the  "  chalaziferous 
membrane." 

Throughout  the  remainder  of  the  second  division  of  the  oviduct,  the 
mucous  membrane  exudes  an  albuminous  substance,  which  is  deposited 
in  successive  layers  round  the  yolk,  inclosing  the  chalaziferous  mem- 
brane and  the  chalazae.  This  substance, 
the  so-called  albumen,  or  "white  of  egg," 
is  gelatinous  in  consistency,  nearly  trans- 
parent, and  of  a  faint  amber  color.  It  is 
deposited  in  greater  abundance  in  front 
of  the  advancing  egg  than  behind  it,  and 
thus  forms  a  conical  projection  anteriorly, 
while  behind,  its  outline  is  parallel  with 
the  spherical  surface  of  the  yolk.  In  this 
way,  the  egg  acquires,  when  covered  with 
its  albumen,  an  ovoid  form,  of  which 
one  end  is  round,  the  other  pointed  ;  the 
pointed  extremity  being  directed  down- 
ward, as  the  egg  descends  along  the 
oviduct. 

In  the  third  division  of  the  oviduct 
(f)i  which  is  about  nine  centimetres  in 
length,  the  mucous  membrane  is  arranged 
in  longitudinal  folds,  which  are  narrower 
arid  more  closely  packed  than  in  the 
preceding  portion.  The  material  secreted 
in  this  part  condenses  into  a  firm  fibrous 
covering,  composed  of  three  different 
layers  which  closely  embrace  the  surface 
of  the  albuminous  mass,  forming  a  tough, 
flexible,  semi-opaque  envelope  for  the 
whole.  These  layers  are  known  as  the 
external,  middle,  and  internal  fibrous 
membranes  of  the  egg. 

Finally  the  egg  passes  into  the  fourth 
division  of  the  oviduct  (gr),  which  is  wider 
than  the  rest  of  the  canal,  but  only  a 
little  over  five  centimetres  in  length. 
Here  the  mucous  membrane,  which  is 
arranged  in  abundant  projecting,  leaf- 
like  villosities,  exudes  a  fluid  rich  in 

FEMALE  GENERATIVE  ORGANS  OF  THE  FOWL. — a.  Ovary,  b.  Graafian  follicle, 
from  which  the  egg  has  just  been  discharged,  c.  Yolk,  entering  upper  extremity  of  oviduct. 
d,  e.  Second  division  of  oviduct,  in  which  the  chalaziferous  membrane,  chalazse,  and  albumen 
are  formed.  /.  Third  portion,  in  which  the  fibrous  shell  membranes  are  produced,  g.  Fourth 
portion  laid  open,  showing  the  egg  completely  formed,  with  its  calcareous  shell,  h.  Narrow 
canal  through  which  the  egg  is  discharged. 


EGG  AND  FEMALE  ORGANS  OF  GENERATION.    691 

calcareous  salts.  The  most  external  of  the  three  membranes  above 
described  is  permeated  by  this  secretion ;  and  soon  afterward,  owing  to 
the  reabsorption  of  its  fluid  parts,  the  calcareous  matter  begins  to  crys- 
tallize in  the  fibrous  network  of  the  membrane.  This  deposit  of  calcare- 
ous matter  goes  on,  growing  thicker  and  more  condensed,  until  the 
external  envelope  is  converted  into  a  white,  opaque,  brittle,  calcareous 
shell,  which  incloses  the  remaining  portions  and  protects  them  from 
injury.  The  egg  is  then  forced  through  a  narrow  portion  of  the  oviduct 
(/?,),  and,  gradually  dilating  the  passages  by  its  conical  extremity,  is 
finally  discharged  from  the  external  orifice. 

The  egg  of  the  fowl,  after  its  expulsion,  consists,  accordingly,  of  vari- 
ous parts ;  some  of  which,  as  the  yolk  and  the  vitelline  membrane, 
entered  into  its  original  formation,'  while  the  remainder  have  been 
deposited  round  it  during  its  passage  through  the  oviduct. 

After  the  discharge  of  the  egg  there  is  a  partial  evaporation  of  its 
watery  ingredients,  which  are  replaced  by  air  penetrating  through  the 
pores  of  the  shell  at  its  rounded  extremity.  The  air  thus  introduced 
accumulates  between  the  middle  and  internal  fibrous  membranes,  form- 
ing a  cavity  or  air-chamber  (</),  at  the  rounded  end  of  the  egg.  Very 

Fig.  227. 


Diagram  of  FOWL' 8  EGO.— a.  Yolk.  b.  Vitelline  membrane,  c.  Chalaziferous 
membrane,  d.  Albumen.  e,f.  Middle  and  internal  shell  membranes,  g.  Air-chamber. 
h.  Calcareous  shell. 

soon,  the  external  layers  of  the  albumen  liquefy ;  and  the  vitellus,  being 
specifically  lighter  than  the  albumen,  rises  toward  the  surface  of  the 
egg,  with  the  cicatricula  uppermost.  This  part  presents  itself  almost 
immediately  on  breaking  open  the  egg  at  any  point  corresponding  to 
the  equator  of  the  yolk,  and  is  placed  in  the  most  favorable  position 
for  the  action  of  warmth  and  atmospheric  air  in  the  development  of  the 
chick. 

The  vitellus,  therefore,  is  still  the  essential  constituent  part,  even  in 
the  large  and  highly  complicated  fowl's  egg ;  while  the  remainder  con- 


692 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


sists  of  nutritious  material,  provided  for  the  support  of  the  embryo, 
and  of  protective  envelopes,  like  the  shell  and  fibrous  membranes. 

In  the  quadrupeds,  another  important  modification  of  the  oviducts 
takes  place.  In  these  animals,  the  egg,  which  is  originally  of  minute 
size,  is  retained  within  the  generative  passages  of  the  female  during  the 
development  of  the  embryo.  While  the  upper  part  of  the  ovi(Juct, 
accordingly,  is  quite  narrow,  and  serves  merely  to  transmit  the  egg 
from  the  ovary,  and  to  supply  it  with  a  little  albuminous  secretion,  the 
lower  portions  are  much  increased  in  size,  and  are  lined  with  a  mucous 
membrane  which  is  adapted  to  provide  for  the  protection  and  nourish- 
ment of  the  embryo  during  gestation.  The  upper  and  narrower  por- 
tions of  the  oviduct  are  known  as  the  "Fallopian  tubes,"  from  Fallopius1 
who  first  described  them  in  the  'human  female ;  while  the  lower  and 


UTERUS    AND  OVARIES  OP  THE  Sow.— a,  a.  Ovaries.    6,  b.  Fallopian  tubes. 
c,  c.  Horns  of  the  uterus,     d.  Body  of  the  uterus,    e.  Vagina. 

more  highly  developed  portions  constitute  the  uterus.  The  two  halves 
of  the  uterus  unite  with  each  other  upon  the  median  line  near  their 
inferior  termination,  to  form  a  central  organ,  termed  its  "body;"  while 
the  ununited  parts  are  known  as  its  "cornua"  or  "horns." 

In  the  human  species,  the  ovaries  consist  of  Graafian  follicles,  imbed- 
ded in  a  somewhat  dense  connective  tissue,  supplied  witli  an  abundance 
of  bloodvessels,  and  covered  with  an  opaque,  yellowish- white  layer  of 
fibrous  tissue,  called  the  "  albugineous  tunic."  Over  the  whole  is  a  layer 
of  peritoneum,  which  is  reflected  upon  the  bloodvessels  supplying  the 
ovary,  and  is  continuous  with  the  broad  ligaments  of  the  uterus  ;  but 
which  elsewhere  is  closely  consolidated  with  the  albugineous  tunic. 

The  oviducts  commence  by  a  wide  expansion,  provided  with  fringed 
edges,  called  the  "  fimbriated  extremity  of  the  Fallopian  tube."  The 
Fallopian  tubes  themselves  are  narrow  and  convoluted,  terminating,  on 
each  side,  in  the  upper  part  of  the  body  of  the  uterus.  The  body  of  the 
uterus,  in  the  human  species,  is  so  much  developed  at  the  expense  of  the 
cornua,  that  the  latter  hardly  appear  to  have  an  existence,  and  no  trace 
of  them  is  visible  externally.  But  on  opening  the  uterus,  its  cavity  is 

1  Opera  Omnia.     Francofurti,  1600.     Observations  Anatomicae,  p.  421. 


EGG  AND  FEMALE  ORGANS  OF  GENERATION. 


693 


seen  to  be  somewhat  triangular  in  shape,  its  two  superior  angles  running 
out  to  join  the  lower  extremities  of  the  Fallopian  tubes.  This  portion 
evidently  consists  of  the  cornua,  which  have  been  consolidated  with  the 
body  of  the  uterus,  and  enveloped  in  its  thickened  layer  of  muscular 
fibres. 

Fig.  229. 


GENERATIVE  OROAKS  OF  THE  HUMAN  FEMALE.— a,  a.  Ovaries,    ft,  6.  Fallopian 
tubes,    c.  Body  of  the  uterus,    d.  Cervix,    e.  Vagina. 

The  cavity  of  the  body  of  the  uterus  terminates  below  by  a  con- 
stricted portion,  termed  the  os  internum,  by  which  it  is  separated  from 
the  cervix.  These  two  cavities  are  not  only  different  from  each  other 
in  shape,  but  also  in  the  structure  of  their  mucous  membrane  and  in  the 
functions  which  they  perform. 

The  mucous  membrane  of  the  body  of  the  uterus  in  its  usual  condi- 
tion is  smooth  and  rosy  in  color,  and  closely  adherent  to  the  subjacent 
muscular  tissue.  It  consists  of  tubular  follicles,  ranged  side  by  side, 
and  opening  by  distinct  orifices  upon  its  free  surface.  The  secretion  of 
these  follicles  is  destined  for  the  nutrition  of  the  embryo  during  the 
earlier  periods  of  its  formation. 

The  internal  surface  of  the  cervix,  on  the  other  hand,  is  raised  in 
prominent  ridges,  arranged  usually  in  two  lateral  sets,  diverging  from  a 
central  longitudinal  ridge ;  presenting  the  appearance  known  as  the 
"arbor  vitae  uterina."  The  follicles  of  this  part  of  the  uterine  mucous 
membrane  are  of  a  globular  or  sac-like  form,  and  secrete  a  tenacious 
mucus,  which  serves,  during  gestation,  to  block  up  the  cavity  of  the 
cervix,  and  thus  to  prevent  the  escape  or  injury  of  the  egg. 

The  cavity  of  the  cervix  uteri  is  terminated  inferiorly  by  a  second 
constriction,  the  "  os  externum  ;"  and  below  this  comes  the  vagina, 
which  constitutes  the  last  division  of  the  female  generative  passages. 

The  accessory  female  organs  of  generation  consist,  therefore,  of  ducts 
or  tubes,  by  means  of  which  the  egg  is  conveyed  from  within  outward. 
These  ducts  vary  in  the  degree  and  complication  of  their  development, 


694:    EGG  AND  FEMALE  ORGANS  OF  GENERATION. 

in  different  kinds  of  animals,  according  to  the  importance  of  the  func- 
tion which  they  perform.  In  the  lower  orders,  they  serve  mainly  to 
convey  the  egg  to  the  exterior,  and  to  supply  it  more  or  less  abundantly 
with  an  albuminous  secretion  ;  while  in  the  mammalia  and  in  man,  they 
are  adapted  to  the  more  important  office  of  retaining  the  egg  during  the 
period  of  gestation,  and  of  providing  during  the  same  time  for  the  nour- 
ishment of  the  embryo. 


CHAPTER    IV. 

THE   SEMINAL   FLUID,   AND   THE   MALE   ORGANS    OF 

GENERATION. 

THE  mature  egg  is  not  by  itself  capable  of  being  developed  into  the 
embryo.  If  simply  discharged  from  the  ovary  and  carried  through  the 
oviducts  to  the  exterior,  it  soon  dies  and  is  decomposed,  like  any  other 
portion  of  the  body  separated  from  its  connections.  It  is  only  when 
fecundated  by  the  seminal  fluid  of  the  male,  that  it  is  stimulated  to  con- 
tinued development,  and  becomes  capable  of  more  complete  organiza- 
tion. 

The  product  of  the  male  generative  organs  is  a  colorless,  somewhat 
viscid,  albuminous  fluid,  containing  minute  filamentous  bodies,  the  sper- 
matozoa. This  name  has  been  given  to  the  bodies  in  question  on  ac- 
count of  their  exhibiting,  when  recently  discharged,  a  very  active  and 
continuous  movement  suggesting  the  idea  of  an  independent  animal 
organization. 

Anatomical  Characters  of  the  Spermatozoa. — The  spermatozoa  of  man 
(Fig.  230,  a)  are  about  .045  millimetre  in  length,  according  to  the  mea- 
surements of  Kolliker.  Their  anterior  extremity  presents  a  somewhat 
flattened  triangular-shaped  enlargement,  termed  the  "head,"  which  con- 
stitutes about  one-tenth  part  the  entire  length  of  the  spermatozoon. 
The  remaining  portion  is  a  slender  filamentous  prolongation,  called  the 
"tail,"  which  tapers  gradually  backward,  becoming  so  exceedingly  deli- 
cate toward  its  extremity,  that  it  is  difficult  to  be  seen  except  when  in 
motion.  There  is  no  further  organization  visible  in  any  part  of  the 
spermatozoon  ;  and  the  whole  appears  to  consist,  so  far  as  can  be  seen 
by  the  microscope,  of  a  homogeneous  substance.  The  terms  head  and 
tail,  as  remarked  by  Bergmann  and  Leuckart,1  are  not  used,  when  de- 
scribing the  different  parts  of  the  spermatozoon,  in  the  same  sense  as 
that  in  which  they  would  be  applied  to  the  corresponding  parts  of  an 
animal ;  but  simply  for  the  sake  of  convenience,  as  one  might  speak  of 
the  head  of  an  arrow  or  the  tail  of  a  comet. 

In  the  lower  vertebrate  animals,  the  spermatozoa  have  the  same  gen- 
eral form  as  in  man  ;  that  is,  they  are  filamentous  bodies,  with  the  ante- 
rior extremity  more  or  less  enlarged.  In  the  rabbit,  the  head  is  roundish 
and  flattened  in  shape,  somewhat  resembling  a  blood  globule.  In  the 
rat  (Fig.  230,  6)  they  are  much  larger  than  in  man,  measuring  nearly 
0.20  millimetre  in  length.  The  head  is  of  a  conical  form,  about  one- 

1  Vergleichende  Physiologie.     Stuggart,  1852. 

(695) 


696 


MALE    ORGANS    OF    GENERATION. 


Fig.  230.  twentieth  the  whole  length  of 

the  filament,  and  often  slightly 
curved  at  its  anterior  extremity. 
In  the  frog  and  in  reptiles  gen- 
erally, the  spermatozoa  are  lon- 
ger than  in  quadrupeds.  In 
Menobranchus,  the  great  Amer- 
ican water-lizard,  they  are  of 
very  unusual  size  (Fig.  230,  c), 
measuring  not  less  than  0.57 
millimetre  in  length,  about  one- 
third  of  which  is  occupied  by 
the  head,  or  enlarged  portion 
of  the  filament. 

The  most  remarkable  peculi- 
arity of  the  spermatozoa,  as  seen 
under  the  microscope,  is  their 
rapid  and  energetic  movement. 
In  a  drop  of  fresh  seminal  fluid, 
if  kept  sufficiently  moistened 
and  at  its  normal  temperature, 
the  numberless  filaments  with 
which  it  is  crowded  are  seen  to 
be  in  a  state  of  incessant  mo- 
tion. In  many  species  of  ani- 
mals, the  movement  of  the  sper- 
matozoa strongly  resembles  that  of  a  tadpole ;  particularly  when,  as  in 
the  mammalia,  they  consist  of  a  short,  well-defined  head,  followed  by 
a  long  and  slender  tail.  The  tail-like  filament  keeps  up  a  constant  lat- 
eral vibratory  movement,  by  which  the  spermatozoon  is  driven  from 
place  to  place  in  the  seminal  fluid,  as  a  fish  or  a  tadpole  is  propelled 
through  the  water.  In  other  instances,  as  in  the  Triton,  or  water  lizard, 
the  spermatozoa  have  a  continuous  wrrithing  or  spiral-like  movement ; 
presenting  a  peculiarly  elegant  appearance  when  large  numbers  are 
viewed  together. 

It  is  this  movement  which  gave  origin  to  the  name  of  spermatozoa, 
to  designate  the  filaments  of  the  spermatic  fluid.  But,  notwithstanding 
its  active  character,  and  its  resemblance  in  mechanism  to  the  locomo- 
tion of  certain  animals,  it  has  no  analogy  with  a  voluntary  act. 

The  spermatozoa  are  organic  forms,  produced  in  the.  testicles,  and 
constituting  a  part  of  their  tissue;  just  as  the  eggs,  which  are  pro- 
duced in  the  ovaries,  naturally  form  a  part  of  the  texture  of  these  or- 
gans. Like  the  egg,  the  spermatozoon  is  destined  to  be  discharged 
from  the  organ  where  it  grew,  and  to  retain,  for  a  certain  time  after- 
ward, its  vital  properties.  One  of  these  properties  is  its  power  of  move- 
ment ;  but  this  does  not  indicate  the  possession  of  independent  vitality, 
and  is  not  even  necessarily  a  proof  of  its  animal  origin.  The  move- 


SPERM  ATOZO  A.— a.  Human,    b.  Of  the  rat. 
c.  Of  Menobranchus.    Magnified  480  times. 


MALE  ORGANS  OF  GENERATION.          697 

ment  of  a  spermatozoon  is  not  more  active  than  that  of  a  bacterium 
cell,  or  that  of  the  ciliated  zoospores  of  certain  fresh-water  algae.  It 
is  more  strictly  analogous  to  the  motion  of  a  ciliated  epithelium  cell 
when  detached  from  its  mucous  membrane,  which  will  sometimes  con- 
tinue for  many  hours,  if  kept  under  favorable  conditions  of  temperature 
and  moisture.  The  power  of  movement  manifested  by  the  spermatozoa 
also  continues  for  a  time  after  their  separation  from  the  rest  of  the  body  ; 
but  it  is  limited  in  duration,  and  after  a  certain  interval  comes  to  an 
end. 

In  order  to  preserve  their  vitality,  the  spermatozoa  must  be  kept  at 
or  near  the  normal  temperature  of  the  body,  and  preserved  from  the 
contact  of  air  or  other  unnatural  fluids.  If  the  seminal  fluid  be  allowed 
to  dry,  or  if  it  be  diluted  by  water,  in  the  case  of  birds  and  quadrupeds, 
or  if  it  be  subjected  to  extremes  of  heat  or  cold,  the  motion  ceases,  and 
the  spermatozoa  soon  begin  to  disintegrate. 

Formation  of  the  Spermatozoa. — The  spermatozoa  are  produced  in  the 
interior  of  certain  glandular-looking  organs,  the  testicles,  which  are 
characteristic  of  the  male,  as  the  ovaries  are  characteristic  of  the  female. 
In  man  and  mammalia,  the  testicles  are  solid,  ovoid-shaped  bodies,  com- 
posed of  long,  narrow,  convoluted  tubes,  the  "  seminiferous  tubes,"  some- 
what similar  to  the  tubuli  uriniferi  of  the  kidneys.  They  lie  for  the 
most  part  closely  in  contact  with  each  other,  nothing  intervening  between 
them  except  capillary  bloodvessels  and  a  little  connective  tissue.  They 
commence,  by  rounded  extremities,  near  the  external  surface  of  the 
testicle  and  pursue  an  intricately  convoluted  course  toward  its  central 
and  posterior  part.  They  are  not  strongly  adherent  to  each  other,  but 
may  be  readily  unravelled  by  manipulation. 

According  to  the  investigations  of  Kolliker,  the  formation  of  the 
spermatozoa  takes  place  within  peculiar  cells  occupying  the  cavity  of 
the  seminiferous  tubes.  As  the  age  of  puberty  approaches,  beside  the 
ordinary  pavement  epithelium  lining  the  tubes,  other  cells  or  vesicles 
of  larger  size  make  their  appearance,  each  containing  from  one  to  fifteen 
or  twenty  nuclei,  with  nucleoli.  In  the  interior  of  these  vesicles  sper- 
matozoa are  formed;  their  number  corresponding  usually  with  that  of 
the  nuclei.  They  are  developed  in  bundles  of  from  ten  to  twenty,  held 
together  by  the  membranous  substance  surrounding  them,  but  are  after- 
ward set  free  by  the  liquefaction  of  the  vesicle,  and  then  nearly  fill  the 
cavity  of  the  seminiferous  ducts,  being  mingled  only  with  a  minute 
quantity  of  transparent  fluid. 

While  in  the  seminiferous  tubes,  the  spermatozoa  are  always  inclosed 
in  their  parent  vesicles ;  they  are  liberated,  and  mingled  together,  only 
after  entering  the  rete  testis  and  the  head  of  the  epididymis. 

Accessory  Male  Organs  of  Generation. — Beside  the  testicles,  which 
are  the  essential  parts  of  the  male  generative  apparatus,  there  are  certain 
accessory  organs,  by  which  the  seminal  fluid  is  conveyed  to  the  exterior, 
and  mingled  with  various  secretions  which  assist  in  the  accomplishment 
of  its  function. 
45 


MALE    ORGANS    OF    GENERATION. 

As  the  sperm  leaves  the  testicle,  it  consists  almost  entirely  of  sperma- 
tozoa, crowded  together  in  an  opaque,  white,  semi-fluid  mass,  which  fills 
the  vasa  efFerentia,  and  distends  their  cavities.  It  then  enters  the  single 
duct  which  forms  the  body  and  lower  extremity  of  the  epididymis,  fol- 
lowing the  long  and  tortuous  course  of  this  tube,  until  it  reaches  the  vas 
deferens ;  through  which  it  is  conveyed  onward  to  the  vesiculae  seminalis. 
Throughout  this  course,  it  is  mingled  with  a  scanty  mucus-like  fluid, 
secreted  by  the  walls  of  the  epididymis  and  vas  deferens.  The  vesiculse 
seminales  contain  also  a  glairy  fluid,  produced  by  secretion  from  their 
walls,  which  serves  some  secondary  purpose  in  completing  the  formation 
of  the  sperm.  One  of  its  functions  is  no  doubt  to  dilute  the  mass  of 
spermatozoa,  as  they  arrive  from  the  testicles,  and  thus  allow  them 
liberty  of  motion;  as  well  as  to  increase  the  volume  of  the  seminal  fluid 
and  enable  it  to  be  expelled  by  the  muscular  contraction  of  the  parts 
about  the  urethra.  Kolliker  has  found  that  the  spermatozoa  in  the  vas 
deferens  and  epididymis  are  generally  motionless  ;  and  that  they  exhibit 
their  characteristic  movements  only  in  the  vesiculse  seminales  and  in  the 
ejaculated  sperm. 

At  the  moment  of  the  final  evacuation  of  the  sperm,  it  first  passes 
from  the  vesiculae  seminales  into  the  prostatic  portion  of  the  urethra, 
where  it  meets  with  the  secretion  of  the  prostate  gland,  which  is  then 
poured  out  in  unusual  abundance ;  and  farther  on,  there  are  added  the 
secretions  of  Cowper's  glands  and  of  the  remaining  mucous  follicles  of 
the  urethra.  All  these  fluids  increase  the  quantity  of  the  sperm,  and 
serve  as  vehicles  for  the  transport  of  the  spermatozoa. 

Necessary  Conditions  of  Fecundation  by  the  Seminal  Fluid. — There 
are  several  conditions  which  are  essential  to  the  successful  accomplish- 
ment of  the  act  of  fecundation. 

First,  the  spermatozoa  must  be  present  and  in  a  state  of  active 
vitality.  Of  all  the  organic  ingredients,  derived  from  different  sources, 
which  go  to  make  up  the  mixed  seminal  fluid,  as  discharged  from  the 
urethra,  it  is  the  spermatozoa  which  constitute  its  essential  part.  They 
are  the  true  fecundating  element  of  the  sperm,  while  the  others  are  of 
secondary  importance,  and  perform  only  accessory  functions. 

Spallanzani1  found  that  if  frog's  sperm  be  passed  through  a  succes- 
sion of  filters,  so  as  to  separate  the  solid  from  the  liquid  portions,  the 
filtered  fluid  is  destitute  of  fecundating  properties  ;  while  the  sperma- 
tozoa entangled  in  the  filter,  if  mixed  with  a  sufficient  quantity  of  fluid 
of  the  requisite  density  for  dilution,  may  still  be  successfully  used  for 
the  artificial  impregnation  of  eggs.  It  is  well  known  that  animals  or 
men,  after  removal  of  both  testicles,  are  incapable  of  impregnating  the 
female,  notwithstanding  that  all  the  other  generative  organs  may  remain 
uninjured.  The  seminal  fluid,  furthermore,  must  be  in  a  fresh  condition, 
so  that  the  spermatozoa  retain  their  anatomical  characters  and  their 
active  movement.  The  experiments  of  Spallanzani  have  shown  that, 

1  Experiences  pour  servir  a  FHistoire  de  la  Generation.     Gen&ve,  1786. 


MALE  ORGANS  OF  GENERATION  699 

if  the  above  conditions  be  preserved,  the  seminal  fluid,  removed  from 
the  spermatic  ducts  of  the  male,  is  capable  of  fecundating  the  eggs  of 
the  female.  But  if  allowed  to  remain  exposed  to  the  atmosphere,  or  to 
an  unnatural  temperature,  it  becomes  inert.  So  long  as  the  spermatozoa 
continue  in  active  motion,  they  are  usually  found  to  retain  their  physio- 
logical properties  ;  the  cessation  of  this  movement,  on  the  other  hand, 
being  a  sign  that  their  vitality  is  exhausted,  and  that  they  are  no  longer 
capable  of  impregnating  the  egg. 

Secondly,  both  eggs  and  spermatozoa  must  have  arrived  at  a  certain 
degree  of  development  before  fecundation  can  take  place.  Previous  to 
this  time  the  immature  eggs  are  incapable  of  being  impregnated,  and  the 
imperfectly  developed  spermatozoa  have  not  yet  acquired  their  fecun- 
dating power.  The  necessary  process  of  growth  takes  place  within  the 
generative  organs ;  and  when  it  is  complete,  both  the  spermatozoa  of 
the  male  and  the  eggs  of  the  female  are  ready  to  be  discharged,  and  are 
in  condition  to  exert  upon  each  other  the  necessary  influence. 

The  fecundating  power  of  the  spermatozoa,  when  fully  developed,  is 
exceedingly  active.  Spallanzani  found  that  one-fifth  of  a  gramme  of 
the  seminal  fluid  of  the  frog,  diffused  in  water,  was  sufficient  for  the 
impregnation  of  several  thousand  eggs.  The  process  seems  to  be  ac- 
complished almost  instantaneously,  "  since  eggs  which  were  allowed  to 
remain  in  the  fecundating  mixture  for  only  one  second  proved  to  be 
impregnated,  and  were  afterward  hatched  at  the  usual  period." 

Thirdly,  the  spermatozoa  must  come  into  direct  contact  with  the  egg 
or  its  immediate  envelopes.  Spallanzani  first  demonstrated  this  by 
attaching  mature  eggs  to  the  concave  surface  of  a  watch-glass,  which 
he  placed,  in  an  inverted  position,  over  a  second  watch-glass  containing 
fresh  seminal  fluid.  The  eggs,  allowed  to  remain  in  this  way  for  several 
hours,  exposed  to  the  vapor  of  the  fluid  but  without  touching  its  surface, 
were  afterward  found  to  have  failed  of  impregnation  ;  while  others,  which 
were  actually  moistened  with  the  same  seminal  fluid,  became  developed 
into  living  tadpoles. 

Finally,  the  physiological  act  of  fecundation  is  accomplished  by  the 
entrance  of  the  spermatozoa  into  the  interior  of  the  egg,  through  the 
vitelline  membrane,  and  their  union  with  the  substance  of  the  vitellus. 
This  fact  was  first  observed  by  Martin  Barry1  in  the  fecundated  egg 
from  the  Fallopian  tube  of  the  rabbit.  It  has  subsequently  been  seen 
by  Newport2  in  the  frog,  by  Bischoff,  by  Coste,  by  Robin3  in  a  species  of 
leech,  by  Flint4  in  the  pond  snail,  and  by  Weil,5  in  repeated  instances,  in 
the  rabbit.  According  to  some  of  these  observations,  the  mechanism  of 
penetration  is  by  means  of  a  natural  orifice  or  "  micropyle"  existing  in 


1  Philosophical  Transactions.     London,  1840,  p.  533,  and  1843,  p.  33. 

2  Philosophical  Transactions,  1853,  p.  271. 

3  Journal  de  la  Physiologic  de  1'Homme  et  des  Animaux.     Paris,  1862,  tome 
v.  p.  80. 

4  Physiology  of  Man.     New  York,  1874,  vol.  v.  p.  352. 

6  Strieker's  Medizinischer  Jahrbucher.     Wien,  1873,  p.  18. 


700          MALE  ORGANS  OF  GENERATION. 

the  vitelline  membrane,  as  first  indicated  by  Barry.  In  others  no  such 
orifice  has  been  visible;  the  spermatozoa  appearing  to  perforate  the  sub- 
stance of  the  vitelline  membrane  by  the  impulsive  movement  of  their 
filamentous  extremity  (Newport).  Such  a  mode  of  penetration  is  not 
inadmissible,  since  the  much  larger  embryos  of  the  tsenia  and  trichina 
(page  675)  make  their  way  without  difficulty  through  the  substance  of 
the  intestinal  mucous  membrane. 

After  their  arrival  in  the  interior  of  the  vitelline  cavity,  the  sperma- 
tozoa disappear  as  distinct  organic  elements.  Their  substance  unites 
with  that  of  the  vitellus  ;  and  thenceforward  the  fecundated  egg  con- 
sists of  materials  derived  from  both  the  male  and  female  organisms. 
The  greater  portion  of  this  material  is  that  produced  by  the  female ; 
but  that  which  is  supplied  from  the  seminal  filaments  of  the  male  is 
equally  essential  for  the  production  of  an  embryo.  The  offspring, 
accordingly,  may  exhibit  resemblances  to  either  or  both  of  the  indi- 
vidual parents,  since  it  originates  from  a  union  of  both  the  generative 
products. 

Union  of  the  Sexes. — In  most  of  the  lower  animals  there  is  a  peri- 
odical development  of  the  testicles  in  the  male,  corresponding  in  time 
with  that  of  the  ovaries  in  the  female.  As  the  ovaries  enlarge  and  the 
eggs  ripen  in  the  one  sex,  so  in  the  other  the  testicles  increase  in  size,  as 
the  season  of  reproduction  approaches,  and  become  turgid  with  sper- 
matozoa. The  accessory  organs  of  generation  at  the  same  time  share 
the  unusual  activity  of  the  testicles,  and  become  increased  in  vascularity 
and  ready  to  perform  their  part  in  the  reproductive  function. 

In  fishes,  as  a  general  rule,  where  the  testicles  occupy,  in  the  abdomen 
of  the  male,  the  same  relative  position  as  the  ovaries  in  the  female,  these 
organs  enlarge,  become  distended  with  their  contents,  and  project  into 
the  peritoneal  cavity.  Each  of  the  two  sexes  is  then  at  the  same  time 
under  the  influence  of  a  corresponding  excitement.  The  unusual  de- 
velopment of  the  reproductive  organs  reacts  upon  the  general  system, 
and  produces  a  state  of  peculiar  excitability,  known  as  the  condition  of 
"erethism."  The  female,  distended  with  eggs,  feels  the  stimulus  which 
leads  to  their  expulsion ;  while  the  male,  bearing  the  weight  of  the 
enlarged  testicles  and  the  accumulation  of  newly-developed  spermatozoa, 
is  impelled  by  a  similar  sensation  to  the  discharge  of  the  seminal  fluid. 
The  two  sexes  are  led  by  instinct  at  this  season  to  frequent  the  same 
situations.  The  female  deposits  her  eggs  in  some  spot  favorable  to  the 
protection  and  development  of  the  young ;  after  which  the  male,  appa- 
rently attracted  and  stimulated  by  the  sight  of  the  new-laid  eggs,  dis- 
charges upon  them  the  seminal  fluid,  and  their  impregnation  is  accom- 
plished. It  is  in  this  way  that  fecundation  takes  place  in  nearly  all  the 
osseous  fishes,  as  the  trout,  the  salmon,  and  the  stickleback. 

In  instances  like  the  above,  where  the  male  and  female  generative 
products  are  discharged  separately,  the  subsequent  contact  of  the  semi- 
nal fluid  with  the  eggs  would  seem  to  be  dependent  on  the  occurrence 
of  fortuitous  circumstances,  and  their  impregnation,  therefore,  liable  to 


MALE  ORGANS.  OF  GENERATION.          701 

fail.  But,  in  point  of  fact,  the  simultaneous  functional  excitement  of 
the  two  sexes,  and  the  operation  of  corresponding  instincts,  leading 
them  to  ascend  the  same  rivers  and  to  frequent  the  same  spots,  provide 
with  sufficient  certainty  for  the  impregnation  of  the  eggs.  The  number 
of  eggs  produced  by  the  female  is  also  very  large,  the  ovaries  being 
often  so  distended  as  nearly  to  fill  the  abdominal  cavity;  so  that, 
although  many  of  the  eggs  may  be  accidentally  lost,  a  sufficient  number 
will  still  be  impregnated  to  provide  for  the  continuation  of  the  species. 

In  many  of  the  cartilaginous  fishes,  on  the  other  hand,  as  in  sharks, 
rays,  and  skates,  an  actual  contact  takes  place  between  the  two  sexes  at 
the  time  of  reproduction,  and  the  seminal  fluid  of  the  male  is  introduced 
into  the  generative  passages  of  the  female.  Thus  the  eggs  are  fecunda- 
ted while  still  in  the  body  of  the  female,  and  in  many  species  go  through 
with  a  nearly  complete  development  in  this  situation  and  are  born  alive. 

In  the  frog,  the  male  fastens  himself  upon  the  back  of  the  female  by 
means  of  the  anterior  limbs,  which  retain  their  hold  by  a  kind  of  spas- 
modic contraction.  This  continues  for  one  or  more  days,  during  which 
time  the  mature  eggs,  which  have  been  discharged  from  the  ovary,  are 
passing  downward  through  the  oviducts.  As  they  are  expelled  from  the 
anus,  the  seminal  fluid  of  the  male  is  discharged  upon  them,  and  impreg- 
nation takes  place. 

In  serpents,  lizards,  and  turtles,  the  sperm  is  introduced  into  the  female 
generative  passage  at  the  time  of  copulation,  by  means  of  a  single  or 
double  erectile  male  organ.  Of  these  animals,  some  species  lay  their 
eggs  immediately  after  fecundation,  others  retain  them  until  the  embryo 
is  partly  or  fully  developed. 

In  birds,  the  spermatozoa  are  introduced  into  the  sexual  orifice  of 
the  female,  and  make  their  way  into  the  upper  portion  of  the  oviduct, 
where  they  may  be  found  in  active  motion,  mingled  with  the  fluids  of 
this  canal.1  The  vitellus  is  thus  fecundated  immediately  upon  its-  dis- 
charge from  the  ovary,  and  before  it  has  become  surrounded  with  the 
albuminous  and  membranous  envelopes  supplied  by  the  middle  and 
lower  portions  of  the  oviduct. 

Lastly,  in  the  human  species  and  in  mammalians,  where  the  impreg- 
nated egg  is  to  be  retained  in  the  body  of  the  female  parent  during  the 
whole  period  of  its  development,  the  seminal  fluid  is  introduced  into  the 
vagina  and  uterus  by  sexual  congress,  and  meets  the  egg  at  or  soon 
after  its  discharge  from  the  ovary.  A  close  correspondence  between  the 
periods  of  sexual  excitement,  in  the  male  and  the  female,  is  visible  in 
many  of  these  animals,  as  well  as  in  fish,  birds,  and  reptiles.  This  is 
the  case  in  most  species  which  produce  young  but  once  a  year,  as  the 
deer,  the  wolf,  and  the  fox.  In  others,  such  as  the  dog,  the  rabbit,  and 
the  guinea  pig,  where  several  broods  of  young  are  produced  during  the 
year,  or  where,  as  in  man,  the  generative  epochs  of  the  female  recur  at 
short  intervals,  the  time  of  impregnation  is  comparatively  indefinite, 

1  Foster  and  Balfour,  Elements  of  Embryology.     London,  1874,  p.  21. 


702          MALE  ORGANS  OF  GENERATION. 

and  the  generative  apparatus  of  the  male  is  almost  constantly  in  a  state 
of  full  development.  It  is  excited  to  action  at  particular  periods,  ap- 
parently by  some  influence  derived  from  the  condition  of  the  female. 

In  quadrupeds  and  in  the  human  species,  the  contact  of  the  sperm 
with  the  egg,  and  the  fecundation  of  the  latter,  take  place  in  the  gene- 
rative passages  of  the  female ;  either  in  the  uterus,  the  Fallopian  tubes, 
or  upon  the  surface  of  the  ovary;  in  each  of  which  situations  the  sper- 
matozoa have  been  found,  after  the  accomplishment  of  sexual  inter- 
course. 


CHAPTEE    Y. 

PERIODICAL    OYULATION,    AND    THE    FUNCTION 
OF    MENSTRUATION. 

I.  Periodical  Ovulation. 

THE  periodical  ripening  of  the  eggs  and  their  discharge  from  the 
generative  organs  constitute  the  process,  known  by  the  name  of  "ovula- 
tion,"  which  may  be  considered  as  the  primary  act  of  reproduction. 
The  characteristic  phenomena  which  distinguish  the  performance  of  this 
function  depend  upon  the  following  general  laws,  which  apply  with  but 
little  variation  to  all  classes  of  animals. 

1st.  Eggs  exist  originally  in  the  ovaries,  as  part  of  their  natural 
structure.  In  fish,  reptiles,  and  birds,  the  ovary  is  of  comparatively 
simple  texture,  consisting  only  of  a  number  of  Graafian  follicles,  united 
by  an  intervening  stroma  of  loose  connective  tissue,  and  thus  aggre- 
gated into  the  form  of  a  rounded,  elongated,  or  lobulated  organ.  In  the 
mammalians  and  in  man,  its  essential  constitution  is  the  same;  but  its 
connective  tissue  is  denser  and  more  abundant,  and  the  figure  of  the 
organ  is  more  compact.  But  in  all  classes  the  interior  of  each  Graafian 
follicle  is  occupied  by  an  egg,  from  which  the  embryo  is  afterward  pro- 
duced. 

The  process  of  reproduction  was  formerly  regarded  as  essentially 
different  in  the  oviparous  and  the  viviparous  animals.  In  oviparous 
animals,  such  as  most  fishes  and  reptiles  and  all  birds,  the  young 
animal  was  well  known  to  be  formed  from  an  egg  produced  by  the 
female ;  while  in  the  viviparous  species,  or  those  which  bring  forth  their 
young  alive,  as  certain  fishes  and  reptiles  and  all  the  mammalians, 
the  embryo  was  supposed  to  originate  in  the  body  of  the  female  in 
consequence  of  sexual  intercourse.  But  by  the  aid  of  the  microscope, 
as  employed  in  the  examination  of  the  different  organs  and  tissues,  it 
was  subsequently  found  that,  in  mammalians  also,  the  ovaries  contain 
eggs.  The  mammalian  eggs  had  previously  escaped  observation  owing 
to  their  comparatively  simple  structure  and  minute  size;  but  they  were 
nevertheless  found  to  possess  all  the  essential  characters  belonging  to 
the  larger  eggs  of  the  oviparous  animals. 

The  true  difference  in  the  process  of  reproduction,  between  the  two 
classes,  is  therefore  merely  an  apparent,  not  a  fundamental  one.  In  the 
oviparous  fish,  reptiles,  and  birds,  the  egg  is  discharged  by  the  female 
before  or  immediately  after  impregnation,  and  the  embryo  is  subse- 
quently developed  and  hatched  externally.  In  quadrupeds  and  in  the 
human  species,  on  the  other  hand,  the  egg  is  retained  within  the  body 

(  703  ) 


704  OVULATION    AND    MENSTRUATION. 

of  the  female  until  the  embryo  is  developed  ;  and  the  membranes  are 
ruptured  and  the  young  expelled  at  the  same  time.  In  all  classes, 
viviparous  as  well  as  oviparous,  the  young  is  produced  from  an  egg ; 
and  in  all  classes  the  egg,  sometimes  larger  and  sometimes  smaller,  but 
always  consisting  essentially  of  a  vitellus  and  a  vitelline  membrane,  is 
contained  originally  in  the  interior  of  an  ovarian  follicle. 

The  egg  is  accordingly  an  integral  part  of  the  ovarian  tissue.  It 
exists  there  long  before  the  generative  function  is  established,  iind  dur- 
ing the  earliest  periods  of  life.  It  may  be  found  without  difficulty  in 
the  newly  born  female  infant,  and  may  even  be  detected  in  the  foetus 
before  birth.  Its  growth  and  nutrition  are  provided  for  in  the  same 
manner  with  that  of  other  portions  of  the  bodily  structure. 

2d.  The  ovarian  eggs  become  more  fully  developed  at  a  certain  age 
when  the  generative  function  is  about  to  be  established.  During  the 
early  periods  of  life,  the  ovaries  and  their  contents,  like  many  other 
organs,  are  imperfectly  developed.  They  exist,  but  they  are  as  yet 
inactive  and  incapable  of  performing  their  special  function.  In  the 
young  chick,  for  example,  the  ovary  is  of  small  size;  and  the  eggs, 
instead  of  presenting  the  voluminous,  yellow,  opaque  vitellus  which  they 
afterward  exhibit,  are  minute,  transparent,  and  colorless.  In  young 
quadrupeds,  and  in  the  human  female  during  infancy  and  childhood,  the 
ovaries  are  equally  inactive.  They  are  small,  friable,  and  of  a  nearly 
homogeneous  appearance  to  the  naked  eye ;  presenting  none  of  the 
enlarged  follicles,  filled  with  transparent  fluid,  which  afterward  become 
a  characteristic  feature  of  the  organ.  At  this  time,  accordingly,  the 
female  is  incapable  of  bearing  young,  because  the  ovaries  are  inactive, 
and  the  eggs  which  they  contain  immature. 

But  at  a  certain  period,  which  varies  in  the  time  of  its  occurrence  for 
different  species  of  animals,  the  sexual  apparatus  begins  to  enter  upon  a 
state  of  activity.  The  ovaries  increase  in  size,  and  their  circulation 
becomes  more  active.  The  eggs,  which  have  previously  remained  qui- 
escent, take  on  a  rapid  growth,  and  the  structure  of  the  vitellus  is 
completed  by  a  deposit  of  semi-opaque  granular  matter  in  its  interior. 
Arrived  at  this  state,  the  eggs  are  ready  for  impregnation,  and  the 
female  becomes  capable  of  bearing  young.  She  is  then  said  to  have 
arrived  at  the  state  of  "puberty,"  or  that  condition  in  which  the  gene- 
rative organs  are  fully  developed.  This  change  is  accompanied  by  a 
visible  alteration  in  the  S3rstem  at  large,  which  indicates  the  complete 
development  of  the  entire  organism.  In  man}7-  birds,  the  plumage  as- 
sumes at  this  period  more  varied  and  brilliant  colors ;  and  in  the  com- 
mon fowl,  the  comb,  or  "crest,"  enlarges  and  becomes  red  and  vascular. 
In  the  American  deer  (Cervus  virginanus),  the  coat,  which  during  the 
first  year  is  mottled  with  white,  becomes  in  the  second  year  of  a  uniform 
tawny  or  reddish  tinge.  In  nearly  all  species,  the  limbs  become  more 
compact  and  the  body  more  rounded ;  and  the  whole  external  appear- 
ance is  so  altered,  as  to  indicate  that  the  animal  has  arrived  at  the 
period  of  puberty,  and  is  capable  of  reproduction. 


PERIODICAL    OVULATION.  705 

3d.  Successive  crops  of  eggs,  in  the  adult  female,  ripen  and  are  dis- 
charged independently  of  sexual  intercourse.  The  original  formation 
of  the  germ,  in  the  bodies  of  viviparous  animals,  was  formerly  sup- 
posed to  be  a  consequence  of  sexual  intercourse.  Even  after  it  became 
known  that  the  ovaries  of  these  animals  contain  eggs  before  impregna- 
tion, the  discharge  of  the  egg  from  its  follicle  was  thought  to  occur  only 
under  the  influence  of  fecundation ;  and  the  rupture  of  a  follicle  was 
consequently  regarded  as  an  indication  that  sexual  intercourse  had  taken 
place. 

But  subsequent  observation  showed  that  not  only  the  existence,  but 
also  the  ripening  and  discharge  of  the  egg,  are  phenomena  dependent 
on  the  structure  and  functional  activity  of  the  female  organism.  In 
many  fish  and  reptiles,  the  mature  eggs  leave  the  ovary,  pass  through 
the  oviducts,  and  are  discharged  externally  before  coming  in  contact 
with  the  seminal  fluid  of  the  male.  In  the  domestic  fowl  it  is  a  matter 
of  common  observation  that  the  hen,  if  well  supplied  with  nourishment, 
will  continue  to  lay  fully  formed  eggs  without  the  presence  of  the  cock ; 
only  these  eggs,  not  having  been  fecundated,  are  incapable  of  producing 
chicks.  In  oviparous  animals,  therefore,  the  discharge  of  the  egg,  as 
well  as  its  formation,  may  take  place  independently  of  sexual  inter- 
course. 

This  is  also  the  case  in  the  viviparous  quadrupeds.  The  observa- 
tions of  Bischoff,  Pouchet,  and  Coste,  on  the  sheep,  the  pig,  the  bitch, 
and  the  rabbit,  have  demonstated  that  if  the  female  be  carefully  kept 
from  the  male  until  after  the  period  of  puberty  is  established,  and  then 
killed,  examination  of  the  ovaries  will  sometimes  show  that  Graafian 
follicles  have  matured,  ruptured,  and  discharged  their  eggs,  though  no 
sexual  intercourse  has  taken  place.  Sometimes  the  follicles  are  found 
distended  and  prominent  upon  the  surface  of  the  ovary  ;  sometimes  re- 
cently ruptured  and  collapsed ;  and  sometimes  in  various  stages  of  cica- 
trization and  atrophy.  Bischoff,1  in  several  instances  of  this  kind,  found 
the  unimpregnated  eggs  in  the  oviduct,  on  their  way  to  the  cavity  of 
the  uterus.  In  species  of  animals  where  the  ripening  of  the  eggs  takes 
place  at  short  intervals,  as  in  the  sheep,  the  pig,  or  the  cow,  it  is  very 
rare  to  examine  the  ovaries  where  traces  of  a  more  or  less  recent  rup- 
ture of  the  Graafian  follicles  are  not  distinctly  visible. 

One  of  the  most  important  facts,  derived  from  these  observations,  is 
that  the  ovarian  eggs  become  developed  and  are  discharged  in  succes- 
sive crops,  which  follow  each  other  at  periodical  intervals.  In  the  ovary 
of  the  fowl  (Fig.  226),  it  may  be  seen  at  a  glance  that  the  eggs  grow 
and  ripen,  one  after  the  other,  like  fruit  upon  a  vine.  In -this  instance, 
the  process  of  evolution  is  rapid ;  and  it  is  easy  to  distinguish,  at  the 
same  time,  eggs  which  are  almost  microscopic  in  size,  colorless,  and 
transparent ;  those  which  are  larger,  somewhat  opaline,  and  yellowish 

1  M6moire  sur  la  chQte  p£riodique  de  1'oeuf,  Annales  des  Sciences  Naturelles, 
Paris,  Aotit — Septembre,  1844. 


706  OVULATION    AND    MENSTRUATION. 

in  hue  ;  and  finally  those  which  are  fully  developed,  opaque,  of  a  deep 
orange  color,  and  nearly  ready  to  leave  the  ovary. 

Here,  the  difference  between  the  undeveloped  and  the  mature  eggs 
consists  mainly  in  the  size  of  the  vitellus,  which  is  very  much  larger 
than  in  the  quadrupeds.  The  ovarian  follicle  is  distended  .ind  ruptured, 
and  the  egg  finally  discharged,  owing  to  the  pressure  exerted  by  the 
increased1  size  of  the  vitellus. 

In  man  and  mammalians,  on  the  other  hand,  the  microscopic  egg 
never  becomes  large  enough  to  distend  the  Graafian  follicle  by  its  own 
size.  The  rupture  of  the  follicle  and  the  liberation  of  the  egg  are  accord- 
ingly provided  for,  in  these  instances,  by  a  different  mechanism. 

In  the  earlier  periods  of  life,  in  man  and  the  mammalians,  the  egg  is 
contained  in  a  Graafian  follicle  which  closely  embraces  its  exterior,  and 
is  consequently  hardly  larger  than  the  egg  itself.  As  puberty  ap- 
proaches, the  follicles  situated  near  the  free  surface  of  the  ovary  become 
enlarged  by  the  accumulation  of  serous  fluid  in  their  cavity.  At  that 
time,  the  ovary,  if  cut  open,  shows  a  considerable  number  of  globular, 
transparent  vesicles,  the  smaller  of  which  are  deep  seated,  but  which 
increase  in  size  as  they  approach  the  free  surface  of  the  organ.  These 
are  the  Graafian  follicles,  which,  in  consequence  of  the  advancing  matu- 
rity of  their  eggs,  gradually  enlarge  at  the  arrival  of  the  period  of 
generation. 

The  Graafian  follicle  then  consists  of  a  closed  globular  sac,  the  exter- 
nal wall  of  which,  though  quite  translucent,  has  a  fibrous  texture,  and  is 
well  supplied  with  bloodvessels.  This  fibrous  and  vascular  wall  is  dis- 
tinguished by  the  name  of  the  "  vesicular  membrane."  It  is  not  very 
firm  in  texture,  and  if  roughty  handled  is  easily  ruptured. 

The  vesicular  membrane  is  lined  throughout  by  a  layer  of  minute 
granular  cells,  which  form  for  it  a  kind  of  epithelium.  This  layer  is 
termed  the  membrana  granulosa.  It  adheres  but  slightly  to  the  vesicu- 
lar membrane,  and  may  easily  be  detached  by  careless  manipulation 
before  the  follicle  is  opened,  being  then  mingled,  in  the  form  of  light 
flakes  and  shreds,  with  the  serous  fluid  contained  in  its  interior. 

At  the  most  superficial  part  of  the  Graafian  follicle  the  membrana 
granulosa  is  thicker  than  elsewhere.  Its  cells  are  here  accumulated,  in 
a  kind  of  mound  or  "heap,"  which  has  received  the  name  of  the  cumu- 
lus proligerus.  It  is  also  called  the  discus  proligerus,  because  the 
thickened  mass,  when  viewed  from  above,  has  a  nearly  circular  or  disk- 
like  form.  In  the  centre  of  this  thickened  portion  of  the  membrana 
granulosa  the  egg  is  imbedded.  It  is  accordingly  always  situated  at 
the  most  superficial  portion  of  the  follicle,  and  advances  in  this  way 
toward  the  surface  of  the  ovary. 

As  the  period  approaches  at  which  the  egg  is  to  be  discharged,  the 
Graafian  follicle  becomes  more  vascular,  and  enlarges  by  an  increased 
exudation  into  its  cavity.  It  then  begins  to  project  from  the  surface 
of  the  ovary,  still  covered  by  the  albugineous  tunic  and  its  peritoneal 


PERIODICAL    OVULATION. 


707 


investment.  (Fig.  231.)     The  constant  accumulation  of  fluid  in  the  fol- 
licle exerts  such  a  pressure  from  within  outward,  that  the  albugineous 

Fig.  231. 


GRAAFIAN  FOLLICLE,  nearthe  period  of  rupture.-  a.  Vesicular  membrane.  6.  Membrana 
granulosa.  c.  Cavity  of  follicle,  d.  Egg.  e.  Peritoneal  surface.  /.  Tunica  albuginea.  g,  g. 
Tissue  of  the  ovary. 


Fig.  232. 


tunic  and  the  peritoneum  gradually  yield  before  it ;  until  the  Graafian 
follicle  protrudes  from  the  ovary  as  a  tense,  rounded,  translucent  vesicle, 
in  which  fluctuation  can  be  readily 
perceived  on  applying  the  fingers 
to  its  surface.  Finally,  the  pro- 
cess of  effusion  and  distension  still 
going  on,  the  wall  of  the  vesicle 
yields  at  its  most  prominent  por- 
tion, the  contained  fluid  is  driven 
out  with  a  gush,  by  the  elastic  re- 
action of  the  ovarian  tissue,  carry- 
ing with  it  the  egg,  still  entangled 
in  the  cells  of  the  membrana 
granulosa. 

The  rupture  of  the  Graafian 
follicle  is  accompanied,  in  some 
instances,  by  hemorrhage  from  its 
internal  surface,  by  which  its  cavity 

is  filled  with  blood.  This  occurs  in  the  human  species,  also  in  the  pig, 
and  to  some  extent  in  several  other  of  the  lower  animals.  Sometimes, 
as  in  the  cow,  where  no  immediate  hemorrhage  takes  place,  the  Graafian 
follicle,  when  ruptured,  simply  collapses ;  after  which  a  slight  exudation, 
more  or  less  tinged  with  blood,  is  poured  out  during  the  course  of  a 
few  hours. 

This  process  occurs  in  one  or  more  Graafian  follicles  at  a  time,  according 
to  the  number  of  young  produced  at  a  birth.  In  the  bitch  and  the  sow, 
where  each  litter  consists  of  from  six  to  twenty  young  ones,  a  similar 
number  of  eggs  ripen  and  are  discharged  at  each  period.  In  the  mare, 
in  the  cow,  and  in  the  human  female,  where  there  is  usually  but  one 


OVART  WITH  GRAAFIAN  FOLLICLE 
RUPTURED:  at  a,  the  egg,  just  discharged, 
with  a  portion  of  the  membrana  granulosa. 


708  OVULATION    AND    MENSTRUATION. 

foetus  at  a  birth,  the  eggs  are  matured  singly,  and  the  Graafian  follicles 
ruptured,  one  after  the  other,  at  successive  periods  of  ovulation. 

4th.  The  ripening  and  discharge  of  the  egg  are  accompanied  by  a  pe- 
culiar condition  of  the  general  system,  known  as  the  "  rutting"  condition, 
or  "  oestruation."  The  congestion  and  functional  activity  manifested  by 
the  ovaries  at  each  period  of  ovulation,  act  by  sympathy  upon  the  other 
generative  organs  and  produce  in  them  a  greater  or  less  degree  of  ex- 
citement, according  to  the  particular  species  of  animal.  Usually  there 
is  a  certain  amount  of  congestion  of  the  entire  generative  apparatus. 
The  secretions  of  the  vagina  and  neighboring  parts  are  more  particularly 
affected,  being  increased  in  quantity  and  altered  in  quality.  In  the  bitch, 
the  vaginal  mucous  membrane  becomes  red  and  tumefied,  and  pours  out 
a  secretion  which  is  more  or  less  tinged  with  blood.  The  vaginal  secre- 
tions acquire  at  this  time  a  peculiar  odor,  which  appears  to  attract  the 
male,  and  to  excite  in  him  the  sexual  impulse.  An  unusual  tumefaction 
and  redness  of  the  vagina  and  vulva  are  also  perceptible  in  the  rabbit ; 
and  in  some  species  of  apes  there  is  not  only  a  bloody  discharge  from 
the  vulva,  but  also  an  engorgement  and  infiltration  of  the  neighboring 
parts,  extending  to  the  skin  of  the  buttocks,  the  thighs,  and  the  under 
part  of  the  tail.1 

The  system  at  large  is  also  visibly  affected  by  the  process  going  on 
in  the  organs  of  generation.  In  the  cow,  the  approach  of  an  cestrual 
period  is  marked  by  unusual  restlessness.  The  animal  partially  loses 
her  appetite.  She  frequently  stops  browsing,  looks  about  uneasily,  runs 
from  one  side  of  the  field  to  the  other,  and  then  recommences  feeding,  to 
be  disturbed  again  in  a  similar  manner  after  a  short  interval.  The 
motions  are  rapid  and  nervous,  and  the  hide  often  rough  and  disordered; 
and  the  whole  aspect  of  the  animal  indicates  the  presence  of  some  special 
excitement.  After  oestruation  is  fully  established,  the  vaginal  secretions 
show  themselves  in  unusual  abundance,  and  so  continue  for  one  or  two 
days ;  after  which  the  symptoms  subside,  and  the  animal  returns  to  her 
usual  condition. 

It  is  a  noticeable  fact,  in  this  connection,  that  the  female  of  these 
animals  will  allow  the  approach  of  the  male  only  during  and  immedi- 
ately after  the  oestrual  period ;  that  is,  when  the  egg  is  recently  dis- 
charged, and  ready  for  impregnation.  At  other  times,  when  sexual 
intercourse  would  be  necessarily  fruitless,  the  instinct  of  the  animal 
leads  her  to  avoid  it ;  and  the  concourse  of  the  sexes  is  accordingly 
made  to  correspond  in  time  with  the  maturity  of  the  egg  and  its  apti- 
tude for  fecundation. 

II.  Menstruation. 

In  the  human  female,  the  return  of  the  period  of  ovulation  is  marked 
by  a  group  of  phenomena  which  are  known  as  menstruation,  and  which 
are  of  sufficient  importance  to  be  described  lay  themselves. 

1  Pouchet,  ThSorie  positive  de  1'ovulation.     Paris,  1847,  p.  230. 


MENSTRUATION.  709 

During  infancy  and  childhood  the  sexual  system  is  inactive.  No  dis- 
charge of  eggs  takes  place  from  the  ovaries,  and  no  external  phenomena 
show  themselves,  connected  with  the  reproductive  function. 

But  at  the  age  of  fourteen  or  fifteen  years,  a  change  begins  to  mani- 
fest itself.  The  limbs  become  rounder,  the  breasts  increase  in  size,  and 
the  entire  aspect  undergoes  a  peculiar  alteration,  which  indicates  ap- 
proaching maturity.  At  the  same  time  a  discharge  of  blood  takes  place 
from  the  generative  passages,  accompanied  by  some  disturbance  of  the 
general  system,  and  the  female  is  then  known  to  have  arrived  at  the 
period  of  puberty. 

Afterward,  the  bloody  discharge  returns  at  regular  intervals  of  four 
weeks  ;  and,  on  account  of  this  recurrence,  corresponding  with  succes- 
sive lunar  months,  its  phenomena  are  designated  by  the  name  of  the 
"  menses"  or  the  "  menstrual  periods."  The  menses  return  with  regu- 
larity, from  the  time  of  their  first  appearance,  until  the  age  of  about 
forty-five  years.  During  this  period,  the  female  is  capable  of  bearing 
children,  and  sexual  intercourse  is  liable  to  be  followed  by  pregnanc}'. 
After  the  forty-fifth  year,  the  periods  first  become  irregular,  and  then 
cease  altogether ;  and  their  final  disappearance  is  an  indication  that 
pregnancy  cannot  again  take  place. 

During  the  period  above  referred  to,  from  the  age  of  fifteen  to  forty- 
five  years,  the  regularity  and  completeness  of  the  menstrual  periods 
indicate  to  a  great  extent  the  aptitude  of  individual  females  for  im- 
pregnation. All  causes  of  ill  health  which  derange  menstruation  are 
apt  at  the  same  time  to  interfere  with  pregnancy ;  so  that  women  whose 
menses  are  regular  and  natural  are  more  likely  to  become  pregnant, 
after  sexual  intercourse,  than  those  in  whom  the  periods  are  absent  or 
irregular. 

Jf  pregnancy  happen  to  take  place,  however,  at  any  time  within  the 
normal  period,  the  menses  are  suspended  during  its  continuance.  They 
usually  remain  absent,  after  delivery,  until  the  end  of  lactation,  when 
the}'  recommence,  and  continue  to  recur  at  their  regular  periods,  as 
before. 

The  menstrual  discharge  consists  of  mucus  mingled  with  blood. 
When  the  period  is  about  to  come  on,  the  female  is  affected  with  a 
certain  degree  of  discomfort  and  lassitude,  a  sense  of  weight  in  the 
pelvis,  and  more  or  less  disinclination  to  society.  These  symptoms 
are  in  some  instances  slightly  pronounced,  in  others  more  troublesome. 
An  unusual  discharge  of  vaginal  mucus  then  begins  to  take  place,  soon 
becoming  yellowish  or  rusty  brown  in  color,  from  the  admixture  of  a 
certain  proportion  of  blood ;  and  by  the  second  or  third  day  the  dis- 
charge has  the  appearance  of  nearly  pure  blood.  The  unpleasant  sen- 
sations, at  first  manifest,  then  usually  subside ;  and  the  discharge,  after 
continuing  for  two  or  three  days  longer,  grows  more  scanty.  Its  color 
changes  from  red  to  a  brownish  or  rusty  tinge,  until  it  finally  disap- 
pears altogether,  and  the  period  comes  to  an  end. 

The   menstrual   epochs   of  the  human  female   correspond   with   the 


710  OVULATION    AND    MENSTRUATION. 

periods  of  osstruation  in  the  lower  animals.  Their  general  resemblance 
to  these  periods  is  very  evident.  Like  them,  they  are  absent  in  the 
immature  female,  and  begin  to  take  place  only  at  the  period  of  puberty, 
when  the  aptitude  for  impregnation  commences.  Like  them,  they  recur 
during  the  child-bearing  period  at  regular  intervals,  and  are  liable  to 
the  same  interruption  by  pregnancy.  Finally,  their  disappearance 
corresponds  with  the  cessation  of  fertility. 

The  periods  of  oestruation,  in  many  of  the  lower  animals,  are  accom- 
panied with  an  unusual  discharge  from  the  generative  passages,  fre- 
quently more  or  less  tinged  with  blood.  In  the  human  female  the 
bloody  discharge,  though  more  abundant  than  in  other  instances,  differs 
only  in  degree  from  that  in  many  species  of  animals. 

But  the  most  complete  evidence  that  the  period  of  menstruation  is  in 
reality  that  of  ovulation,  is  derived  from  the  results  of  direct  observa- 
tion. A  sufficient  number  of  instances  have  been  observed  to  show  that 
at  the  menstrual  epoch  a  Graafian  follicle  becomes  enlarged,  ruptures, 
and  discharges  its  egg.  Cruikshank1  noticed  such  a  case  so  long  ago 
as  1797.  Ne'grier2  relates  two  instances  in  which,  after  sudden  death 
during  menstruation,  a  bloody  and  ruptured  Graafian  follicle  was  found 
in  the  ovary.  BischofT3  speaks  of  four  similar  cases,  in  three  of  which 
the  follicle  was  just  ruptured,  and  in  the  fourth  distended,  prominent, 
and  ready  to  burst.  Coste4  met  with  several  of  the  same  kind.  Michel5 
found  a  follicle  ruptured  and  filled  with  blood  in  a  woman  who  was 
executed  for  murder  while  the  menses  were  present.  Two  instances 
are  reported  by  Letheby,6  in  women  who  died  while  under  observation 
in  the  London  hospitals,  in  one  of  which  he  succeeded  in  finding  the 
ovum,  which  had  been  expelled  from  the  ovary,  in  the  contents  of  the 
corresponding  Fallopian  tube.  We  have  also  seen  a  Graafian  follicle 
recently  ruptured  and  filled  with  blood,  in  a  woman  who  died  on  the 
second  day  of  menstruation. 

Ovulation.  accordingly,  in  the  human  female,  accompanies  and  forms 
a  part  of  menstruation.  As  the  menstrual  period  comes  on,  a  conges- 
tion takes  place  in  nearly  the  whole  of  the  generative  apparatus  ;  in  the 
Fallopian  tubes  and  the  uterus,  as  well  as  in  the  ovaries  and  their 
contents.  One  of  the  Graafian  follicles  is  especially  the  seat  of  vascular 
excitement  It  becomes  distended  by  the  fluid  accumulated  in  its  cavity, 
projects  from  the  surface  of  the  ovary,  and  is  finally  ruptured ;  the 
process  taking  place  essentially  in  the  same  manner  as  in  the  mammalian 
animals. 

It  is  not  certain  at  what  particular  period  of  the  menstrual  flow  the 
rupture  of  the  follicle  and  discharge  of  the  egg  take  place.  According 

1  Philosophical  Transactions.     London,  1^97,  p.  135. 

2  Recherches  sur  les  Ovaires.     Paris,  1840,  p.  78. 

3  Annales  des  Sciences  Natnrelles.     Paris,  Aout,  1844. 

4  Histoire  du  DSveloppement  des  Corps  Organises.    Paris,  1847,  tome  i.  p.  221. 
6  American  Journal  of  the  Medical  Sciences.     Philadelphia,  July,  1848. 

6  Philosophical  Transactions.     London,  1852,  p.  57. 


MENSTRUATION.  711 

to  the  observations  of  Bischoff,  Pouchet,  and  Raciborski,  the  regular 
time  for  this  rupture  and  discharge  is  not  at  the  commencement,  but 
toward  the  termination  of  the  period.  According  to  those  of  Coste,1 
the  follicle  ruptures  sometimes  in  the  early  part  of  the  menstrual  epoch, 
sometimes  later.  So  far  as  we  can  learn,  therefore,  the  precise  period 
is  not  invariable.  Like  the  menses  themselves,  it  may  take  place  a 
little  earlier,  or  a  little  later,  according  to  circumstances  ;  but  it  always 
occurs  in  connection  with  the  menstrual  flow,  and  constitutes  the  essen- 
tial part  of  the  catamenial  process. 

The  egg,  when  discharged  from  the  ovary,  enters  the  fimbriated 
extremity  of  the  Fallopian  tube,  and  commences  its  passage  toward 
the  uterus.  The  mechanism  by  which  it  finds  its  way  into  and  through 
the  Fallopian  tube  is  different,  in  quadrupeds  and  the  human  species, 
and  in  birds  and  reptiles.  In  the  latter,  the  bulk  of  the  egg  or  eggs  is 
so  great  as  to  fill  or  even  to  distend  the  cavity  of  the  oviduct ;  and  the 
mass  is  accordingly  embraced  by  the  muscular  wall  of  the  canal  and 
carried  downward  by  its  peristaltic  action.  In  the  mammalians,  on  the 
other  hand,  the  egg  is  microscopic  in  size.  The  wide  extremity  of  the 
Fallopian  tube,  directed  toward  the  ovary,  is  lined  with  ciliated  epithe- 
lium; and  the  movement  of  the  cilia,  which  is  from  the  ovary  toward 
the  uterus,  produces  a  kind  of  vortex,  by  which  the  egg  is  drawn  toward 
the  narrow  portion  of  the  tube,  and  thence  conducted  to  the  cavity  of 
the  uterus. 

Accidental  causes  may  sometimes  disturb  the  regular  course  of 
passage  of  the  egg.  It  may  be  arrested  at  the  surface  of  the  ovary, 
and  thus  fail  to  enter  the  tube  at  all.  If  it  be  fecundated  and  go  on  to 
partial  development  in  this  situation,  it  will  give  rise  to  "  ovarian 
pregnancy."  The  egg  may  escape  from  the  fimbriated  extremity  of  the 
Fallopian  tube  into  the  peritoneal  cavity,  and  form  attachments  to  a 
neighboring  organ,  causing  "  abdominal  pregnancy  ;"  or  finally,  it  may 
stop  in  some  part  of  the  Fallopian  tube,  and  so  give  origin  to  u  tubal 
pregnancy." 

The  egg,  immediately  upon  its  discharge  from  the  ovary,  is  ready  for 
impregnation.  If  sexual  intercourse  take  place  about  that  time,  the 
egg  and  the  spermatozoa  meet  in  some  part  of  the  female  generative 
passages,  and  fecundation  is  accomplished.  It  appears  from  the  obser- 
vations of  Bischoff,  Coste,  and  Martin  Barry2  upon  rabbits,  that  the 
contact  between  the  egg  and  the  spermatozoa  may  take  place  either  in 
the  uterus  or  any  part  of  the  Fallopian  tubes,  or  even  upon  the  surface 
of  the  ovary.  If,  on  the  other  hand,  sexual  coitus  do  not  take  place, 
the  egg  passes  down  to  the  uterus  unimpregnated,  loses  its  vitality  after 
a  short  time,  and  is  carried  away  with  the  uterine  secretions. 

It  is  easily  understood,  therefore,  why  sexual  intercourse  should  be 
more  liable  to  be  followed  by  pregnancy  when  occurring  about  the 

1  Histoire  du  DSveloppement  des  Corps  Organises.    Paris,  1847,  tome  i.  p.  221. 
8  Philosophical  Transactions.     London,  1839,  p.  315. 


712  OVULATION    AND    MENSTRUATION. 

menstrual  epoch  than  at  other  times.  This  fact,  established  as  a  matter 
of  observation  by  practical  obstetricians,  depends  upon  the  coincidence 
in  time  between  the  occurrence  of  menstruation  and  the  discharge  of  the 
egg.  Before  its  discharge,  the  egg  is  immature,  and  unfit  for  impregna- 
tion ;  and  after  the  menstrual  period  has  passed,  it  loses  its  freshness 
and  vitality.  The  exajct  length  of  time,  preceding  and  following  the 
menses,  during  which  impregnation  is  possible,  has  not  been  ascer- 
tained. The  spermatozoa,  on  the  one  hand,  retain  their  vitality  for  an 
unknown  period  after  coition,  and  the  egg  for  an  unknown  period  after 
its  discharge.  Both  these  occurrences  may  either  precede  or  follow 
each  other  within  certain  limits,  and  impregnation  may  still  take  place; 
but  the  precise  extent  of  these  limits  is  uncertain,  and  is  probably  more 
or  less  variable  in  different  individuals. 

The  above  facts  indicate  the  true  explanation  of  certain  exceptional 
cases,  in  which  fertility  exists  without  menstruation.  Various  authors 
(Churchill,  Reid,  Yelpeau)  have  related  instances  of  fruitful  women  in 
whom  the  menses  were  scanty  and  irregular,  or  even  entirely  absent. 
The  menstrual  flow  is  only  the  external  accompaniment  of  a  more 
important  process  tnking  place  within.  It  is  habitually  scanty  in  some 
individuals,  and  abundant  in  others.  Such  variations  depend  upon  the 
condition  of  vascular  activity  of  the  system  at  large,  or  of  the  uterine 
organs  in  particular ;  and  though  the  bloody  discharge  is  usually  an 
index  of  the  general  aptitude  of  these  organs  for  impregnation,  it  is 
not  an  absolute  or  indispensable  requisite.  Provided  a  mature  egg  be 
discharged  from  the  ovary  at  the  appointed  period,  menstruation  properly 
speaking  exists,  and  pregnancy  is  possible. 

The  blood  which  escapes  during  the  menstrual  flow  is  supplied  by  the 
uterine  mucous  membrane.  If  the  cavity  of  the  uterus  be  examined 
after  death  during  menstruation,  its  internal  surface  is  found  smeared 
with  a  sanguineous  fluid,  which  may  be  traced  through  the  uterine 
cervix  into  the  vagina.  The  Fallopian  tubes  are  sometimes  congested, 
and  filled  with  a  similar  bloody  discharge.  The  menstrual  blood  has 
also  been  seen  to  exude  from  the  uterine  orifice  in  cases  of  procidentia 
uteri,  as  well  as  in  the  natural  condition  by  examination  with  the 
vaginal  speculum.  It  is  discharged  by  a  kind  of  capillary  hemorrhage, 
and,  as  a  general  rule,  does  not  form  a  visible  coagulum,  owing  to  its 
being  gradually  exuded  from  many  minute  points,  and  mingled  with  a 
large  quantity  of  mucus.  When  poured  out  more  rapidly  or  in  larger 
quantity  than  usual,  as  in  menorrhagia,  the  menstrual  blood  coagulates 
in  the  same  manner  as  that  derived  from  other  sources.  Its  discharge 
takes  place  from  the  whole  extent  of  the  mucous  membrane  of  the  body 
of  the  uterus,  and  is,  at  the  same  time,  the  consequence  and  the  natural 
termination  of  the  periodical  congestion  of  the  parts. 


CHAPTEE    VI. 

THE    CORPUS    LUTBUM,   AND    ITS    CONNECTION 
WITH  MENSTRUATION   AND   PREGNANCY. 

AFTER  the  rupture  of  the  Graafian  follicle  at  the  menstrual  period,  a 
bloody  cavity  is  left  in  the  ovary,  which  is  subsequently  obliterated  by 
a  kind  of  granulating  process,  somewhat  similar  to  the  healing  of  an 
abscess.  The  office  of  the  Graafian  follicle  is  to  provide  for  the  forma- 
tion and  growth  of  the  egg  within  the  ovary.  After  the  ripening  and 
discharge  of  the  egg,  the  Graafian  follicle  has  no  longer  any  function  to 
perform.  It  then  only  remains  for  it  to  pass  through  a  process  of 
obliteration,  as  an  organ-  which  has  become  obsolete.  While  undergoing 
this  process,  the  Graafian  follicle  is  at  one  time  converted  into  a  pecu- 
liar, solid,  spheroidal  body,  called  the  corpus  luteum;  a  name  derived 
from  the  yellow  color  which  it  acquires  at  a  certain  period  of  its  forma- 
tion. 

In  different  species  of  mammalians,  the  corpus  luteum  is  characterized 
by  certain  peculiarities  of  size,  color,  rapidity  of  growth,  and  disappear- 
ance, which  are  distinctive  for  each  particular  kind  of  animal ;  although 
.  the  general  process  of  its  formation  and  atrophy  is  the  same  in  all.  In 
the  human  female  it  is  marked  by  a  moderately  large  size,  a  brilliant 
yellow  hue  at  a  certain  period  of  its  development,  and  the  presence  of 
blood  in  its  central  cavity,  distinguishable  by  its  color  for  two  or  three 
weeks  after  the  rupture  of  the  follicle.  The  details  of  its  growth  and 
retrocession,  which  follow  a  certain  regular  course  during  the  normal 
recurrence  of  the  menstrual  periods,  are  modified  to  an  appreciable 
degree  by  the  occurrence  of  pregnancy.  In  the  first  instance,  it  is 
known  as  the  corpus  luteum  of  menstruation;  in  the  second  as  the 
corpus  luteum  of  pregnancy. 

I.  Corpus  Luteum  of  Menstruation. 

At  each  menstrual  epoch,  in  the  human  female,  a  Graafian  follicle 
swells,  protrudes  from  the  surface  of  the  ovary,  ruptures,  and  discharges 
its  mature  egg.  At  the  moment  of  rupture,  or  immediately  afterward, 
a  somewhat  abundant  hemorrhage  takes  place  from  the  follicle,  and 
its  cavity  is  filled  with  blood.  This  blood  coagulates  soon  after  its 
exudation,  as  it  would  if  extravasated  elsewhere,  and  the  coagulum 
is  retained  in  the  interior  of  the  Graafian  follicle.  The  opening  by  which 
the  egg  makes  its  escape  is  usually  a  minute  rounded  perforation,  often 
not  more  than  one  millimetre  in  diameter.  A  small  probe,  introduced 


714 


CORPUS    LUTEUM. 


233. 


GRAAFIAN  FOLLICLE 
of  the  human  ovary;  re- 
cently ruptured  during 
mestruation,  and  filled  with 
coagulated  blood ;  longitu- 
dinal section. — a.  Tissue  of 
the  ovary,  containing  un- 
ruptured  Graaflan  follicles. 
b.  Vesicular  membrane  of 
the  ruptured  follicle,  c. 
Point  of  rupture. 


through  this  opening,  passes  directly  into  the  cavity  of  the  Graafian 
follicle.  If  the  follicle  be  opened  at  this  time  by  a  longitudinal  incision 
through  the  substance  of  the  ovary  (Fig.  233), 
it  will  be  seen  to  form  a  globular  cavity,  between 
one  and  two  centimetres  in  diameter,  containing 
a  soft,  recent,  dark-colored  coagulum.  The  co- 
agulum  has  no  organic  connection  with  the  walls 
of  the  follicle,  but  lies  loose  in  its  cavity,  and 
may  be  easily  turned  .out  with  the  handle  of  a 
knife.  There  is  sometimes  a  slight  mechanical 
adhesion  of  the  clot  to  the  edges  of  the  lacerated 
opening ;  but  there  is  no  continuity  of  substance 
between  them,  and  the  clot  may  be  separated  by 
careful  manipulation.  The  membrane  of  the 
vesicle  presents  at  this  time  a  smooth,  trans- 
parent, and  vascular  internal  surface. 

An  important  change  soon  afterward  begins 
to  take  place,  both  in  the  central  coagulum  and 
in  the  vesicular  membrane. 

The  clot,  which  is  at  first  large,  soft,  and 
gelatinous,  begins  to  contract;  and  the  serum 
separates  from  the  coagulum  proper.  The  serum, 
as  it  separates,  is  absorbed  by  the  neighboring 
parts;  and  the  clot,  accordingly,  grows  smaller  and  denser  than  before. 
At  the  same  time  the  coloring  matter  of  the  blood  undergoes  the  usual 
changes  which  occur  in  it  after  extravasation,  and  is  partially  reab- 
sorbed  together  with  the  serum.  This  second  change  is  somewhat  less 
rapid  than  the  former,  but  a  diminution  of  color  is  very  perceptible  in 
the  clot,  at  the  expiration  of  two  weeks  from  the  rupture  of  the  follicle. 
The  vesicular  membrane  during  this  time  is  beginning  to  undergo  a 
process  of  development,  by  which  it  becomes  thickened  and  convoluted, 
and  tends  partially  to  fill  the  cavity  of  the  follicle.  The  hypertrophy 
and  convolution  of  the  vesicular  membrane  commences  first  and  pro- 
ceeds most  rapidly  at  the  deeper  part  of  the  follicle,  opposite  the  situa- 
tion of  the  rupture.  From  this  point,  the  membrane  becomes  thinner 
and  less  convoluted  as  it  approaches  the  surface  of  the  ovary  and  the 
edges  of  the  ruptured  orifice. 

At  the  end  of  three  weeks,  the  hypertrophy  of  the  vesicular  mem- 
brane has  reached  its  maximum.  The  ruptured  Graafian  follicle  has 
now  become  so  completely  solidified  by  the  growth  above  described, 
and  by  the  condensation  of  its  clot,  that  it  presents  the  appearance  of 
a  new  bod}r  imbedded  in  the  ovarian  tissue,  and  receives  the  name  of 
corpus  luteum,  although  its  yellow  color  is  not  yet  distinctly  developed. 
It  forms  a  perceptible  prominence  on  the  surface  of  the  ovary,  and  may 
be  felt  as  a  well-defined  rounded  tumor,  nearly  always  somewhat  flat- 
tened from  side  to  side.  It  measures  about  19  millimetres  in  length 


CORPUS  LUTEUM  OF  MENSTRUATION. 


715 


Fig.  234. 


HUMAN  OVARY  cut  open,  show- 
ing a  corpus  luteum,  divided  longi- 
tudinally ;  three  weeks  after  men- 
struation. From  a  girl,  twenty  years 
of  age,  dead  of  haemoptysis. 


and  about   12  millimetres  in  depth.     On  its  surface  may  be  seen  a 
minute  cicatrix,  occupying  the  spot  of  the  original  rupture. 

On  cutting  it  open  at  this  time  (Fig.  234),  the  corpus  luteum  is  seen 
to  consist,  as  above  described,  of  a  central  coagulum  and  a  convoluted 
wall.  The  coagulum  is  semi-transparent, 
of  a  gray  or  light  greenish  color,  more  or 
less  mottled  with  red.  The  convoluted 
wall  is  about  3  millimetres  thick  at  its 
deepest  part,  and  of  an  indefinite  yellow- 
ish or  rosy  hue,  not  very  different  in 
tinge  from  the  rest  of  the  ovarian  tissue. 
The  convoluted  wall  and  the  contained 
clot  lie  simply  in  contact  with  each  other, 
as  at  first,  without  any  intervening  or- 
ganic connection ;  and  they  may  still  be 
readily  separated  from  each  other  by  the 
handle  of  a  knife  or  the  flattened  end  of 
a  probe.  The  whole  corpus  luteum  may 
also  be  stripped  out,  or  enucleated  from 
the  ovarian  tissue,  just  as  might  have 
been  done  with  the  Graafian  follicle  pre- 
viously to  its  rupture.  When  separated 
in  this  way  from  the  neighboring  parts,  it  presents  itself  under  the 
form  of  a  solid  globular  or  flattened  mass,  with  a  convoluted  external 
surface  covered  with  the  remains  of  the  connective  tissue  by  which  it; 
was  previously  united  with  the  substance  of  the  ovary. 

We  have  had  an  opportunity  of  examining  a  corpus  luteum  of  this 
period,  in  an  ovary  immediately  after  its  removal  from  the  body  of  the 
living  woman.  It  was  on  the  occasion  of  the  extirpation  by  Prof.  T,  T. 
Sabine,  in  1874,  of  the  left  ovary  for  obstinate  ovarian  neuralgia,  from 
an  unmarried  woman,  otherwise  healthy,  25  years  of  age.1  The  last 
menstrual  period  had  terminated  exactly  three  weeks  before  the  date 
of  the  operation,  and  a  new  one  commenced  twenty-four  hours  after- 
ward. The  extirpated  ovary  presented  a  perfectly  normal  appearance, 
and  contained  a  corpus  luteum  similar  in  all  respects  to  that  represented 
in  Figure  234.  Its  convoluted  wall  was  fully  formed,  without  any  dis- 
tinctly marked  yellow  tinge,  and  the  central  coagulum  was  partly,  but 
not  entirely,  decolorized.  The  patient  recovered  without  difficulty. 

After  the  third  week  from  the  close  of  menstruation,  the  corpus 
luteum  passes  into  a  retrograde  condition.  It  diminishes  perceptibly 
in  size,  and  the  central  coagulum  continues  to  be  absorbed  and  loses 
still  farther  its  coloring  matter.  The  whole  body  undergoes  a  process 
of  partial  atrophy ;  and  at  the  end  of  the  fourth  week  it  is  less  than  10 
millimetres  in  its  longest  diameter  (Fig.  235).  The  external  cicatrix 
may  still  usually  be  seen,  as  well  as  the  point  where  the  central  coagu- 


1  New  York  Medical  Journal,  January,  1875,  p.  37. 


716 


CORPUS    LUTEUM. 


Fig.  235. 


HUMAN  OVARY,  show- 
ing a  corpus  luteum,  four 
weeks  after  menstruation; 
from  a  woman  dead  of  apo- 
plexy. 


lum  comes  in  contact  with  the  peritoneal  surface.  There  is  still  no 
organic  connection  between  the  central  coagulum  and  the  convoluted 
wall ;  but  the  partial  condensation  of  the  clot 
and  the  continued  folding  of  the  wall  prevent 
the  separation  of  the  two  being  so  easily  accom- 
plished as  before.  The  entire  corpus  luteum 
may  still  be  extracted  from  its  bed  in  the  ova- 
rian tissue. 

The  color  of  the  convoluted  wall,  during  this 
stage,  instead  of  fading,  like  that  of  the  fibrinous 
coagulum,  becomes  more  strongly  marked.  From 
having  a  dull  yellowish  or  rosy  hue,  as  at  first, 
it  gradually  assumes  a  more  decided  yellow. 
This  change  of  color  is  produced  simultane- 
ously with  a  kind  of  fatty  degeneration  which 
takes  place  in  its  texture ;  a  large  quantity  of 
oil-globules  being  deposited  in  it  at  this  time, 
which  are  recognizable  under  the  microscope. 
At  the  end  of  the  fourth  week,  the  alteration  in 
hue  is  complete ;  and  the  outer  wall  of  the  cor- 
pus luteum  is  then  of  a  clear  chrome  yellow  color,  by  which  it  is  readily 
distinguished  from  the  neighboring  tissues. 

After  this  period,  the  process  of  degeneration  goes  on  rapidly.     The 
clot  becomes  more  dense  and  shrivelled,  and  is  converted  into  a  minute, 

stellate,  white,  or  reddish-white  cicatrix.  The 
yellow  wall  becomes  softer  and  more  friable, 
and  shows  less  distinctly  the  marking  of  its 
convolutions.  At  the  same  time  its  surface 
becomes  confounded  with  the  central  coagu- 
lum on  the  one  hand,  and  with  the  neighbor- 
ing parts  on  the  other,  so  that  it  is  no  longer 
possible  to  separate  them  fairly  from  each 
other.  At  the  end  of  eight  or  nine  weeks 
(Fig.  236)  the  whole  mass  is  reduced  to  the 
condition  of  an  insignificant,  yellowish,  cica- 
trix-like  spot,  measuring  about  6  millimetres 
in  its  longest  diameter,  in  which  the  original 
texture  of  the  corpus  luteum  can  be  recog- 
nized only  by  the  peculiar  folding  and  color- 
ing of  its  constituent  parts.  Subsequently 
its  atrophy  goes  on  less  rapidly,  and  a  period  of  seven  or  eight  months 
sometimes  elapses  before  its  complete  disappearance. 

The  corpus  luteum,  accordingly,  is  a  formation  which  results  from 
the  obliteration  of  a  ruptured  Graafian  follicle.  Under  ordinary  con- 
ditions, a  corpus  luteum  is  produced  at  every  menstrual  period ;  and 
notwithstanding  the  rapidity  of  its  retrogression  and  atrophy,  a  new 
one  is  always  formed  before  its  predecessor  has  entirely  disappeared. 


Fig.  236. 


HUMAN  OVARY,  showing  a 
corpus  luteum,  nine  weeks  after 
menstruation  ;  from  a  girl  dead 
of  tubercular  meningitis. 


CORPUS    LUTEUM    <JF    PKEGNANCY.  717 

When,  therefore,  we  examine  the  ovaries  of  a  healthy  female,  in  whom 
the  menses  have  recurred  with  regularity  for  some  time  previous  to 
death,  several  corpora  lutea  will  be  met  with,  in  different  stages  of 
growth.  We  have  found,  under  such  circumstances,  four,  five,  six,  and 
even  eight  corpora  lutea  in  the  ovaries  at  the  same  time,  perfectly  dis- 
tinguishable by  their  texture,  though  very  small,  and  most  of  them  in 
a  state  of  advanced  retrogression.  They  finally  disappear  altogether, 
and  the  number  of  those  present  in  the  ovary  no  longer  corresponds 
with  that  of  the  Graafian  follicles  which  have  been  ruptured. 

II.  Corpus  Lnteum  of  Pregnancy. 

The  process  above  described  takes  place  at  every  menstrual  period, 
independently  of  impregnation  and  sexual  intercourse.  The  mere  pre- 
sence of  a  corpus  luteum,  therefore,  is  no  indication  that  pregnancy  has 
existed,  but  only  that  a  Graafian  follicle  has  been  ruptured  and  its 
contents  discharged.  It  is  found,  nevertheless,  that  when  pregnancy 
takes  place,  the  appearance  of  the  corpus  luteum  becomes  so  modified  as 
to  be  readily  distinguished  from  that  which  follows  the  ordinary  men- 
strual process. 

The  distinction  between  these  two  kinds  of  corpora  lutea  is  not  an 
essential  or  fundamental  difference ;  since  they  both  originate  in  the 
same  way,  and  are  composed  of  the  same  structures.  It  is  only  a  differ- 
ence in  the  rapidity  and  degree  of  their  development.  While  the  corpus 
luteum  of  menstruation  passes  rapidly  through  its  different  stages,  and 
is  soon  reduced  to  a  condition  of  atroplrv,  that  of  pregnancy  continues 
.its  development  for  a  longer  time,  attains  a  larger  size  and  firmer 
organization,  and  disappears  at  a  much  later  period. 

This  variation  in  the  history  of  the  corpus  luteum  depends  upon  the 
condition  of  the  pregnant  uterus.  This  organ  exerts  a  sympathetic 
action,  during  pregnancy,  upon  many  other  parts  of  the  system.  The 
stomach  becomes  irritable,  the  appetite  is  capricious,  and  even  the 
mental  faculties  and  the  moral  disposition  are  frequently  more  or  less 
affected.  The  ovaries  feel  the  influence  of  gestation  more  decidedly 
than  other  organs,  since  they  are  more  closely  connected  with  the  uterus 
in  the  ordinary  performance  of  their  function.  The  moment  that  preg- 
nancy takes  place,  menstruation  is  arrested.  No  more  eggs  come  to 
maturity,  and  no  more  Graafian  follicles  are  ruptured,  during  the  whole 
period  of  gestation.  It  is  not  surprising  that  the  growth  of  the  corpus 
luteum  should  also  be  modified,  by  an  influence  which  affects  so  pro- 
foundly the  system  at  large,  as  well  as  the  ovaries  in  particular. 

During  the  first  three  weeks  of  its  formation  the  growth  of  the  corpus 
luteum  is  the  same  in  the  impregnated  as  in  the  unimpregnated  condition. 
But  after  that  time  a  difference  becomes  manifest.  Instead  of  com- 
mencing a  retrograde  course  during  the  fourth  week,  the  corpus  luteum 
of  pregnancy  continues  its  development.  The  external  wall  grows 
thicker,  and  its  convolutions  more  abundant.  Its  color  changes,  as 


718 


CORPUS    LUTEUM. 


Fig.  237. 


CORPUS  LUTEUM  of  pregnancy,  at  the  end 
of  the  second  month  ;  from  a  woman  dead  from 
induced  abortion. 

Fig.  238. 


previously  described,  to  a  bright  yellow ;  and  there  is  a  deposit  of  fatty 
matter  in  the  form  of  microscopic  globules. 

By  the  end  of  the  second  month,  the  corpus  luteum  has  so  increased 
in  size  as  to  measure  22  millimetres  in  length  by  12  or  13  millimetres 
in  depth  (Fig.  23?).  The  central  coagulurn  has  by  this  time  become 
almost  entirely  decolorized,  and  presents  the  appearance  of  a  purely 

fibrinous  deposit.  Sometimes 
it  is  found  that  a  part  of  the 
serum,  during  its  separation 
from  the  clot,  has  accumulated 
in  the  centre  of  the  mass,  as 
was  the  case  in  Fig.  237,forn> 
ing  a  little  cavity  containing  a 
clear  fluid  and  inclosed  by  a 
fibrinous  layer,  the  remains  of 
the  solid  portion  of  the  clot. 
The  existence  of  such  a  cavit}^ 
however,  is  only  an  occasional, 
not  a  constant,  phenomenon. 
More  frequently,  the  fibrinous 
clot  is  solid  throughout,  the 
serum  being  gradually  ab- 
sorbed, as  it  separates  sponta- 
neously from  the  coagulum. 

During  the  third  and  fourth 
months,  the  enlargement  of  the 
corpus  luteum  continues  ;  and 
at  the  end  of  that  time  it 
may  measure  22  millimetres 
in  length  by  18  or  19  milli- 
metres in  depth.  Its  flattened 
form  is  very  manifest,  so  that, 
in  a  longitudinal  section,  it 
may  present  a  nearly  circular 
outline,  as  in  Fig.  238,  while  in  a  transverse  section  it  is  a  narrow  oval. 
The  convoluted  wall  is  still  more  highly  developed  than  before,  having 
a  thickness,  at  its  deepest  part,  of  nearly  5  millimetres,  or  double  that 
presented  at  the  same  point  in  the  corpus  luteum  of  menstruation,  when 
at  its  largest  size.  Its  color,  however,  has  already  begun  to  fade,  and  is 
of  a  dull  yellowish  tinge.  The  central  coagulum,  perfectly  colorless  and 
fibrinous  in  appearance,  is  often  so  much  flattened  by  the  lateral  com- 
pression of  its  mass,  that  it  is  hardly  2  millimetres  in  thickness.  The 
other  relations  between  the  different  parts  remain  the  same. 

The  corpus  luteum  has  now  attained  its  maximum  of  development, 
and  continues  without  any  very  perceptible  alteration  during  the  fifth 
and  sixth  months.  It  then  begins  to  retrograde,  diminishing  in  size 
during  the  seventh  and  eighth  months.  Its  external  wall  fades  still 


CORPUS  LUTKUM  of  pregnancy,  at  the  end  of 
the  fourth  month  ;  from  a  woman  dead  by  poison. 


CORPUS  LUTEUM  OF  PREGNANCY. 


719 


Fig.  239. 


CORPUS  LUTEUM  of 
pregnancy,  at  term,  from  a 
woman  dead  in  delivery 
from  rupture  of  the  uterus. 


more,  becoming  of  a  faint  yellowish-white  color,  not  unlike  that  pre- 
sented at  the  end  of  the  third  week.  Its  texture  is  thick,  soft,  and 
elastic,  and  it  is  strongly  convoluted.  An  abundance  of  fine  red  vessels 
can  be  seen  penetrating  from  the  exterior  into 
the  interstices  of  its  convolutions.  The  central 
coagulum  is  reduced  by  this  time  to  the  condi- 
tion of  a  whitish  radiated  cicatrix. 

Its  atrophy  continues  during  the  ninth  month. 
At  the  termination  of  pregnancy,  it  is  reduced  in 
size  to  12  or  13  millimetres  in  length  and  less 
than  10  millimetres  in  depth.  (Fig.  239.)  It  is 
then  of  a  faint  indefinite  hue,  but  little  contrasted 
with  the  remaining  tissues  of  the  ovary.  The 
central  cicatrix  has  become  very  small,  and  ap- 
pears only  as  a  thin  whitish  lamina,  with  radi- 
ating processes  which  penetrate  between  the  in- 
terstices of  the  convolutions.  The  whole  mass 
is  still  quite  firm  to  the  touch,  and  is  readily 
distinguishable,  both  from  its  size  -and  texture, 
as  a  prominent  feature  in  the  ovarian  tissue, 
and  a  reliable  indication  of  pregnancy.  The 
convoluted  structure  of  the  external  wall  is  very 
perceptible,  and  the  point  of  rupture,  with  its  external  peritoneal  cicatrix, 
still  distinctly  visible. 

After  delivery,  the  corpus  luteum  retrogrades  rapidly.  At  the  end  of 
eight  or  nine  weeks,  it  has  become  so  much  altered  that  its  color  is  no 
longer  distinguishable,  although  indications  of  its  convoluted  structure 
may  still  be  discovered  by  close  examination.  These  traces  of  its 
existence  remain  for  a  long  time  afterward,  more  or  less  concealed  in 
the  ovarian  tissue.  We  have  distinguished  them,  in  one  instance,  so 
late  as  nine  and  a  half  months  after  delivery.  They  finally  disappear 
entirely,  together  with  the  external  cicatrix  which  previously  marked 
their  situation. 

During  the  existence  of  gestation,  the  process  of  menstruation  being 
suspended,  no  new  Graafian  follicles  are  ruptured,  and  no  new  corpora 
lutea  are  produced ;  and  as  the  old  ones,  formed  before  the  period  of 
conception,  fade  and  disappear,  the  corpus  luteum  which  marks  the 
occurrence  of  pregnancy  after  a  time  exists  alone  in  the  ovary.  In 
twin  pregnancies,  we  of  course  find  two  corpora  lutea  in  the  ovaries ; 
but  these  are  precisely  similar  to  each  other,  and,  being  evidently  of  the 
same  date,  need  not  give  rise  to  any  confusion.  Where  there  is  but  a 
single  foetus  in  the  uterus,  and  the  ovaries  contain  two  corpora  lutea  of 
similar  appearance,  one  of  them  belongs  to  an  embryo  which  has  been 
blighted  in  the  early  part  of  pregnancy,  and  has  failed  of  its  develop- 
ment. The  remains  of  the  blighted  embryo  may  sometimes  be  dis- 
covered, in  such  cases,  in  some  part  of  the  Fallopian  tube,  where  it  has 
been  arrested  in  its  descent  toward  the  uterus. 


720 


COKPUS    LUTEUM. 


After  lactation  has  come  to  an  end,  the  ovaries  resume  their  ordinary 
function.  The  Graafian  follicles  mature  and  rupture  in  succession,  as 
before,  and  new  corpora  lutea  follow  each  other  in  alternate  develop- 
ment and  disappearance. 

The  corpus  luteuin  of  menstruation,  therefore,  differs  from  that  of 
pregnancy  in  the  extent  of  its  development  and  the  duration  of  its 
existence.  While  the  former  passes  through  all  the  important  phases 
of  its  growth  and  decline  in  a  period  of  two  months,  the  latter  lasts 
from  nine  to  ten  months,  and  presents,  during  a  great  portion  of  the 
time,  a  larger  size  and  a  more  solid  organization.  Even  in  the  corpus 
luteum  of  pregnancy,  the  bright  yellow  color,  which  is  so  important  a 
characteristic,  is  only  temporary  in  duration;  not  making  its  appearance 
till  about  the  end  of  the  fourth  week,  and  again  disappearing  after  the 
sixth  month. 

The  following  table  contains,  in  a  condensed  form,  the  characters  of 
the  corpus  luteum,  as  belonging  to  the  two  different  conditions  of  men- 
struation and  pregnancy,  corresponding  with  different  periods  of  its 
development. 


CORPUS  LUTEUM  OF  MENSTRUATION.    CORPUS  LUTEUM  OF  PREGNANCY. 


At  the  end  of 
three  iveeks. 
One  month. 

Two  months. 


Four  months. 


Six  months. 


Nine  months. 


Twelve  by  nineteen  millimetres  in  diameter;  central  clot  reddish; 

convoluted  wall  pale. 
Smaller  ;  convoluted  wall  bright 

yellow  ;  clot  still  reddish. 
Reduced  to  the  condition  of  an 

insignificant  cicatrix. 


Absent  or  unnoticeable. 


Absent. 


Absent. 


Larger;  convoluted  wall  bright 
yellow;  clot  still  reddish. 

Twelve  by  twenty-two  milli- 
metres in  diameter ;  convo- 
luted wall  bright  yellow  ;  clot 
perfectly  decolorized. 

Eighteen  by  twenty-two  millime- 
tres in  diameter ;  clot  pale  and 
fibrinous;  convoluted  wall  dull 
yellow. 

Still  as  large  as  at  the  end  of 
the  second  month.  Clot  fibri- 
nous. Convoluted  wall  paler. 

Ten  by  thirteen  millimetres  in 
diameter;  central  clot  con- 
verted into  a  radiating  cica- 
trix ;  external  wall  tolerably 
thick  and  convoluted,  but 
without  any  bright  yellow 
color. 


CHAPTEE  VII. 

DEVELOPMENT  OF  THE  IMPREGNATED  EGG— SEG- 
MENTATION OF  THE  VITELLUS  — BLASTODERM- 
FORMATION  OF  ORGANS  IN  THE  FROG. 

THE  egg,  while  still  contained  within  the  ovarian  follicle,  passes 
through  a  series  of  consecutive  changes,  by  which  it  is  finally  brought 
to  the  condition  of  maturity.  During  this  period  it  increases  in  size, 
from  the  insignificant  dimensions  which  it  presents  in  the  earlier  stages 
of  its  formation,  to  those  of  its  complete  development  as  an  ovarian 
egg.  The  vitellus,  at  first  transparent  and  colorless,  is  not  only  en- 
larged, but  becomes  more  or  less  granular  and  opaque  by  the  deposit 
of  new  material  in  a  different  form  ;  and  in  birds  and  reptiles  it  assumes 
a  distinctive  hue,  which  is  generally  orange  or  yellow.  These  modifica- 
tions are  due  to  the  spontaneous  growth  of  the  egg  and  the  parts  in 
which  it  is  inclosed ;  and  they  mark  a  continuous  process  of  develop- 
ment taking  place  independently  in  the  generative  organs  of  the  female. 
The  last  change  which  occurs  in  the  ovarian  egg,  and  that  which  indi- 
cates its  complete  maturity,  is  the  disappearance  of  the  germinative 
vesicle.  This  body,  which  is  in  general  a  distinctive  feature  of  the  ova- 
rian egg,  disappears  a  short  time  previous  to  its  expulsion,  or  even  when 
it  is  just  on  the  point  of  leaving  the  Graafian  follicle. 

The  egg,  therefore,  at  the  time  of  its  discharge  from  the  ovary,  con- 
sists solely  of  the  mature  vitellus,  inclosed  in  the  vitelline  membrane ; 
and  in  this  condition  it  meets  with  the  spermatozoa,  usually  in  some 
part  of  the  Fallopian  tube.  By  the  contact  of  the  male  elements,  and 
their  union  with  its  own  substance,  a  new  stimulus  is  imparted  to  its 
growth;  and  while,  if  unimpregnated,  its  vitality,  on  arriving  at  this 
point,  would  have  reached  its  termination,  the  fecundated  egg,  on  the 
contrary,  starts  upon  a  more  extensive  course  of  development,  by  which 
it  is  finally  converted  into  the  body  of  the  young  animal. 

Deposit  of  Albuminous  Layers  in  the  Fallopian  Tube. — The  egg,  in 
the  first  place,  as  it  passes  down  the  Fallopian  tube,  becomes  covered 
with  an  albuminous  secretion.  In  birds,  this  secretion  is  very  abun- 
dant, and  is  deposited  in  successive  layers  around  the  vitellus,  forming 
the  so-called  "  white  of  egg  "  In  reptiles,  it  is  also  poured  out  in  con- 
siderable quantity,  and  serves  for  the  nourishment  of  the  egg  during  its 
early  growth.  In  mammalians,  albuminous  matter  is  supplied  in  the 
same  way,  though  in  smaller  quantity,  by  the  mucous  membrane  of  the 
Fallopian  tube,  and  envelops  the  egg  in  a  layer  of  nutritious  material. 
This  albuminous  layer,  although  its  absolute  quantity  is  very  small,  is 

(721) 


722 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 


Fig.  240. 


sufficiently  abundant,  in  proportion  to  the  size  of  the  mammalian -egg; 

and  it  serves  for  the  supply  of  organic  material  in  the  earlier  stages  of 

development,  before  the  egg  has  established  its  connection  with  the 

uterine  mucous  membrane. 

Segmentation  of  the  Vitellus. — A  very  important  change  now  takes 

place  in  the  impregnated  egg,  which  is  known  as  the  division,  or  seg- 
mentation, of  the  vitellus.  A  furrow 
shows  itself,  running  round  the  globular 
mass  of  the  vitellus  in  a  vertical  direction, 
which  gradually  deepens  until  it  has  di- 
vided the  vitellus  into  two  separate  halves 
or  hemispheres  (Fig.  240,  a.)  Almost  at 
the  same  time  another  furrow,  running  at 
right  angles  with  the  first,  penetrates  the 
substance  of  the  vitellus,  and  cuts  it  in  a 
transverse  direction.  The  vitellus  is  thus 
divided  into  four  equal  portions  (Fig.  240, 
6),  the  edges  and  angles  of  which  are 
rounded  off,  and  which  are  still  contained 
in  the  cavity  of  the  vitelline  membrane. 
The  spaces  between  them  and  the  internal 
surface  of  the  vitelline  membrane  are  oc- 
cupied by  a  transparent  fluid. 

The  process  thus  commenced  goes  on 
by  a  successive  formation  of  furrows  and 
sections,  in  various  directions.  The  four 
vitelline  segments  already  produced  are 
subdivided  into  sixteen,  the  sixteen  into 
sixty-four,  and  so  on ;  until  the  whole  vi- 
tellus is  converted  into  a  mulberry-shaped 
mass  of  minute,  nearly  spherical  bodies, 
called  the  "vitelline  spheres."  (Fig.  240,  c.) 
The  vitelline  spheres  have  a  somewhat 
firmer  consistency  than  the  original  sub- 
stance of  the  vitellus ;  and  this  consistency 
appears  to  increase  as  they  multiply  in 
numbers  and  diminish  in  size.  At  last 
they  become  so  abundant  as  to  be  closely 
crowded  together  and  compressed  into  po- 
lygonal forms.  (Fig.  240,  d.}  They  have 
by  this  time  been  converted  into  a  layer  of 
cells,  surrounding  the  original  central  cav- 
ity of  the  egg,  and  themselves  enveloped 
by  the  vitelline  membrane. 
The  segmentation  of  the  vitellus  constitutes  the  primary  act  in  the 

development  of  the  impregnated  egg.     It  is  this  remarkable  process 

which  is  the  sign  that  fecundation  has  taken  place,  and  that  the  forma- 


SEGMENTATION  OF  THE 
VIT  KLLUS. 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG.     723 

tion  of  an  embryo  has  commenced.  It  takes  place  in  all  species  of 
animals,  although  it  varies  in  detail  according  to  the  special  constitu- 
tion of  the  egg,  and  the  presence  or  absence  of  accessory  parts.  In  all 
the  mammalia,  as  well  as  in  many  of  the  invertebrates,  where  the  vitellus 
is  very  small,  and  where  the  body  of  the  embryo  immediately  after  its 
formation  is  to  be  supplied  with  nourishment  from  without,  the  process 
is  that  described  above.  In  the  birds,  in  scaly  reptiles,  and  in  many 
fish,  where  the  vitellus  or  yolk  is  of  large  size,  and  contains  additional 
nutritive  matter,  segmentation  takes  place  only  in  a  thin  layer  which 
occupies  the  surface  of  the  great  mass  of  the  yolk ;  and,  beginning  at 
one  spot,  extends  thence  from  within  outward,  so  that  it  advances  more 
rapidly  at  the  centre  of  the  segmenting  region  than  at  its  periphery. 
But  in  all  cases  segmentation  of  the  vitellus  is  the  first  change  to  occur 
in  the  process  of  development,  and  its  result  is  alwaj^s  the  same,  namely, 
to  divide  the  vitellus,  which  was  at  first  of  uniform  texture  throughout, 
into  a  great  number  of  minute  bodies,  which  soon  present  the  character 
of  animal  cells. 

Blastoderm,  or  Germinal  Membrane. — The  cells  which  are  formed,  in 
the  manner  above  described,  by  the  segmentation  of  the  vitellus,  become 
more  closely  packed  as  they  increase  in  number ;  and  finally,  by  their 
mutual  contact,  and  adhesion  at  their  adjacent  edges,  they  serve  to  form 
a  continuous  organized  membrane,  known  as  the  germinal  membrane 
or  blastoderm. 

During  the  formation  of  this  membrane,  moreover,  the  egg,  while 
passing  through  the  Fallopian  tube,  increases  in  size.  The  albuminous 
matter  with  which  it  is  enveloped  becomes  liquefied  ;  and,  being  absorbed 
by  endosmosis  through  the  vitelline  membrane,  furnishes  the  material 
for  the  more  solid  and  extensive  growth  of  the  newly-formed  structures. 
A  certain  quantity  of  fluid  also  accumulates  in  the  central  cavity  of  the 

egg- 

The  next  change  which  takes  place  consists  in  the  division  or  splitting 
of  the  blastoderm  into  two  layers,  which  are  known  as  the  external  and 
internal  blastodermic  layers.  They  are  both  still  composed  exclusively 
of  cells ;  but  those  of  the  external  layer  are  smaller  and  more  compact, 
while  those  of  the  internal  are  larger  and  less  consistent.  The  egg  then 
has  the  form  of  a  globular  sac,  the  walls  of  which  consist  of  three  con- 
centric layers,  tying  in  contact  with  and  inclosing  each  other,  namely : 
1st,  the  structureless  vitelline  membrane  on  the  outside;  2d,the  external 
blastodermic  layer,  composed  of  cells  ;  and  3d,  the  internal  blastodermic 
layer,  also  composed  of  cells.  The  cavity  of  the  egg  is  occupied  by  an 
albuminous  fluid,  absorbed  from  the  exterior  and  destined  to  serve  as 
nutritious  material. 

It  is  by  this  process  that  the  simple  globular  mass  of  the  vitellus  is 
converted  into  an  organized  structure.  For  the  blastoderm,  although 
consisting  only  of  cells  which  are  nearly  uniform  in  size  and  shape,  is 
nevertheless  an  organized  membrane,  made  up  of  anatomical  elements. 
It  is  the  first  sign  of  distinct  organization  which  makes  its  appearance 


124:     DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 

in  the  egg ;  and  as  soon  as  it  is  completed,  the  body  of  the  foetus  is 
formed.  The  blastoderm  is,  in  fact,  the  foetus  in  its  earliest  condition ; 
for  although  its  texture  is  at  this  time  exceedingly  simple,  all  the  various 
organs  of  the  body  will  afterward  be  produced  from  it  by  the  modifica- 
tion of  its  different  parts.  The  further  process  of  formation  is  com- 
paratively simple  in  some  classes  of  animals,  more  complicated  in 
others ;  and  its  general  features  are  most  easily  understood  by  com- 
mencing with  the  study  of  embryonic  development  as  it  takes  place  in 
the  frog. 

Formation  of  Organs  in  the  Embryo. — The  egg  of  the  frog,  when  dis- 
charged and  fecundated,  is  deposited  in  the  water,  enveloped  in  an  elastic 
cushion  of  albuminous  matter.  It  is  thus  freely  exposed  to  the  light, 
the  air,  and  the  moderate  warmth  of  the  sun's  rays,  and  is  supplied, 
with  an  abundance  of  moisture  and  appropriate  nutritious  rftaterial. 
Its  development  is  distinguished  accordingly  by  a  character  of  great 
simplicity ;  since  the  whole  of  the  vitellus  is  directly  converted  into  the 
body  of  the  embryo.  There  are  no  accessory  organs  required,  and  con- 
sequently no  complications  of  the  formative  process. 

The  two  blastodermic  layers,  above  described,  represent  together  the 
commencement  of  the  body  of  the  embryo.  They  serve,  however,  for 
the  production  of  two  different  systems;  and  the  entire  process  of  their 
development  may  be  expressed  as  follows:  The  external  blastodermic 
layer  produces  the  skin,  the  cerebro-spinal  axis,  and  the  organs  of  ani- 
mal life ;  while  the  internal  layer  produces  the  mucous  membrane  of 
the  alimentary  canal,  and  the  organs  of  nutrition. 

The  first  sign  of  advancing  organization  in  the  external  blastodermic 
layer  shows  itself  in  a  thickening  and  condensation  of  its  structure. 
The  thickened  portion  has  the  form  of  an  elongated  oval  spot,  termed 

the  "embryonic  spot"  (Fig.  241),  the  wide 
edges  of  which  are  somewhat  more  opaque 
than  the  rest  of  the  blastoderm.  Inclosed 
within  these  opaque  edges  is  a  narrower 
colorless  and  transparent  space,  the  "  area 
pellucida,"  and  in  its  centre  is  a  delicate 
line,  or  furrow,  running  longitudinally  from 
front  to  rear,  called  the  u  primitive  trace." 
In  the  anterior  portion  of  the  area  pel- 
lucida, the  substance  of  the  blastoderm  rises 
up  in  such  a  manner  as  to  form  two  nearly 

Diagrammatic  view  of  the  IM-  parallel  ridges  or  plates,  which  approach 
PKEGNATED  E o o ,  showing  the  each  other,  from  side  to  side,  over  what 

SSSS^S-T1 *e"ucl"a'  win  be  the  dorsal  '"i*0" of  the  embry°' 

and  are  therefore  called  the  "  dorsal  plates." 

Between  them  is  included  a  groove,  termed  the  "medullary  groove." 
The  dorsal  plates  gradually  meet  each  other  and  coalesce  upon  the 
median  line,  thus  converting  the  intervening  groove  into  a  canal.  The 
coalescence  of  the  edges  of  the  two  dorsal  plates  takes  place  first  in  the 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 


725 


anterior  part  of  the,,  are^pellucida  and  extends  gradually  backward  •, 
and  when  it  is  «jtoule)te  throughout  their  length,  the  whole  of  the 
medullary  groove^BmbeenjKyiverted  into  a  closed  canal.  This  is  the 
"medullary  canal  ]^^d  in  its  cavity  will  afterward  be  formed  the  cere- 
bro-spinal  axis,  by  a  growth  of  nervous  matter  from  its  internal  surface. 
At  its  anterior  extremity,  the  medullary  canal  is  large  and  rounded,  to 
accommodate  the  brain  and  the  medulla  oblongata;  its  remainder  is 
narrow,  and  pointed  posteriorly,  and  is  destined  to  contain  the  spinal 
cord. 

In  a  diagrammatic  section  of  the  egg  at  this  stage,  made  transversely 
to  the  longitudinal  axis  of  the  embryo  (Fig.  242),  the  dorsal  plates  may 
be  seen  approaching  each  other  above,  on  each  side  of  the  medullary 
groove.  At  a  more  advanced  period  (Fig.  243)  they  are  fairly  united 
with  each  other,  and  inclose  the  cavity  of  the  medullary  canal.  At 


Fi?.  242. 


Fig.  243. 


Diagrammatic  section  of  the  impregnated 
EGG  in  an  early  stage  of  development.— 1. 
External  blastodermic  layer.  2,  2.  Dorsal 
plates.  3.  Internal  blastodermic  layer. 


IMPREGNATED  Eoo,  at  a  somewhat 
more  advanced  period. — 1.  Point  of  union 
between  the  abdominal  plates.  2,  2.  Dor- 
sal plates  united  with  each  other  on  the 
median  line  and  inclosing  the  medullary 
canal.  3,3.  Abdominal  plates.  4.  Section 
of  the  spinal  column,  with  laminae  and  ribs. 
6.  Internal  blastodermic  layer. 


the  same  time,  the  edges  of  the  thickened  portion  of  the  blastoderm 
grow  outward  and  downward,  extending  over  the  lateral  portions  of  the 
vitelline  mass.  These  are  called  the  "abdominal  plates;"  and,  as  they 
enlarge,  they  tend  to  approach  each  other  below  and  inclose  the  abdo- 
minal cavity,  as  the  dorsal  plates  united  above,  and  inclosed  the  medul- 
lary canal.  At  last  the  abdominal  plates  actually  unite  on  the  median 
line  (at  i,  Fig.  243),  embracing  the  whole  of  the  internal  blastodermic 
layer  ( 5 ),  which  incloses  in  turn  the  remains  of  the  original  vitellus  and 
the  albuminous  fluid  accumulated  in  its  cavity. 

During  this  time,  there  is  formed,  in  the  thickened  central  part  of 
the  blastoderm,  immediately  beneath  the  medullary  canal,  a  longitudinal 
cartilaginous  cord,  the  "chorda  dorsalis."  Around  the  chorda  dorsalis 


726 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 


are  afterward  developed  the  bodies  of  the  vertebrae  (Fig.  243,4),  and. 
the  oblique  processes  of  the  vertebrae  run  upward  from  this  point  into 
the  dorsal  plates,  while  the  transverse  processes  and  ribs  run  outward 
and  downward  in  the  abdominal  plates,  to  encircle  more  or  less  com- 
pletely the  corresponding  portion  of  the  body. 

In  a  longitudinal  section  of  the  egg,  made  while  this  process  is  going 
on,  the  thickened  portion  of  the  external  blastodermic  layer  (Fig-.  244,  i) 
may  be  seen  in  profile.  The  anterior  portion  (2),  which  will  form  the 
head,  is  thicker  than  the  posterior  (  3  ),  which  will  form  the  tail.  As  the 
whole  mass  grows  rapidly,  both  in  the  anterior  and  the  posterior  direc- 
tion, the  head  becomes  thick  and  voluminous,  while  the  tail  begins  to 
project  backward,  and  the  egg  assumes  an  elongated  form.  (Fig.  245.) 


Fig.  244. 


Fig.  245. 


Diagram  of  FROG'S  EGO,  in  an  early  EGG  OF  FROG,  in  process  of  develop- 

stage    of  development;  longitudinal  sec-  ment. 

tion. — 1.  Thickened  portion  of  external 
blastodermic  layer.  2.  Anterior  extremity 
of  the  embryo.  3.  Posterior  extremity.  4. 
Internal  blastodermic  layer.  6.  Cavity  of 
vitellus. 

The  abdominal  plates  also  meet  upon  its  under  surface,  and  complete 
the  closure  of  the  abdominal  cavity.  The  internal  blastodermic  layer 
is  seen,  in  the  longitudinal  section  of  the  egg,  embraced  by  the  abdo- 
minal plates,  and  inclosing,  as  before,  the  remains  of  the  vitellus. 

As  development  goes  on  (Fig.  246),  the  head  becomes  larger,  and 
shows  traces  of  the  formation  of  organs  of  special  sense.     The  tail  also 

Fig.  246. 


EGG  OF  FROG,  farther  advanced. 


increases  in  size,  and  projects  farther  from  the  posterior  extremity  of 
the  embryo.  The  spinal  cord  runs  in  a  longitudinal  direction  from  front 
to  rear,  and  its  anterior  extremity  enlarges,  to  form  the  brain  and  me- 
dulla oblongata.  In  the  mean  time,  the  internal  blastodermic  layer, 
which  is  subsequently  converted  into  the  intestinal  canal,  has  been  shut 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG.     727 

in  by  the  abdominal  walls,  and  still  forms  a  closed  sac,  of  slightly 
elongated  figure,  without  inlet  or  outlet.  Afterward,  the  mouth  is 
formed  by  means  of  a  perforation,  which  takes  place  through  both 
external  and  internal  layers  at  the  anterior  extremity;  while  a  similar 
perforation,  at  the  posterior  extremity,  results  in  the  formation  of  the 
anus. 

By  a  continuation  of  the  same  process,  the  different  portions  of  the 
external  blastodermic  layer  are  further  developed,  resulting  in  the  com- 
plete formation  of  the  various  parts  of  the  skeleton,  the  integument, 
the  organs  of  special  sense,  and- the  voluntary  muscles  and  nerves.  The 
tail  at  the  same  time  acquires  sufficient  size  and  strength  to  be  capable 
of  acting  as  an  organ  of  locomotion.  (Fig.  247.)  The  intestinal  canal, 

Fig.  247. 


TADPOLE,  fully  developed. 


which  has  been  formed  from  the  internal  blastodermic  layer,  is  at  first  a 
short,  wide,  and  nearly  straight  tube,  running  directly  from  the  mouth 
to  the  anus.  It  soon,  however,  begins  to  grow  faster  than  the  abdominal 
cavity  which  incloses  it,  becoming  longer  and  narrower,  and  is  at  the 
same  time  thrown  into  numerous  curvilinear  folds. 

Arrived  at  this  period,  the  young  tadpole  ruptures  the  vitelline  mem- 
brane, by  which  he  has  heretofore  been  inclosed,  and  leaves  the  cavity 
of  the  egg.  He  at  first  fastens  himself  upon  the  remains  of  the  albu- 
minous matter  deposited  round  the  egg,  and  feeds  upon  it  for  a  short 
period.  He  soon^  however,  acquires  sufficient  strength  and  activity  to 
swim  about  freely  in  search  of  other  food,  propelling  himself  by  means 
of  his  large,  membranous,  and  muscular  tail.  The  alimentary  canal 
increases  in  length  and  becomes  spirally  coiled  up  in  the  abdominal 
cavity,  attaining  a  length  from  seven  to  eight  times  greater  than  that  of 
the  entire  body. 

After  a  time,  a  change  takes  place  in  the  external  form  of  the  animal. 
The  posterior  limbs  are  the  first  to  make  their  appearance,  by  budding 
or  sprouting  from  the  sides  of  the  body  at  the  base  of  the  tail,  (Fig. 
248.)  The  anterior  extremities  are  for  a  time  concealed  beneath  the 
integument,  but  afterward  become  liberated,  and  show  themselves  ex- 
ternally. At  first  both  the  fore  and  hind  legs  are  very  small,  incom- 
plete in  structure,  and  useless  for  purposes  of  locomotion.  They  soon, 
however,  increase  in  size  and  strength ;  while  the  tail,  on  the  contrary, 
ceases  to  grow,  and  becomes  shrivelled  and  atrophied.  The  limbs,  in 
fact,  are  destined  finally  to  replace  the  tail  as  organs  of  locomotion  ;  and 


728     DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 

a  time  at  last  arrives  (Fig.  249)  when  the  tail  has  altogether  disappeared, 
while  the  legs  have  become  fully  developed,  muscular,  and  powerful. 
Then  the  animal,  heretofore  confined  to  an  aquatic  mode  of  life,  becomes 
capable  of  living  upon  land,  and  a  transformation  is  effected  from  the 
tadpole  into  the  frog. 

Fig.  248.  Fig.  249. 


TA  DPOLE,  with  limbs  beginning  to  be  formed.  Perfect  FROG. 

During  the  same  time,  other  changes  of  equal  importance  take  place 
in  the  internal  organs.  The  tadpole  at  first  breathes  by  gills  ;  but  these 
organs  subsequently  become  atrophied,  and  are  replaced  by  lungs.  The 
structure  of  the  mouth,  also,  of  the  integument,  and  of  the  circulatory 
system,  is  altered  to  correspond  with  the  varying  conditions  and  wants 
of  the  growing  organism ;  and  all  these  changes  taking  place,  in  part 
successively  and  in  part  simultaneously,  bring  the  animal  at  last  to  a 
state  of  complete  formation. 

The  process  of  development,  as  thus  far  described,  may  be  recapitu- 
lated as  follows : 

1.  The  germinal  membrane  or  blastoderm,  produced  b}r  the  segmenta- 
tion of  the  vitellus,  consists  of  two  cellular  layers,  namely,  an  external 
and  an  internal  blastodermic  layer. 

2.  The  external  blastodermic  layer  incloses  by  its  dorsal  plates  the 
cerebro-spinal  canal,  and  by  its  abdominal  plates  the  abdominal  or 
visceral  cavity. 

3.  The  internal  blastodermic  layer  forms  the  intestinal  canal,  which 
becomes  lengthened  and  convoluted,  and  communicates  with  the  exterior 
by  a  mouth  and  anus  of  secondary  formation. 

4.  Finally,  the  cerebro-spinal  axis  and  its  nerves,  the  skeleton,  the 
organs  of  special  sense,  the  integument,  and  the  voluntar}^  muscles,  are 
developed  from  the  external  blastodermic  layer ;  while  the  anterior  and 
posterior  extremities  are  formed  from  the  same  layer  by  a  process  of 
sprouting,  or  continuous  growth. 


CHAPTEE  VIII. 

FORMATION  OF  THE  EMBRYO  IN  THE  FOWL'S  EGG. 

IN  the  preceding  chapter  a  condensed  description  has  been  given  of 
the  general  phenomena  of  embryonic  development,  as  illustrated  in  the 
egg  of  the  frog  This  species  is  useful  as  an  example,  to  exhibit  the 
progressive  alterations  of  form  which  lead  to  the  final  production  of 
a  vertebrate  animal  out  of  the  fecundated  vitellus,  uncomplicated  by  the 
presence  of  any  accessory  organs.  But  the  development  of  the  chick,  in 
the  egg  of  the  fowl  during  incubation,  has  been  found  more  favorable 
for  the  study  of  certain  important  details.  The  readiness  with  which  the 
fowl's  egg  may  be  obtained  in  all  the  successive  stages  of  incubation, 
and  the  convenient  size  of  the  embryo  in  the  earlier  periods  of  its  forma- 
tion, have  made  it  a  favorite  subject  of  investigation  for  embryologists ; 
and  some  of  the  most  valuable  discoveries  in  this  department  of  physi- 
ology have  resulted  from  observations  upon  the  young  chick  and  the 
mode  of  formation  of  its  different  organs. 

The  Yolk  and  the  Cicatricula. — The  yolk  of  the  fowl's  egg  represents 
something  more  than  the  vitellus  proper.  Its  principal  mass  consists 
of  an  opaque,  yellow,  semifluid  substance,  the  "yellow  yolk,"  which 
solidifies  on  boiling,  owing  to  its  large  proportion  of  albuminous  matter. 
This  substance  contains  a  great  abundance  of  soft,  spherical,  finely 
granular  bodies,  from  25  to  100  mmm.  in  diameter. 

The  yellow  yolk  is  surrounded  everywhere  by  a  thin  layer  of  nearly 
colorless  appearance,  the  "  white  yolk,"  which  contains,  instead  of  the 
granular  spheres  described  above,  smaller  globular  bodies  with  one  or 
more  brightly  refracting  masses  in  their  interior.  The  albuminous 
matter  of  the  white  yolk,  furthermore,  does  not  solidify  firmly  on  the 
application  of  heat;  so  that  in  a  boiled  egg  the  thin  outer  stratum  of  this 
substance  remains  semifluid.  There  is  also  a  spot  in  the  centre  of  the 
yolk-sphere,  which  is  occupied  by  the  same  material,  and  which  conse- 
quently remains  soft  in  the  boiled  egg ;  the  central  cavity  thus  left 
communicating  with  the  surface  of  the  yolk  by  a  narrow  passage,  like 
the  neck  of  a  flask. 

The  whole  yolk  is  thus  formed  of  two  substances,  which  are  distin- 
guished from  each  other  by  their  microscopic  characters  and  by  their 
comparative  coagulability  at  the  temperature  of  boiling  water.  Neither 
of  the  two  corresponds  with  the  granular  vitellus  of  the  mammalian  egg ; 
and  the  yolk,  as  a  whole,  constitutes  a  deposit  of  nutritious  material, 
superadded  to  the  vitellus  proper,  and  destined  to  be  absorbed  for  the 
support  of  the  embryonic  tissues.  This  yolk,  however,  is  formed,  in. 
47  (  729  ) 


730  FORMATION    OF    THE    EMBRYO. 

birds,  within  the  ovarian  follicle,  and  is,  in  respect  to  its  volume,  the 
main  constituent  of  the  ovarian  egg. 

At  one  point  upon  the  surface  of  the  yolk  of  the  fowl's  egg,  while  still 
contained  within  the  ovarian  follicle,  there  is  a  whitish  circular  spot 
about  5  millimetres  in  diameter,  lying  immediately  beneath  the  vitelline 
membrane.  This  is  the  cicatricula.  It  is  a  thin  layer  of  uniformly 
granular  material,  containing  none  of  the  spherical  bodies  found  in  the 
white  and  yellow  yolk.  Its  granules  are  imbedded  in  a  homogeneous 
substance  of  viscid  consistency,  by  which  they  are  agglutinated  into  a 
disk-like  mass.  In  its  centre  is  contained  the  germinative  vesicle, 
which  is  distinctly  visible  by  its  transparency  and  well-defined  outline, 
until  the  mature  egg  is  ready  to  leave  the  ovary,  when  it  disappears, 
as  in  other  classes  of  animals.  The  cicatricula  of  the  fowl's  egg  cor- 
responds, therefore,  in  its  structure,  though  not  in  its  form,  with  the 
entire  vitellus  of  the  mammalian  egg.  Its  position  is  always  exactly 
above  the  tubular  prolongation  of  white  yolk,  already  described  as 
leading  to  the  central  cavity  of  the  egg. 

Formation  of  the  Blastoderm. — The  fowl's  egg  is  fecundated  soon 
after  leaving  the  ovary,  and  while  in  the  upper  portion  of  the  ovi- 
duct. The  segmentation  of  the  cicatricula  then  begins,  by  a  furrow 
which  passes  across  its  disk,  and  which  is  followed  by  others  running 
in  different  directions.  By  the  continued  multiplication  of  these  fur- 
rows, the  substance  of  the  cicatricula  is  divided  successively  into 
smaller  and  smaller  portions;  the  process  beginning  and  proceeding 
most  rapidly  at  its  centre,  but  extending  thence  outward  to  the  peri- 
phery. When  these  divisions  have  become  reduced  in  size  and  increased 
in  number  to  a  certain  degree,  they  present,  as  in  other  instances,  the 
form  and  structure  of  distinct  cells.  The  cells  are  in  two  layers.  Those 
of  the  upper  layer  are  smaller,  more  numerous,  cylindrical  or  prismatic 

Fig.  250. 


VERTICAL  SECTION  THROUGH  A  PORTION  OF  THE  BLASTODERM  of  a  fowl's 
egg,  at  the  commencement  of  incubation.— 1.  Upper  cellular  layer.  2.  Lower  cellular  layer. 
3,  3.  Larger  cells,  found  in  small  number  beneath  those  of  the  lower  layer.  (Foster  and  Bal- 
four.) 

in  form,  standing  upright  side  by  side,  like  the  cells  of  columnar  epithe- 
lium, and  adherent  to  each  other  by  their  adjacent  surfaces.  According 
to  Foster  and  Balfour1  they  have  a  very  uniform  size  of  9  mmm.,  and 
most,  if  not  all  of  them  are  provided  with  a  distinct  oval  nucleus-  The 

1  Elements  of  Embryology.     London,  1874,  p.  17. 


FORMATION  OF  THE  EMBRYO.  731 

cells  of  the  lower  layer  are  rather  larger,  more  globular  in  form,  and  less 
closely  united  with  each  other.  The  whole  forms  an  organized  cellular 
membrane,  the  blastoderm,  which,  occupies  the  place  of  the  original 
cicatricula. 

Thus  the  blastoderm,  or  germinal  membrane,  is  formed  in  the  impreg- 
nated fowl's  egg  by  a  process  of  segmentation  essentially  similar  to  that 
which  takes  place  in  eggs  of  other  kinds.  It  presents  the  appearance  of 
a  thin  sheet,  of  uniform  texture,  composed  of  nothing  but  cells,  lying 
at  one  spot  upon  the  surface  of  the  yolk.  Its  formation,  which  begins 
immediately  after  the  impregnation  of  the  egg,  continues,  under  the 
influence  of  the  animal  temperature,  during  the  eighteen  or  twenty  hours 
that  the  egg  is  retained  in  the  oviduct  for  the  deposit  of  its  albumen  and 
external  envelopes.  According  to  Foster  and  Balfour,  it  has  reached  the 
condition  of  a  distinct  cellular  membrane  at  the  time  of  the  expulsion 
of  the  egg.  If  afterward  kept  at  a  low  temperature  it  remains  in  this 
state ;  but,  if  subjected  to  natural  or  artificial  incubation  at  a  tempera- 
ture of  38°  (100°  F.),  it  goes  on  to  the  further  development  of  the  body 
of  the  embryo. 

Folds  of  the  Blastoderm. — The  form  of  the  body  of  the  embryo  and 
of  its  different  parts  is  sketched  out,  in  all  cases,  by  means  of  a  series 
of  folds,  which  show  themselves  at  various  points  in  the  blastoderm. 
This  membrane  presents  at  first  a  flat  surface ;  or,  i'f  it  have  a  certain 
degree  of  convexity,  corresponding  with  that  of  the  }Tolk  upon  which  it 
lies,  this  convexity  is  perfectly  uniform,  and  is  too  slightly  pronounced 
to  be  appreciable  within  the  limits  of  the  blastoderm.  But  as  soon  as 
development  begins  to  make  a  definite  progress,  this  uniformity  of  sur- 
face is  broken  by  the  appearance  of  folds  or  ridges,  which  are  directed 
longitudinally  or  transversely,  and  which  thus  mark  the  lines  of  separa- 
tion between  different  parts  of  the  blastoderm.  Such  a  fold,  running  in 
a  curvilinear  direction  from  side  to  side,  marks  the  position  of  the  head 
of  the  embryo,  and  is  called  the  "  head-fold."  The  free  border  of  this 
mass,  projecting  forward  and  above  the  neighboring  portion  of  the  blas- 
toderm, becomes  in  fact  the  head,  which,  as  well  as  the  neck,  is  curved 
more  and  more  forward  and  downward,  in  the  subsequent  stages  of 
embryonic  growth,  with  the  deepening  of  the  fold  which  first  gave  origin 
to  it  as  a  distinct  part.  A  similar  transverse  curvilinear  fold  at  the 
posterior  portion  of  the  area  pellucida,  marks  off  the  hinder  extremity 
of  the  embryo,  and  is  called  the  "  tail-fold."  Longitudinal  folds  are 
also  formed  in  the  same  manner,  one  on  each  side,  which  fix  the  lateral 
limits  of  the  body  of  the  embryo. 

By  this  means,  a  certain  portion  of  the  blastoderm  becomes  distinctly 
marked  off  from  the  rest.  The  part  included  within  the  transverse  and 
longitudinal  folds  is  immediately  recognizable  as  the  body  of  the  embryo; 
while  that  which  remains  outside  these  limits  becomes  developed  into 
accessory  organs,  playing  an  important  though  secondary  part  in  the 
history  of  development.  This  forms  a  marked  distinction  between  the 
process  as  it  takes  place  in  the  fowl's  egg,  and  that  already  described  in 


732  FORMATION    OF    THE    EMBRYO. 

the  egg  of  the  frog.  In  the  frog,  the  whole  of  the  blastoderm  serves  for 
the  formation  of  the  body  of  the  embryo.  In  the  fowl,  only  a  portion 
of  it  is  immediately  devoted  to  that  object ;  while  the  remainder  extends 
itself  over  the  voluminous  yolk,  to  be  employed  for  the  absorption  of 
nutritious  material  and  its  indirect  transfer  to  the  embryonic  tissues. 

But  even  within  the  limits  of  the  body  of  the  embryo,  similar  folds 
of  the  blastoderm  become  visible,  and  are  the  principal  means  of  forma- 
tion for  its  different  organs.  The  earliest  permanent  appearances  of 
this  kind  are  the  longitudinal  ridges  which  include  between  them  the 
"medullary  groove"  (Fig.  252,  I.),  and  which  afterward,  by  coalescing 
with  each  other  along  the  median  line  of  the  back,  inclose  the  medul- 
lary canal  (Fig.  252,  II.).  That  these  ridges  or  "  dorsal  plates,"  as  well 
as  the  groove  between  them,  are  produced  by  the  formation  of  folds,  is 
plain  from  the  fact  that  the  surface  of  the  groove,  while  still  open,  is 
continuous,  over  its  undulating  borders,  with  that  of  the  neighboring 
part  of  the  blastoderm  ;  and  that  after  its  closure,  its  cavity  is  lined 
with  a  layer  of  cells  identical  in  form  with  those  on  the  free  surface  of 
the  blastoderm  above.  It  is  also  shown,  by  transverse  sections  of  the 
embryo  (His,  Foster  and  Balfour),  that  the  folds  in  question  pass 
through  the  whole  thickness  of  the  outer  blastodermic  layer.  Accord- 
ing to  Foster  and  Balfour,  the  medullary  canal,  in  the  fowl's  egg,  is 
completely  closed  at  the  region  of  the  head  on  the  second  day  of  incu- 
bation ;  after  which  the  coalescence  of  its  edges  goes  on  progressively 
from  before  backward. 

The  closure  of  the  abdomen  in  front,  and  the  conversion  of  the  inner 
layer  of  the  blastoderm  into  an  intestinal  canal,  take  place  by  a  similar 
production  of  lateral  folds,  approaching  each  other  along  the  median 
line.  For,  as  the  limits  of  the  body  of  the  embryo  are  marked  off,  on 
each  side,  from  the  rest  of  the  blastoderm  by  an  inverted  fold,  when 
this  fold  becomes  deeper  its  borders  are  brought  nearer  to  each  other. 
Thus  the  body  of  the  embryo  is  at  first  spread  out  on  the  surface  of  the 
vitellus,  lying,  as  it  were,  upon  the  mucous  membrane  of  its  open  alimen- 
tary canal  But  as  the  folds  which  mark  its  lateral  borders  penetrate 
more  deeply  below  the  surface  (Fig.  252,  IV.),  the  sides  of  the  embryo 
shut  in  between  them  a  portion  of  this  mucous  membrane,  and  at  last 
completely  inclose  it  in  the  abdominal  cavity,  in  the  same  manner  as  the 
dorsal  folds  inclose  the  medullary  canal. 

The  folds  of  the  blastoderm,  which  thus  determine  the  configuration 
of  the  embryo,  are  the  result  of  a  special  activity  of  growth  in  par- 
ticular parts  of  the  blastodermic  layers.  If  the  blastoderm  were  to 
grow  only  at  its  edges,  these  would  simply  extend  farther  and  farther 
over  the  vitellus,  the  central  portion  remaining  as  before.  Or  if  it  were 
to  increase  at  a  uniform  rate  in  all  its  parts  at  the  same  time,  its  form 
would  not  necessarily  be  subjected  to  any  special  alteration.  This  is 
what  really  takes  place  during  the  production  of  the  blastoderm  itself. 
The  segmentation  of  the  vitellus,  and  the  organization  of  the  cellular 
layers,  go  on  with  a  similar  activity  in  all  directions,  extending  uni- 


FORMATION    OF    THE    EMBRYO.  783 

formly  from  the  centre  outward.  The  blastoderm  accordingly,  when 
completed,  is  a  smooth,  even  membrane,  having  the  same  texture 
throughout. 

But  when  the  process  of  incubation  commences,  the  blastoderm  grows 
more  rapidly  at  particular  points,  and  along  certain  lines  of  direction, 
than  elsewhere.  What  may  be  the  determining  cause  of  such  a  con- 
centration of  growth  in  special  situations,  it  is  impossible  to  say ;  but 
its  result  is  that  the  blastoderm,  enlarging  more  rapidly  in  one  direction 
than  another,  is  thrown  into  undulations,  which  indicate,  by  their  posi- 
tion and  size,  the  unequal  expansion  of  the  blastodermic  membrane. 
Thus,  if  it  grow  more  rapidly  at  one  particular  point  than  in  any  of  the 
surrounding  parts,  it  will  form  at  that  spot  a  conical  eminence  or  de- 
pression, according  as  it  meets  with  less  resistance  above  or  below.  If 
a  similar  rapidity  of  increase  were  to  affect  a  considerable  portion  of  the 
membrane  along  a  transverse  line,  the  consequence  would  be  a  transverse 
fold ;  and  if  the  same  thing  were  to  occur  in  an  antero-posterior  direc- 
tion, it  would  cause  a  longitudinal  fold.  The  subsequent  history  of  em- 
bryonic development  shows  continual  repetitions  of  this  process,  often 
on  a  much  larger  scale  than  that  exhibited  in  the  blastoderm.  The 
folds  of  the  intestinal  canal,  the  valvulae  conniventes  of  its  mucous 
membrane,  the  convolutions  of  the  brain,  and  the  tubular  windings  of 
the  perspiratory  glands,  with  many  other  analogous  forms,  are  pro- 
duced in  a  similar  way.  All  these  structures  are  at  first  smooth  or 
straight.  They  become  thrown  into  folds  or  convolutions  at  some  period 
during  the  development  of  the  embryo,  whenever  they  grow  more 
rapidly  than  the  surrounding  parts. 

Position  of  the  Embryo  in  the  Egg. — Although  the  blastoderm  is  at 
first  apparently  of  uniform  structure  throughout,  yet  each  particular 
part  has  from  the  beginning  a  physiological  individuality,  which  leads 
to  its  subsequent  development  into  a  special  organ  or  part  of  an  organ. 
This  is  evident  from  the  manner  in  which  the  local  activity  of  nutrition 
gives  rise  to  the  appearance  of  folds,  running  in  definite  directions,  and 
determining  in  this  way  the  future  location  of  the  head,  the  tail,  and 
the  sides  of  the  body.  But  it  is  manifested  still  more  remarkably  in 
the  position  assumed  by  the  entire  embtyo.  The  yolk  of  the  fowl's  egg 
has  a  nearly  regular  spherical  form ;  and  the  cicatricula,  as  well  as  the 
blastoderm  into  which  it  is  converted,  is  a  circular  spot  upon  its  surface. 
The  ovoid  form  presented  by  the  whole  egg,  with  one  round  and  one 
pointed  extremity,  is  given  to  it  by  the  deposit  of  albumen  round  the 
yolk,  in  the  middle  and  lower  parts  of  the  oviduct,  after  fecundation 
has  taken  place.  And  yet,  when  the  rudiments  of  the  embryo  first 
become  peceptible  in  the  area  pellucida,  it  is  so  placed  as  to  lie  cross- 
wise to  the  long  axis  of  the  egg,  with  its  right  side  toward  the  round 
end  and  its  left  side  toward  the  pointed  end.  The  exceptions  to  this 
rule  are  so  few  as  to  show  that,  even  before  incubation  has  commenced, 
one  particular  portion  of  the  circular  blastoderm  is  destined  to  become 


734  FORMATION  OF  THE  EMBRYO. 

the  head  and  another  portion  the  tail ;  and  consequently  that  every  one 
of  the  future  organs  of  the  embryo  has  its  point  of  origin  already  fixed. 

Division  of  the  Blastodermic  Layers. — The  blastoderm  when  first 
formed  consists,  as  above  described,  of  two  layers  of  cells ;  those  of  the 
external  layer  being  cylindrical  and  compact,  those  of  the  internal, 
larger,  rounded,  and  more  loosely  connected.  The  outer  blastodermic 
layer  forms  the  tegumentary  surface  of  the  body  and  the  cavity  of  the 
cerebro-spinal  axis ;  the  inner  is  converted  into  the  mucous  membrane 
of  the  alimentary  canal.  But  between  the  two  there  soon  appears 
another  formation  of  cells,  which  is  sometimes  spoken  of  as  the  third 
or  "  intermediate"  blastodermic  layer.  The  cells  of  this  layer  are  in 
immediate  contact  with,  and  more  or  less  adherent  to,  those  of  the  two 
others  ;  but  they  are  rounded  in  form  and  rather  loosely  united,  in  com- 
parison both  with  those  above  and  below.  The  intermediate  layer,  in 
the  blastoderm  of  the  fowl's  egg,  is  distinctly  formed,  according  to 
Foster  and  Balfour,  in  the  first  twelve  hours  of  incubation. 

The  exact  number  and  designation  of  the  fundamental  layers  of  the 
blastoderm  has  been  and  still  is  the  main  point  of  discrepancy  in  the 
writings  of  embryologists.  There  is  no  difference  of  opinion  as  to  the 
existence  or  destination  of  the  two  principal  layers,  namely,  the  external 
and  internal,  which  are  the  first  to  make  their  appearance,  as  above 
described.  They  form  respective^  thQ  basis  for  the  production  of  the 
external  sensitive  integument  and  cerebro-spinal  axis  on  the  one  hand, 
and  for  the  lining  of  the  alimentary  canal  with  its  adjacent  glandular 
organs  on  the  other.  But  the  intermediate  portion,  formerly  described 
as  the  u  vascular  layer,"  is  connected  both  with  the  organs  of  animal 
life  and  with  those  of  digestion  and  nutrition.  It  is,  therefore,  by  some 
regarded  as  an  independent  layer,  equal  in  original  importance  to  the 
other  two ;  by  others  as  an  accessory  formation,  destined  to  aid  in  the 
development  of  both  the  external  and  internal  parts.  According  to 
His,1  whose  observations  are  among  the  most  extensive  and  valuable 
in  the  department  of  embryology,  the  most  appropriate  enumeration  is 
the  older  one,  of  an  external  and  internal  blastodermic  layer ;  since  the 
cells  of  the  intermediate  portion  remain  attached  partty  to  the  outer 
and  partly  to  the  inner  layer,  when  the  separation  between  the  two 
takes  place  in  the  manner  now  to  be  described. 

Immediately  underneath  the  medullary  canal,  along  the  axial  line  of 
the  body  of  the  embryo,  there  is  formed  in  the  intermediate  layer  of 
the  blastoderm  a  cylindrical  cord,  termed  the  "chorda  dorsalis"  (Fig. 
252,  6),  which  marks  the  situation  of  the  future  spinal  column.  For 
a  certain  distance  on  each  side  of  the  chorda  dorsalis,  the  component 
parts  of  the  blastoderm  remain  in  contact  with  each  other  throughout 
its  thickness.  But  farther  outward,  toward  the  edges  of  the  embryo, 
it  separates,  by  a  horizontal  division  or  cleavage,  into  two  laminae,  an 
outer  and  inner,  or  upper  and  lower.  This  cleavage  takes  place  appa- 

1  Unsere  Korperform.     Leipzig,  1875,  p.  38. 


FORMATION    OF    THE    EMBRYO.  735 

rently  in  consequence  of  an  unequal  rapidity  of  growth  in  the  two  blas- 
todermic  layers.  Both  layers  are  now  extending  outward,  downward, 
and  inward,  by  the  deepening  of  the  lateral  longitudinal  folds ;  tending 
to  approach  the  median  line  and  thus  shut  in  the  abdomen  and  ali- 
mentary canal.  But  the  external  layer,  which  is  to  form  the  walls  of 
the  abdomen,  grows  more  rapidly,  and  tends  to  inclose  a  larger  space, 
than  the  internal  layer,  which  is  to  form  the  lining  membrane  of  the 
intestine.  Wherever  this  happens,  a  separation  takes  place  between 
the  two,  at  the  expense  of  the  intermediate  layer,  some  of  the  cells  of 
which  remain  attached  to  the  external  and  some  to  the  internal  blasto- 
dermic  Ia'er. 


VERTICAL  SECTION  OF  A  PORTION  OP  THE  BLASTODERM  OF  THE  FOWL'S  EGG, 
in  process  of  separation  into  two  laminae.— 1.  External  blastodermic  layer.  2.  Internal 
blastodermic  layer.  3.  Cells  of  the  intermediate  layer,  partly  drawn  out  into  filamentous 
extensions.  Magnified  250  diameters.  (His.) 

The  cleavage  or  division  of  the  blastoderm  into  two  laminae,  as  above 
described,  does  not  take  place  everywhere  simultaneously.  It  occurs 
here  and  there,  as  the  process  of  growth  becomes  more. active  in  par- 
ticular spots.  But  the  general  course  of  its  extension  is  from  without 
inward,  or  from  the  lateral  borders  of  the  embryo  toward  the  median 
line.  It  does  not,  however,  reach  the  median  line,  but  leaves  a  con- 
siderable space  around  the  chorda  dorsalis  and  on  each  side  of  it  still 
undivided,  when  the  lateral  portions  of  the  blastoderm  are  already 
completely  separated  into  their  two  laminse. 

By  the  separation  of  the  laminse  of  the  blastoderm  thus  effected,  a 
space  or  interval  (Fig.  252,  5)  is  left  between  the  two.  This  space,  when 
the  closure  of  the  abdominal  walls  is  accomplished,  becomes  the  perito- 
neal cavity.  The  cells  of  the  intermediate  layer  subsequently  give  rise 
to  the  development  of  muscular  tissue  ;  and  that  portion  which,  in  the 
separation  of  the  two  laminse,  continues  adherent  to  the  external  layer, 
produces  the  voluntary  muscles  of  the  chest  and  abdomen.  The  por- 
tion remaining  adherent  to  the  internal  layer,  on  the  other  hand,  pro- 
duces the  involuntary  muscular  coat  of  the  alimentary  canal.  In  Figure 
252,  II.,  III.,  and  IV.,  these  two  portions  of  the  intermediate  la}?er, 
which  give  rise  respectively  to  voluntary  and  involuntary  muscular 
tissue,  are  seen  shaded  with  parallel  lines. 

Primitive  Vertebrae — Formation  of  the  Spinal  Column  and  it*  Mus- 
cles.— Already  on  the  second  day  of  incubation  there  have  appeared, 
on  each  side  of  the  chorda  dorsalis  and  medullary  canal,  a  number 


736 


FORMATION    OF    THE    EMBRYO. 


of  rectangular  masses  arranged  in  longitudinal  series,  almost  exactly 
similar  to  each  other,  and  separated  by  regular  transverse  divisions. 
They  resemble  strongly  in  their  appearance  the  simpler  component  parts 
of  a  spinal  column,  and,  in  fact,  form  the  basis  out  of  which  this  struc- 

Fig.  252. 


TRANSVERSE  SECTION  OF  THE  CHICK-EMBRYO,  at  different  stages  of  development. 
Magnified  40  diameters. 

I.  On  the  second  day  of  incubation. 

II.  Between  the  second  and  third  days. 

III.  On  the  third  day. 

IV.  On  the  fourth  day. 

1.  Medullary  groove.  2.  Medullary  canal.  3.  External  blastodermic  layer.  4.  Internal 
blastodermic  layer.  5.  Space  of  separation  between  the  two  laminae  of  the  blastoderm; 
future  peritoneal  cavity.  6.  Chorda  dorsalis.  7.  Primitive  vertebrae.  8.  Aorta.  9.  Cavity 
of  the  intestine.  (His.) 

ture  will  afterward  be  developed.  But  they  do  not  represent  imme- 
diately and  exclusively  the  bodies  of  the  vertebrae.  They  are  to  serve, 
not  only  for  the  formation  of  these  organs,  but  also  for  that  of  the  spinal 
muscles  on  the  one  hand  and  of  the  muscular  layer  of  the  aorta  on  the 
other.  They  are  therefore  known  as  the  primitive  vertebras.  In  a 
transverse  section  of  these  bodies  (Fig.  252,  7 )  there  is  an  evident  dis- 


FORMATION    OF    THE    EMBRYO.  737 

tinction  between  their  central  portion  or  nucleus,  and  their  external 
portion  or  shell.  The  nucleus  is  more  transparent,  and  will  afterward 
supply  the  cartilaginous  deposit  for  the  permanent  vertebrae ;  the  shell 
has  a  radiating  striated  texture,  and  serves  for  the  formation  of  mus- 
cular tissue. 

On  the  second  day  of  incubation  (Fig.  252,  I.)  the  primitive  verte- 
brae, as  seen  in  transverse  section,  have  the  form  of  a  narrow  oval,  with 
a  small  nucleus  and  a  comparatively  thick  and  perfectly  continuous 
shell.  From  the  second  to  the  third  day  (Fig.  252,  II.)  the  nucleus 
grows  more  rapidly  than  the  outer  parts,  which  it  pushes  upward  and 
downward  ;  and  the  shell  begins  to  show  indications  of  a  separation 
into  upper  and  lower  portions.  On  the  third  day  (Fig.  252,  III.)  this 
separation  is  complete ;  and  the  upper  portion  of  the  shell,  taking  a 
position  more  or  less  parallel  with  the  outline  of  the  body  at  this  point, 
will  become  the  layer  of  voluntary  muscles  about  the  spinal  column. 
Its  lower  portion  recedes  farther  from  above  downward,  and  approaches 
the  situation  of  the  double  aorta  (  8  ),  which  it  will  afterward  supply  with 
its  involuntary  muscular  layer.  In  a  section  of  the  embryo  at  the 
fourth  day  (Fig,  252,  IV.)  the  final  position  of  these  two  muscular 
layers  is  distinctly  marked  ;  the  projection  of  the  spinal  ridge,  on  the 
one  hand,  having  become  higher  and  steeper,  and,  on  the  other,  the 
double  aorta  having  been  fused  into  a  single  vascular  canal. 

The  nucleus  of  the  primitive  vertebra,  in  the  mean  time,  extends 
upward  and  inward,  in  such  a  manner  as  to  surround  both  the  medul- 
lary canal  and  the  chorda  dorsalis,  which  it  embraces  in  a  tissue  of  new 
formation.  This  tissue  afterward  supplies  the  cartilage,  both  of  the 
bodies  of  the  vertebrae,  and  of  the  oblique  processes  which  inclose  the 
spinal  canal  at  its  sides  and  behind.  But  when  these  cartilages  are 
formed,  it  is  observed  that  they  do  not  correspond  in  situation  with  the 
original  primitive  vertebrae.  A  new  segmentation  takes  place,  by  which 
the  lines  of  separation  between  the  successive  permanent  vertebrae  pass 
through  the  middle  of  what  were  the  primitive  vertebrae  j1  and  conse- 
quently each  permanent  vertebra  is  formed  out  of  the  adjacent  halves 
of  two  primitive  vertebrae.  The  chorda  dorsalis,  included  in  the  car- 
tilaginous matrix  of  the  bodies  of  the  vertebrae,  ceases  to  grow  in  a 
corresponding  ratio  with  the  neighboring  parts,  becomes  atrophied,  and 
disappears ;  while  the  bodies  of  the  vertebrae,  which  surround  it,  are 
rapidly  enlarged,  and  assume  the  form  and  size  of  the  principal  com- 
ponent parts  of  the  spinal  column. 

1  Foster  and  Balfour,  Elements  of  Embryology.     London,  1874,  p.  153. 


CHAPTEE    IX. 

DEVELOPMENT  OF  ACCESSORY  ORGANS  IN  THE 
IMPREGNATED  EGG.  UMBILICAL  YESICLE,  AM- 
NION,  AND  ALLANTOIS. 

THUS  far,  the  process  of  development  has  been  followed  as  it  relates 
to  the  primary  formation  of  the  principal  parts  of  the  body  of  the 
emb^o.  In  some  species  of  animals  this  includes  all  the  important 
structures  which  show  themselves  in  the  impregnated  egg;  the  embryo 
arriving  ver}r  soon  at  a  stage  of  growth  in  which  it  is  liberated  by  the 
rupture  of  the  vitelline  membrane  and  is  already  capable  of  carrying  on 
an  independent  existence.  But  in  many  fish  and  reptiles,  and  in  all 
birds  and  mammalia,  there  are  additional  structures  which  aid  in  the 
nutrition  of  the  young  animal  during  the  middle  and  later  periods  of  its 
development.  In  these  instances,  the  whole  of  the  blastoderm  is  not 
immediately  converted  into  the  tissues  of  the  embryo.  Certain  por- 
tions, both  of  its  external  and  internal  layers,  remain  outside  the  limits 
of  the  body,  and  perform,  in  this  situation,  the  function  of  accessory 
organs.  These  organs  are  the  umbilical  vesicle,  the  amnion,  and  the 
allantois. 

Umbilical  Vesicle. 

In  the  frog's  embryo  (page  725),  the  abdominal  plates,  closing  to- 
gether in  front,  join  each  other  upon  the  median  line,  and  shut  in  directly 
the  whole  of  the  vitellus,  which  is  thus  inclosed  in  the  intestinal  sac 
formed  by  the  internal  blastodermic  layer. 

In  other  instances,  the  abdominal  plates  do  not  immediately  embrace 
the  whole  of  the  vitelline  mass,  but  tend  to  close  together  at  some  inter- 
mediate  point ;    so  that  the  vitellus  is  con- 
p'  stricted,  and  divided  into  two  portions,  one 

internal,  and  one  external.  (Fig.  253.)  As 
development  proceeds,  the  body  of  the  embryo 
increases  in  size  out  of  proportion  to  the 
vitelline  sac,  and  the  constriction  just  men- 
tioned becomes  at  the  same  time  more  strongly 
marked;  so  that  the  separation  between  the 
internal  and  external  portions  of  the  vitelline 
EGG  OF  FISH,  showing  for-  gac  is  near]y  complete.  The  internal  blasto- 

mation  of  umbilical  vesicle.  J 

dermic   layer  is  by  this  means  divided  into 

two  portions,  one  of  which  forms  the  intestinal  canal,  while  the  other, 
remaining  outside,  forms  a  sac-like  appendage  to  the  abdomen,  known 
by 'the  name  of  the  umbilical  vesicle. 
(738) 


AMNION    AND    ALLANTOIS.  739 

The  umbilical  vesicle  is  accordingly  lined  by  a  portion  of  the  internal 
blastodermic  layei;,  continuous  with  the  mucous  membrane  of  the  intes- 
tine ;  and  covered  by  a  portion  of  the  external  blastodermic  layer,  con- 
tinuous with  the  integument  of  the  abdomen. 

After  the  young  animal  leaves  the  egg,  the  umbilical  vesicle  in  some 
species  becomes  shrunken  and  atrophied  by  the  absorption  of  its  con- 
tents ;  while  in  others,  the  abdominal  walls  gradually  extend  over  it, 
and  crowd  it  back  into  the  abdomen;  the  nutritious  matter  which  it 
contains  passing  from  the  cavity  of  the  vesicle  into  that  of  the  intes- 
tine by  the  narrow  passage  remaining  open  between  them. 

In  the  human  species,  on  the  other  hand,  as  well  as  in  quadrupeds, 
the  umbilical  vesicle  becomes  more  completely  separated  from  the  ab- 
domen.    There  is  at  first  a  wide  communication  be- 
tween the  cavity  of  the  umbilical  vesicle  and  that  of  Fig.  254. 

the  intestine  ;  subsequently  this  communication  is 
gradually  narrowed  by  the  constriction  of  the  ab- 
dominal walls;  and  this  constriction  proceeds  so  far 
that  the  opposite  surfaces  of  the  canal  at  least  come 
in  contact  with  each  other  and  adhere  together,  so 
that  the  passage  previously  existing,  between  the 
cavitjr  of  the  intestine  and  that  of  the  umbilical 
vesicle,  is  obliterated,  and  the  vesicle  is  then  con- 
nected with  the  abdomen  only  by  an  impervious 
cord.  This  cord  afterward  elongates,  and  becomes  with  umbilical  vesi- 


converted  into  a  slender  pedicle  (Fig.  254),  emerging  aou 


from  the  abdomen  of  the  foetus,  and  connected  by  its 
farther  extremity  with  the  umbilical  vesicle,  which  is  filled  with  a  trans- 
parent, colorless  fluid.  The  umbilical  vesicle  is  distinctly  visible  in  the 
human  foetus  so  late  as  the  end  of  the  third  month.  After  that  period 
it  diminishes  in  size,  and  is  gradually  lost  in  the  advancing  development 
of  the  neighboring  parts. 

Amnion  and  Allantois. 

The  amnion  and  allantois  are  two  organs  which  can  be  best  studied 
in  connection  with  each  other,  since  they  are  closely  related  in  physio- 
logical importance;  the  office  of  the  first  being  to  pro  vide  for  the  forma- 
tion of  the  second.  The  amnion  is  developed  from  the  external  blasto- 
dermic layer  ;  the  allantois  from  the  internal  Ia3^er.  The  amnion  is  so 
called  probably  from  the  Greek  d.tm?,  a  young  lamb  ;  on  account  of  its 
having  been  first  observed  as  a  foetal  envelope  in  this  animal.  The 
name  of  the  allantois  is  also  derived  from  the  Greek  axxayr  <mSij>$,  owing 
to  its  elongated  or  sausage-like  form  in  the  pig,  and  some  other  of  the 
domestic  animals. 

In  the  frog's  egg.  the  embryo  is  abundantly  supplied  with  moisture, 
air,  and  nourishment  from  without.  The  absorption  of  oxygen  and  of 
albuminous  liquids,  and  the  exhalation  of  carbonic  acid,  so  far  as  it 
is  produced,  can  readily  take  place  through  the  simple  membranes  of 


740          ACCESSORY    ORGANS    IN    IMPREGNATED    EGG. 

the  egg ;  especially  as  the  time  occupied  in  the  formation  of  the  pri- 
mary organs  is  very  short,  and  the  greater  part  of  the  process  of  de- 
velopment remains  to  be  accomplished  after  the  young  animal  leaves 
the  egg. 

But  in  birds  and  quadrupeds,  the  time  required  for  the  development 
of  the  embryo  within  the  egg  is  longer.  The  young  animal  acquires  a 
more  perfect  organization  during  the  time  that  it  remains  inclosed  by 
its  membranes ;  and  the  processes  of  absorption  and  exhalation  neces- 
sary for  its  growth,  being  increased  in  activity  to  a  corresponding 
degree,  require  a  special  organ  for  their  accomplishment.  This  organ, 
destined  to  bring  the  blood  of  the  foetus  into  relation  with  the  atmo- 
sphere and  external  sources  of  nutrition,  is  the  allantois. 

In  the  frog,  the  internal  blastodermic  layer,  forming  the  intestinal 
mucous  membrane,  is  everywhere  inclosed  by  the  external  layer,  form- 
ing the  integument.  But  in  the  higher  animals  a  portion  of  this  internal 
layer,  which  is  the  seat  of  the  greatest  vascularity,  and  which  is  des- 
tined to  produce  the  allantois,  is  brought  into  contact  with  the  external 
membrane  of  the  egg  for  purposes  of  exhalation  and  absorption  ;  and 
this  can  only  be  accomplished  by  opening  a  passage  for  it  through  the 
external  blastodermic  layer.  This  is  done  in  the  following  manner  by 
the  formation  of  the  amnion. 

Soon  after  the  body  of  the  embryo  has  begun  to  be  formed,  by  the 
thickening  and  involution  of  the  external  blastodermic  layer,  a  second- 
ary fold  of  this  layer  rises  up  on  all  sides  about 
Fig.  255.  the  edges  of  the  newly-formed  embryo ;  so  that 

its  body  appears  as  if  sunk  in  a  kind  of  depres- 
sion, and  surrounded  with  a  membranous  ridge, 
as  in  Fig.  255.  The  embryo  (c)  is  here  seen  in 
profile,  with  the  external  membranous  folds,  above 
mentioned,  rising  up  in  advance  of  the  head,  and 
behind  the  posterior  extremity.  The  same  thing 

takeS  PlaCC  On  the   tw°    sides  °f  the  foetllS>  ^  the 

formation  of  lateral  folds  simultaneously  with  the 
*PP<^ance  of  those  in  front  and  behind.  As 
these  folds  are  destined  to  form  the  amnion,  they 

*™  Called  tlle  "  amni°tic  folds'" 

The  amniotic  folds  continue  to  grow,  extend- 
ing forward,  backward,  and  laterally,  until  they  approach  each  other  at 
a  point  over  the  back  of  the  embryo  (Fig.  256):  Their  opposite  edges 
afterward  come  in  contact  with  each  other  at  this  point,  and  adhere 
together,  so  as  to  shut  in  a  space  (Fig.  256,  b)  between  their  inner  sur- 
face and  the  body  of  the  embryo.  This  space,  which  contains  a  thin 
layer  of  clear  fluid,  is  the  amniotic  cavity. 

There  now  appears  a  prolongation  or  diverticulum  (Fig.  256,  c), 
growing  from  the  posterior  portion  of  the  intestinal  canal,  and  follow- 
ing the  course  of  the  amniotic  fold  which  has  preceded  it ;  occupying, 
as  it  gradually  enlarges  and  protrudes,  the  space  left  vacant  by  the 


AMNION    AND    ALLANTOIS. 


741 


Fig.  256. 


Diagram  of  the  FECUN- 
DATED EGG,  farther 
advanced  — a.  Umbilical 
vesicle,  b.  Amniotic  cav- 
ity, c.  Allantois. 


Fig.  257. 


rising  up  of  the  amniotic  fold.  This  diverticulum  is  the  commencement 
of  the  allantois.  It  is  an  elongated  membranous  sac,  continuous  with 
the  posterior  portion  of  the  intestine,  and  con- 
taining bloodvessels  derived  from  those  of  the 
intestinal  circulation.  The  cavity  of  the  allantois 
is  also  continuous  with  the  cavity  of  the  intes- 
tine. 

After  the  amniotic  folds  have  approached  and 
touched  each  other,  as  above  described,  over  the 
back  of  the  embryo,  the  adjacent  surfaces,  thus 
brought   in   contact,  fuse   together,  so   that  the 
cavities  of  the  two  folds,  coming  respectively  from 
front  and  rear,  are  separated   only  by  a  single 
membranous  partition  (Fig.  251,  c)  running  from 
the  inner  to  the  outer  lamina  of  the   amniotic 
folds.      This    partition    is    soon   afterward   atro- 
phied and  disappears ;  and  the  inner  and  outer  laminae  become  conse- 
quently separated  from  each   other.     The  inner  lamina  (Fig.  257,  a) 
which  remains  continuous  with  the  integument  of  the  foetus,  inclosing 
the  body  of  the  embryo  in  a  distinct  cavity,  is 
called  the  amnion  (Fig.  258,  6),  and  its  cavity  is 
known  as  the  amniotic  cavity.     The  outer  lamina 
of  the  amniotic  fold,  on  the  other  hand  (Fig. 
257,  6),  recedes   farther   and  farther   outward, 
until  it  comes  in  contact  with  the  original  vitel- 
line  membrane,  still  covering  the  exterior  of  the 
egg.    It  at  last  fuses  with  the  vitelline  membrane 
and  unites  with  its  substance,  so  that  the  two 
form  but  one.     This  membrane,  resulting  from 
the  union  and  consolidation  of  two  others,  con- 
stitutes then  the  external  investing  membrane  of 
the  egg. 

The  allantois,  in  the  mean  time,  increases  in 
size  and  vascularity.  Following  the  course  of 
the  amniotic  folds  as  before,  it  insinuates  itself 
between  them,  and  thus  comes  in  contact  with 
the  external  membrane  above  described.  It  then 
begins  to  expand  laterally,  enveloping  more  and 

more  the  body  of  the  embryo,  and  bringing  its  vessels  into  contact  with 
the  external  investing  membrane  of  the  egg. 

By  a  continuation  of  this  process,  the  allantois  at  last  envelops  com- 
pletely the  body  of  the  embryo,  together  with  the  amnion;  its  two 
extremities  coming  in  contact  with  each  other,  and  fusing  together  over 
the  back  of  the  embryo,  in  the  same  manner  as  the  amniotic  folds  had 
previously  done.  (Fig.  258.)  It  lines,  therefore,  the  whole  internal 
surface  of  the  investing  membrane  with  a  flattened,  vascular  sac,  the 


Diagram  of  the  FECTTN. 
DATED  EGG,  with  allan- 
tois nearly  complete.— a. 
Inner  lamina  of  amniotic 
fold.  6.  Outer  lamina  of 
ditto,  c.  Point  where  the 
amniotic  folds  come  in 
contact.  The  allantois  is 
seen  penetrating  between 
the  inner  and  outer  lami- 
nae of  the  amuiotic  folds. 


742          ACCESSORY    ORGANS    IN    IMPREGNATED    EGG. 

vessels  of  which  come  from  the  interior  of  the  body  of  the  embryo,  and 
which  still  communicates  with  the  cavity  of  the  intestinal  canal. 

It  is  evident,  accordingly,  that  there  is  a  close  connection  between 
the  formation  of  the  amnion  and  that  of  the 
Fig.  258.  allantois.     For  it  is  only  by  this  means  that 

the  allantois,  which  is  an  extension  of  the  in- 
ternal blastodermic  layer,  can  come  to  be 
situated  outside  the  embryo  and  the  amnion, 
and  thus  brought  into  relation  with  surround- 
in  or  media.  The  two  laminae  of  the  amniotic 

O 

folds,  by  separating  from  each  other  as  above 
described,  open  a  passage  for  the  allantois,  and 
allow  it  to  come  in  contact  with  the  external 
Diagram  of  the  FECUNDA-     membranous  investment  of  the  egg. 

TED  EGG,  with  the  allantois  _.        .   ,       .      _     .  -  ,7  .    .          mu 

fully  formed. —  a.  Umbilical         Pnysiological  Action  of  the  Allantois. —  Ihe 

vesicle,  b.  Amnion.   c.  Allan-    physiological   action   of  the   allantois,  in  its 

simplest  form,  may  be  studied  with  advantage 

in  the  fowl's  egg,  where  it  forms  an  extensive  and  highly  vascular 
organ,  but  does  not  present  any  important  modifications  of  its  original 
structure. 

The  egg  of  the  fowl  contains,  when  first  laid,  an  abundant  deposit  of 
semi-solid  albuminous  matter  in  which  the  yolk  is  enveloped.  This 
affords,  in  connection  with  the  yolk,  a  sufficient  quantity  of  moisture 
and  organic  nutriment  for  the  growth  of  the  embryo.  The  necessaiy 
warmth  is  supplied  by  the  body  of  the  fowl  in  incubation ;  and  the 
atmospheric  gases  can  pass  and  repass  without  difficulty  through  the 
porous  shell  and  its  lining  membranes.  On  the  commencement  of  incu- 
bation, a  liquefaction  takes  place  in  the  albumen  immediately  above  that 
part  of  the  yolk  which  is  occupied  by  the  blastoderm  ;  so  that  the  vitel- 
lus  rises  toward  the  surface,  by  virtue  of  its  specific  gravity,  and  the 
blastoderm  comes  to  be  placed  almost  immediately  underneath  the 
lining  membrane  of  the  egg-shell.  The  body  of  the  embryo  is  thus 
placed  in  the  most  favorable,  position  for  the  reception  of  warmth  and 
other  necessary  external  influences.  The  liquefied  albumen  is  absorbed 
by  the  vitelline  membrane,  and  the  yolk  thus  becomes  larger,  softer,  and 
more  diffluent  than  before  the  commencement  of  incubation. 

As  soon  as  the  circulatory  apparatus  of  the  embryo  has  been  fairly 
formed,  two  minute  arteries  are  seen  to  run  out  from  its  lateral  edges 
and  spread  into  the  neighboring  parts  of  the  blastoderm,  breaking  up 
into  inosculating  branches,  and  covering  the  adjacent  portions  of  the 
yolk  with  a  plexus  of  capillary  bloodvessels.  The  space  occupied  in 
the  blastoderm  by  these  vessels  is  called  the  area  vasculosa.  The  blood 
is  returned  from  it  to  the  body  of  the  embryo  by  two  veins  which  pene- 
trate beneath  its  edges,  one  near  the  head  and  one  near  the  tail. 

The  area  vasculosa  increases  in  extent  as  the  development  of  the 
embryo  proceeds,  and  its  circulation  becomes  more  active.  It  covers 
the  upper  half  or  hemisphere  of  the  yolk  ;  and  then,  passing  this  point, 


AMNION    AND    ALLANTOIS.  743 

it  embraces  more  and  more  of  the  inferior  hemisphere,  its  vessels  con- 
verging toward  the  opposite  pole  of  the  yolk. 

The  function  of  the  area  vasculosa  is  to  absorb  nourishment  from  the 
cavity  of  the  vitelline  sac.  As  the  albumen  liquefies  during  the  process 
of  incubation,  it  passes  by  endosmosis  into  the  vitelline  cavity ;  the 
whole  yolk  growing  constantly  larger  and  more  fluid  in  consistency. 
The  blood  of  the  embryo,  circulating  in  the  vessels  of  the  area  vasculosa, 
absorbs  the  oleagino-albuminous  matters  of  the  vitellus,  and,  carrying 
them  back  to  the  embryo  by  the  returning  veins,  supplies  the  tissues 
and  organs  with  appropriate  nourishment. 

During  this  period  the  amnion  and  the  allantois  have  been  also  in 
process  of  formation.  At  first  the  body  of  the  embryo  lies  upon  its 
abdomen,  as  heretofore  described ;  but,  as  it  increases  in  size,  it  alters 
its  position  so  as  to  lie  upon  its  left  side.  The  allantois,  emerging  from 
the  posterior  portion  of  the  abdominal  cavity,  turns  upward  over  the 
body  of  the  embryo,  and  comes  in  contact  with  the  shell  membrane.  It 
then  spreads  out  rapidly,  extending  toward  the  two  extremities  and  down 
the  sides  of  the  egg,  enveloping  the  embryo  and  the  vitelline  sac,  and 
taking  the  place  of  the  albumen  which  has  been  liquefied  and  absorbed. 

The  umbilical  vesicle  is  at  the  same  time  formed  by  the  separation  of 
part  of  the  yolk  from  the  abdomen  of  the  chick ;  and  the  vessels  of  the 
original  area  vasculosa,  which  were  at  first  distributed  over  the  yolk, 
now  ramify  upon  the  surface  of  the  umbilical  vesicle. 

At  last  the  allantois,  by  its  continued  growth,  envelops  nearly  the 
whole  of  the  remaining  contents  of  the  egg ;  so  that  toward  the  later 
periods  of  incubation,  at  whatever  point  we  open  the  egg,  the  internal 
surface  of  the  shell  membrane  is  found  to  be  lined  with  a  vascular  ex- 
pansion. This  expansion  is  the  allantois,  supplied  by  arteries  emerging 
from  the  body  of  the  embryo. 

The  allantois  is  accordingly  adapted,  by  its  structure  and  position,  to 
perform  the  office  of  a  respiratory  organ.  The  air  penetrates  from  the 
exterior  through  the  porous  shell  and  its  lining  membranes,  and  acts 
upon  the  blood  in  the  vessels  of  the  allantois  much  in  the  same  manner 
that  the  air  in  the  lungs  of  the  adult  animal  acts  upon  the  blood  in  the 
pulmonary  capillaries.  Examination  of  the  egg,  at  various  periods  of 
incubation,  shows  that  changes  take  place  in  it  which  are  entirely  anal- 
ogous to  those  of  respiration. 

The  egg,  in  the  first  place,  during  the  development  of  the  embr}ro, 
loses  water  by  exhalation.  This  exhalation  is  not  a  simple  effect  of 
evaporation,  but  is  the  result  of  the  nutritive  changes  going  on  in  the 
interior  of  the  egg ;  since  it  does  not  take  place,  except  in  a  compara- 
tively slight  degree,  in  unimpregated  eggs,  or  in  those  which  are  not 
incubated,  though  freely  exposed  to  the  air.  The  exhalation  of  fluid  is 
also  essential  to  the  processes  of  development ;  since  it  has  been  found, 
in  hatching  eggs  ~by  artificial  warmth,  that  if  the  air  of  the  hatching 
chamber  become  unduly  charged  with  moisture,  so  as  to  retard  or  pre- 
vent further  exhalation,  the  development  of  the  embryo  is  arrested.  The 
loss  of  weight  during  natural  incubation,  mainly  due  to  the  exhalation 


744          ACCESSORY    ORGANS    IN    IMPREGNATED    EGG. 

of  water,  has  been  found  by  Baudrimont  and  St.  Ange1  to  be  over  15 
per  cent,  of  the  entire  weight  of  the  egg. 

Secondly,  the  egg  absorbs  oxygen  and  exhales  carbonic  acid.  The 
two  observers  above  mentioned,  ascertained  that  during  eighteen  days' 
incubation,  the  egg  absorbs  nearly  2  per  cent,  of  its  weight  of  oxygen, 
while  the  quantity  of  carbonic  acid  exhaled  from  the  sixteenth  to  the 
nineteenth  day  amounts  to  nearly  £  of  a  gramme  in  twenty-four  hours. 
It  is  also  observed  that  in  the  egg  during  incubation,  as  well  as  in  the 
adult  animal,  more  oxygen  is  absorbed  than  is  returned  by  exhalation 
under  the  form  of  carbonic  acid. 

The  allantois,  however,  is  not  simply  an  organ  of  respiration;  it 
takes  part  also  in  the  absorption  of  nutritious  matter.  As  the  process 
of  development  advances,  the  skeleton  of  the  young  chick,  at  first  carti- 
laginous, begins  to  ossify.  The  calcareous  matter,  necessary  for  ossifi- 
cation, is  in  great  part  derived  from  the  shell.  The  shell  is  perceptibly 
lighter  and  more  fragile  toward  the  end  of  incubation  than  at  first ;  and, 
at  the  same  time,  the  calcareous  ingredients  of  the  bones  increase  in 
quantity.  The  lime-salts,  requisite  for  ossification,  are  apparently  ab- 
sorbed from  the  shell  by  the  vessels  of  the  allantois,  and  thus  transferred 
to  the  skeleton  of  the  growing  chick ;  so  that,  in  the  same  proportion 
that  the  former  becomes  weaker,  the  latter  grows  stronger.  The  dimi- 
nution in  density  of  the  shell  is  connected  not  only  with  the  develop- 
ment of  the  skeleton,  but  also  with  the  final  escape  of  the  chick  from 
the  egg.  This  deliverance  is  accomplished  mainly  by  the  movements 
of  the  chick  itself,  which  become,  at  a  certain  period,  sufficiently  vigor- 
ous to  break  out  an  opening  in  the  attenuated  shell.  The  first  fracture 
is  generally  accomplished  by  a  stroke  from  the  end  of  the  bill ;  and  it 
is  precisely  at  this  point  that  the  solidification  of  the  skeleton  is  most 
advanced.  The  egg-shell,  therefore,  which  at  first  serves  for  the  pro- 
tection of  the  embryo,  afterward  furnishes  the  materials  which  are  used 
to  accomplish  its  own  demolition,  and  at  the  same  time  to  effect  the 
escape  of  the  fully  developed  chick. 

Toward  the  latter  periods  of  incubation,  the  allantois  becomes  more 
adherent  to  the  internal  surface  of  the  shell-membrane.  At  last,  when 
the  chick,  arrived  at  the  full  period  of  development,  escapes  from  its 
confinement,  the  allantoic  vessels  are  torn  off  at  the  umbilicus ;  and  the 
allantois  itself,  cast  off  as  an  effete  organ,  is  left  behind  in  the  cavity 
of  the  abandoned  shell. 

Both  the  amnion  and  the  allantois  are,  therefore,  formations  belong- 
ing to  the  embryo,  and  constituting,  for  a  time,  accessory  but  essential 
parts  of  its  organization.  Developed  from  the  peripheral  portions  of 
the  outer  and  inner  blastodermic  layers,  they  are  important  organs 
during  the  middle  and  latter  periods  of  incubation  ;  but  when  the  chick 
lias  become  fully  developed,  and  is  ready  to  carry  on  an  independent 
existence,  they  are  thrown  off  as  obsolete  structures,  their  place  being 
afterward  supplied  b}'  organs  belonging  to  the  adult  condition. 

1  DSveloppement  du  Foetus.     Paris,  1850,  p.  143. 


CHAPTEE  X. 


DEVELOPMENT  OF  THE  IMPREGNATED  EGG  AND 
ITS  MEMBRANES  IN  THE  HUMAN  SPECIES.  AM- 
NION  AND  CHORION. 

IN  the  human  species,  as  well  as  in  the  lower  animals,  the  foetus  is 
enveloped  in  two  membranes,  an  inner  and  an  outer,  derived  respec- 
tively from  extensions  of  the  external  and  internal  blastodermic  layers, 
and  consequently  parts  of  the  emb^onic  organism.  While  the  inner 
of  these  envelopes  has  the  same  characters  as  elsewhere,  the  outer  one 
presents  such  modifications  of  structure  as  to  have  received  a  distinct 
name.  In  the  lower  animals,  therefore,  the  foetal  membranes  are  called 
the  amnion  and  the  allantois;  in  man,  they  are  known  as.  the  amnion 
and  the  chorion. 

Amnion. 

The  formation  of  the  amnion  in  the  human  species  takes  place  in  the 
same  manner  as  that  already  described  (p.  740),  namely,  by  the  growth 
of  a  circumvallation  or  fold  of  the  external  blastodermic  layer,  which 
extends  itself  in  such  a  way  that  its  edges  meet  and  coalesce  over  the 
back  of  the  embryo,  thus  inclosing  it  in  a  distinct  cavity. 


Fig.  259. 


Fig.  260. 


HUMAN  EMBRYO  AND  ITS  ENVEL- 
OPES, about  the  end  of  the  first  month. 
—1.  Umbilical  vesicle.  2.  Amnion.  3, 
Chorion. 


HUMAN  EMBRYO  AND  ITS  ENVEL- 
OPES, at  the  end  of  third  month;  showing 
the  enlargement  of  the  amnion.. 


At  the  time  of  its  formation,  the  amnion  closely  embraces  the  body 
of  the  embryo,  so  that  there  is  hardly  any  space  between  the  two ;  the 
opposite  surfaces  lying  in   contact  with  each   other,  like  those  of  the 
48  (  745  ) 


746     DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 

peritoneum  in  the  adult.  This  space  afterward  enlarges  somewhat  and 
becomes  the  amniotic  cavity,  containing  a  little  colorless,  transparent, 
serous  fluid,  the  amniotic  fluid.  But  throughout  the  earlier  periods  of 
development  the  cavity  of  the  amnion  is  small,  as  compared  with  that 
of  the  entire  egg ;  and  the  space  between  the  amnion  and  the  external 
membrane,  or  chorion  (Fig.  259;,  is  occupied  by  an  amorphous  gelati- 
nous material,  in  which  the  umbilical  vesicle  and  its  stem  lie  imbedded. 
Subsequent!}^  the  amnion  enlarges  more  rapidly,  in  comparison  with 
the  remaining  parts  of  the  egg,  and  thus  encroaches  upon  the  layer  of 
gelatinous  material  by  which  it  is  surrounded.  At  the  same  time  the 
amniotic  fluid  increases  in  quantity  (Fig.  260) ;  so  that  a  considerable 
space  is  left  around  the  embryo,  which  is  supported  by  the  uniform 
pressure  of  the  surrounding  fluid.  The  amnion  continues  to  enlarge  at 
this  increased  rate  of  growth  until  about  the  beginning  of  the  fifth 
month,  when  it  comes  in  contact  with  the  inner  surface  of  the  chorion  ; 
the  gelatinous  material  previously  intervening  between  them  having 
disappeared,  or  being  reduced  to  a  nearly  imperceptible  layer. 

Chorion. 

The  chorion,  in  the  human  species,  is  the  external  enveloping  mem- 
brane of  the  embryo.  It  originates,  like  the  corresponding  envelope  in 
the  lower  animals,  by  a  protrusion  or  outgrowth  from  the  posterior  por- 
tion of  the  primitive  alimentary  canal,  which,  insinuating  itself  between 
the  two  laminae  of  the  amniotic  fold,  spreads  gradually  over  and  around 
the  inner  lamina  or  amnion  proper,  so  as  to  occupy  finally  a  position  out- 
side of  it.  It  there  meets  with  the  two  thin  layers  which  have  preceded 
it  in  this  situation,  namely  the  outer  lamina  of  the  amniotic  fold,  and 
the  original  vitelline  membrane  of  the  egg.  But  these  two  layers,  ceas- 
ing to  grow,  while  the  new  structures  and  the  whole  egg  are  rapidly 
enlarging,  disappear  as  distinct  membranes,  and  their  place  is  taken  by 
the  chorion,  which  thus  becomes,  alone,  the  external  investment  of  the 
egg- 

So  far,  the  history  of  development  of  the  chorion  is  the  same  with 
that  of  the  allantois.  But  the  peculiarity  which  distinguishes  it  is  that, 
in  expanding  over  and  around  the  other  parts,  it  does  not  present  the 
form  of  a  double  sac  containing  fluid,  but  of  a  single  vascular  sheet  or 
membrane,  like  that  of  the  skin.  It  is  on  this  account  that  in  the 
human  species  it  is  called  the  chorion,  while  in  the  lower  animals  it 
retains  the  name  of  allantois. 

Nevertheless,  the  chorion,  like  the  allantois,  is  at  its  commencement 
a  hollow  sac  or  canal  with  a  blind  extremity,  the  cavity  of  which  is  a 
continuation  of  that  of  the  intestine.  But  this  cavity  does  not  extend 
i\t  any  time  for  more  than  a  short  distance  outside  the  body  of  the 
embryo.  Beyond  this  point  it  becomes  obliterated,  its  membranous 
walls  remaining  in  contact  with  and  adherent  to  each  other,  forming  a 
solid  membrane,  as  above  described.  Inside  the  body  of  the  embryo, 
on  the  other  hand,  it  retains  the  form  of  a  membranous  sac ;  and  this 


CHORION. 


"47 


Fig.  261. 


portion  afterward  becomes,  in  the  process  of  further  development,  the 
urinary  bladder.  The  rounded  cord  or  "urachus,"  which,  in  the  adult, 
runs  from  the  superior  fund  us  of  the  bladder  to  the  situation  of  the 
umbilicus  in  the  abdomen,  is  the  vestige  of  the  obliterated  canal  of  the 
primitive  chorion. 

The  next  peculiarity  of  the  chorion  is,  that  it  becomes  shaggy.  Even. 
while  the  egg  is  still  very  small,  and  has  but  recently  found  its  way  into 
the  uterine  cavity,  its  exterior  is  already  covered  with  transparent  villi 
(Fig.  259),  which  increase  the  extent  of  its  surface,  and,  assist  in  the 
absorption  of  fluids  from  without.  The  villi  are  at  this  time  quite  sim- 
ple in  form,  and  homogeneous  in  structure. 

As  the  egg  increases  in  size,  the  villi  elongate,  and  become  ramified 
by  the  repeated  budding  of  lateral  offshoots.  After  this  process  has 
continued  for  some  time,  the  outer 
surface  of  the  chorion  presents  a  uni- 
formly shaggy  appearance,  owing  to  its 
being  covered  everywhere  with  com- 
pound villosities. 

The  villosities,  when  examined  by 
the  microscope,  have  an  exceedingly 
characteristic  appearance.  They  origi- 
nate from  the  surface  of  the  chorion  by 
a  somewhat  narrow  stem,  and  divide 
into  secondary  and  tertiary  branches 
of  varying  size  and  figure;  some  of 
them  filamentous,  others  club-shaped, 
many  of  them  irregularly  swollen  at 
various  points.  All  terminate  by 
rounded  extremities,  giving  to  the 
whole  tuft  a  certain  resemblance  to 
some  varieties  of  sea-weed.  The  larger 
trunks  and  branches  of  the  villosity 
are  seen  to  contain  minute  nuclei,  im- 
bedded in  a  nearly  homogeneous,  or 
finely  granular  substratum.  The 

smaller  ones  appear,  under  a  low  magnifying  power,  simply  granular  in 
texture. 

The  villi  of  the  chorion  are  quite  unlike  any  other  structure  to  be 
met  with  in  the  body.  Whenever  we  find,  in  the  uterus,  any  portion  of 
a  membrane  having  villosities  of  this  character,  it  is  certain  that  preg- 
nancy has  existed ;  for  such  villosities  can  only  belong  to  the  chorion, 
and  the  chorion  itself  is  a  part  of  the  foetus.  The  presence  of  portions 
of  a  shaggy  chorion  is  therefore  as  satisfactory  proof  of  the  existence 
of  pregnancy,  as  if  the  body  of  the  foetus  itself  had  been  found. 

While  the  villosities  just  described  are  in  process  of  formation,  the 
chorion  receives  a  supply  of  bloodvessels  from  the  interior  of  the  body 
of  the  embryo.  The  arteries,  which  are  a  continuation  of  those  dis- 


Compound  villosity  of  the  HUMAN 
CHORION,  ramified  extremity.  From 
a  three  months'  foetus.  Magnified  30 
diameters. 


748   .  DEVELOPMENT  OF  THE  IMPREGNATED  EGG. 

tributed  to  the  alimentary  canal,  pass  out  along  the  canal  of  communi- 
cation to  the  chorion  and  ramify  over  its  surface.  The  embryo  at  this 
time  has  reached  such  an  activity  of  growth  that  it  requires  to  be  sup- 
plied with  nourishment  by  means  of  vascular  absorption,  instead  of  the 
slow  process  of  imbibition  hitherto  taking  place  through  the  compara- 
tively structureless  villi  of  the  chorion.  The  capillary  bloodvessels,  with 

which  the  chorion  is  supplied,  begin  to  pene- 
Fig.  262.  trate  the  substance  of  its  villosities.     They 

enter  the  base  or  stem  of  each  villus,  and. 
following  the  division  of  its  compound  rami- 
fications, reach  the  rounded  extremities  of 
its  terminal  offshoots.    Here  they  turn  upon 
themselves  in  loops  (Fig  262),  and  retrace 
heir  course,  to  unite  finally  with  the  venous 
runks  of  the  chorion. 

The  villi  of  the  chorion  are,  accordingly,  an- 
alogous in  structure  and  function  to  those  of 
the  intestine  ;  their  power  of  absorption  cor- 
responding with  the  abundance  of  their  rami- 
fications, and  the  extent  of  their  vascularity. 

Extremity  of  a  VILLOSITY  ,,,.      ,  ,       -,  ,         „  ,,         ,       . 

OP  THE  CHORION,  magnified  Hie  bloodvessels  of  the  chorion,  further- 
iso  diameters;  showing  the  ar-  mOre,  are  all  derived  from  the  abdomen  of 

rangement  of  bloodvessels  in  its        .        _ '  .      ,,         . 

interior.  the  foetus ;  and  all  substances  absorbed  by 

them  are  transported  to  the  interior  of  the 

body,  and  used  for  the  nourishment  of  its  tissues.  The  chorion,  there- 
fore, as  soon  as  its  villi  and  bloodvessels  are  completely  developed,  be- 
comes an  active  organ  in  the  nutrition  of  the  fo3tus ;  and  constitutes 
the  only  means  by  which  new  material  is  introduced  from  without. 

The  third  event  of  importance  in  the  history  of  the  chorion  is  that 
after  being  at  first  uniformly  shaggy  throughout,  it  afterward  becomes 
partially  bald.  (Fig.  260.)  This  change  begins  about  the  end  of  the 
second  month,  commencing  at  a  point  opposite  the  insertion  of  the 
foetal  bloodvessels.  The  villosities  of  this  region  cease  growing;  and 
while  the  entire  egg  continues  to  enlarge,  they  fail  to  keep  pace  with 
the  progressive  expansion  of  the  chorion.  They  accordingly  become  at 
this  part  thinner  and  more  scattered,  leaving  the  surface  of  the  chorion 
comparatively  bald.  This  baldness  increases  in  extent,  spreading  over 
the  adjacent  portions  of  the  chorion,  until  at  least  two-thirds  of  its  sur- 
face have  become  nearly  or  quite  destitute  of  villosities. 

At  the  opposite  pole  of  the  egg,  namely,  that  which  corresponds  with 
the  insertion  of  the  foetal  bloodvessels,  the  villosities  of  the  chorion, 
instead  of  becoming  atrophied,  continue  to  grow ;  and  this  portion  be- 
comes even  more  shaggy  and  thickly  set  than  before.  The  consequence 
is  that  the  chorion  afterward  presents  a  different  appearance  at  different 
parts  of  its  surface.  The  greater  part  is  smooth;  but  a  certain  portion, 
constituting  about  one-third  of  the  whole,  is  covered  with  a  soft,  spongy 
mass  of  long,  thicks-set,  compound  villosities.  It  is  this  thickened 


CHORION.  749 

portion  which  is  afterward  concerned  in  the  formation  of  the  placenta; 
while  the  remaining  smooth  portion  continues  to  be  known  under  the 
name  of  the  chorion.  The  placental  portion  of  the  chorion  becomes  dis- 
tinctly limited  in  outline  by  about  the  end  of  the  third  month. 

The  vascularity  of  the  chorion  keeps  pace,  in  its  different  parts,  with 
the  atrophy  and  development  of  its  villosities.  As  the  villosities  shrivel 
and  disappear  over  a  part  of  its  extent,  the  bloodvessels  with  which  they 
were  supplied  diminish  in  abundance ;  and  the  smooth  portion  of  the 
chorion  finally  shows  only  a  few  straggling  vessels  running  over  its  sur- 
face, but  not  connected  with  any  abundant  capillary  plexus.  In  the 
thickened  portion,  on  the  other  hand,  the  bloodvessels  lengthen  and 
ramify  to  an  extent  corresponding  with  that  of  the  villosities  in  which 
they  are  situated.  The  arteries,  coming  from  the  abdomen  of  the  foetus, 
divide  into  branches  which  enter  the  villi,  and  penetrate  through  their 
whole  extent ;  forming,  at  the  placental  portion  of  the  chorion,  a  mass 
of  tufted  and  ramified  vascular  loops,  while  the  rest  of  the  membrane 
has  a  comparatively  scanty  vascular  supply. 

The  chorion,  accordingly,  is  the  external  investing  membrane  of  the 
egg,  produced  by  an  outgrowth  from  the  body  of  the  embryo  ;  and  the 
placenta,  so  far  as  it  consists  of  the  foetal  membranes,  is  a  part  of  the 
chorion,  distinguished  from  the  rest  by  the  local  development  of  its  villi 
and  bloodvessels. 


CHAPTEE  XI. 

DEVELOPMENT  OF  THE   DECIDUAL  MEMBRANE, 
AND  ATTACHMENT  OF  THE  EGG  TO  THE  UTERUS. 


IN  the  human  species,  where  the  development  of  the  embryo  is  com- 
pleted within  the  cavity  of  the  uterus,  the  egg  depends  for  its  nutrition 
and  growth  upon  materials  derived  from  the  organism  of  the  female 
parent.  The  immediate  source  of  supply  for  this  purpose  is  the  mucous 
membrane  of  the  uterus,  which  becomes  unusually  developed  and  in- 
creased in  functional  activity  during  the  period  of  gestation.  The 
uterine  mucous  membrane,  when  thus  modified  in  structure,  is  known 
as  the  decidual  membrane,  or  the  decidua.  It  has  received  this  name 
because  it  is  exfoliated  and  discharged  at  the  same  time  that  the  egg 
itself  is  expelled  from  the  uterus. 

The  mucous  membrane  of  the  body  of  the  uterus,  in  the  unimpreg- 
nated  condition,  is  thin  and  delicate,  and  presents  a  smooth  internal 
surface.  There  is  no  distinct  layer  of  connective  tissue  between  it  and 
the  muscular  substance  of  the  uterus ;  so  that  the  mucous  membrane 
cannot  here,  as  in  most  other 

organs,  be  readily  separated  Fig.  264. 

by  dissection  from  the  subja- 
cent parts.  The  structure  of 
the  mucous  membrane,  how- 
ever, is  sufficiently  well 
marked.  It  consists,  through- 
Fig.  263. 


UTERINE  Mucous  MEM- 
BRANE, from  the  unimpregnated 
uterus,  in  vertical  section,  a.  Free 
surface,  b.  Attached  surface.  Mag- 
nified  about  10  diameters. 


UTERINE  TUBULES,  from  the  mucous  mem- 
brane of  an  unimpregnated  human  uterus.  Mag- 
nified 125  diameters. 


out,  of  tubular  follicles,  ranged  side  by  side,  and  running  perpendicu- 
larly to  its  free  surface.  Near  this  surface,  they  are  nearly  straight ;  but 
toward  the  deeper  part  of  the  mucous  membrane,  where  they  terminate 
in  blind  extremities,  they  become  more  or  less  wavy  or  spiral  in  their 
(  T50  ) 


DECIDUA    REFLEXA.  751 

course.  The  tubules  are  about  0.05  millimetre  in  diameter,  and  are 
lined  with  columnar  epithelium.  They  occupy  the  entire  thickness  of 
the  uterine  mucous  membrane,  their  closed  extremities  resting  upon 
the  subjacent  muscular  tissue,  while  their  mouths  open  into  the  cavity 
of  the  uterus.  A  few  fine  bloodvessels  penetrate  the  mucous  membrane 
from  below,  and,  running  upward  between  the  tubules,  encircle  their 
superficial  extremities  with  a  capillary  network.  There  is  no  connective 
tissue  in  the  uterine  mucous  membrane,  but  only  a  few  isolated  nuclei 
and  spindle-shaped  fibre-cells,  scattered  between  the  tubules. 

Decidua  Vera. —  As  the  fecundated  egg  descends  through  the  Fal- 
lopian tube,  the  uterine  mucous  membrane  takes  on  an  increased 
activity  of  growth.  It  becomes  tumefied  and  vascular ;  and,  as  it  in- 
creases in  thickness,  it  projects,  in  rounded  eminences  or  folds,  into 
the  uterine  cavity.  (Fig.  265.)  In  .this  process  the  uterine  tubules  in- 
crease in  length,  and  also  become  wider ;  so  that  their  open  mouths  may 
be  readily  seen  by  the  naked  eye  upon  the  uterine  surface,  as  numerous 
minute  perforations.  According  to  the  observations  of  Kolliker,  so 
early  as  the  end  of  the  first  week  they  have  increased  to  three  or  four 
times  their  original  length  and  width,  so  that  they  measure  at  this  time 
on  the  average  nearly  0.20  millimetre  in  diameter,  The  bloodvessels  of 
the  mucous  membrane  also  enlarge  and  communicate  freely  with  each 
other ;  the  vascular  network  between  and  around  the  tubules  becoming 
more  extensive  and  abundant.  The  internal  surface  of  the  uterus,  after 
this  process  has  been  for  some  time  going  on,  presents  a  thick,  rich,  soft, 
velvety,  and  vascular  lining,  quite  different  in  appearance  from  that 
which  is  to  be  found  in  the  unimpregnated  condition.  It  is  now  known 
as  the  decidua ;  and  in  order  to  distinguish  it  from  a  similar  growth  of 
subsequent  formation,  it  has  received  the  special  name  of  the  decidua 
vera. 

The  production  of  the  decidua  is  confined  to  the  body  of  the  uterus, 
the  mucous  membrane  of  the  cervix  taking  no  part  in  the  process,  but 
retaining  its  original  appearance.  The  decidual  membrane  commences 
above,  at  the  orifices  of  the  Fallopian  tubes,  and  ceases  below,  at  the 
situation  of  the  os  intern um.  The  cavity  of  the  cervix,  meanwhile,  is 
filled  with  an  abundant  secretion  of  its  peculiarly  viscid  mucus,  which 
blocks  up  its  passage,  and  protects  the  internal  cavity.  If  the  uterus 
be  opened,  therefore,  in  this  condition,  its  internal  surface  will  be  seen 
lined  with  the  decidua  vera,  which  is  continuous,  at  the  os  internum, 
with  the  unaltered  mucous  membrane  of  the  cervix  uteri. 

Decidua  Reflexa. — As  the  fecundated  egg  passes  the  lower  orifice  of 
the  Fallopian  tube,  it  insinuates  itself  between  the  opposite  surfaces  of 
the  uterine  mucous  membrane,  and  becomes  lodged  in  one  of  the  furrows 
or  depressions  between  the  folds  of  the  decidua.  (Fig.  265.)  At  this 
situation  an  adhesion  subsequently  takes  place  between  the  external 
membranes  of  the  egg  and  the  uterine  decidua.  At  the  point  where 
the  egg  thus  becomes  fixed,  a  still  more  rapid  development  takes  place 
in  the  uterine  mucous  membrane.  Its  projecting  folds  grow  up  around 


752       DEVELOPMENT    OF    THE    DEC1DUAL    MEMBRANE. 


the  egg  in  such  a  manner  as  to  partially  inclose  it  in  a  kind  of  circum- 
vallation,  and  to  shut  it  off,  mure  or  less  completely,  from  the  general 


Fig.  265. 


Fig-.  2(;«. 


IMPREGNATED  UTERUS;  showingfor- 
mation  of  decidua.  The  decidua  is  repre- 
sented in  black;  and  the  egg  is  seen,  at  the 
fundus  of  the  uterus,  engaged  between  two 
of  its  projecting  folds. 


IMPREGNATED  UTERUS,  with  project- 
ing folds  of  decidua  growing  up  around  the 
egg.  The  narrow  opening,  where  the  edges 
of  the  folds  approach  each  other,  is  seen 
over  the  most  prominent  portion  of  the  egg. 


iif.  267. 


cavity  of  the  uterus.  (Fig.  266.)  The  egg  thus  comes  to  be  contained 
in  a  special  cavity  of  its  own,  which  still  communicates  for  a  time  with 
the  general  cavity  of  the  uterus,  by  an  opening  situated  over  its  most 

prominent  portion.  As  the  process  of  growth 
goes  on,  this  opening  becomes  narrower,  while 
the  decidual  folds  approach  each  other  OA^er 
the  surface  of  the  egg.  At  last  these  folds 
touch  each  other  and  unite,  forming  a  kind  of 
cicatrix  which  remains  for  a  certain  time,  to 
mark  the  situation  of  the  original  opening. 

When  the  development  of  the  uterus  has 
reached  this  point  (Fig.  267),  the  egg  is  com- 
pletely inclosed  in  a  cavity  of  its  own  ;  being 
everywhere  covered  with  a  decidual  layer  of 
new  formation,  which  has  gradually  enveloped 
it,  and  by  which  it  is  concealed  from  view 
when  the  uterine  cavity  is  laid  open.  This 
newly-formed  layer,  enveloping  the  projecting 
portion  of  the  egg,  is  called  the  Decidua 
reflexa ;  because  it  is  reflected  over  the  egg  from  the  general  surface 
of  the  uterine  mucous  membrane.  The  orifices  of  the  uterine  tubules, 
in  consequence  of  the  manner  in  which  the  decidua  reflexa  is  formed, 
are  to  be  seen  not  only  on  its  external  surface,  or  that  which  looks 
toward  the  cavity  of  the  uterus,  but  also  on  its  internal  surface,  or  that 
which  looks  toward  the  egg. 

The  decidua  vera,  therefore,  is  the  original  mucous  membrane  lining 
the  surface  of  the  uterus.  The  decidua  reflexa  is  a  new  formation, 
which  grows  up  around  the  egg  and  incloses  it  in  a  distinct  cavity. 


IMPREGNA.TKD  UTERUS; 
showing  the  egg  completely  in- 
closed by  the  decidua  reflexa. 


ATTACHMENT  OF  EGG  TO  UTERUS.         753 

If  abortion  occur  at  this  time,  the  mucous  membrane  of  the  uterus, 
that  is,  the  decidua  vera,  is  thrown  off,  and  brings  with  it  the  egg  and 
the  decidua  reflexa.  On  examining  the  mass  so  discharged,  the  egg 
will  be  found  imbedded  in  the  substance  of  the  decidual  membrane. 
One  side  of  the  membrane,  where  it  has  been  torn  away  from  its  attach- 
ment to  the  uterus,  is  ragged  ;  the  other  side,  corresponding  to  the  cavity 
of  the  uterus,  is  smooth  or  gently  convoluted,  and  exhibits  distinctly 
the  orifices  of  the  uterine  tubules;  while  the  egg  itself  can  only  be 
extracted  by  cutting  through  the  decidual  membrane,  either  from  one 
side  or  the  other,  and  opening  in  this  way  the  special  cavity  in  which  it 
is  inclosed. 

During  the  formation  of  the  decidua  reflexa,  the  entire  egg,  as  well 
as  the  body  of  the  uterus  which  contains  it,  has  considerably  enlarged. 
That  portion  of  the  uterine  mucous  membrane  situated  immediately 
underneath  the  egg,  and  to  which  it  first  became  attached,  has  also  con- 
tinued to  increase  in  thickness  and  vascularity.  The  remainder  of  the 
decidua  vera,  however,  ceases  to  grow  as  before,  and  no  longer  keeps 
pace  with  the  increasing  size  of  the  egg  and  of  the  uterus.  It  is  still 
thick  and  vascular  at  the  end  of  the  third  month  ;  but  after  that  period 
it  becomes  comparatively  thinner  and  less  glandular,  while  the  activity 
of  growth  is  concentrated  in  the  egg,  and  in  that  portion  of  the  uterine 
mucous  membrane  with  which  it  is  in  immediate  contact. 

Attachment  of  the  Egg  to  the  Uterus.  —  While  the  above  changes  are 
taking  place  in  the  lining  membrane  of  the  uterus,  the  formation  of  the 
embryo,  and  the  development  of  the  amnion 
and  chorion   have  been  going  on  simultane-  Fig.  268. 

ously  ;  and  soon  after  the  entrance  of  the 
egg  into  the  uterine  cavity,  the  chorion  is 
everywhere  covered  with  projecting  villosities. 
These  villosities  insinuate  themselves  into  the 
uterine  tubules,  or  between  the  folds  of  the 
decidual  surface  ;  penetrating  in  this  way  into 
little  cavities  of  the  uterine  mucous  mem- 
brane. When  the  formation  of  the  decidua 
reflexa  is  completed,  the  chorion  has  already 
become  uniformly  shaggy  ;  and  its  villosities, 
spreading  in  all  directions  from  its  external 
surface,  penetrate  everywhere  both  into  the 

.       ,     ,,  IMPREGNATED   UTERUS, 

decidua  vera  beneath  it  and  into  the  decidua    showing  the  connection  he- 
reflexa  witn  which  it  is  covered.     In-  this  way    tween  the  viiiositiea  of  the 

c        chorion  and  the  decidual  mem- 


.  , 

the  egg  becomes  entangled  with  the  decidua, 

and  cannot  be  readily  separated  from  it  with- 

out rupturing  some  of  the  filaments  which  have  grown  from  its  surface, 

and  have  penetrated  the  substance  of  the  decidua.     The  nutritious  fluids, 

exuded  from  the  glandular  textures  of  the  decidua,  are  now  imbibed  by 

the  villosities  of  the  chorion  ;  and  a  more  rapid  supply  of  nourishment 


754       DEVELOPMENT    OF    THE    DECIDUAL    MEMBRANE. 


Fig.  269. 


is  thus  provided,  corresponding  in  abundance  with  the  greater  size  of 
the  egg. 

Yery  soon  the  activity  of  absorption  is  still  further  increased.  The 
chorion  becomes  vascular,  by  the  formation  of  bloodvessels  emerging 
from  the  body  of  the  embryo  and  penetrating  everywhere  into  the  villo- 
sities  with  which  it  is  covered.  Each  villosity  then  contains  a  vascular 
loop,  imbedded  with  itself  in  the  substance  of  the  decidua,  and  serving 
to  absorb  from  the  uterine,  mucous  membrane  the  materials  for  the 
growth  of  the  embryo. 

Subsequently,  the  vascular  tufts  of  the  chorion,  which  are  at  first  uni- 
formly distributed  over  its  surface,  disappear  throughout  the  greater 

part  of  its  extent,  while  they  become  still 
further  developed  and  concentrated  at  a 
particular  point,  the  situation  of  the 
future  placenta.  This  is  the  spot  at 
which  the  egg  is  in  contact  with  the  de- 
cidua. Here,  both  the  decidual  membrane 
and  the  tufts  of  the  chorion  continue  to 
increase  in  thickness  and  vascularity ; 
while  elsewhere,  over  the  prominent  por- 
tion of  the  egg,  the  chorion  not  only  be- 
comes bare  of  villosities  and  compara- 
tively destitute  of  bloodvessels,  but  the 
decidua  reflexa,  which  is  in  contact  with 
it,  also  loses  its  activity  of  growth  and 
becomes  expanded  into  a  thin  layer,  with- 
out any  remaining  trace  of  glandular  fol- 
licles. 

The  uterine  mucous  membrane  is  there- 
fore developed,  during  gestation,  in  such  a  way  as  to  provide  for  the 
nourishment  of  the  embryo  in  the  different  stages  of  its  growth.  At  first, 
the  whole  of  it  is  uniformly  increased  in  thickness  (decidua  vera).  Next, 
a  portion  of  it  grows  upward  around  the  egg,  and  covers  its  projecting 
surface  (decidua  reflexa).  Afterward,  both  the  decidua  reflexa  and  the 
greater  part  of  the  decidua  vera  diminish  in  the  activity  of  their  growth, 
and  lose  their  importance  as  a  means  of  nourishment  for  the  embryo ; 
while  that  part  which  is  in  contact  with  the  vascular  tufts  of  the  chorion 
continues  to  grow,  becoming  excessively  developed,  and  taking  part  in 
the  formation  of  the  placenta. 


PREGNANT  UTERUS;  showing 
the  formation  of  the  placenta  by 
the  united  development  of  a  portion 
of  the  decidua  and  the  villosities  of 
the  chorion. 


CHAPTER   XII. 


THE   PLACENTA. 

IN  all  instances  in  which,  as  in  man  and  the  mammalians,  the  em- 
bryo is  dependent,  for  the  materials  of  its  growth,  upon  nutritious  fluids 
supplied  by  the  uterus,  the  communication  between  them  is  established 
by  means  of  two  vascular  membranes.  One  of  these  membranes,  the 
chorion  or  the  allantois,  is  a  part  of  the  embryo;  the  other  is  the  mucous 
membrane  of  the  uterus.  By  their  more  or  less  intimate  juxtaposition, 
the  fluids  transuded  from  the  bloodvessels  of  the  mother  are  absorbed 
by  those  of  the  embryo,  and  thus  a  transfer  of  nutriment  takes  place 
from  the  maternal  to  the  foetal  organism. 

In  some  species  of  animals,  the  connection  between  the  maternal  and 
foetal  membranes  is  a  simple  one.  In  the  pig,  for  example,  the  uterine 
mucous  membrane  is  everywhere  uniformly  vascular;  its  only  pecu- 
liarity consisting  in  the  presence  of  transverse  folds,  which  project 
inward  from  its  surface,  like  the  valvulse  conniventes  of  the  small  in- 
testine. The  external  investing  membrane  of  the  egg,  or  the  allantois, 
is  also  smooth  and  uniformly  vascular.  No  special  development  of 
tissue  or  of  vessels  occurs  at  any  part  of  these  membranes,  and  no  adhe- 
sion takes  place  between  them.  The  vascular  allantois  of  the  foetus  is 
simply  in  close  apposition  with  the  vascular  mucous  membrane  of  the 
uterus;  each  of  the  two  contiguous  surfaces  following  the  undulations 

Fig.  270. 


Diagram  oftheFoiTAL  PIG,  with  its  membranes,  in,  the  uterus;  showing  the  relation  of 
the  allantoic  and  uterine  surfaces.— a,  a,  6,  6.  Walls  of  the  uterus,  c,  c.  Cavity  of  the  uterus. 
d.  Amnion.  e,  e,  Allantois. 

presented  by  the  other.  (Fig.  2TO.)  By  this  arrangement,  transudation 
and  absorption  take  place  from  the  bloodvessels  of  the  mother  to  those 
of  the  foetus,  in  sufficient  quantity  to  provide  for  the  nutrition  of  the 
latter.  When  parturition  takes  place,  a  moderate  contraction  of  the 
uterus  is  sufficient  to  expel  its  contents.  The  egg,  displaced  from  its 
original  position,  slides  forward  over  the  surface,  of  the  uterine  mucous 

(  755  ) 


756  THE    PLACENTA. 

membrane,  and  is  discharged  without  any  hemorrhage  or  laceration  of 
the  parts. 

In  other  instances,  there  is  a  more  intimate  connection,  at  certain 
points,  between  the  foetal  and  maternal  structures.  In  the  cow,  the 
sheep,  and  the  ruminating  animals  generally,  the  external  membrane  of 
the  egg,  beside  being  everywhere  supplied  with  branching  bloodvessels, 
presents,  scattered  over  its  surface,  a  large  number  of  distinct  rounded 
or  oval  spots,  at  each  of  which  it  is  covered  with  thickly  set,  tufted, 
vascular  prominences.  These  spots  are  called  cotyledons,  or  cups,  be- 
cause each  one  is  surrounded  by  a  raised  rim  or  fold,  which  embraces  a 
corresponding  rounded  mass  projecting  from  the  internal  surface  of  the 
uterus.  This  projecting  portion  of  the  uterine  mucous  membrane  is 
also  abundantly  supplied  with  bloodvessels;  and  the  tufted  vascular 
loops  projecting  from  the  surface  of  the  foetal  membrane  (Fig.  271,  6,  6) 
dip  down  into  its  substance  and  are  entangled  with  those  belonging  to 

Fig.  271. 


COTYLEDON,  from  the  pregnant  uterus  of  the  cow.-o.  Internal  surface  of  the  allantois. 
b,  b.  Foetal  bloodvessels,  c,  c.  Surface  of  uterine  mucous  membrane,  d,  d.  Maternal  blood- 
vessels. 

the  uterus  (d,  d).  There  is  no  absolute  adhesion  between  the  two  sets 
of  vessels,  but  only  an  interlacement  of  their  ramified  extremities ;  and 
by  careful  manipulation  the  foetal  portion,  with  its  villosities,  may  be 
extricated  from  the  maternal  portion  without  the  laceration  of  either. 

In  the  carnivorous  animals,  a  similar  highly  developed,  vascular  por- 
tion of  the  allantois  runs,  in  the  form  of  a  single  broad  belt  or  band, 
round  its  middle  part ;  and  this  corresponds  in  situation  with  an  equally 
developed  zone  of  the  uterine  mucous  membrane.  Here  the  foetal  and 
maternal  structures  are  adherent  to  each  other ;  while,  elsewhere, 
toward  the  two  extremities  of  the  egg,  they  lie  simply  in  contact. 
When  gestation  comes  to  an  end  in  these  animals,  and  the  foetus,  with 


THE    PLACENTA. 


757 


its  membranes,  is  expelled,  the  thickened  zone  of  uterine  mucous  mem- 
brane is  detached  at  the  same  time,  and  its  place  is  afterward  made 
good  by  a  new  growth. 

In  the  human  species,  as  shown  in  the  preceding  chapter,  the  perma- 
nently thickened  portions  of  the  chorion  and  decidua,  united  with  each 
other  by  mutual  interpenetration  and  growth,  form  a  single,  flattened, 
cake-like  mass  of  rounded  form,  oceupj'ing  rather  less  than  one-third 
of  the  surface  of  the  chorion,  and  corresponding  to  a  similar  extent  of 
the  inner  surface  of  the  uterus.  This  mass,  consisting  of  the  foetal  and 
maternal  elements  combined,  is  the  placenta. 

The  complete  development  of  the  placenta  takes  place  in  the  follow- 
ing manner : 

The  villi  of  the  chorion,  when  first  formed,  penetrate  into  follicles 
situated  in  the  substance  of  the  uterine  mucous  membrane;  and  after 
becoming  vascular,  they  are  developed  into  tufted  ramifications  of 
bloodvessels,  each  one  of  which  turns  upon  itself  in  a  loop  at  the  ex- 
tremity. At  the  same  time  the  uterine  follicle,  into  which  the  villus 
has  penetrated,  enlarges  to  a  similar  extent ;  sending  out  branching 
diverticula,  corresponding  with  the  multiplied  ramifications  of  the 
villus.  The  growth  of  the  follicle  and  that  of  the  villus  thus  go  on 
simultaneously  and  keep  pace  with  each  other ;  the  latter  constantly 
advancing  as  the  cavity  of  the  former  enlarges. 

But  it  is  not  only  the  uterine  follicles  which  increase  in  size  and  in 
complication  of  structure  at  this  period.  The  capillary  bloodvessels, 
which  lie  between  them  and  ramify  over  their  exterior,  also  become 
unusually  developed.  They  enlarge  and  inosculate  freely  with  each 
other ;  so  that  every  uterine  folli- 


cle is  covered  with  a  network  of 
dilated  capillaries,  derived  from 
the  bloodvessels  of  the  original 
decidua. 

As  the  formation  of  the  pla- 
centa goes  on,  the  anatomical  ar- 
rangement of  the  foetal  bloodves- 
sels remains  the  same.  They 
continue  to  form  vascular  loops, 
penetrating  deeply  into  the  de- 
cidual  membrane ;  only  they  be- 
come more  elongated,  and  their 
ramifications  more  abundant  and 
tortuous.  The  maternal  capilla- 
ries, however,  on  the  outside  of 


Fig.  272. 


Extremity  of  a  FOETAL  TUFT,  from  the 
human  placenta  at  term,  in  its  recent  condi- 
tion.— a,  a.  Capillary  bloodvessels.  Magnified 
135  diameters. 


the  uterine  follicles,  become  con- 
siderably altered  in  their  anatomi- 
cal relations.  They  enlarge  in 

all  directions,  and,  by  encroaching  upon  the  spaces  situated  between 
them,  fuse  successively  with  each  other ;  and,  losing  gradually  in  this 


758  THE    PLACENTA. 

way  the  characters  of  a  capillary  network,  become  dilated  into  sinuses, 
which  communicate  freely  with  the  vessels  in  the  muscular  walls  of  the 
uterus.  As  the  original  capillary  plexus  occupied  the  entire  thickness 
of  the  hypertrophied  decidua,  the  vascular  sinuses,  into  which  it  is  thus 
converted,  are  equally  extensive.  They  commence  at  the  external  sur- 
face of  the  placenta,  where  it  is  in  contact  with  the  muscular  walls  of 
the  uterus,  and  extend  through  its  whole  thickness,  quite  to  the  surface 
of  the  foetal  chorion. 

As  the  maternal  sinuses  grow. inward,  the  vascular  tufts  of  the  cho- 
rion grow  outward,  and  extend  also  through  the  entire  thickness  of  the 
placenta.  In  the  latter  periods  of  pregnancy,  the  development  of  the 
bloodvessels,  both  in  the  foetal  and  maternal  portions  of  the  placenta, 
is  so  excessive  that  all  the  other  tissues,  which  originally  coexisted 
with  them,  have  nearly  disappeared.  If  a  villus  from  the  foetal  portion 
of  the  placenta  be  examined  at  this  time  by  transparency,  in  the  fresh 
condition  (Fig.  272)  it  will  be  seen  that  its  bloodvessels  are  covered 
only  with  a  layer  of  homogeneous,  or  finely 
granular  material,  about  7  mmm.  in  thickness, 
in  which  are  imbedded  small  oval-shaped  nu- 
clei, similar  to  those  seen  at  an  earlier  period 
in  the  villosities  of  the  chorion.  The  placental 
villus  is  now,  therefore,  hardly  anything  more 
than  a  congeries  of  ramified  and  tortuous  vas- 
cular loops ;  its  remaining  substance  having 
been  atrophied  and  absorbed  in  the  excessive 
growth  of  the  bloodvessels,  the  abundance  and 
development  of  which  can  be  readily  shown  by 
injection  from  the  umbilical  arteries.  (Fig. 

Extremity  of  a  FOSTAL  ^^  The  uterine  follicles  have  at  the  same 
TUFT  of  the  human  piacen-  time  lost  their  original  structure,  and  have 
become  mere  vascular  sinuses,  into  which  the 
tufted  foetal  bloodvessels  are  received,  as  the 
villosities  of  the  chorion  were  at  first  received  into  the  uterine  fol- 
licles. 

Finally,  the  walls  of  the  foetal  bloodvessels  having  come  into  close 
apposition  with  the  walls  of  the  maternal  sinuses,  the  two  become  adhe- 
rent and  fuse  together ;  so  that  a  time  at  last  arrives  when  we  can  no 
longer  separate  the  foetal  vessels,  in  the  substance  of  the  placenta,  from 
the  maternal  sinuses,  without  lacerating  either  the  one  or  the  other, 
owing  to  the  adhesion  which  has  taken  place  between  them. 

The  placenta,  therefore,  when  perfectly  formed,  has  the  structure 
which  is  shown  in  the  accompanying  diagram  (Fig.  274),  representing 
a  vertical  section  of  the  organ  through  its  entire  thickness.  At  a,  a,  is 
seen  the  chorion,  receiving  the  umbilical  vessels  from  the  body  of  the 
foetus  through  the  umbilical  cord,  and  sending  out  its  compound  and 
ramified  vascular  tufts  into  the  substance  of  the  placenta.  At  6,  6,  is 
the  attached  surface  of  the  decidua,  or  uterine  mucous  membrane ;  and 


THE    PLACENTA.  759 

at  c,  c,  c,  c,  are  the  orifices  of  uterine  vessels  which  penetrate  it  from 
below.  These  vessels  enter  the  placenta  in  an  extremely  oblique  direc- 
tion, though  they  are  represented  in  the  diagram,  for  the  sake  of  dis- 
tinctness, as  nearly  perpendicular.  When  they  have  once  penetrated 

Fig.  274 


c 

Vertical  section  of  the  PLACENTA,  showing  the  arrangement  of  the  maternal  and  festal 
bloodvessels. — a.  a.  Chorion.    6,6.  Decidua.    c,  c,  c,  c.  Orifices  of  uterine  sinuses. 

the  lower  portion  of  the  decidua,  they  immediately  dilate  into  the  pla- 
cental  sinuses  (represented,  in  the  diagram,  in  black),  which  extend 
through  the  whole  thickness  of  the  organ,  closely  embracing  all  the 
ramifications  of  the  foetal  tufts.  It  will  be  seen,  therefore,  that  the  pla- 
centa, arrived  at  this  stage  of  completion,  is  composed  essentially  of 
nothing  but  bloodvessels.  The  other  tissues  which  originally  entered 
into  its  structure  have  disappeared,  leaving  the  bloodvessels  of  the  foetus 
entangled  with  and  adherent  to  the  bloodvessels  of  the  mother. 

There  is,  however,  no  direct  communication  between  the  foetal  and 
maternal  vessels.  The  blood  of  the  foetus  is  always  separated  from  the 
blood  of  the  mother  by  a  membrane  which  has  resulted  from  the  suc- 
cessive union  and  fusion  of  four  different  membranes,  namely :  first,  the 
membrane  of  the  foetal  villus ;  secondly,  that  of  the  uterine  follicle ; 
thirdly,  the  wall  of  the  foetal  bloodvessel ;  and  fourthly,  the  wall  of  the 
uterine  sinus.  The  membrane,  however,  thus  produced,  is  of  great 
extent,  owing  to  the  abundant  branching  and  subdivision  of  the  foetal 
tufts.  These  tufts,  in  which  the  blood  of  the  foetus  circulates,  are  bathed 
everywhere,  in  the  placental  sinuses,  with  the  blood  of  the  mother;  and 
the  processes  of  absorption  and  exhalation  go  on  between  the  two  with 
a  corresponding  activity. 

It  is  easy  to  demonstrate  the  arrangement  of  the  foetal  tufts  in  the 
human  placenta.  They  can  be  readily  seen  by  the  naked  eye,  and  may 


7(30  THE    PLACENTA. 

be  traced  from  their  attachment  at  the  under  surface  of  the  chorion  to 
their  termination  near  the  uterine  surface  of  the  placenta.  The  ana- 
tomical disposition  of  the  placental  sinuses  is  more  difficult  of  examina- 
tion. During  life,  and  while  the  placenta  is  still  attached  to  the  uterus, 
they  are  filled,  of  course,  with  the  blood  of  the  mother,  and  occupy  fully 
one-half  the  mass  of  the  placenta.  But  when  the  placenta  is  detached, 
the  maternal  vessels  belonging  to  it  are  torn  oif  at  their  necks  (Fig. 
274,  c,  c,  c,  c),  and  the  sinuses,  being  then  emptied  of  blood  by  the  com- 
pression to  which  the  placenta  is  subjected,  are  apparently  obliterated ; 
and  the  foetal  tufts,  falling  together  and  lying  in  contact  with  each 
other,  appear  to  constitute  the  whole  of  the  placental  mass.  The  ex- 
istence of  the  placental  sinuses,  however,  and  their  true  extent,  may  be 
demonstrated  in  the  following  manner. 

If  we  take  the  uterus  of  a  woman  who  has  died  undelivered  at  the 
full  term  or  thereabout,  and  open  it  in  such  a  way  as  to  avoid  wounding 
the  placenta,  this  organ  will  be  seen  remaining  attached  to  the  uterine 
surface,  with  all  its  vascular  connections  complete.  Let  the  foetus  be 
now  removed  by  dividing  the  umbilical  cord,  and  the  uterus,  with  the 
placenta  attached,  placed  under  water,  with  its  internal  surface  upper- 
most. If  the  end  of  a  blowpipe  be  then  introduced  into  one  of  the 
divided  vessels  of  the  uterine  walls,  and  air  forced  in  by  gentle  insuffla- 
tion, we  can  easily  inflate,  first,  the  vascular  sinuses  of  the  uterus,  and 
next,  the  deeper  portions  of  the  placenta ;  and  lastly,  the  bubbles  of  air 
insinuate  themselves  every  where  between  the  foetal  tufts,  and  appear  in 
the  most  superficial  portions  of  the  placenta,  immediately  underneath 
the  transparent  chorion  (a,  a,  Fig.  274) ;  thus  showing  that  the  pla- 
cental sinuses,  which  freely  communicate  with  the  uterine  vessels,  occupy 
the  entire  thickness  of  the  placenta,  and  are  equally  extensive  with  the 
tufts  of  the  chorion.  We  have  verified  this  fact  in  the  above  manner, 
on  six  different  occasions,  and  in  the  presence  of  Prof.  C.  R.  Oilman, 
Prof.  Geo.  T.  Elliot,  Prof.  Henry  B.  Sands,  Prof.  T.  G.  Thomas,  Dr.  T. 
C.  Finnell,  and  various  other  medical  gentlemen  of  New  York.  The 
same  thing  has  been  done  by  Prof.  A.  Flint,  Jr.,1  with  a  similar  result. 

If  the  placenta  be  detached  and  examined  separately,  it  will  be  found 
to  present  upon  its  uterine  surface  a  number  of  openings,  which  are  ex- 
tremely oblique  in  position,  and  bounded  on  one  side  by  a  very  thin 
crescentic  edge.  These  are  the  orifices  of  the  uterine  bloodvessels, 
passing  into  the  placenta  and  torn  off  at  their  necks,  as  above  described ; 
and  by  carefully  following  them  with  the  probe  and  scissors,  they  are 
found  to  lead  at  once  into  extensive  empty  cavities  (the  placental 
sinuses),  situated  between  the  foetal  tufts.  These  cavities  are  filled 
during  life  with  the  maternal  blood  ;  and  there  is  every  reason  to  believe 
that  before  delivery,  while  the  circulation  is  going  on,  the  placenta  is  at 
least  twice  as  large  as  after  it  has  been  detached  and  expelled  from  the 
uterus. 

1  Flint,  Physiology  of  Man.     New  York,  18^4,  vol.  v.  p.  382. 


THE    PLACENTA.  761 

The  placenta,  accordingly,  is  a  double  organ,  formed  partly  by  the 
chorion  and  partly  by  the  decidua ;  and  consisting  of  maternal  and  foetal 
bloodvessels,  entangled  and  united  with  each  other. 

The  part  which  this  organ  takes  in  the  development  of  the  foetus  is 
of  primary  importance.  From  the  date  of  its  formation,  at  about  the 
beginning  of  the  fourth  month,  it  constitutes  the  only  channel  through 
which  nourishment  is  conveyed  from  the  mother  to  the  foetus.  The 
nutritious  materials,  which  circulate  in  the  blood  of  the  maternal 
sinuses,  pass  through  the  intervening  membrane,  and  enter  the  blood  of 
the  foetus.  The  healthy  or  injurious  regimen,  to  which  the  mother  is 
subjected,  will  accordingly  exert  an  influence  upon  the  child.  Even 
medicinal  substances,  taken  by  the  mother  and  absorbed  into  the  circu- 
lation, may  transude  through  the  placental  vessels,  and  thus  exert  a 
specific  effect  upon  the  foetal  organization. 

The  placenta  is,  furthermore,  an  organ  of  exhalation  as  well  as  of 
absorption.  The  excrementitious  matters,  produced  in  the  circulation 
of  the  foetus,  are  undoubtedly  in  great  measure  disposed  of  by  transu- 
dation  through  the  walls  of  the  placental  vessels,  to  be  afterward  dis- 
charged by  the  excretory  organs  of  the  mother.  The  sj^stem  of  the 
mother  may  therefore  be  affected  in  this  manner  by  influences  derived 
from  the  foetus.  It  has  been  observed  in  the  lower  animals,  that  when 
the  female  has  two  successive  litters  of  young  *by  different  males,  the 
young  of  the  second  litter  will  sometimes  bear  marks  resembling  those 
of  the  first  male.  In  these  instances,  the  influence  which  produces  the 
external  mark  is  transmitted  by  the  first  male  to  the  foetus,  from  the 
foetus  to  the  mother,  and  from  the  mother  to  the  foetus  of  the  second 
litter. 

It  is  also  through  the  placental  circulation  that  those  disturbing  effects 
are  produced  upon  the  nutrition  of  the  foetus,  which  result  from  sud- 
den shocks  or  injuries  inflicted  upon  the  mother.  There  is  little  room 
for  doubt  that  various  deformities  and  deficiencies  of  the  foetus,  confor- 
mably to  the  popular  belief,  originate,  in  certain  cases,  from  nervous 
impressions  experienced  b}*  the  mother.  The  mode  in  which  these  effects 
may  be  produced  is  readily  understood  from  the  anatomy  and  functions 
of  the  placenta.  It  is  well  known  how  easily  nervous  impressions  will 
disturb  the  circulation  in  the  brain,  the  face,  or  the  lungs;  and  the 
uterine  circulation  is  quite  as  readily  influenced  by  similar  causes,  as 
shown  in  cases  of  amenorrhcea  and  menorrhagia.  If  a  nervous  shock 
may  excite  premature  contraction  in  the  muscular  fibres  of  the  pregnant 
uterus  and  produce  abortion,  it  is  undoubtedly  capable  of  disturbing 
the  circulation  of  the  blood  in  the  same  organ.  But  the  foetal  circulation 
is  dependent,  to  a  great  extent,  on  the  maternal.  The  two  sets  of  vessels 
are  united  in  the  placenta,  and  as  the  foetal  blood  has  much  the  same 
relation  to  the  maternal,  that  the  blood  in  the  pulmonary  capillaries  has 
to  the  air  in  the  pulmonary  air-cells,  it  must  be  liable  to  derangement 
from  similar  causes.  And  lastly,  as  the  nutrition  of  the  foetus  is  pro- 
vided for  wholly  by  the  placenta,  it  will  suffer  from  any  disturbance  of 
49 


762  THE    PLACENTA. 

the  placental  circulation.  These  effects  may  be  manifested  either  in  the 
general  atrophy  and  death  of  the  foetus,  or  in  the  imperfect  develop- 
ment of  particular  parts ;  just  as  in  the  adult  a  morbid  action  may  ope- 
rate upon  the  entire  system,  or  may  show  itself  in  some  one  organ,  which 
is  more  particularly  sensitive  to  its  influence. 


CHAPTEE   XIII. 


DISCHARGE    OF    THE    FCETUS    AND    PLACENTA. 
REGENERATION    OF   THE   UTERINE   TISSUES. 

DURING  the  growth  of  the  embryo  and  its  membranes,  and  the 
development  of  the  uterine  mucous  membrane  into  the  decidua  and 
placenta,  the  muscular  tissue  of  the  uterus  also  increases  in  thickness, 
while  the  whole  organ  enlarges,  to  accommodate  the  greater  volume  of 
its  contents.  This  increase  of  substance,  which  is  mainly  due  to  an  un- 
usual growth  in  the  muscular  walls  of  the  organ,  gives  it  a  sufficient 
degree  of  contractile  power  for  the  expulsion  of  the  foatus  at  the  time 
of  delivery. 

The  enlargement  of  the  amniotic  cavity,  and  the  increased  quantity 
of  the  amniotic  fluid,  also  provide  the  requisite  space  and  freedom  for 
the  intra-uterine  movements  of  the  foetus.  These  movements  begin  to 
be  perceptible  about  the  fifth  month,  at  which  time  the  development  of 
the  muscular  system  has  become  sufficient  to  allow  it  a  certain  amount 
of  functional  activity.  During  the  latter  months  of  pregnancy  they 
become  more  frequent  and  vigorous,  and  may  often  be  felt  by  the  hand 
of  the  observer  applied  to  the  abdomen  over  the  region  of  the  uterus. 

The  attachment  of  the  embryo  to  the  investing  membranes  of  the  egg 
is  at  first  by  a  very  short  and  comparatively  wide  funnel-shaped  con- 
nection, consisting  of  the  com- 
mencement of  the  chorion,  a  part 
of  the  amnion,  and  an  abundant 
deposit  of  gelatinous  material 
between  the  two,  containing  the 
stem  of  the  umbilical  vesicle. 
Subsequently,  as  the  amniotic 
cavity  enlarges,  the  body  of  the 
embiyo  recedes  farther  from  the 
inner  surface  of  the  chorion,  by 
the  elongation  of  its  connecting 
part ;  and  this  part  consequently 
begins  to  present  the  appearance 
of  a  cord  (Fig,  275).  It  is  still 
surrounded  with  a  thick  layer  of 
gelatinous  matter,  by  which  it  is 
separated  from  its  amniotic  in- 
vestment. As  it  emerges  from 

the  abdomen  of  the  embryo  at  a"  point  where  the  abdominal  walls  will 
afterward  close  round  it,  to  form  the    umbilicus,  it   is  known   by  the 

(763) 


Fig.  275. 


HUMAN  EMBRYO  AND  ITS  MEM- 
BRANES, in  the  early  period  of  gestation; 
showing  the  commencement  of  formation  of 
the  umbilical  cord. 


764 


DISCHARGE    OF    FCETUS    AND    PLACENTA. 


name  of  the  umbilical  cord.  It  contains  the  bloodvessels  passing  out 
from  the  body  of  the  embryo  to  the  chorion  and  placenta. 

After  the  third  month  the  umbilical  cord  and  its  bloodvessels  elongate 
even  more  rapidly  than  is  required  by  the  increase  in  size  of  the  amniotic 
cavity.  They  consequently  assume  a  twisted  form,  the  two  umbilical 
arteries  winding  round  the  vein  in  a  spiral  direction. 

The  direction  of  the  spiral  is  not  always  the  same.  Prof.  McLane 
has  recorded  observations  made  in  regard  to  this  point  upon  260  um- 
bilical cords  at  term,  partty  in  his  private  practice  and  partly  at  the 
Nursery  and  Child's  Hospital,  New  York.  Of  this  number,  in  138 
cases  the  direction  of  the  spiral  was  from  left  to  right ;  in  112  cases, 
from  right  to  left;  and  in  the  10  remaining  instances  it  was  doubtful, 
the  twist  being  too  imperfectly  marked  for  decision.  This  gives  nearly 
the  following  percentage  as  the  result  of  all  the  observations : 

DIRECTION  OF  THE  SPIRAL  TWIST  OF  THE  HUMAN  UMBILICAL  CORD. 

From  left  to  right 53  per  cent. 

From  right  to  left 43        " 

Indeterminate 4        " 


Fig.  276. 


100 

There  is,  accordingly,  no 
marked  preponderance  in  fre- 
quency of  the  twist  in  either 
direction.  Two  cases  of  twins 
are  included  in  the  above  list ; 
in  the  first  of  which  both  um- 
bilical cords  turned  from  right 
to  left ;  in  the  second,  one  of 
them  turned  from  right  to  left, 
the  other  from  left  to  right. 
In  two  instances,  the  cord 
presented  turns  in  opposite 
directions  in  different  parts  of 
its  length. 

The  gelatinous  matter,  al- 
ready described  as  existing 
between  the  amnion  and  cho- 
rion, and  which  disappears 
elsewhere,  accumulates,  on 
the  contrary,  in  the  cord  in 
considerable  quantity,  cover- 
ing the  vessels  with  a  thick, 
elastic  envelope,  which  protects  them  from  accidental  compression  or 
obliteration.  The  whole  is  covered  by  an  extension  of  the  amnion, 
which  is  continuous  at  one  extremity  with  the  integument  of  the  abdo- 
men, and  invests  the  cord  with  an  uninterrupted  sheath,  like  the  finger 
of  a  glove. 


PREGNANT  HUMAN  UTERUS  AND  ITS 
CONTENTS,  about  the  end  of  the  seventh  month  ; 
showing  the  relations  of  the  cord,  placenta,  and 
membranes.— 1.  Decidua  vera.  2.  Decidua  reflexa. 
3.  Chorion.  4.  Amnion. 


DISCHARGE    OF    FCETUS    AND    PLACENTA.  765 

The  cord  also  contains,  for  a  certain  period,  the  pedicle  or  stem  of 
the  umbilical  vesicle.  The  situation  of  this  vesicle,  necessarily,  is 
always  between  the  chorion  and  the  amnion.  Its  pedicle  gradually 
elongates  with  the  growth  of  the  umbilical  cord ;  and  the  vesicle  itself, 
which  generally  disappears  soon  after  the  third  month,,  sometimes  re- 
mains as  late  as  the  fifth,  sixth,  or  seventh.  According  to  Mayer,  it 
may  even  be  found,  by  careful  search,  at  the  termination  of  pregnancy. 
In  the  middle  and  latter  periods  of  gestation,  it  presents  itself  as  a 
small,  flattened  vesicle,  situated  beneath  the  amnion,  at  a  variable  dis- 
tance from  the  insertion  of  the  umbilical  cord.  A  minute  bloodvessel 
is  often  seen  running  to  it  from  the  cord,  and  ramifying  upon  its 
surface. 

The  decidua  reflexa,  during  the  latter  months  of  pregnancy,  is  con- 
stantly distended  by  the  increasing  size  of  the  egg,  and  finally  pressed 
against  the  opposite  surface  of  the  decidua  vera.  By  the  end  of  the 
seventh  month,  the  decidua  vera  and  reflexa  are  in  contact,  though  still 
distinct  and  capable  of  being  easily  separated.  After  that  time,  they 
become  confounded  with  each  other,  forming  at  last  only  a  single,  thin, 
friable,  semi-opaque  layer,  in  which  no  trace  of  glandular  structure  can 
be  discovered. 

This  is  the  condition  of  things  at  the  termination  of  pregnancy. 
Then,  the  time  having  arrived  for  parturition  to  take  place,  the  hyper- 
trophied  muscular  walls  of  the  uterus  contract  upon  its  contents,  and 
the  egg  is  discharged,  together  with  the  decidual  membrane. 

In  the  human  species,  as  well  as  in  most  quadrupeds,  the  membranes 
of  the  egg  are  usually  ruptured  during  the  process  of  parturition  ;  and 
the  foetus  escapes  first,  the  placenta  and  the  rest  of  the  appendages  fol- 
lowing a  few  moments  afterward.  Occasionally  the  egg  is  discharged 
entire,  and  the  foetus  afterward  liberated  by  the  laceration  of  the  mem- 
branes. In  each  case  the  mode  of  separation  and  expulsion  is  essen- 
tially the  same. 

The  process  of  parturition,  therefore,  consists  in  a  separation  of  the 
decidual  membrane,  which,  on  being  discharged,  brings  away  the  ovum 
with  it.  The  greater  part  of  the  decidua.  vera,  having  fallen  into  a 
state  of  atrophy  during  the  latter  months  of  pregnancy,  is  by  this  time 
nearly  destitute  of  vessels,  and  separates  without  perceptible  hemor- 
rhage. That  portion  which  enters  into  the  formation  of  the  placenta  is, 
on  the  contrary,  excessively  vascular;  and  when  the  placenta  is  sepa- 
rated, and  its  maternal  vessels  torn  off  at  their  insertion,  a  gush  of 
blood  takes  place,  which  accompanies  or  immediately  follows  the  birth 
of  the  foetus.  This  hemorrhage,  which  occurs  at  the'time  of  parturition, 
does  not  come  immediately  from  the  uterine  vessels.  It  consists  of 
blood  which  was  contained  in  the  placental  sinuses,  and  which  is  ex- 
pelled from  them  owing  to  the  compression  of  the  placenta  by  the 
muscular  walls  of  the  uterus.  Since  the  whole  amount  of  blood  thus 
lost  was  previously  employed  in  the  placental  circulation,  and  since  the 
placenta  itself  is  thrown  off  at  the  same  time,  no  unpleasant  effect  is- 


766  DISCHARGE    OF    FCETUS    AND    PLACENTA. 

produced  upon  the  mother  by  such  a  hemorrhage,  because  the  propor- 
tion of  blood  in  the  rest  of  the  vascular  system  remains  the  same. 
Uterine  hemorrhage  at  the  time  of  delivery  becomes  injurious  only 
when  it  continues  after  complete  separation  of  the  placenta ;  in  which 
case  it  is  supplied  by  the  mouths  of  the  uterine  vessels,  left  open  by 
failure  of  the  uterine  contractions.  These  vessels,  in  natural  parturi- 
tion, are  instantly  closed,  after  separation  of  the  placenta,  by  the  con- 
traction of  the  uterine  muscular  fibres.  They  pass,  as  already  men- 
tioned, in  an  exceedingly  oblique  direction,  from  the  uterus  to  the 
placenta;  and  the  muscular  fibres,  which  cross  them  transversely  above 
and  below,  necessarily  close  their  orifices  by  constriction  as  soon  as 
they  are  thrown  into  a  state  of  functional  activity 

Regeneration  of  the  Uterine  Tissues  after  Delivery. — Both  the  mu- 
cous membrane  and  muscular  tissue  of  the  uterus,  which  are  the  seat 
of  an  unusual  growth  during  pregnancy,  are  afterward  replaced  by 
corresponding  tissues  of  new  formation.  The  mucous  membrane,  or 
decidua,  is  discharged  at  the  time  of  delivery ;  and  the  hypertrophied 
muscular  tissue,  which  has  served  its  purpose  in  the  expulsion  of  the 
foetus,  undergoes  soon  afterward  a  process  of  retrogression  and  atrophy. 

A  remarkable  phenomenon  connected  with  the  renovation  of  the  ute- 
rine tissues,  is  the  appearance  in  the  uterus,  during  pregnancy,  of  a 
new  mucous  membrane,  growing  underneath  the  old,  and  ready  to  take 
the  place  of  the  latter  after  its  discharge. 

If  the  internal  surface  of  the  body  of  the  uterus  be  examined  imme- 
diately after  parturition,  it  will  be  seen  that  at  the  spot  where  the  pla- 
centa was  attached,  every  trace  of  mucous  membrane  has  disappeared. 
The  muscular  fibres  of  the  uterus  are  here  exposed  and  bare  ;  while  the 
mouths  of  the  ruptured  uterine  sinuses  are  also  visible,  with  their  thin 
edges  hanging  into  the  cavity  of  the  uterus,  and  their  orifices  plugged 
with  bloody  coagula. 

Over  the  rest  of  the  uterine  surface  the  decidua  vera  has  also  disap- 
peared. Here,  however,  notwithstanding  the  loss  of  the  original  mucous 
membrane,  the  muscular  fibres  are  not  perfectly  bare,  but  °re  covered 
with  a  semi-transparent  film,  of  whitish  color  and  soft  consistency. 
This  film  is  an  imperfect  mucous  membrane  of  new  formation,  which 
begins  to  be  produced,  underneath  the  old  decidua  vera,  as  early  as 
the  beginning  of  the  eighth  month.  We  have  seen  this  very  dis- 
tinctly in  the  uterus  of  a  woman  who  died  undelivered  at  the  above 
period.  The  old  mucous  membrane,  or  decidua  vera,  is  at  this  time 
somewhat  opaque,  and  of  a  slightly  yellowish  color,  owing  to  partial 
fatty  degeneration.  It  is  easily  separated  from  the  subjacent  parts, 
on  account  of  the  atrophy  of  its  vascular  connections ;  and  the  new 
mucous  membrane,  situated  beneath  it,  is  distinguishable  by  its  fresh 
color  and  semi-transparent  aspect. 

The  mucous  membrane  of  the  cervix  uteri,  which  takes  no  part  in 
the  formation  of  the  decidua,  is  not  thrown  off  in  parturition ;  and  after 


DISCHARGE    OF    FCETUS    AND    PLACENTA. 


767 


MUSCULAR  FIBRES  OF  THE  UNIMPREG- 
NATED  HUMAN  UTERUS;  from  a  woman  aged 
40,  dead  of  phthisis  pulmonaiis. 

Fig.  278. 


delivery  it  may  be  seen  to  ter-  Fig.  277. 

minate  at  the  os  intern um  by 
an  uneven,  lacerated  edge, 
where  it  was  formerly  contin- 
uous with  the  decidua  vera. 

Subsequent!}',  a  regeneration 
of  the  mucous  membrane  takes 
place  over  the  whole  extent  of 
the  body  of  the  uterus.  The 
mucous  membrane  of  new  for- 
mation, which  is  already  in 
existence  at  the  time  of  de- 
livery, becomes  thickened  and 
vascular ;  and  glandular  tu- 
bules are  gradually  developed 
in  its  substance.  At  the  end  of 
two  months  after  delivery,  ac- 
cording to  Longet1  and  Heschl,2 
it  has  regained  the  natural 
structure  of  uterine  mucous 
membrane.  It  unites  at  the  os 
interum,  by  a  linear  cicatrix, 
with  the  mucous  membrane  of 
the  cervix,  and  the  traces  of 
laceration  at  this  spot  after- 
ward cease  to  be  visible.  At 
the  point,  however,  where  the 
placenta  was  attached,  the  re- 
generation of  the  mucous  mem- 
brane is  less  rapid ;  and  a  cica- 
trix-like  spot  is  often  visible 
at  this  situation  for  several 
months  after  delivery. 

The  corresponding  change 
in  the  muscular  tissue  of  the 
uterus  consists  in  the  fatty  de- 
generation of  its  fibres.  The 

muscular  fibres  of  the  unimpregnated  uterus  are  pale,  flattened,  spindle- 
shaped  bodies  (Fig.  277),  homogeneous  or  faintly  granular  in  appear- 
ance, and  measuring  about  50  mmm.  in  length.  During  gestation  these 
fibres  increase  considerably  in  size.  Their  texture  becomes  more  dis- 
tinctly granular,  and  their  outlines  more  strongly  marked.  An  oval 
nucleus  also  shows  itself  in  the  central  part  of  each  fibre.  The  entire 


MUSCULAR  FIBRES  OF  THE  HUM. 
RUS,  ten  days  after  parturition;  from  f 
dead  of  puerperal  fever. 


UTE- 
woman 


1  Traitfc  de  Physiologic.     Paris,  1850,  G6n6ration,  p.  173. 

2  Zeitschrift  der  K.  K.  Gesellschaft  der  Aerzte,  in  Wien,  1852. 


768 


DISCHARGE    OF    FCBTUS    AND    PLACENTA. 


Fig.  279. 


walls  of  the  uterus,  at  the  time  of  delivery,  are  composed  of  such  mus- 
cular fibres,  arranged  in  circular,  oblique,  and  longitudinal  bundles. 

About  the  end  of  the  first  week  after  delivery,  these  fibres  begin  to 
undergo  a  fatty  degeneration.  (Fig.  278.)  Their  granules  become  larger 
and  more  prominent,  and  soon  assume  the  appearance  of  fat  granules, 
deposited  in  the  substance  of  the  fibre.  The  deposit,  thus  commenced, 

increases  in  abundance,  and 
the  granules  continue  to  en- 
large until  they  become  con- 
verted into  fully  formed  fat 
globules,  which  fill  the  interior 
of  the  fibre  more  or  less  com- 
pletely, and  mask,  to  a  certain 
extent,  its  anatomical  charac- 
ters. (Fig.  279.)  The  fatty 
degeneration,  thus  induced, 
gives  to  the  uterus  a  softer 
consistency,  and  a  pale  yellow- 
ish color  which  is  characteristic 
of  this  period.  The  altered 
muscular  fibres  are  afterward 
absorbed,  and  gradually  give 
place  to  others  of  new  forma- 
tion, which  already  begin  to 
show  themselves  before  the 
old  ones  have  disappeared. 

The  process  finally  results  in  a  complete  renovation  of  the  muscular 
substance  of  the  uterus.  The  organ  becomes  again  reduced  in  size,  com- 
pact in  tissue,  and  of  a  pale  ruddy  hue,  as  in  the  unimpregnated  con- 
dition. The  entire  renewal  or  reconstruction  of  the  uterus  is  completed, 
according  to  Heschl,  about  the  end  of  the  second  month  after  delivery 


MUSCULAR  FIBRES  OF  HUMAN  UTERUS^ 
three  weeks  after  parturition;  from  a  woman  dead 
of  peritonitis. 


CHAPTEE  XIV. 


Fig.  280. 


DEVELOPMENT  OF  THE  NERVOUS  SYSTEM,  ORGANS 
OF   SENSE,  SKELETON,  AND   LIMBS. 

THE  first  trace  of  the  cerebro-spinal  axis  in  the  embryo  consists  of  the 
two  longitudinal  folds  of  the  external  blastoderraic  layer,  which  include 
between  them  the  median  furrow,  known  as  the  "  medullary  groove" 
(page  724).  The  two  folds,  after  uniting  by  their  corresponding  edges 
on  the  median  line,  over  the  back  of  the  embryo, 
convert  the  groove  into  a  canal,  the  "  medullary 
canal ;"  and  it  is  within  this  canal  that  the  cerebro- 
spinal  axis  is  formed. 

The  mode  of  its  formation  is  by  the  growth  of 
nervous  matter  upon  the  inner  surface  of  the  medul- 
lary canal ;  and  this  canal,  which  becomes  the  cerebro- 
spinal  canal,  is  accordingly  lined  with  a  secondary 
internal  sheath  of  nervous  matter,  which  also  has 
the  form  of  a  tubular  membranous  canal,  with  a.  con- 
tinuous central  cavity.  This  is  the  cerebro-spinal 
axis,  which  thus  forms  a  hollow  cylindrical  cord  of 
nervous  matter,  running  in  a  longitudinal  direction 
within  the  cerebro-spinal  canal.  Anteriorly  it  ex- 
pands into  a  bulbous  enlargement  corresponding  to 
the  brain.  Its  middle  portion,  constituting  the  spinal 
cord,  is  nearly  cylindrical ;  and  posteriorly,  at  its 
caudal  extremity,  it  terminates  by  a  pointed  enlarge- 
ment. 

The  next  change  which  shows  itself  is  a  division  of  the  anterior  bul- 
bous enlargement  into  three  secondary  compartments  or  vesicles,  par- 
tially separated  from  each  other  by  incomplete  transverse  constrictions. 
These  are  known  as  the  cerebral  vesicles,  from  which  the  different  parts 
of  the  encephalon  are  afterward  to  be  developed.  The  first  or  most 
anterior  vesicle  is  destined  to  form  the  hemispheres ;  the  second  or 
middle,  the  tubercula  quadrigemina  ;  the  third,  or  posterior,  the  medulla 
oblongata.  All  three  vesicles  are  still  hollow,  and  their  cavities  com- 
municate freely  with  each  other  through  the  intervening  orifices. 

Very  soon  the  anterior  and  posterior  cerebral  vesicles  undergo  a  fur- 
ther division,  the  middle  one  remaining  undivided.  The  anterior  vesicle 
thus  separates  into  two  portions,  of  which  the  first,  or  larger,  consti- 
tutes the  hemispheres,  while  the  second,  or  smaller,  becomes  the  optic 

(769) 


Formation    of    the 

CEREBRO-SriNAL 

Axis.  —  a,  b.  Spinal 
cord  c.  Cephalic  ex- 
tremity, d.  Caudal 
extremity. 


770 


DEVELOPMENT    OF    THE    NERVOUS    SYSTEM. 


thalami.     The  third  vesicle  also  separates  into  two  portions,  of  which 
the  anterior  becomes  the  cerebellum,  the  posterior  the  medulla  oblongata. 


Fig.  281. 


Fig.  282. 

* 


FOJTAL  PlG,  1§  centimetre  long,  showing  the  condition 
of  the  brain  and  spinal  cord.— 1.  Hemispheres.  2.  Tubercula 
quadrigemina.  3.  Cerebellum.  4.  Medulla  oblongata. 

There  are,  therefore,  at  this  time  five  cerebral 
vesicles,  all  of  which  communicate  with  each 
other  and  with  the  central  cavity  of  the  spinal 
cord.  The  entire  cerebro-spinal  axis  also  be- 
comes strongly  curved  in  an  anterior  direction, 
corresponding  with  the  anterior  curvature  of 
the  body  of  the  embryo  (Fig.  282) ;  so  that  the 
middle  vesicle,  or  that  of  the  tubercula  quadri- 
2.  vesicle  of  the  tubercula  gemina,  occupies  a  prominent  angle  at  the  upper 

quadrigemina.     3.   Vesicle 


Formation  of  the  CERK- 


of  the  medulla  oblongata. 


part  of  the  encephalon,  while  the  hemispheres  and 
the  medulla  oblongata  are  situated  below  it,  ante- 
riorly and  posteriorly.  At  first  the  relative  size  of  the  various  parts 
of  the  encephalon  is  very  different  from  that  presented  in  the  adult 
condition.  The  hemispheres  are  hardly  larger  than  the  tubercula  quad- 
rigemina; and  the  cerebellum  is  inferior  in  size  to  the  medulla  oblongata. 
Soon  afterward,  the  relative  position  and  volume  of  the  parts  begin  to 
alter.  The  hemispheres  and  tubercula  quadrigemina  grow  faster  than 
the  posterior  portions  of  the  encephalon ;  and  the  cerebellum  becomes 
doubled  backward  over  the  medulla  oblongata.  (Fig.  283.)  Subse- 


Fig.  283. 


Fig.  284. 


FCETAL  P i o,  three  centimetres  long. 
— 1.  Hemispheres.  2.  Tubercula  quadri- 
gemina. 3.  Cerebellum.  4  Medulla  ob- 
longata. 


HEAD  OF  FCETAL  PIG,  nine  centimetres 
long.— 1  Hemispheres.  3.  Cerebellum.  4.  Me- 
dulla oblongata. 


quently,  the  hemispheres  enlarge  more  rapidly,  growing  upward  and 
backward,  so  as  to  cover  both  the  optic  thalami  and   the  tubercula 


DEVELOPMENT    OF    THE    NERVOUS    SYSTEM.  771 

quadrigemina  (Fig.  284) ;  the  cerebellum  tending  in  the  same  way  to 
grow  backward,  and  projecting  farther  in  this  direction  over  the  medulla 
oblongata.  The  subsequent  history  of  the  development  of  the  enceph- 
alon  is  mainly  a  continuation  of  the  same  process  ;  the  relative  dimen- 
sions of  the  parts  constantly  changing,  so  that  the  hemispheres  become, 
in  the  adult  condition  (Fig.  285),  the  largest  division  of  the  encephalon. 


Fig.  285. 


BRAIN  OF  ADULT  PIG. — 1.  Hemispheres.    3.  Cerebellum.    4.  Medulla  oblongata. 

while  the  cerebellum  is  next  in  size,  and  covers  the  upper  portion  of 
the  medulla  oblongata.  The  surfaces  of  the  hemispheres  and  cerebellum, 
which  are  at  first  smooth,  become  afterward  convoluted ;  thus  increasing 
still  farther  the  extent  of  their  nervous  matter.  In  the  human  foetus 
the  cerebral  convolutions  begin  to  appear  about  the  beginning  of  the 
fifth  month  (Longet),  and  grow  deeper  and  more  abundant  during  the 
remainder  of  foetal  life. 

The  lateral  portions  of  the  brain  growing  at  the  same  time  more 
rapidly  than  that  on  the  median  line,  they  project  on  each  side  outward 
and  upward ;  and  by  folding  over  against  each  other  toward  the  median 
line,  they  form  the  right  and  left  hemispheres,  separated  by  the  longi- 
tudinal fissure.  A  similar  process  of  growth  in  the  spinal  cord  results 
in  the  formation  of  its  two  lateral  halves,  and  the  anterior  and  posterior 
median  fissures  of  the  cord.  Elsewhere  the  median  fissure  is  less  com- 
plete, as,  for  example,  between  the  two  lateral  halves  of  the  cerebellum 
or  those  of  the  medulla  oblongata ;  but  it  exists  everywhere,  and  marks 
more  or  less  distinctly  the  division  between  the  two  sides  of  the  nervous 
centres,  produced  by  the  excessive  growth  of  their  lateral  portions.  In 
this  way  the  whole  cerebro-spinal  axis  is  converted  into  a  double  organ, 
equally  developed  upon  the  right  and  left  sides,  and  partially  divided 
by  longitudinal  median  fissures. 

Organs  of  Special  Sense.— The  eyes  are  formed  by  a  diverticulum 
which  grows  out  on  ench  side  from  the  first  cerebral  vesicle.  This 
diverticulum  is  at  first  hollow,  its  cavity  communicating  with  that  of 
the  hemisphere.  Afterward,  the  passage  between  the  two  is  filled  with 
a  deposit  of  nervous  matter,  and  becomes  the  optic  nerve.  The  globular 
portion  of  the  diverticulnm,  which  is  converted  into  the  globe  of  the 
eye,  has  a  thin  layer  of  nervous  matter  deposited  upon  its  internal  sur- 


772  DEVELOPMENT    OF    THE    NERVOUS    SYSTEM. 

face,  which  becomes  the  retina ;  the  rest  of  its  cavity  being  occupied 
by  a  gelatinous  substance,  the  vitreous  body.  The  crystalline  lens  is 
formed  in  a  distinct  follicle,  which  is  an  ofl'shoot  of  the  integument,  and 
becomes  partially  imbedded  in  the  anterior  portion  of  the  eyeball.  The 
cornea  also  is  originally  a  part  of  the  integument,  and  remains  some- 
what opaque  until  a  late  period  of  development.  It  becomes  nearly 
transparent  a  short  time  before  birth. 

The  iris  is  a  muscular  septum,  formed  in  front  of  the  crystalline  lens. 
Its  central  opening,  which  afterward  becomes  the  pupil,  is  at  first  closed 
by  a  vascular  membrane,  the  pupillary  membrane,  passing  across  the 
axis  of  the  eye.  The  bloodvessels  of  this  membrane,  which  are  derived 
from  those  of  the  iris,  subsequently  become  atrophied.  They  disappear 
first  from  its  centre,  and  recede  gradually  toward  its  circumference ; 
returning  upon  themselves  in  loops,  the  convexities  of  which  are  directed 
toward  the  centre.  The  pupillary  membrane  itself  finally  becomes  atro- 
phied, following  in  this  retrograde  process  the  direction  of  its  receding 
bloodvessels,  namely,  from  the  centre  outward.  It  has  completely  dis- 
appeared by  the  end  of  the  seventh  month.  (Cruveilhier.) 

The  eyelids  are  formed  by  folds  of  the  integument,  which  project 
from  above  and  below  at  the  situation  of  the  eyeball.  They  grow  so 
rapidly  during  the  second  and  third  months  that  their  free  margins 
come  in  contact  and  adhere  together,  so  that  at  that  time  they  cannot 
be  separated  without  some  violence.  They  remain  adherent  from  this 
period  until  the  seventh  month  (Guy),  when  their  margins  separate  and 
they  become  free  and  movable.  In  carnivorous  animals  (dogs  and  cats), 
the  eyelids  do  not  separate  from  each  other  until  eight  or  ten  days  after 
birth. 

The  internal  ear  is  formed  in  a  somewhat  similar  manner  with  the 
eyeball,  by  an  offshoot  from  the  third  cerebral  vesicle ;  the  passage 
between  them  filling  up  by  a  deposit  of  white  substance,  which  becomes 
the  auditory  nerve.  The  tympanum  and  auditory  meatus  are  botli 
offshoots  from  the  external  integument. 

Skeleton  and  Limbs. — At  a  very  early  period  of  development  there 
appears,  immediately  beneath  the  medullary  canal,  a  cylindrical  cord, 
termed  the  chorda  dorsalis  (page  725).  It  consists  of  a  tubular  sheath 
containing  a  mass  cf  simple  cells,  closely  packed  together  and  united 
by  adhesive  material.  It  does  not  become  a  permanent  part  of  the 
skeleton,  but  is  a  temporary  organ  destined  to  disappear  as  development 
proceeds. 

On  each  side  of  the  chorda  dorsalis  there  is  formed  a  series  of  rec- 
tangular plates,  the  "  primitive  vertebrae,"  a  portion  of  whose  substance 
is  devoted  to  the  formation  of  muscular  tissue,  while  another  portion 
becomes  the  basis  for  the  permanent  vertebrae.  The  latter  are  de- 
posited in  the  form  of  cartilaginous  plates,  which  encircle  the  chorda 
dorsalis  in  a  series  of  rings,  corresponding  in  number  with  the  bodies 
of  the  future  vertebrae.  The  rings  increase  in  thickness  from  without 
inward,  encroaching  upon  the  substance  of  the  chorda  dorsalis,  and 


SKELETON    AND    LIMBS.  773 

finally  taking  its  place  altogether.  The  thickened  rings,  thus  solidified 
by  cartilaginous  deposit,  become  the  bodies  of  the  vertebrae  ;  while  their 
transverse  and  articulating  processes,  with  the  laminae  and  spinous  pro- 
cesses, are  formed  by  outgrowths  from  the  bodies  in  various  directions. 

When  the  union  of  the  dorsal  plates  upon  the  median  line  fails  to 
take  place,  the  spinal  canal  remains  open  at  that  situation,  and  presents 
the  malformation  known  as  spina  bifida.  This  may  consist  simply  in 
a  fissure  of  the  spinal  canal,  more  or  less  extensive,  in  which  case  it 
may  sometimes  be  cured,  or  may  even  close  spontaneously ;  or  it  may 
be  complicated  with  either  an  imperfect  development  or  complete  absence 
of  the  spinal  cord  at  the  same  spot,  producing  permanent  paralysis  of 
the  lower  extremities. 

The  entire  skeleton  is  at  first  cartilaginous.  The  first  points  of  ossifi- 
cation show  themselves  about  the  beginning  of  the  second  month,  almost 
simultaneously  in  the  clavicle  and  the  lower  jaw.  Then  come,  in  the 
following  order,  the  femur,  humerus,  and  tibia,  the  superior  maxilla,  the 
bodies  of  the  vertebrae,  the  ribs,  the  vault  of  the  cranium,  the  scapula 
and  the  pelvis,  the  metacarpus  and  metatarsus,  and  the  phalanges  of  the 
fingers  and  toes.  The  bones  of  the  carpus  are  all  cartilaginous  at  birth, 
and  do  not  begin  to  ossify  until  a  year  afterward.  According  to  Cru- 
veilhier,  the  calcaneum,  the  cuboid,  and  sometimes  the  astragalus,  begin 
their  ossification  during  the  latter  periods  of  foetal  life,  but  the  remainder 
of  the  tarsus  is  cartilaginous  at  birth.  The  lower  extremity  of  the 
femur,  according  to  the  same  authority,  shows  a  point  of  ossification  at 
birth  ;  all  the  other  extremities  of  the  long  bones  being  still  in  a  carti- 
laginous condition  at  this  time.  The  scaphoid  bone  of  the  tarsus  and 
the  pisiform  bone  of  the  carpus  are  the  last  to  commence  their  ossifica- 
tion, several  years  after  birth.  Nearly  all  the  bones  ossify  from  several 
distinct  points ;  the  ossification  spreading  as  the  cartilage  increases  in 
size,  and  the  various  bony  pieces,  thus  produced,  uniting  with  each 
other  at  a  later  period,  usually  some  time  after  birth. 

The  limbs  appear  by  a  budding  process,  as  offshoots  of  the  external 
blastodermic  layer.  They  are  at  first  mere  rounded 'elevations,  without 
any  separation  between  the  fingers  and  toes,  or  any  distinction  between 
the  different  articulations.  Subsequently  the  free  extremity  of  each 
limb  becomes  divided  into  the  phalanges  of  the  fingers  or  toes ;  and 
afterward  the  articulations  of  the  wrist  and  ankle,  knee  and  elbow, 
shoulder  and  hip,  appear  successively  from  below  upward. 

The  lower  limbs  in  man  are  less  rapid  in  development  than  the  upper. 
Both  the  legs  and  the  pelvis  are  very  slightly  developed  in  the  early 
periods  of  growth,  as  compared  with  the  spinal  column,  to  which  they 
are  attached.  The  inferior  extremity  of  the  spinal  column,  formed  by 
the  sacrum  and  coccyx,  projects  at  first  beyond  the  pelvis,  forming  a 
tail,  which  is  curled  forward  toward  the  adbomen,  and  terminates  in  a 
pointed  extremity.  The  entire  lower  half  of  the  body,  with  the  spinal 
column  and  appendages,  is  also  twisted,  from  left  to  right ;  so  that  the 
pelvis  is  not  only  curled  forward,  but  also  faces  at  right  angles  to  the 


774: 


DEVELOPMENT    OF    THE    NERVOUS    SYSTEM. 


Fig.  286. 


direction  of  the  head  and  upper  part  of  the  body.     Subsequently  the 
spinal  column  becomes  straighter  and  loses  its  twisted  form.     At  the 

same  time  the  pelvis  and  the  muscular  parts 
seated  upon  it  grow  so  much  faster  than  the 
sacrum  and  coccyx,  that  the  latter  become 
concealed  under  the  adjoining  soft  parts, 
and  the  rudimentary  tail  disappears. 

The  integument  of  the  embryo  is  at  first 
thin,  vascular,  and  transparent.  It  after- 
ward becomes  thicker,  more  opaque,  and 
whitish  in  color.  Even  at  birth,  however, 
it  is  considerably  more  vascular  than  in  the 
adult  condition,  and  its  ruddy  color,  due  to 
its  transparency  and  the  abundance  of  its 
capillary  bloodvessels,  is  strongly  marked. 
The  hairs  begin  to  appear  about  the  middle 
of  intra-uterine  life;  showing  themselves 
first  upon  the  eyebrows,  afterward  upon  the 
scalp,  trunk  and  extremities.  The  nails  are 
in  process  of  formation  from  the  third  to 
the  fifth  month  ;  and,  according  to  Kolliker, 

are  covered  with  a  layer  of  epidermis  until  after  the  latter  period.  The 
sebaceous  matter  of  the  cutaneous  glandules  accumulates  upon  the  skin 
after  the  sixth  month,  and  forms  a  whitish,  semi-solid,  oleaginous  layer, 
the  vernix  caxeosa,  which  is  most  abundant  in  the  flexures  of  the  joints, 
between  the  folds  of  the  integument,  behind  the  ears,  and  upon  the  scalp. 


HUMAN  EMBRYO,  about  one 
month  old.  Showing  the  large 
Bize  of  the  head  and  upper  parts 
of  the  body;  the  twisted  form  of 
the  spinal  column  ;  the  rudiment- 
ary condition  of  the  upper  and 
lower  extremities  ;  and  the  rudi- 
mentary tail  at  the  end  of  the 
spinal  column. 


CHAPTBE    XV. 


DEVELOPMENT    OF  THE   ALIMENTAEY   CANAL 
AND  ITS   APPENDAGES. 

THE  intestinal  canal  is  formed,  as  already  described  (page  726),  from 
the  internal  blastodermic  layer  which  curves  downward  and  inward  on 
each  side,  and  is  thus  converted  into  a  cylindrical  tube,  terminating  at 
each  extremity  in  a  cul-de-sac,  and  inclosed  by  the  external  blastodermic 
layer.  The  abdominal  walls  do  not  unite  with  each  other  upon  the 
median  line  until  after  the  formation  of  the  intestinal  canal ;  so  that, 
during  a  certain  period,  the  abdomen  of  the  embryo  is  widely  open  in 
front,  presenting  a  long  oval  excavation,  in  which  the  intestinal  tube  is 
situated,  running  from  its  anterior  to  its  posterior  extremity. 

Stomach  and  Intestine. — The  formation  of  the  stomach  takes  place  in 
the  following  manner :  The  alimentary  canal,  originally  straight,  soon 
presents  two  lateral  curvatures  at  the  upper  part  of  the  abdomen ;  the 
first  to  the  left,  the  second  to  the  right.  The  first  of  these  curvatures 
becomes  expanded  into  a  wide  sac,  projecting  laterally  from  the  median 
line  into  the  left  hypochondrium,  forming  the  great  pouch  of  the 
stomach.  The  second  curvature,  directed  to  the  right,  marks  the 
boundary  between  the  stomach  and  the  duodenum  ;  and  the  tube  at 
that  point,  becoming  constricted  and  furnished  with  an  unusually  thick 
circular  layer  of  muscular  fibres,  is  converted  into  the  pylorus.  Im- 
mediately below  the  pylorus,  the  duodenum  turns  to  the  left ;  and  these 
curvatures,  increasing  in  num- 


ber and  complexity,  form  the  con- 
volutions of  the  small  intestine. 
The  large  intestine  assumes  a 
spiral  curvature ;  ascending  on 
the  right  side,  then  crossing 
over  to  the  left  as  the  transverse 
colon,  and  again  descending  on 
the  left  side,  to  terminate  by  the 
sigmoid  flexure  in  the  rectum. 

The  curvatures  of  the  intes- 
tinal canal,  which  take  place  in 
an  antero-posterior,  as  well  as  in 
a  lateral  direction,  may  be  best 
studied  in  a  profile  view,  as  in 
Fig.  287.  The  abdominal  walls 
are  here  still  imperfectly  closed, 


Fig.  287. 


Formation  of  the  ALIMENTARY  CANAL.— 
a,  b.  Commencement  of  amnion.  c,  c.  Intestine. 
d.  Pharynx,  e.  Urinary  bidder.  /  Allantois 
or  chorion.  g.  Umbilical  \esicle. 


(775) 


776    DEVELOPMENT  OF  THE  ALIMENTARY  CANAL 

leaving  a  wide  opening  at  a,  6,  where  the  integument  of  the  foetus  is 
continuous  with  the  commencement  of  the  amniotic  membrane.  The 
intestine  makes  at  first  a  single  angular  turn  forward,  and  opposite  the 
most  prominent  portion  of  this  angle  is  to  be  seen  the  stem  of  the  um- 
bilical vesicle  (g).  A  short  distance  below  this  point  the  intestine  sub- 
sequently enlarges  in  calibre,  and  the  situation  of  this  enlargement 
marks  the  commencement  of  the  colon.  The  two  portions  of  the  intes- 
tine, after  this  period,  become  widely  different  from  each  other.  The 
upper  portion,  which  is  the  small  intestine,  grows  most  actively  in 
the  direction  of  its  length,  and  becomes  a  long,  narrow,  convoluted 
tube ;  while  the  lower  portion,  which  is  the  large  intestine,  increases 
rapidly  in  diameter,  but  elongates  less  than  the  former.  The  rectum  is 
the  part  of  the  large  intestine  which  alters  least  its  form  and  position. 
It  elongates  comparatively  little,  retains  its  position  for  the  most  part 
upon  the  median  line,  and  as  its  name  indicates,  continues  to  follow  a 
nearly  straight  course;  presenting  only  a  moderate  antero-posterior 
curvature  corresponding  with  the  hollow  of  the  sacrum,  and  a  slight 
lateral  obliquity,  from  its  upper  portion  which  is  placed  a  little  toward 
the  left,  to  the  anus  which  is  situated  upon  the  median  line.  At  first 
forming  the  blind  extremity  of  the  large  intestine,  it  subsequently  com- 
municates with  the  exterior  by  a  perforation  which  becomes  the  anus. 
In  the  chick-embryo,  according  to  Burdach,1  the  perforation  of  the  anus 
appears  on  the  fifth  day  of  incubation  ;  in  the  human  embryo  it  is 
formed  during  the  seventh  week.  In  certain  instances,  this  opening 
fails  to  take  place,  and  the  rectum  is  still  closed  at  birth;  presenting 
the  malformation  known  as  imperforate  anus.  If  the  rectum  be  other- 
wise fully  developed,  it  may  sometimes  be  felt,  distended  with  meconium, 
immediately  under  the  integument ;  and  an  artificial  opening  may  be 
successfully  made  by  an  incision  at  the  anal  region.  In  other  cases, 
there  is  also  a  deficiency,  more  or  less  extensive,  of  the  rectum  itself, 
the  large  intestine  terminating  in  the  upper  portion  of  the  pelvic  cavity. 

At  the  point  of  junction  between  the  small  and  the  large  intestine,  a 
lateral  diverticulum  of  the  latter  shows  itself,  and  increases  in  extent, 
until  the  ileum  seems  at  last  to  be  inserted  obliquely  into  the  side  of  the 
colon.  The  diverticulum  of  the  colon  is  at  first  conical  in  shape  ;  but 
afterward  that  portion  which  forms  its  free  extremity  becomes  narrow, 
elongated,  and  sometimes  twisted  upon  itself,  forming  the  appendix 
vermiformis  ;  while  the  remaining  portion,  which  is  continuous  with  the 
intestine,  becomes  exceedingly  enlarged,  and  forms  the  caput  coli. 

The  caput  coli  and  the  appendix  vermiformis  are  at  first  situated  near 
the  umbilicus ;  but  between  the  fourth  and  fifth  months  (Cruveilhier) 
their  position  is  altered,  and  they  become  fixed  in  the  right  iliac  region. 
During  the  first  six  months  the  internal  surface  of  the  small  intestine  is 
smooth.  At  the  seventh  month,  the  valvulae  conniventes  begin  to  ap- 
pear, after  which  they  increase  slowly  in  size,  but  are  still  comparatively 

1  Trait6  de  Physiologie,  traduit  par  Jourdan.    Paris,  1838,  tome  iii.  pp.  274,  468. 


AND    ITS    APPENDAGES. 


777 


Fig.  288. 


undeveloped  at  the  time  of  birth.  The  division  of  the  colon  into  sacculi 
by  longitudinal  and  transverse  bands,  is  also  an  appearance  which  pre- 
sents itself  only  during  the  last  half  of  foetal  life.  Previous  to  that 
time,  the  colon  is  smooth  and  cylindrical,  like  the  small  intestine. 

After  the  small  intestine  is  formed,  it  increases  rapidly  in  length.  It 
grows,  at  this  time,  faster  than  the  walls  of  the  abdomen ;  so  that  it 
can  no  longer  be  contained  in  the  abdominal 
cavity,  but  protrudes,  under  the  form  of  an 
intestinal  loop,  or  hernia,  from  the  umbilical 
opening.  (Fig.  288.)  In  the  human  em- 
bryo, this  protrusion  of  the  intestine  can  be 
readily  seen  during  the  latter  part  of  the 
second  month.  At  a  subsequent  period, 
the  walls  of  the  abdomen  grow  more  rapidly 
than  the  intestine ;  and,  gradually  envelop- 
ing the  hernial  protrusion,  at  last  reinclose 
it  in  the  cavity  of  the  abdomen. 

Owing  to  imperfect  development  of  the 
abdominal  walls,  and  incomplete  closure  of 
the  umbilicus,  the  intestinal  protrusion, 
which  is  normal  during  the  early  stages  of 
foetal  life,  sometimes  remains  at  birth,  and 
thus  produces  congenital  umbilical  hernia. 
As  the  parts  at  this  time  have  a  natural 
tendency  to  unite  with  each  other,  if  the 
hernial  protrusion  be  returned  within  the  abdomen,  and  retained  by 
simple  pressure  for  a  sufficient  period,  the  defect  is  usually  remedied, 
and  a  permanent  cure  effected.  The  conditions  are  different  in  a  hernia 
in  the  adult,  where  it  is  due  to  pressure  from  within,  and  a  gradual 
yielding  of  the  fibrous  tissues.  As  the  natural  period  for  the  closure 
of  the  abdominal  orifices  has  passed,  the  intestine  may  be  retained 
within  the  abdomen,  in  such  cases,  by  mechanical  means,  but  usually 
escapes  again  when  the  pressure  is  taken  off. 

The  contents  of  the  intestine,  which  accumulate  during  foetal  life,  vary 
in  different  parts  of  the  alimentary  canal.  In  the  small  intestine  they 
are  semifluid  in  consistency,  of  a  light  yellowish  or  grayish-white  color 
in  the  duodenum,  yellow,  reddish-brown,  and  greenish-brown  below.  In 
the  large  intestine  they  are  dark  greenish  and  pasty  in  consistency  ; 
and  the  contents  of  this  portion  of  the  alimentary  canal  have  received 
the  name  of  meconium,  from  their  resemblance  to  inspissated  poppy- 
juice.  The  meconium  contains  a  large  quantity  of  fat,  as  well  as  various 
insoluble  substances,  probably  the  residue  of  epithelial  and  mucous 
accumulations.  It  does  not  exhibit  any  trace  of  the  biliary  substances 
proper  (taurocholates  and  glycocholates)  when  examined  by  Petteni- 
kofer's  test ;  and  cannot  therefore  be  regarded  as  resulting  from  the 
accumulation  of  bile.  In  the  contents  of  the  small  intestine,  on  the 
contrary,  according  to  Lehmann,  slight  traces  of  bile  may  be  found,  as 
50 


FCETAL  Pio,  showing  the  pro. 
truding  loop  of  intestine,  forming 
umbilical  hernia;  from  a  speci- 
men in  the  author's  possession. 
From  the  convexity  of  the  loop  a 
thin  filament  ia  seen  passing  to 
the  umbilical  vesicle,  which,  in 
the  pig,  has  a  flattened,  leaf-like 
form. 


778    DEVELOPMENT  OF  THE  ALIMENTARY  CANAL 

early  as  between  the  fifth  and  sixth  months.  We  have  found  distinct 
traces  of  bile  in  the  small  intestine  at  birth,  but  it  is  even  then  in  ex- 
tremely small  quantity,  and  is  sometimes  altogether  absent. 

The  meconium,  therefore,  and  the  intestinal  contents  generally,  are 
not  composed  principally,  or  even  to  any  measurable  extent,  of  the 
secretions  of  the  liver.  They  appear  rather  to  be  derived  from  the 
mucous  membrane  of  the  intestine.  Even  their  yellowish  and  greenish 
color  does  not  depend  on  the  presence  of  bile,  since  the  yellow  color 
first  shows  itself  about  the  middle  of  the  small  intestine,  and  not  at  its 
upper  extremity.  The  material  which  afterward  accumulates  appears 
to  extend  from  this  point  upward  and  downward,  gradually  filling  the 
intestine,  and  becoming,  in  the  ileum  and  large  intestine,  darker  colored 
and  more  pasty  as  gestation  advances. 

It  is,  perhaps,  of  some  importance  in  this  connection,  that  the  amni- 
otic  fluid,  during  the  latter  half  of  foetal  life,  finds  its  way,  in  greater  or 
less  abundance,  into  the  stomach,  and  through  that  into  the  intestinal 
canal.  Small  cheesy-looking  masses  are  sometimes  to  be  found  at  birth 
in  the  fluid  contained  in  the  stomach,  which  are  seen  on  microscopic 
examination  to  be  portions  of  the  vernix  caseosa  exfoliated  from  the 
skin  into  the  amniotic  cavity,  and  afterward  introduced  through  the 
oesophagus  into  the  stomach.  According  to  Kolliker,  the  downy  hairs 
of  the  foetus,  exfoliated  from  the  skin,  are  often  swallowed  in  the  same 
way,  and  may  be  found  in  the  meconium. 

The  gastric  juice  is  not  secreted  before  birth ;  the  contents  of  the 
stomach  being  generally  in  small  quantity,  clear,  nearly  colorless,  and 
neutral  or  alkaline  in  reaction. 

Liver. — The  liver  is  developed  at  a  very  early  period.  Its  size  in 
proportion  to  that  of  the  entire  body  is  much  greater  in  the  early 
months  than  at  birth  or  in  the  adult  condition.  In  the  foetal  pig  we 
have  found,  the  relative  size  of  the  liver  greatest  within  the  first  month, 
when  it  amofliits  to  nearly  12  per  cent  of  the  entire  weight  of  the  body. 
Afterward  it  grows  less  rapidly  than  other  parts,  and  its  relative 
weight  diminishes  successively  to  10  per  cent,  and  6  per  cent.;  being 
reduced  before  birth  to  3  or  4  per  cent.  In  man,  also,  the  weight  of 
the  liver  at  birth  is  between  3  and  4  per  cent,  of  that  of  the  entire 
body. 

The  glycogenic  function  of  the  liver  commences  during  foetal  life, 
and  at  birth  the  tissue  of  the  organ  is  abundantly  saccharine.  In  the 
early  periods  of  gestation,  however,  sugar  is  produced  in  the  foetus  from 
other  sources  than  the  liver.  In  very  young  foetuses  of  the  pig,  both 
the  allantoic  and  amniotic  fluids  are  saccharine  a  considerable  time 
before  glucose  makes  its  appearance  in  the  liver.  Even  the  urine,  in 
half-grown  foetal  pigs,  contains  an  appreciable  quantity  of  sugar,  and 
the  young  animal  is  normally,  at  this  period,  in  a  diabetic  condition. 
The  glucose  disappears  before  birth,  as  shown  by  Bernard,1  from  both 

1  LeQons  de  Physiologie  ExpSrimentale.     Paris,  1855,  p.  398. 


AND    ITS    APPENDAGES.  779 

the  urine  and  the  amniotic  fluid ;  while  the  liver  begins  to  produce  the 
saccharine  substance  which  it  contains  after  birth. 

Lungs,  Thoracic  Cavity,  and  Diaphragm. — The  anterior  portion  of 
the  alimentary  canal,  which  occupies  the  region  of  the  neck,  is  the 
oesophagus.  It  is  straight,  and,  at  first,  very  short ;  but  it  subsequently 
increases  in  length,  simultaneously  with  the  growth  of  the  neighboring 
parts.  As  the  oesophagus  lengthens,  the  lungs  begin  to  be  developed 
by  a  protrusion  from  the  anterior  portion  of  the  oesophagus,  represent- 
ing the  commencement  of  the  trachea.  This  protrusion  soon  divides 
into  two  symmetrical  branches,  which  themselves  elongate  and  become 
repeatedly  subdivided,  forming  the  bronchial  tubes  and  their  ramifica- 
tions. At  first,  the  lungs  project  into  the  upper  part  of  the  abdominal 
cavity ;  for  there  is  still  no  distinction  between  the  chest  and  abdomen. 
Afterward,  a  horizontal  partition  begins  to  form  on  each  side,  at  the 
level  of  the  base  of  the  lungs,  which  gradually  closes  together  to  form 
the  diaphragm,  and  which  finally  shuts  off  the  cavity  of  the  chest  from 
that  of  the  abdomen.  Before  the  closure  of  the  diaphragm  is  com- 
plete, an  opening  exists  by  which  the  peritoneal  and  pleural  cavities 
communicate  with  each  other.  In  some  instances  the  development  of 
the  diaphragm  is  arrested  at  this  point,  either  on  one  side  or  the  other, 
and  the  opening  remains  permanent.  The  abdominal  organs  then  par- 
tially protrude  into  the  cavity  of  the  chest  on  that  side,  forming  con- 
genital diaphragmatic  hernia.  The  lung  on  the  affected  side  usually 
remains  in  a  state  of  imperfect  development.  Diaphragmatic  hernia  of 
this  character  is  more  frequently  found  upon  the  left  side  than  upon 
the  right,  and  may  sometimes  continue  until  adult  life  without  causing 
serious  inconvenience. 

Urinary  Bladder  and  Urethra. — Soon  after  the  formation  of  the 
intestine  a  vascular  outgrowth  takes  place  from  its  posterior  portion, 
which  gradually  protrudes  from  the  open  walls  of  the  abdomen,  until  it 
comes  in  contact  with  the  external  investing  membrane  of  the  egg 
(Fig.  287,  f)]  forming  subsequently,  by  its  continued  growth  and  ex- 
pansion, the  allantois  in  the  lower  animals,  the  chorion  in  man. 

The  chorion,  in  the  portion  immediately  connected  with  the  body  of 
the  embryo,  has,  like  the  allantois,  the  form  of  a  hollow  canal ;  but  as 
it  spreads  out,  to  constitute  the  external  investment  of  the  egg,  it  takes 
the  shape  of  a  continuous  membrane,  forming  the  chorion  proper 
(p.  746).  The  tubular  cavity  of  its  connecting  portion,  the  umbilical 
cord,  subsequently  becomes  obliterated ;  the  obliteration  commencing 
at  its  outer  extremity  and  gradually  proceeding  inward  until  it  reaches 
the  umbilicus.  Inside  the  umbilicus  it  still  proceeds  for  a  certain  dis- 
tance and  then  ceases.  Thus  the  original  protrusion  of  the  intestinal 
canal  within  the  abdomen,  which  gave  rise  to  the  allantois  and  the  cho- 
rion, is  divided  into  two  portions.  The  first  portion,  or  that  imme- 
diately connected  with  the  intestine,  remains  hollow,  and  forms  after- 
ward the  urinary  bladder.  The  second  portion,  between  the  urinary 


780         DEVELOPMENT    OF    THE    ALIMENTARY    CANAL 

bladder  and  the  umbilicus,  is  consolidated  into  a  rounded  cord,  which 
is  termed  the  urachus. 

The  urinary  bladder  is  at  first,  accordingly,  a  pyriform '  sac  (Fig. 
287,  e),  communicating  at  its  base  with  the  lower  portion  of  the  intes- 
tinal canal,  and  continuous  by  its  superior  pointed  extremity  with  the 
solid  cord  of  the  urachus,  by  means  of  which  it  is  attached  to  the  inter- 
nal surface  of  the  abdominal  walls  at  the  situation  of  the  umbilicus. 
Afterward,  the  bladder  loses  this  conical  form,  and  its  superior  fundus 
becomes  in  the  adult  rounded  and  bulging. 

Development  of  the  Mouth  and  Face — The  intestinal  canal  is  at  first 
a  cylindrical  tube,  closed  at  its  anterior  as  well  as  at  its  posterior 
extremity.  In  the  region  of  the  abdomen,  which  in  the  earliest  periods 
of  development  constitutes  nearly  the  whole  length  of  the  body,  the 
blastoderm  separates,  as  previously  described  (p.  735),  into  two  laminae, 
an  outer  and  an  inner.  The  outer  lamina,  consisting  of  the  external 
integument  and  the  subjacent  voluntary  muscles,  forms  the  parietes  of 
the  abdomen.  The  inner  lamina  forms  the  mucous  membrane  of  the 
alimentary  canal,  with  its  covering  of  involuntary  muscular  fibres. 
Owing  to  the  separation  of  these  two  laminae,  there  is  formed  the  peri- 
toneal cavity,  between  the  intestine  on  the  one  side  and  the  abdominal 
walls  on  the  other. 

But  in  the  anterior  part  of  the  body  of  the  embryo,  this  separation 
between  the  two  laminae  of  the  blastoderm  does  not  take  place.  Con- 
sequently, the  corresponding  portion  of  the  alimentary  canal,  namely, 
the  oesophagus,  remains  in  contact  with  the  surrounding  parts ;  and  its 
anterior  rounded  extremity,  the  pharynx  (Fig.  287,  d),  lies  immediately 
underneath  the  head,  covered  in  front  only  by  the  tissues  of  the  external 
blastodermie  layer. 

At  this  time  there  are  formed,  on  the  sides  and  front  of  the  neck,  four 
nearly  transverse  fissures,  the  cervical  fissures,  leading  from  the  exte- 
rior into  the  cavity  of  the  pharynx.  These  fissures,  or  clefts,  are  analo- 
gous to  those  which  exist  permanently  at  the  same  situation  in  fishes, 
where  the  gills  are  located,  and  by  which  the  water,  taken  in  at  the 
mouth,  is  expelled  through  the  sides  of  the  neck.  But  in  the  mamma- 
lian embryo  they  have  only  a  temporary  existence  as  continuous  open- 
ings. The  three  lower  fissures  disappear  entirely  by  the  subsequent 
adhesion  of  their  adjacent  edges ;  and  in  the  chick,  according  to  Foster 
and  Balfour,  are  completely  closed  by  the  seventh  day  of  incubation. 
The  upper  fissure  is  converted  into  a  narrow  canal,  leading  from  the 
exterior  into  the  pharynx,  but  closed  about  its  middle  by  a  transverse 
partition.  The  outer  portion  of  this  canal  becomes  the  external  audi- 
tory meatus ;  the  inner  portion,  the  Eustachian  tube.  The  transverse 
partition  is  the  membrana  tympani. 

The  cervical  fissures  in  man  are  especially  connected  with  the  forma- 
tion of  the  mouth  and  face.  Between  the  fissures  there  are,  of  course, 
bands  or  ridges  of  solid  tissue,  belonging  to  the  external  lamina  of  the 
blastoderm;  and  these  bands, especially  the  upper,  increase  in  growth  to 


AND    ITS    APPENDAGES.  781 

such  an  extent  that  they  become  more  or  less  prominent  folds,  and  have 
received  the  name  of  the  "  visceral  folds."  The  first  visceral  fold  grows 
rapidly  forward,  and  divides  into  two  somewhat  diverging  processes  or 
offshoots,  which  continue  to  become  more  and  more  prominent.  The 
corresponding  processes  from  the  right  and  left  sides  tend  to  approach 
each  other,  and  to  unite  upon  the  median  line.  Those  of  the  lower  pair 
do  so  unite,  and  thus  form  the  inferior  maxilla.  Those  of  the  tipper 
pair,  which  form  the  superior  maxilla,  unite,  not  with  each  other,  but 
with  an  intervening  process  which  grows  from  above  downward,  upon 
the  median  line,  between  them. 

By  this  growth  of  folds  or  processes  in  an  anterior  direction,  and  by 
their  union,  above  and  below,  upon  the  median  line,  there  is  included 
between  them  a  depressed  space,  lined  with  a  continuation  of  the  exter- 
nal blastodermic  layer,  and  situated  immediately  in  front  of  the  extremity 
of  the  pharynx.  This  excavation  is  the  cavity  of  the  mouth,  inclosed 
on  each  side  by  the  processes  of  the  superior  and  inferior  maxillae,  widely 
open  in  front,  but  terminating  at  its  bottom  by  a  blind  pit ;  there  being 
as  yet  no  communication  between  it  and  the  interior. 

Subsequently  an  opening  is  formed  between  the  bottom  or  back  part 
of  the  mouth  and  the  cavity  of  the  pharj-nx,  by  a  perforation  through 
the  substance  of  both  blastodermic  layers  at  that  point.  This  perfora- 
tion takes  place  in  the  human  embryo,  according  to  Burdach,1  during 
the  sixth  week.  The  opening  thus  formed  marks  the  situation  of  the 
fauces;  and  the  alimentary  canal  is  thus  made  to  communicate  with 
the  exterior.  The  lining  membrane  of  the  mouth  is  consequently  de- 
rived from  the  external  blastodermic  layer,  is  a  continuation  of  the 
external  integument,  and  the  muscles  sur- 
rounding it  are  voluntary  muscles ;  while  the  Fig.  289. 

mucous  membrane  of  the  pharynx  and  oeso- 
phagus is  derived  from  the  internal  blasto- 
dermic layer,  and  is  surrounded  by  involun- 
tary muscles. 

The  completion  of  the  component  parts 
of  the  face  about  the  mouth  is  accomplished 
by  the  continuous  development  of  the  five 
buds  or  processes,  above  described,  which 
grow  together  in  such  a  way  as  to  diminish 
the  size  of  the  originally  wide  oral  orifice,  HUMAN  EMBRYO,  about  one 
and  to  modify  its  form  in  various  directions,  month  old:  showing  the  growth 

/TT        c\nf\  \       mi  T        of  the  frontal  process  downward, 

(Fig.  289.)     The  process  which  grows  di-     and  that  of  th;  8uperior  anrt  in! 
rectly  downward  in  the  median  line  from  the     ferior  maxillary  processes  from 
frontal  region,  is  called  the  frontal  or  inter-    ^  .2SET" '"  '" 
maxillary  process,  because  it  afterward  con- 
tains, in  its  lower  extremity,  the  intermaxillary  bones,  with  the  four 
upper  incisor  teeth.     The  superior  maxillary  processes,  coming  from 

1  TraitS  de  Physiologic  ;  traduit  par  Jourdan.     Paris,  1838,  tome  iii.  p.  468. 


782 


DEVELOPMENT    OF    THE    ALIMENTARY    CANAL 


Fi<r.  290. 


the  sides,  unite  with  the  intermaxillary  process,  to  form  the  upper  jaw. 
In  quadrupeds  the  intermaxillary  bones,  containing  the  upper  incisor 
teeth,  remain  distinct  from  those  of  the  superior  maxilla,  the  line  of 
demarcation  between  them  being  indicated  by  a  suture.  In  man,  as  a 
general  rule,  they  are  consolidated  with  each  other,  the  only  permanent 
suture  being  that  on  the  median  line,  between  the  right  and  left  halves 
of  the  upper  jaw.  According  to  Geoffroy  Saint-Hilaire,1  a  permanent  line 
of  suture  sometimes  remains  between  the  intermaxillary  and  the  superior 
maxillary  bones. 

The  two  inferior  maxillary  processes  unite  with  each  other,  making 
the  lower  border  of  the  cavity  of  the  mouth,  and  form,  by  their  union 
upon  the  median  line,  the  inferior  maxilla.  In  quadrupeds  the  two 

inferior  maxillary  bones  remain  perma- 
nently divided  by  a  median  suture;  but  in 
man  they  are  consolidated  into  a  single 
piece  during  the  first  year  after  birth. 

As  the  intermaxillary  process  grows 
from  above  downward,  it  becomes  double 
at  its  lower  extremity,  and  at  the  same 
time  gives  origin  to  two  lateral  offshoots, 
which  curl  round  and  inclose  two  circular 
orifices,  the  anterior  nares  (Fig.  290);  the 
offshoots  themselves  becoming  the  alse 
nasi.  The  external  border  of  the  ala  nasi 
subsequently  adheres  to  the  superior  maxil- 
lary process,  leaving  only  a  curved  crease 
or  furrow  at  the  side  of  the  nose,  which 

marks  the  line  of  union  between  them.  In  many  of  the  quadrupeds, 
this  furrow  remains  partially  open,  extending,  as  a  curvilinear  cleft,  out- 
ward and  upward  from  the  orifice  of  the  nostril. 

The  mouth  at  this  time  is  wide  and  gap- 
ing, owing  to  the  incomplete  development 
of  the  upper  and  lower  jaw  and  the  com- 
parative insufficiency  of  the  lips  and 
cheeks.  The  soft  parts  afterward  increase 
in  growth,  and  thus  gradually  diminish 
the  size  of  the  oral  orifice  (Fig.  291).  The 
lips  and  cheeks  arise  by  folds  of  the  in- 
tegument and  subjacent  muscular  layers, 
which,  projecting  respectively  from  above 
downward,  from  below  upward,  and  from 
behind  forward,  form  the  permanent  bor- 
ders of  the  opening  of  the  mouth.  The 
upper  lip  in  man  presents  a  median  furrow, 
possession.  bordered  by  two  slightly  elevated  ridges, 


HEAD  OP  HUMAN  EMBRYO 
at  about  the  sixth  week.  From  a 
specimen  in  the  author's  possession. 


1  Histoire  des  Anomalies  de  1'Organization.     Paris,  1832,  tome  i.  p.  581. 


AND    ITS    APPENDAGES.  783 

corresponding  with  the  union  of  the  superior  maxillary  and  the  inter- 
maxillary processes.  The  lower  lip,  like  the  inferior  maxilla,  is  com- 
pletely consolidated  upon  the  median  line,  and  usually  shows  no  trace 
of  its  double  origin. 

In  some  instances,  the  superior  maxillary  and  the  intermaxillary 
processes  fail  to  unite  with  each  other,  giving  rise  to  the  malformation 
known  as  hare-lip.  The  fissure,  in  cases  of  hare-lip,  is  consequently 
situated,  as  a  general  rule,  not  in  the  median  line,  but  a  little  to  one 
side  of  it,  corresponding  with  the  outer  edge  of  the  intermaxillary  pro- 
cess. Sometimes  the  same  deficiency  exists  on  both  sides,  forming 
u  double  hare-lip ;"  in  which  case,  if  the  fissure  extend  through  the  bony 
structures,  the  central  piece  of  the  superior  maxilla,  detached  from  the 
remainder,  contains  the  upper  incisor  teeth,  and  corresponds  with  the 
intermaxillary  bone  of  the  lower  animals.  In  one  instance,  observed 
by  Wyman,1  the  fissure  of  hare-lip  was  situated  in  the  median  line,  the 
two  intermaxillary  bones  not  having  united  with  each  other. 

The  eyes  at  an  early  period  are  upon  the  sides  of  the  head  (Fig.  289). 
As  development  proceeds,  they  come  to  be  situated  farther  forward 
(Fig.  290),  their  axes  being  divergent  and  directed  obliquely  forward 
and  outward.  At  a  still  later  period  they  are  placed  on  the  anterior 
plane  of  the  face  (Fig.  291),  and  have  their  axes  nearly  parallel  and 
looking  directly  forward.  This  change  in  situation  is  effected  by  the 
more  rapid  growth  of  the  posterior  and  lateral  portions  of  the  head, 
which  enlarge  in  such  a  manner  as  to  alter  the  relative  position  of  the 
parts  seated  in  front. 

The  palate  is  formed  by  a  septum  between  the  mouth  and  nares, 
which  arises  on  each  side  as  a  horizontal  offshoot  from  the  superior 
maxilla.  The  two  plates  afterward  unite  upon  the  median  line,  forming 
a  complete  partition  between  the  oral  and  nasal  cavities.  The  right 
and  left  nasal  passages  are  separated  from  each  other  by  a  vertical 
plate  (vomer),  which  grows  from  above  downward  and  fuses  with  the 
palatal  plates  below.  Fissure  of  the  palate  is  caused  by  a  deficiency 
of  one  of  the  horizontal  maxillary  plates.  It  is  accordingly  situated  a 
little  on  one  side  of  the  median  line,  and  is  frequently  associated  with 
hare-lip  and  fissure  of  the  upper  jaw.  The  fissures  of  the  palate  and  of 
the  jaw  are  often  continuous  with  each  other. 

The  anterior  and  posterior  arches  of  the  palate  are  incomplete  trans- 
verse partitions  which  grow  inward  from  the  sides  of  the  fauces,  subse- 
quently to  the  perforation  of  the  pharynx  and  its  communication  with 
the  oral  cavity.  Owing  to  the  muscular  tissue  which  the}^  contain,  the 
orifice  of  the  alimentary  canal  thus  becomes  capable  of  constriction  or 
enlargement,  according  to  its  condition  of  functional  activity. 

1  Transactions  of  the  Boston  Society  for  Medical  Improvement,  March  9th,  1863. 


CHAPTEK  XVI. 


DEVELOPMENT  OF  THE  WOLFFIAN 
NEYS,  AND  INTERNAL  ORGANS 
TION. 


BODIES,  KID- 
OF   GENERA- 


THE  first  trace  of  a  urinary  apparatus  in  tho  embryo  consists  of  two 
long,  fusiform  organs,  which  make  their  appearance  in  the  abdomen  at 
a  very  early  period,  one  on  each  side  the  spinal  column,  and  which  are 
known  by  the  name  of  the  Wolffian  bodies.  They  are  fully  formed,  in 
the  human  subject,  toward  the  end  of  the  first  month  (Coste),  at  which 
time  they  are  the  largest  organs  in  the  abdomen,  extending  from  just 
below  the  heart,  nearly  to  the  posterior  extremity  of  the  body.  In  the 
foetal  pig,  when  thirteen  or  fourteen  millimetres  in  length,  the  Wolffian 
bodies  are  rounded  and  kidney-shaped,  and  oc- 
cupy a  large  part  of  the  abdominal  cavity.  Their 
combined  weight  is  at  this  time  a  little  over  3  per 
cent,  of  that  of  the  entire  body  ;  a  proportion 
which  is  seven  or  eight  times  as  large  as  that  of 
the  kidneys  in  the  adult  condition.  There  are, 
indeed,  at  this  period  only  three  organs  of  no- 
ticeable size  in  the  abdomen,  namely,  the  liver, 
which  has  begun  to  be  formed  at  the  upper  part 
of  the  abdominal  cavity  ;  the  intestine,  which  is 
already  somewhat  convoluted,  and  occupies  a 
central  position  ;  and  the  Wolffian  bodies,  which 
project  on  each  side  the  spinal  column. 

The  Wolffian  bodies,  in  their  intimate  structure, 
closely  resemble  the  adult  kidney.  They  consist 
of  secreting  tubules,  lined  with  epithelium,  run- 
ning transversely  from  the  inner  to  the  outer  edges 
of  the  organs,  and  terminating  at  their  extremities  by  rounded  dilata- 
tions. Into  each  of  these  dilated  extremities  is  received  a  globular  coil 
of  capillary  bloodvessels,  or  glomerulus,  similar  to  those  of  the  kidney. 
The  tubules  of  the  Wolffian  body  empty  into  a  common  excretory  duct, 
which  leaves  the  organ  at  its  lower  extremity,  and  communicates  with 
the  intestinal  canal,  at  the  point  where  the  diverticulum  of  the  allantois 
is  given  off,  and  where  the  urinary  bladder  is  afterward  to  be  situated. 
The  principal  distinction  in  structure,  between  the  Wolffian  bodies  and 
the  kidneys,  consists  in  the  size  of  the  tubules  and  of  their  glomernli  ; 
these  elements  being  considerably  larger  in  the  Wolffian  body  than  in 


PIG,  13  milli- 
metres long;  from  a  spe- 
cimen in  the  author's  pos- 
session.—1.  Heart.  2.  An- 
terior limb.  3.  Posterior 
limb.  4.  Wolffian  body. 
The  abdominal  walls  have 
been  cut  away,  in  order 
to  show  the  position  of 
the  Wolfflan  bodies. 


the  kidney.      In  the 
(  784  ) 


foetal  pig,  when  3j  or  4  centimetres  in  length, 


DEVELOPMENT    OF    THE    WOLFFIAN    BODIES,   ETC.      785 

at  which  time  both  organs  coexist,  the  diameter  of  the  tubules  of  the 
Wolffian  body  is  0.125  millimetre,  while  in  the  kidney  of  the  same  foetus, 
the  diameter  of  the  tubules  is  only  0.034  millimetre.  The  glomeruli  in 
the  Wolffian  bodies  measure  0.55  millimetre  in  diameter,  while  those  of 
the  kidney  measure  only  0.14  millimetre.  The  Wolffian  bodies  are  there- 
fore urinary  organs,  so  far  as  regards  their  anatomical  structure,  and 
are  sometimes  known  by  the  name  of  the  "  false  kidneys."  There  is 
little  doubt  that  they  perform,  at  this  early  period,  a  function  analogous 
to  that  of  the  kidneys,  and  separate  from  the  blood  of  the  embryo  an 
excrementitious  fluid  which  is  discharged  into  the  cavity  of  the  allantois. 

Subsequently,  the  Wolffian  bodies  increase  for  a  time  in  size,  though 
not  so  rapidly  as  the  other  organs.  Their  relative  magnitude  con- 
sequently diminishes.  Still  later,  they  suffer  an  absolute  atrophy,  and 
become  gradually  less  perceptible.  In  the  human  embryo,  they  are 
hardly  to  be  detected  after  the  end  of  the  second  month  (Longet),  and 
in  the  quadrupeds  they  completely  disappear  long  before  birth. 

The  kidneys  are  formed  just  behind  the  Wolffian  bodies,  and  are  at 
first  entirely  concealed  by  them  in  a  front  view,  the  kidneys  being  at 
this  time  not  more  than  one-fourth  or  one-fifth  part  the  size  of  the 
Wolffian  bodies.  (Fig.   293.)      The   kidneys 
subsequently  enlarging,   while  the  Wolffian 
bodies  diminish,  the  proportion  between  the 
two  organs  is    reversed ;    and    the  Wolffian 
bodies  appear  as  small  rounded  masses,  sit- 
uated on  the  anterior  surface  of  the  kidneys. 
(Figs.  294  and  295).     The  kidneys,  during 
this  period,  grow  more  rapidly  in  an  upward 
than  in  a  downward  direction,  so  that  the 
Wolffian  bodies  come  to   be   situated    near 
their  inferior  extremity. 

The  kidneys,  during  the  succeeding  pe- 
riods  of  foetal  life,  become  in  turn  very  largely 
developed  in  proportion  to  the  rest  of  the  author's  possession.— i.  Woif- 
internal  organs ;  attaining  a  size,  in  the  foetal  fian  body>  2>  Kidney- 
pig,  equal  to  more  than  two  per  cent,  in  weight  of  the  entire  body. 
This  proportion  again  diminishes  before  birth,  owing  to  the  increased 
development  of  other  parts.  In  the  human  foetus  at  birth,  the  weight 
of  the  two  kidneys,  taken  together,  is  6  parts  per  thousand  of  that  of 
the  entire  body. 

Internal  Organs  of  Generation. — About  the  same  time  that  the  kid- 
neys are  formed  behind  the  Wolffian  bodies,  two  oval-shaped  organs 
make  their  appearance  in  front,  on  the  inner  side  of  the  Wolffian  bodies 
and  between  them  and  the  spinal  column.  These  bodies  are  the  inter- 
nal organs  of  generation ;  namely,  the  testicles  in  the  male,  and  the 
ovaries  in  the  female.  At  first  they  occupy  the  same  situation  and 
present  the  same  appearance,  whether  the  foetus  is  afterward  to  be 
male  or  female.  (Fig.  294.) 


786      DEVELOPMENT    OF    THE    WOLFFIAN    BODIES,   ETC. 

A  short  distance  above  the  internal  organs  of  generation  there  com- 
mences, on  each  side,  a  narrow  tube  which  runs  from  above  downward 

along  the  anterior  border  of  the  Wolffian  body, 

Fig.  294. immediately   in  front  of,   and  parallel   with 

the  excretory  duct  of  this  organ.  The  two 
tubes  then  approach  each  other  below  ;  and, 
joining  upon  the  median  line,  einpt}',  together 
with  the  ducts  of  the  Wolffian  bodies,  into 
the  base  of  the  allantois,  or  what  will  after- 
ward be  the  urinary  bladder.  These  tubes 
serve  as  the  excretory  ducts  of  the  internal 
organs  of  generation  ;  and  will  afterward  be- 
come the  vasa  deferentia  in  the  male,  and 

INTERNAL    ORGAN a    OP      .,       .„   ,,  .    ,        .       ,,        ,,         -• 

GENERATION,  in  a  foetal  pig  the  Fallopian  tubes  m  the  female.  Accord- 
iy2  centimetres  long.  From  a  ing  to  Coste,  the  vasa  deferentia  at  an  early 

specimen  in  the  author's  pos-  ,     -,        .,,      .,  ,.   -, 

session  - 1,  i.  Kidneys.  2,  2.  period  are  disconnected  with  the  testicles ; 
Wolffian  bodies.  3,3  internal  and  originate,  like  the  Fallopian  tubes,  by 
or^i>efsgerruHnarytbSildCder  free  extremities,  presenting  each  an  open 
turned  over  in  front.  5.  intea-  orifice.  Afterward  the  vasa  deferentia  be- 
come adherent  to  the  testicles,  and  establish 

a  communication  with  the  tubuli  seminiferi.  In  the  female,  the  Fallo- 
pian tubes  remain  permanently  disconnected  with  the  ovaries,  except  by 
the  edge  of  the  fimbriated  extremity ;  which  in  many  of  the  lower  ani- 
mals becomes  closely  adherent  to  the  ovary,  and  envelops  it  more  or 
less  completely  in  a  distinct  sac. 

Male  Organs  of  Generation  ;  Descent  of  the  Testicles. — In  the  male 
foetus  there  now  commences  a  change  of  place  in  the  internal  organs 
of  generation,  which  is  known  as  the  u  descent  of  the  testicles."  Jr. 
consequence  of  this  change,  the  testicles,  which  are  at  first  placed 
near  the  middle  of  the  abdomen  and  in  front  of  the  kidneys,  come  at 
last  to  be  situated  in  the  scrotum,  outside  and  below  the  abdominal 
cavity.  They  also  become  inclosed  in  a  distinct  serous  sac,  the  tunica 
vaginalis  testis.  This  apparent  movement  of  the  testicles  is  accom- 
plished in  the  same  manner  as  that  of  the  Wolffian  bodies,  namely,  by 
a  disproportionate  growth  of  the  middle  and  upper  portions  of  the 
abdomen  and  of  the  tissues  above  the  testicles,  so  that  the  relative 
position  of  the  organs  becomes  altered. 

By  the  upward  enlargement  of  the  kidneys,  both  the  Wolffian  bodies 
and  the  testicles  are  soon  found  to  occupy  an  inferior  position.  (Fig. 
295.)  At  the  same  time,  a  slender  rounded  cord  (not  represented  in  the 
figure)  passes  from  the  lower  extremity  of  each  testicle  in  an  outward 
and  downward  direction,  crossing  the  vas  deferens  a  short  distance  above 
its  union  with  its  fellow  of  the  opposite  side.  Below  this  point,  the  cord 
spoken  of  continues  to  run  obliquely  outward  and  downward ;  and, 
passing  through  the  abdominal  walls  at  the  situation  of  the  inguinal 
canal,  is  inserted  into  the  subcutaneous  tissue  near  the  symphysis  pubis. 
The  lower  part  of  this  cord  becomes  the  gubernaculum  testis.  It  con- 


DEVELOPMENT    OF    THE    WOLFFIAN    BODIES,   ETC.      787 


Fiir.  295. 


INTERNAL  ORGANS  OF  (JKNEBA- 
TION  in  a  foetal  pi£  nearly  10  centimetres 
long.  From  a  specimen  in  the  author's 
possession.— 1, 1.  Kidneys.  2, 2.  Wolffian 
bodies.  3,  3.  Testicles.  4.  Urinary  blad- 
der. 6.  Intestine. 


tains  muscular  fibres,  which  may  be  easily  detected,  in  the  human  foetus, 

during  the  latter  half  of  intra-uterine 

life.     At  the  period  of  birth,  however, 

or  soon  afterward,  they  have  usually 

disappeared. 

That  portion  of  the  excretory  tube 
of  the  testicle  which  is  situated  out- 
side the  crossing  of  the  gubernaculum, 
is  destined  to  become  afterward  con- 
voluted, and  converted  into  the  epi- 
didymis,  That  which  is  situated 
inside  the  same  point  remains  com- 
paratively straight,  but  becomes  con- 
siderably elongated,  and  is  finally 
known  as  the  vas  deferens. 

As  the  testicles  descend  still  far- 
ther in  the  abdomen,  they  continue  to 
grow,  while  the  Wolffian  bodies,  on 
the  contrary,  become  smaller  ;  and  at 
last,  when  the  testicles  have  arrived  at  the  internal  inguinal  ring,  the 
Wolffian  bodies  have  altogether  disappeared,  or  have  become  so  altered 
that  they  are  no  longer  recognizable.  In  the  human  foetus,  the  testicles 
reach  the  internal  inguinal  ring  about  the  termination  of  the  sixth 
month  (Wilson). 

During  the  succeeding  month,  a  protrusion  of  the  peritoneum  takes 
place  through  the  inguinal  canal,  in  advance  of  the  testicle;  the  last- 
named  organ  still  continuing  its  descent.  As  it  passes  into  the  scrotum, 
loops  of  muscular  fibres  are  given  off  from  the  lower  border  of  the  in- 
ternal oblique  muscle  of  the  abdomen,  extending  downward  with  the 
testicle,  upon  it  and  upon  the  elongating  spermatic  cord.  These  con- 
stitute afterward  the  cremaster  muscle. 

At  last,  the  testicles  descend  quite  to  the  bottom  of  the  scrotum. 
The  convoluted  portion  of  the  efferent  duct,  namely,  the  epididymis, 
remains  attached  to  the  body  of  the  testicle ;  while  the  vas  deferens 
passes  upward,  in  a  reverse  direction,  enters  the  abdomen  through  the 
inguinal  canal,  again  bends  downward,  and  joins  its  fellow  of  the  oppo- 
site side ;  after  which  they  both  open  into  the  prostatic  portion  of  the 
urethra  by  distinct  orifices,  situated  on  either  side  of  the  median  line. 
At  the  same  time,  two  diverticula  arise  from  the  median  portion  of  the 
vasa  deferentia,  and,  elongating  in  a  backward  direction,  beneath  the 
base  of  the  bladder,  become  developed  into  sacculated  reservoirs,  the 
vesiculse  seminales. 

The  left  testicle  is  a  littler  later  in  its  descent  than  the  right ;  but  it 
afterward  passes  farther  into  the  scrotum,  and,  in  the  adult  condition, 
usually  hangs  a  little  lower  than  the  corresponding  organ  on  the  oppo- 
site side. 

After  the  testicle  has  passed  into  the  scrotum,  the  serous  pouch, 


788      DEVELOPMENT    OF    THE    WOLFFIAN"    BODIES,    ETC 


Fig.  296. 


Formation  of  the  TUNICA 
VAGINALIS  TRSTIS.—  1. 
Testicle  nearly  at  the  bottom 
of  the  scrotum.  2.  Cavity  of 
tunica  vaginalis.  3.  Cavity  of 
peritoneum.  4.  Obliterated 
neck  of  peritoneal  sac. 


which  preceded  its  descent,  remains  for  a  time  in  communication  with 
the  peritoneal  cavity.  In  many  of  the  quadrupeds,  as,  for  example,  the 
rabbit,  this  condition  is  permanent ;  and  the  testicle  may  be  alternately 
drawn  downward  into  the  scrotum,  or  retracted 
into  the  abdomen,  by  the  action  of  th&  guber- 
naculum  and  the  cremaster  muscle.  In  the 
human  foetus,  the  two  opposite  surfaces  of  the 
peritoneal  pouch  approach  each  other  at  the 
inguinal  canal,  forming  at  that  point  a  con- 
striction, which  partly  shuts  off  the  testicle 
from  the  cavity  of  the  abdomen.  By  a  con- 
tinuation ot  this  process,  the  serous  surfaces 
come  in  contact,  and,  adhering  together  at 
this  situation  (Fig.  296,  4),  form  a  kind  of 
cicatrix,  by  which  the  cavity  of  the  tunica  va- 
ginalis (2)  is  shut  off  from  the  general  cavity 
of  the  peritoneum(s).  The  tunica  vaginalis 
testis  is,  therefore,  originally  a  part  of  the 
peritoneum,  from  which  it  is  subsequently 
separated  by  the  adhesion  of  its  opposite 
walls. 

The  separation  of  the  tunica  vaginalis  testis  from  the  peritoneum  is 
usually  completed  in  the  human  foetus  before  birth.     But  sometimes  it 
fails  to  take  place  at  the  usual  time,  and  the  intestine  is  then  liable  to 
protrude  into  the  scrotum,  in  front  of  the  spermatic  cord,  giving  rise 
to   congenital    inguinal   hernia.    (Fig.    297.) 
The  parts   implicated   in   this    malformation 
have  still,  as  in  the  case  of  congenital  umbili- 
cal hernia,  a  tendency  to  unite  with  each  other 
and  obliterate  the  opening;  and  if  the  intes- 
tine be  retained  by  pressure  in  the  cavity  of 
the  abdomen,  cicatrization  usually  takes  place 
at  the  inguinal  canal,  and  a  cure  is  effected. 

Female  Organs  of  Generation. — At  an  early 
period  of  development,  the  ovaries  have  the 
same  external  appearance,  and  occupy  the 
same  position  in  the  abdomen,  as  the  testicles 
in  the  opposite  sex.  The  descent  of  the  ovaries 
also  takes  place,  to  a  great  extent,  in  the  same 
manner  with  the  corresponding  change  of 
When,  in  the  early  part  of  this  descent,  they 
have  reached  the  level  of  the  lower  edge  of  the  kidneys,  a  cord,  analogous 
to  the  gubernaculum,  may  be  seen  proceeding  from  their  lower  extremity, 
crossing  the  efferent  duct  on  each  side,  and  passing  downward,  to  be 
attached  to  the  subcutaneous  tissues  at  the  situation  of  the  inguinal 
ring.  That  part  of  the  duct  situated  outside  the  crossing  of  this  cord, 
becomes  convoluted,  and  is  converted  into  the  Fallopian  tube ;  while 


CONGENITAL  INGUINAL 
H  K  R  N  i  A  .—1.  Testicle.  2,  2, 2. 
Intestine. 


position  of  the  testicles. 


DEVELOPMENT    OF    THE    WOLFFIAN    BODIES,    ETC.      789 

that  which  is  inside  the  same  point,  is  developed  into  the  uterus.  The 
upper  portion  of  the  cord  itself  becomes  the  ligament  of  the  ovary  ;  its 
lower  portion,  the  round  ligament  of  the  uterus. 

As  the  ovaries  continue  their  descent,  they  pass  below  and  behind  the 
Fallopian  tubes,  which  perform  at  the  same  time  a  movement  of  rota- 
tion, from  before  backward  and  from  above  downward ;  the  whole, 
together  with  the  ligaments  of  the  ovaries  and  the  round  ligaments, 
being  enveloped  in  double  folds  of  peritoneum,  which  enlarge  with  the 
growth  of  the  parts  included  between  them,  and  constitute  finally  the 
broad  ligaments  of  the  uterus. 

While  these  changes  are  taking  place  in  the  adjacent  organs,  the  two 
lateral  halves  of  the  uterus  fuse  with  each  other  upon  the  median  line, 
and  become  covered  with  an  abundant  layer  of  muscular  fibres.  In  the 
quadrupeds,  the  uterus  remains  divided  at  its  upper  portion,  running 
out  into  two  long  conical  tubes  or  cornua  (Fig.  228),  presenting  the 
form  known  as  the  uterus  bicornis.  In  the  human  species,  the  fusion 
of  the  two  lateral  halves  of  the  organ  is  nearly  complete ;  so  that  the 
uterus  presents  externally  a  somewhat  rounded,  flattened  and  triangular 
figure  (Fig.  229),  with  the  ligaments  of  the  ovary  and  the  round  liga- 
ments passing  off  from  its  superior  angles.  Internally,  the  cavity  of 
the  organ  still  presents  a  strongly  marked  triangular  form,  the  vestige 
of  its  original  division. 

Occasionally  the  human  uterus  in  the  adult  condition  remains  divided 
by  a  vertical  septum,  running  from  the  middle  of  its  fundus  downward 
toward  the  os  internum.  The  organ  may  even  present  a  partial  external 
division,  corresponding  with  the  situation  of  the  internal  septum,  and 
producing  the  malformation  known  as  "  uterus  bicornis,"  or  double 
uterus. 

The  os  internum  and  the  os  externum  are  produced  by  partial  constric- 
tions of  the  original  generative  passage  ;  and  the  anatomical  distinctions 
between  the  body  of  the  uterus,  the  cervix,  and  the  vagina,  arise  from 
the  different  modes  of  development  of  the  mucous  membrane  and  mus- 
cular tunic  in  its  corresponding  portions.  During  foetal  life,  the  neck 
of  the  uterus  grows  faster  than  its  body;  so  that, at  the  period  of  birth, 
the  organ  is  far  from  presenting  the  form  which  it  exhibits  in  the  adult 
condition.  In  the  human  foetus  at  term,  the  cervix  uteri  constitutes 
nearly  two-thirds  of  the  entire  length  of  the  organ ;  while  the  body 
forms  but  little  over  one-third.  The  cervix,  at  this  time,  is  larger  in 
diameter  than  the  body;  so  that  the 'whole  organ  presents  a  tapering 
form  from  below  upward.  The  arbor  vitae  uterina  of  the  cervix  is  at 
birth  very  fully  developed,  and  the  mucous  membrane  of  the  body  is 
also  thrown  into  three  or  four  folds  which  radiate  upward  from  the  os 
internum.  The  cavity  of  the  cervix  is  filled  with  transparent  semi-solid 
mucus. 

The  position  of  the  uterus  at  birth  is  different  from  that  which  it 
assumes  in  adult  life;  nearly  the  entire  length  of  the  organ  being  above 
the  level  of  the  symphysis  pubis,  and  its  inferior  extremity  passing 


790      DEVELOPMENT    OF    THE    WOLFFIAN    BODIES,    ETC. 

below  that  point  only  by  about  six  millimetres.  It  is  also  slightly  ante- 
flexed  at  the  junction  of  the  body  and  cervix.  After  birth,  the  uterus, 
together  with  its  appendages,  continues  to  descend ;  and  at  the  period 
of  puberty  its  fundus  is  situated  just  below  the  level  of  the  symphysis 
pubis. 

The  ovaries  at  birth  are  narrow  and  elongated  in  form.  They  contain 
at  this  time  an  abundance  of  eggs ;  each  inclosed  in  a  Graafian  follicle, 
and  averaging  .04  millimetre  in  diameter.  The  vitellus  is  imperfectly 
formed  in  most  of  them,  and  in  some  is  hardly  to  be  distinguished.  The 
Graafian  follicle  at  this  period  envelops  each  egg  closely,  there  being  no 
fluid  between  its  internal  surface  and  the  exterior  of  the  egg,  but  only 
the  thin  layer  of  cells  forming  the  "membrana  granulosa."  Inside  this 
layer  is  to  be  seen  the  germinative  vesicle,  with  the  germinative  spot, 
surrounded  by  a  faintly  granular  vitellus,  more  or  less  abundant  in  dif- 
ferent parts.  Some  of  the  Graafian  follicles  containing  eggs  are  as  large 
as  .05  millimetre;  others  as  small  as  .02  millimetre.  In  the  very 
smallest,  the  cells  of  the  membrana  granulosa  appear  to  fill  entirely  the 
cavity  of  the  follicle,  concealing  the  rudiments  of  the  primitive  egg. 


CHAPTEE  XVII. 

DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 

THERE  are  three  distinct  forms  assumed  by  the  circulatory  system 
during  different  periods  of  life.  These  different  forms  of  the  circulation 
are  connected  with  the  manner  in  which  nutrition  and  the  renovation  of 
the  blood  are  accomplished  at  different  epochs ;  and  they  follow  each 
other  in  the  progress  of  development,  as  different  organs  are  employed 
in  turn  to  accomplish  the  above  functions.  The  first  form  is  that  of  the 
vitelline  circulation,  which  exists  at  a  period  when  the  vitellus  is  the 
source  of  nutrition  for  the  embryo.  The  second  is  the  placental  circula- 
tion, which  lasts,  in  man  and  the  mammalians,  through  the  greater  part 
of  foetal  life,  and  is  characterized  by  the  existence  of  the  placenta ;  the 
third  is  the  complete  or  adult  circulation,  in  which  the  renovation  and 
nutrition  of  the  blood  are  provided  for  by  the  lungs  and  the  intestinal 
canal. 

Vitelline  Circulation. — When  the  body  of  the  embryo  has  begun  to 
be  formed  in  the  centre  of  the  blastoderm,  a  number  of  bloodvessels 
shoot  out  from  its  sides  and  ramify  over  the  neigh- 
boring parts  of  the  vitelline  sac,  forming  by  their  Fig.  298. 
inosculation  an  abundant  vascular  plexus.     The  area 
occupied   by  this   plexus  around   the  foetus   is   the 
"  area  vasculosa."     In  the  egg  of  the  fish  (Fig.  298), 
the  area  vasculosa  occupies  the  whole  surface  of  the 
vitellus,  outside  the  body  of  the  embryo.     A  number 
of  arteries  pass  out  from  each  side,  supplying  the 
vascular  network;  and  the  blood  is  returned  from        EGG    OP   FISH 
it  to  the  embryo  by  a  principal  vein  which  is  seen     (Jarrabacca),    show- 

,     ,  „  , ,  ing  the  vitelline  cir- 

passmg  upward  along  the  front  of  the  egg,  and  enter-     cuiation. 
ing  the  body  beneath  the  head. 

In  the  egg  of  the  fowl,  the  area  vasculosa  spreads  gradually  over  the 
vitelline  sac  from  within  outward.  It  is  at  first  limited  on  its  external 
border  by  a  terminal  vein  or  sinus,  which  collects  the  greater  part  of 
the  blood  from  the  vascular  plexus  on  each  side,  and  returns  it  to  the 
interior  of  the  embryo  by  a  double  or  single  trunk,  entering,  as  in  the 
fish,  beneath  the  head.  Another  vein,  of  smaller  size,  enters  the  body 
of  the  embryo  near  its  posterior  extremity;  and  a  number  of  others, 
still  smaller,  along  the  sides.  All  these  vessels  gradually  change  in 
relative  importance,  as  the  development  of  the  embryo  proceeds. 
Especially  the  terminal  sinus  becomes  less  distinct  as  the  area  vascu- 
losa extends  farther  over  the  vitelline  sac,  and  the  anterior  and  pos- 

(791) 


792     DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 

terior  venous  trunks  disappear  more  or  less  completely,  to  be  replaced 
in  importance  by  some  of  those  which  enter  upon  the  sides.  The  area 
vasculosa  is  therefore  an  appendage  to  the  circulatory  apparatus  of  the 
embryo,  spread  out  over  the  surface  of  the  vitellus,  and  absorbing  from 
it  the  requisite  materials  for  nutrition. 

In  man  and  the  mammalians,  the  first  formation  of  the  area  vasculosa 
is  not  essentially  different  from  that  presented  in  fishes  and  birds.  But 
owing  to  the  small  size  and  rapid  exhaustion  of  the  vitellus  as  a  source 
of  nourishment,  this  form  of  the  circulation  never  acquires  a  high  degree 
of  development,  and  soon  becomes  retrograde.  It  presents,  however, 
certain  modifications,  which  are  of  importance  as  indicating  the  mode 
of  origin  of  various  parts  of  the  permanent  vascular  system. 

These  modifications  relate  mainly  to  the  arrangement  of  the  arteries 
and  veins  distributing  the  blood  to  the  external  vascular  plexus,  and 
returning  it  thence  to  the  body  of  the  embryo.  As  the  embryo  and  the 
entire  egg  increase  in  size,  there  are  two  arteries  and  two  veins  which 
become  larger  than  the  others,  and  which  subsequently  do  the  whole 
work  of  conveying  the  blood  to  and  from  the  area  vasculosa.  The  two 
arteries  emerge  from  the  lateral  edges  of  the  embryo,  on  the  right  and 
left  sides  ;  while  the  two  veins  enter  at  about  the  same  point  and  nearly 
parallel  with  them.  These  four  vessels  are  termed  the  omphalo-mesen- 
teric  arteries  and  veins. 

The  arrangement  of  the  circulatory  apparatus  in  the  interior  of  the 
body  at  this  time  is  as  follows :  The  heart  is  situated  at  the  median 
line,  immediately  beneath  the  head,  and  in  front  of  the  oesophagus.  It 
receives  at  its  lower  extremity  the  united  trunks  of  the  two  omphalo- 
mesenteric  veins,  and  at  its  upper  extremity  gives  off  two  vessels  which 
almost  immediately  divide  into  two  sets  of  lateral  arches,  bending  back- 
ward along  the  sides  of  the  neck,  and  again  uniting  into  two  trunks 
near  the  anterior  surface  of  the  vertebral  column.  These  trunks  then 
run  from  above  downward,  in  a  nearly  similar  direction,  on  each  side 
the  median  line.  They  are  called  the  vertebral  arteries,  on  account  of 
their  situation,  which  is  parallel  with  that  of  the  vertebral  column. 
They  give  off,  throughout  their  course,  small  lateral  branches,  which 
supply  the  body  of  the  foetus,  and  also  two  larger  branches  —  the 
omphalo-mesenteric  arteries — which  pass  out,  as  above  described,  into 
the  area  vasculosa.  The  two  vertebral  arteries  remain  separate  in  the 
upper  part  of  the  body,  but  fuse  with  each  other  a  little  beneath 
the  level  of  the  heart ;  so  that,  below  this  point,  there  remains  but  one 
large  artery,  the  aorta,  running  from  above  downward  along  the  median 
line,  giving  off  the  omphalo-mesenteric  arteries  to  the  area  vasculosa, 
and  supplying  smaller  branches  to  the  body,  the  walls  of  the  intestine, 
and  the  other  organs  of  the  embryo. 

This  is  the  condition  which  marks  the  first  or  vitelline  circulation. 
A  change  now  begins  to  be  established,  by  which  the  vitellus  is  super- 
seded, as  an  organ  of  nutrition,  by  the  placenta  ;  and  the  second  or  pla- 
cental  circulation  takes  its  place. 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


793 


Fig.  299. 


Diagram  of  the  YOUNG  EMBRYO  AND 
ITS  VESSELS,  showing  the  circulation 
of  the  umbilical  vesicle,  and  also  that  of 
the  allantois,  beginning  to  be  formed. 


Placental  Circulation. — After  the  umbilical  vesicle  has  been  formed 
by  the  process  already  described  (page  738),  a  part  of  the  vitellus  re- 
mains included  in  it,  while  the  rest  is  retained  in  the  abdomen  and 
inclosed  in  the  intestinal  canal.  As 
these  two  organs  (umbilical  vesicle 
and  intestine)  are  originally  parts  of 
the  same  vitelline  sac,  they  remain 
supplied  by  the  same  vascular  sys- 
tem, namely,  the  omphalo-mesenteric 
vessels.  Those  which  remain  within 
the  abdomen  of  the  foetus  supply  the 
mesentery  and  intestine;  but  the 
larger  trunks  pass  outward,  and 
ramify  upon  the  walls  of  the  um- 
bilical vesicle.  (Fig.  299.)  At  first 
there  are,  as  above  mentioned,  two 
omphalo-mesenteric  arteries  emerg- 
ing from  the  body,  and  two  omphalo- 
mesenteric  veins  returning  to  it ;  but 
afterward  the  two  arteries  are  re- 
placed by  a  common  trunk,  while  a 
similar  change  takes  place  in  the  two  veins.  Subsequently,  therefore, 
there  remains  but  a  single  artery  and  a  single  vein,  connecting  the 
internal  and  external  portions  of  the  vitelline  circulation. 

The  vessels  belonging  to  this  system  are  called  the  omphalo-mesen- 
teric vessels,  because  a  part  of  them  (omphalic  vessels)  pass  outward, 
by  the  umbilicus,  or  "  omphalos,"  to  the  umbilical  vesicle,  while  the 
remainder  (mesenteric  vessels)  ramify  upon  the  mesentery  and  the 
intestine. 

At  first,  the  circulation  of  the  umbilical  vesicle  is  more  important 
than  that  of  the  intestine ;  and  the  omphalic  artery  and  vein  appear 
accordingly  as  large  trunks,  of  which  the  mesenteric  vessels  are  small 
branches.  (Fig.  299.)  Afterward  the  intestine  enlarges,  while  the  um- 
bilical vesicle  diminishes ;  and  the  proportion  between  the  two  sets  of 
vessels  is  therefore  reversed.  The  mesenteric  vessels  then  come  to  be 
the  principal  trunks,  while  the  omphalic  vessels  are  minute  branches, 
running  out  along  the  stem  of  the  umbilical  vesicle,  and  ramifying  in  a 
few  scanty  twigs  upon  its  surface.  (Fig.  300). 

In  the  mean  time,  the  allantois  is  formed  by  a  protrusion  from  the 
lower  extremity  of  the  intestine,  which,  carrying  with  it  two  arteries 
and  two  veins,  passes  out  by  the  anterior  opening  of  the  body,  and  comes 
in  contact  with  the  external  membrane  of  the  egg.  The  arteries  of  the 
allantois,  termed  the  umbilical  arteries,  are  supplied  by  branches  of  the 
abdominal  aorta ;  the  umbilical  veins,  on  the  other  hand,  join  the  mesen- 
teric veins,  and  empty  with  them  into  the  venous  extremity  of  the  heart. 
As  the  umbilical  vesicle  diminishes,  the  allantois  enlarges ;  and  the  lat- 
ter is  converted,  in  the  human  subject,  into  a  vascular  chorion,  part  of 
51 


794     DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 

which  is  devoted  to  the  formation  of  the  placenta.  (Fig.  300.)  As  the 
placenta  soon  becomes  the  only  source  of  nutrition  for  the  foetus,  its 
vessels  increase  in  size,  and  preponderate  over  all  the  other  parts  of  the 
circulatory  system.  During  the  early  periods  of  the  formation  of  the 

Fig.  300. 


Diagram  of  the  EMBRYO  AND  ITS  VESSEI/S;  showing  the  second  or  placental  circu- 
lation. The  intestine  has  become  further  developed,  and  the  mesenteric  arteries  have 
enlarged,  while  the  umbilical  vesicle  and  its  vascular  branches  are  reduced  in  size.  The 
large  umbilical  arteries  are  seen  passing  out  to  the  placenta. 

placenta,  there  are,  as  above  mentioned,  two  umbilical  arteries  and  two 
umbilical  veins.  Subsequently  one  of  the  veins  disappears,  and  the 
whole  of  the  blood  is  returned  to  the  foetus  by  the  other,  which  becomes 
enlarged  in  proportion.  For  a  long  time  previous  to  birth,  there  are, 
therefore,  in  the  umbilical  cord  two  umbilical  arteries,  and  but  one 
umbilical  vein. 

Adult  Circulation — The  placental  circulation  is  exchanged,  at  the 
period  of  birth,  for  the  third  or  adult  circulation.  This  is  distinguished 
by  the  disappearance  of  the  placenta  and  the  vessels  connected  with  it, 
and  by  the  entrance  into  activity  of  the  lungs  and  the  alimentary  canal, 
as  the  organs  of  nutrition  and  aeration  for  the  blood.  A  large  propor- 
tion of  the  blood  is  accordingly  turned  into  different  channels,  and  is 
distributed  to  organs  which  were  before  but  scantily  supplied.  This 
change  differs  from  that  which  preceded  it  mainly  in  its  suddenness. 
The  transition  from  the  first  to  the  second  form  of  circulation  is  a 
gradual  one ;  the  vitellus  and  umbilical  vesicle  diminishing  as  the  pla- 
centa enlarges,  and  the  two  organs,  with  their  bloodvessels,  coexisting 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM.     795 

for  a  certain  period.  But  at  the  time  of  birth  the  placenta  is  detached, 
and  the  lungs  brought  into  play,  with  comparative  suddenness;  and 
although  the  pulmonary  circulation  and  respiration  are  not  established 
in  full  activity  until  an  interval  of  some  days  has  elapsed,  yet  the  pla- 
centa is  at  once  withdrawn  from  the  circulatory  system,  and  its  office  is 
assumed  by  the  lungs,  the  skin,  and  the  alimentary  canal. 

The  comparatively  sudden  changes  which  take  place  at  birth  have, 
however,  been  already  provided  for  by  the  gradual  development  of  the 
necessary  organs.  This  is  accompanied  by  corresponding  alterations  in 
both  the  arterial  and  venous  systems. 

Development  of  the  Arterial  System. — At  an  earl}7  period  of  develop- 
ment, the  main  arterial  trunks,  after  passing  off  from  the  anterior  ex- 
tremity of  the  heart,  curve  backward  in  two  sets  of  nearly  parallel 
branches,  toward  the  vertebral  column,  after  which  they  again  become 
longitudinal,  and  receive  the  name  of  the  "vertebral  arteries."  The 
curved  branches  which  pass  along  the  sides  of  the  neck,  from  front  to 
rear,  are  called  the  cervical  arches.  They  run  in  the  substance  of  the 
visceral  folds  existing  in  this  situation  (page  781),  and  are  separated 
from  each  other  by  the  intervening  cervical  fissures.  In  the  chick- 
embryo,  according  to  Foster  and  Balfour,  three  cervical  arches,  in  the 
three  upper  visceral  folds,  have  been  formed  by  the  end  of  the  second 
day  of  incubation.  During  the  third  and  fourth  days,  the  first  and 
second  cervical  arches  become  obliterated,  but  a  fourth  and  a  fifth  be- 
come developed  at  the  same  time,  in  the  substance  of  the  corresponding 
visceral  folds.  Thus  there  are,  in  all,  five  vascular  cervical  arches  ;  but 
only  three  are  to  be  found  coexisting  at  any  one  time. 

In  fishes,  the  cervical  arches  remain,  as  permanent  bloodvessels  sup- 
plying the  gills,  generally  four  in  number  on  each  side,  sometimes  five. 
In  birds  and  mammalians,  some  of  them  disappear  during  the  further 
progress  of  development,  or  leave  only  certain  arterial  inosculations  in 
the  adult,  as  vestiges  of  their  existence  during  the  embryonic  condition. 
Some  of  them,  on  the  other  hand,  remain  as  permanent  vascular  trunks 
or  branches,  forming  important  parts  of  the  adult  arterial  system. 

The  details  relating  to  the  growth  and  subsequent  modification  of 
the  cervical  arches  are  not  all  described  in  the  same  manner  by  different 
observers ;  and  there  seems  to  be  some  variation,  in  this  respect,  in  the 
mammalian  embryo,  as  compared  with  that  of  birds.  The  general  fea- 
tures, however,  of  the  process  of  transformation  are  as  follows. 

The  two  ascending  trunks,  on  the  anterior  part  of  the  neck,  from 
which  the  cervical  arches  are  given  off,  become  the  carotid  arteries. 
The  first  and  second,  that  is,  the  two  upper  cervical  arches,  on  each 
side,  disappear  as  above  mentioned,  or  remain  only  in  the  form  of  small 
and  inconstant  arterial  inosculations.  The  third  arch  becomes  the  sub- 
clavian  artery,  giving  off,  in  an  upward  direction,  the  permanent  verte- 
bral artery,  and  continuing  outward  as  the  axillary  artery,  to  supply 
the  upper  limb.  The  fourth  cervical  arch  undergoes  very  different 
changes  on  the  two  opposite  sides.  On  the  left  side  it  becomes  enor- 


796     DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 

mously  enlarged,  giving  off,  as  secondary  branches,  all  the  arterial 
trunks  going  to  the  head  and  upper  limbs,  and  is  thus  converted  into 
the  permanent  arch  of  the  aorta.  On  the  right  side  the  corresponding 
arch  grows  smaller,  and  ultimately  disappears ;  so  that  at  last  there  is 
only  a  single  aortic  arch,  situated  to  the  left  of  the  median  line,  and 
continuous  below  with  the  thoracic  aorta. 

The  fifth  or  last  cervical  arch  becomes  on  each  side  the  pulmonary 
artery ;  its  external  portion  on  the  right  side  disappearing  at  a  very 
early  period,  but  on  the  left  remaining  for  a  certain  time,  as  the  ductus 
arteriosus,  between  the  pulmonary  artery  and  the  aorta. 

Notwithstanding  that  the  cervical  arches  are  at  first,  as  their  name 
implies,  all  situated  in  the  region  of  the  neck,  their  remains  or  perma- 
nent representatives  in  the  complete  form  of  the  arterial  system,  come 
to  be  placed  farther  downward,  and  are  evejn  found  in  the  cavity  of  the 
chest.  This  is  due  to  the  varying  rapidity  of  growth  in  different  parts, 
at  the  successive  periods  of  embryonic  development.  The  thorax  at 
first  has  no  existence  as  a  distinct  portion  of  the  trunk ;  the  heart 
being  placed  immediately  beneath  the  head,  and  afterward  changing  its 
relative  position  as  the  development  of  the  lungs  goes  forward  and  the 
walls  of  the  chest  expand  to  cover  them.  The  neck,  with  the  esopha- 
gus and  trachea,  also  elongates  in  an  upward  direction,  so  that  the  vas- 
cular organs  at  first  placed  in  the  cervical  region  afterward  occupy  a 
position  lower  down.  In  fishes,  where  the  cervical  arches  are  perma- 
nent and  where  no  lungs  are  developed,  there  is  no  thoracic  cavity,  and 
the  heart  remains  situated  at  the  most  anterior  portion  of  the  trunk,  just 
behind  the  gills. 

Corresponding  changes  take  place,  during  this  time,  in  the  lower  part 
of  the  body.  Here  the  abdominal  aorta  runs  undivided,  upon  the  me- 
dian line,  quite  to  the  end  of  the  spinal  column  ;  giving  off  on  each  side 
lateral  branches,  which  supply  the  intestine  and  the  parietes  of  the  body. 
When  the  allantois  begins  to  be  developed,  two  of  these  lateral  branches 
accompany  it,  and  become,  consequently,  the  umbilical  arteries.  These 
vessels  increase  so  rapidly  in  size,  that  they  soon  appear  as  divisions 
of  the  aortic  trunk ;  while  the  original  continuation  of  the  aorta, 
running  to  the  end  of  the  spinal  column,  appears  as  a  small  branch 
given  off  at  the  point  of  bifurcation.  The  lower  limbs  are  supplied 
by  two  small  branches,  given  off  from  the  umbilical  arteries  near  their 
origin. 

Up  to  this  time,  the  pelvis  and  posterior  extremities  are  but  slightly 
developed.  Subsequently  they  grow  more  rapidly,  in  proportion  to  the 
rest  of  the  body,  and  the  arteries  which  supply  them  enlarge  in  a  corre- 
sponding manner.  That  portion  of  the  umbilical  arteries,  lying  between 
the  bifurcation  of  the  aorta  and  the  origin  of  the  branches  going  to  the 
lower  extremities,  becomes  the  common  iliac  arteries,  which  in  their 
turn  afterward  divide  into  the  umbilical  arteries  proper,  and  the  femorals. 
Subsequently,  in  accordance  with  the  continued  growth  of  the  pelvis 
and  lower  extremities,  the  relative  size  of  their  bloodvessels  is  still 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


797 


Fig.  301. 


further  increased ;  and  at  last  the  arterial  system  in  this  part  of  the 
body  assumes  the  arrangement  which  belongs  to  the  latter  periods  of 
gestation.  The  aorta  divides,  as  before,  into  the  two  common  iliac 
arteries.  These  divide  into  the  external  iliacs  supplying  the  lower  ex- 
tremities, and  the  internal  iliacs  supplying  the  pelvis ;  and  this  division 
is  so  placed  that  the  umbilical  or  hypogastric  arteries  arise  from  the 
internal  iliacs,  of  which  they  now  appear  to  be  secondary  branches. 

After  the  birth  of  the  foetus  and  the  separation  of  the  placenta,  the 
hypogastric  arteries  become  partially  atrophied,  and  are  converted,  in 
the  adult  condition,  into  solid  cords,  running  upward  to  the  umbilicus. 
Their  lower  portion,  however,  remains  pervious, 
and  gives  off  arteries  supplying  the  urinary  blad- 
der. The  terminal  continuation  of  the  original 
abdominal  aorta,  is  the  arteria  sacra  media,  which, 
in  the  adult,  runs  downward  on  the  anterior  sur- 
face of  the  sacrum,  supplying  branches  to  the 
rectum  and  to  the  anterior  sacral  nerves. 

Development  of  the,  Venous  System. — According 
to  the  observations  of  Coste,  the  principal  veins  of 
the  body  consist  at  first  of  two  long  venous  trunks, 
the  vertebral  veins  (Fig.  301),  which  run  along  the 
sides  of  the  vertebral  column,  parallel  with  the 
vertebral  arteries.  They  receive  in  succession  all 
the  intercostal  veins,  and  empty  into  the  heart  by 
two  lateral  trunks  of  equal  size,  the  canals  of  Cu- 
vier.  When  the  inferior  extremities  become  de- 
veloped, their  two  veins,  returning  from  below, 
join  the  vertebral  veins  near  the  posterior  portion 
of  the  body ;  and,  crossing  them,  afterward  unite 
with  each  other,  thus  constituting  another  vein  of 
new  formation  (Fig.  302,  a),  which  runs  upward  a 
little  to  the  right  of  the  median  line,  and  empties 
by  itself  into  the  lower  extremity  of  the  heart. 

The  two  branches,  by  means  of  which  the  veins  of  the  lower  extremi- 
ties thus  unite,  become  afterward  the  common  iliac  veins ;  while  the 
single  trunk  (a)  resulting  from  their  union  becomes  the  vena  cava  in- 
ferior. Subsequently,  the  vena  cava  inferior  becomes  very  much  larger 
than  the  vertebral  veins  ;  and  its  two  branches  of  bifurcation  are  after- 
ward represented  by  the  iliac  veins. 

Above  the  level  of  the  heart,  the  vertebral  and  intercostal  veins  re- 
tain their  relative  size  until  the  development  of  the  superior  extremities 
has  commenced.  Then,  two  of  the  intercostal  veins  increase  in  diameter 
( Fig.  302),  and  become  converted  into  the  right  and  left  subclavians ; 
while  those  portions  of  the  vertebral  veins  situated  above  the  subcla- 
vians become  the  right  and  left  jugular  veins.  Just  below  the  junction 
of  the  jugulars  with  the  subclavians,  a  small  branch  of  communication 
now  appears  between  the  two  vertebrals  (Fig.  302,  6),  passing  over  from 


Diagram  of  the  VE- 
NOUS SYSTEM  in  its 
early  condition ;  show- 
ing the  vertebral  veins 
emptying  into  the  heart 
by  two  lateral  trunks, 
the  "  canals  of  Ouvier." 


798 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


Fig.  302. 


VENOUS  SYSTEM  farther 
advanced,  showing  the  for- 
mation of  the  iliac  and  sub- 
clavian  veins  — a.  Vein  of 
new  formation,  which  he- 
comes  the  inferior  vena  cava. 
b.  Transverse  hr-inoh  of  new 
formation,  which  afterward 
becomes  the  left  vena  inno- 
minata. 


Fig.  303. 


Further  development  of 
the  VENOUS  SYSTEM.— 
The  vertebral  veins  are 
much  diminished  in  size, 
and  the  canal  of  Cuvier,  on 
the  left  side,  is  gradually 
disappearing,  c.  Transverse 
branch  of  new  formation, 
which  is  to  become  the  vena 
azygos  minor. 


left  to  right,  and  emptying  into  the  right  verte- 
brtil  vein  a  little  above  the  level  of  the  heart ; 
so  that  a  part  of  the  blood  coming  from  the 
left  side  of  the  head,  and  the  left  upper  extre- 
mity, still  passes  down  the  left  vertebral  vein 
to  the  heart  upon  its  own  side,  while  a  part 
crosses  over  by  the  communicating  branch  (6), 
and  is  finally  conveyed  to  the  heart  b}7  the 
right  descending  vertebral.  Soon  afterward, 
this  branch  of  communication  enlarges  so 
rapidly  that  it  preponderates  over  the  left 
superior  vertebral  vein,  from  which  it  origi- 
nated (Fig.  303),  and,  serving  then  to  convey 
all  the  blood  from  the  left  side  of  the  head  and 
left  upper  extremity  to  the  right  side  above  the 
heart,  it  becomes  the  left  vena  innominata. 

On  the  left  side,  that  portion  of  the  superior 
vertebral  vein,  which  is  below  the  subclavian, 
remains  as  a  small  branch  of  the  vena  innomi- 
nata,  receiving  the  six  or  seven  upper  inter- 
costal veins ;  while  on  the  right  side  it  becomes 
excessively  enlarged,  receiving  the  blood  of 
both  jugulars  and  both  subclavians,  and  is  con- 
verted into  the  vena  cava  superior. 

The  left  canal  of  Cuvier,  by  which  the  left 
vertebral  vein  at  first  communicates  with  the 
heart,  is  subsequently  atrophied  and  obliterated, 
while  on  the  right  side  it  becomes  excessively 
enlarged,  and  forms  the  lower  extremity  of  the 
vena  cava  superior. 

The  superior  and  inferior  venae  cavse,  accord- 
ingly, do  not  correspond  with  each  other  so  far 
as  regards  their  mode  of  origin,  and  are  not 
to  be  regarded  as  analogous  veins.  The  supe- 
rior vena  cava  is  one  of  the  original  vertebral 
veins  ;  while  the  inferior  vena  cava  is  a  vessel  of 
new  formation,  resulting  from  the  union  of  two 
lateral  trunks  coming  from  the  inferior  extre- 
mities. 

The  remainder  of  the  vertebral  veins  finally 
assume  the  condition  shown  in  Fig.  304,  which 
is  the  complete  or  adult  form  of  the  venous 
circulation.  At  the  lower  part  of  the  abdo- 
men, the  vertebral  veins  send  inward  small 
transverse  branches  of  communication  to  the 
vena  cava  inferior,  between  the  points  at  which 
they  receive  the  intercostal  veins.  These 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


799 


Fig.  304. 


branches  of  communication,  by  increasing  in  size,  become  the  lumbar 
veins  (7),  which,  in  the  adult  condition,  communicate  with  each  other 
by  arched  branches,  a  short  distance  to  the  side 
of  the  vena  cava.  Above  the  level  of  the  lumbar 
arches,  the  vertebral  veins  retain  their  original 
direction.  That  upon  the  right  side  still  re- 
ceives all  the  right  intercostal  veins,  and  becomes 
the  vena  azygos  major  ( 8  ).  It  also  receives  a 
small  branch  of  communication  from  its  fellow 
of  the  left  side  (Fig.  303,  c),  and  this  branch 
soon  enlarges  to  such  an  extent  as  to  bring 
over  to  the  vena  azygos  major  all  the  blood  of 
the  five  or  six  lower  intercostal  veins  of  the  left 
side,  becoming,  in  this  way,  the  vena  azygos 
minor  (9).  The  six  or  seven  upper  intercostal 
veins  on  the  left  side  still  empty,  as  before,  into 
their  own  vertebral  vein  (10),  which,  joining  the 
left  vena  innominata  above,  is  known  as  the 
superior  intercostal  vein.  The  left  canal  of 
Cuvier  has  by  this  time  entirely  disappeared  ; 
so  that  all  the  venous  blood  now  enters  the 
heart  by  the  superior  and  the  inferior  vena  cava. 
But  the  original  vertebral  veins  are  still  con- 
tinuous throughout,  though  much  diminished  in 
size  at  certain  points ;  since  both  the  greater 
and  lesser  azygous  veins  inosculate  below  with 
the  superior  lumbar  veins,  and  the  superior  in- 
tercostal vein  inosculates  below  with  the  lesser 
azygous,  before  it  crosses  to  the  right  side. 

There  are  still  two  parts  of  the  circulatory 
apparatus,  the  development  of  which  presents 

peculiarities  sufficiently  important  to  be  described  separately.  These 
are,  first,  the  liver  and  the  ductus  venosus,  and  secondly,  the  heart  and 
ductus  arteriosus. 

The  Hepatic  Circulation  and  Ductus  Ve- 
nosus.— The  liver  appears  at  a  very  early 
period,  in  the  upper  part  of  the  abdomen,  as 
a  mass  of  glandular  and  vascular  tissue,  de- 
veloped around  the  upper  portion  of  the 
omphalo-mesenteric  vein,  just  below  its  ter- 
mination in  the  heart  (Fig.  305).  As  soon 
as  the  organ  has  attained  a  considerable 
size,  the  omphalo-mesenteric  vein  ( i )  breaks 
up  in  its  interior  into  a  capillary  plexus,  Earlv  form  of  the  HEPATIC 

.   J   1  CIKCULATION.-  1.   Omphalo- 

the   vessels    of    Which     again     unite     into    a  mesenteric  vein.   2.  Hepatic  vein. 

VenOUS   trunk,  which   Conveys   the   blood    to  3-  Heart.    The  dotted  line  show* 

,        ,  m,  .     .  .  the  situation  of   the  future  um- 

the   Heart.       I  he   omphalo-mesenteric   vein    biiicai  vein. 


Adult  condition  of  the 
VENOUS  SYSTEM.  — 1. 
Right  auricle  of  the  heart. 
2.  Vena  cava  superior.  3,3. 
Jugular  veins.  4,  4.  Subcla- 
vian  veins.  5.  Vena  cava 
inferior.  6,  6.  Iliac  veins. 
7.  Lumbar  veins.  8.  Vena 
azygos  major.  9.  Vena 
azygos  minor.  10.  Superior 
intercostal  vein. 


Fig.  305. 


800     DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 

below  the  liver  then  becomes  the  portal  vein ;  while  above  the  liver,  and 
between  that  organ  and  the  heart,  it  receives  the  name  of  the  hepatic 
vein  (2).  The  liver,  accordingly,  is  at  this  time  supplied  with  blood 

entirely  by  the  portal  vein,  coming  from  the 
Fig.  306.  umbilical  vesicle  and  the  intestine ;  and  all 

the  blood  derived  from  this  source  passes 
through  the  hepatic  circulation  before  reach- 
ing the  venous  extremity  of  the  heart. 

But  soon  afterward  the  allantois  makes 
its  appearance,  and  becomes  developed  into 
the  placenta;  and  the  umbilical  vein  re- 
turning from  it  joins  the  omphalo-mesenteric 
vein  in  the  substance  of  the  liver,  and 
takes  part  in  the  formation  of  the  hepatic 

HEPATIC      Cuter  NATION 

farther  advanced.  - 1.  Portal  capillary  plexus.  Since  the  umbilical  vesicle, 
vein.  2  umbilical  vein.  3.  He-  however,  becomes  atrophied,  while  the  intes- 

patic  vein. 

tine  remains  inactive,  at  the  same  time  that 

the  placenta  increases  in  size  and  in  functional  importance,  a  period 
arrives  when  the  liver  receives  more  blood  by  the  umbilical  vein  than  by 
the  portal  vein.  (Fig.  306.)  The  umbilical  vein  then  passes  into  the 
liver  at  the  longitudinal  fissure,  and  supplies  the  left  lobe  entirely  with 
its  own  branches.  To  the  right  it  sends  off  a  large  branch  of  communi- 
cation, which  opens  into  the  portal  vein,  and  partially  supplies  the  right 
lobe  with  umbilical  blood.  The  liver  is  thus  supplied  with  blood  from 
two  different  sources,  the  most  abundant  of  which  is  the  umbilical  vein ; 
and  all  the  blood  entering  the  liver  circulates,  as  before,  through  its 
capillary  vessels. 

But  the  liver  is  much  larger,  in  proportion  to  the  entiro  body,  at  an 
early  period  of  foetal  life  than  in  the  later  months.  In  the  foetal  pig, 
when  very  young,  it  amounts  to  nearly  twelve  per  cent,  of  the  weight 
of  the  whole  body;  while  before  birth  it  diminishes  to  seven,  six,  and 
even  three  or  four  per  cent.  For  some  time,  therefore,  during  the 
latter  part  of  foetal  life,  much  more  blood  returns  from  the  placenta 
than  is  required  for  the  capillary  circulation  of  the  liver.  Accordingly, 
a  vascular  duct  or  canal  is  formed  in  its  interior,  by  which  a  portion  of 
the  placental  blood  is  carried  directly  through  the  organ,  and  conveyed 
to  the  heart  without  having  passed  through  the  hepatic  capillaries.  This 
canal  is  the  Ductus  venosus. 

The  ductus  venosus  is  formed  by  a  gradual  dilatation  of  one  of  the 
hepatic  capillaries  (at  5  Fig.  307),  which,  enlarging  excessively,  be- 
comes converted  into  a  wide  branch  of  communication,  passing  from  the 
umbilical  vein  below  to  the  hepatic  vein  above.  The  circulation  through 
the  liver,  at  this  period,  is  as  follows  :  A  certain  quantity  of  venous  blood 
still  enters  through  the  portal  vein  (i),  and  circulates  in  a  part  of  the 
capillary  system  of  the  right  lobe.  The  umbilical  vein  (2),  bringing  a 
much  larger  quantity  of  blood,  enters  the  liver  a  little  to  the  left,  and 
the  blood  which  it  contains  divides  into  three  principal  streams.  One  of 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


801 


HEPATIC  CIRCULATION  during  the 
latter  part  of  foetal  life.— 1.  Portal  vein. 
2.  Umbilical  vein.  3  Left  branch  of  um- 
bilical vein.  4.  Eight  branch  of  umbili- 
cal vein.  5.  Ductus  venosus.  6.  Hepatic 
vein. 


Fig.  308. 


them  passes  through  the  left  branch  Fig.  307. 

(3)  into  the  capillaries  of  the  left 
lobe;  another  turns  off  through  the 
right  branch  (4),  and,  joining  the 
blood  of  the  portal  vein,  circulates 
through  the  capillaries  of  the  right 
lobe ;  while  the  third  passes  directly 
onward  through  the  ductus  venosus 
(5)  and  reaches  the  hepatic  vein  with- 
out having  passed  through  any  part 
of  the  capillary  plexus. 
'  This  condition  of  the  hepatic  cir- 
culation continues  until  birth.  At 
that  time,  two  important  changes 
take  place.  First,  the  placental  cir- 
culation is  cut  off;  and  secondly,  a 
much  larger  quantity  of  blood  than 
before  begins  to  circulate  through  the 
vessels  of  the  lungs  and  the  intestine. 

The  superabundance  of  blood,  previously  coming  from  the  placenta,  is 
now  diverted  to  the  lungs  ;  while  the  intestinal  canal  becomes  the  sole 
source  of  supply  for  the  hepatic  venous 
blood.  The  following  changes,  there- 
fore, take  place  at  birth  in  the  vessels 
of  the  liver.  (Fig.  308.)  First,  the  um- 
bilical vein  shrivels  and  becomes  con- 
verted into  a  solid  cord  (  2  ).  This  cord 
may  be  seen,  in  the  adult  condition, 
running  from  the  internal  surface  of  the 
abdominal  walls,  at  the  umbilicus,  to 
the  longitudinal  fissure  of  the  liver.  It 
is  then  known  under  the  name  of  the 
round  ligament.  Secondly,  the  ductus 
venosus  also  becomes  obliterated. 
Thirdly,  the  blood  entering  the  liver  by 
the  portal  vein  ( i )  passes  off  by  its 
right  branch,  as  before,  to  the  right  lobe. 
But  in  the  left  branch  (* )  the  course  of 
the  blood  is  reversed.  This  was  for- 
merly the  right  branch  of  the  umbilical 
vein,  its  blood  passing  in  a  direction 
from  left  to  right.  It  now  becomes  the 
left  branch  of  the  portal  vein ;  and  its 

blood  passes  from  right  to  left,  to  be  distributed  to  the  capillary  vessels 
of  the  left  lobe. 

According  to  Guy,  the  umbilical  vein  is  completely  closed  at  the  end 
of  the  fifth  dav  after  birth. 


Adult  form  of  HEPATIC  CIRCU- 
LATION.—1.  Portal  vein.  2.  Oblite- 
rated umbilical  vein,  forming  the  round 
ligament ;  the  continuation  of  the  dot- 
ted lines  through  the  liver  shows  the 
situation  of  the  obliterated  ductus 
venosus.  3.  Hepatic  vein.  4.  Left 
branch  of  portal  vein. 


802 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


The  Heart,  and  Ductus  Arteriosus. — When  the  embryonic  circulation 
is  first  established,  the  heart  is  a  simple  tubular  canal  (Fig.  309),  receiv- 
ing the  veins  at  its  lower  extremity,  and  giving  off  the  arterial  trunks  at 
its  upper  extremity.  In  the  progress  of  growth,  it  soon  becomes  bent 
upon  itself;  so  that  the  entrance  of  the  veins  and  the  exit  of  the  arte- 
ries come  to  be  placed  more  nearly  upon  the  same  horizontal  level 
(Fig.  310)  ;  but  the  entrance  of  the  veins  (i)  is  behind  and  a  little 
below,  while  the  exit  of  the  arteries  (2)  is  in  front  and  a  little  above. 
The  heart  is  then  a  simple  twisted  tube;  and  the  blood  passes  through 
it  in  a  continuous  stream,  turning  upon  itself  at  the  point  of  curvature, 
and  emerging  by  the  arterial  orifice. 

Fig.  309.  Fig.  310.  Fig.  311. 

f, 


Earliest  form  of  the 
FCETAL  HEART.— 1. 
Venous  extremity  2. 
Arterial  extremity. 


FOITAL  HEART,  bent 
upon  itself.— 1.  Venous  ex- 
tremity. 2.  Arterial  extre- 
mity. 


FCETAL  HEART,  divided 
into  right  and  left'  cavities. 
— 1.  Venous  extremity  2. 
Arterial  extremity.  3,  3. 
Pulmonary  branches. 


Soon  afterward,  the  single  cardiac  tube  is  divided  into  two  parallel 
canals,  right  and  left,  by  a  longitudinal  partition,  which  grows  from  the 
inner  surface  of  its  walls  and  follows  the  twisted  course  of  the  organ 
itself.  (Fig.  311.)  This  partition,  which  is  indicated  in  the  figure  by  a 
dotted  line,  extends  a  short  distance  into  the  commencement  of  the 
primitive  arterial  trunk,  dividing  it  into  two  lateral  halves,  one  of  which 
is  in  communication  with  the  right  side  of  the  heart,  the  other  with  the 
left. 

The  pulmonary  branches  (s,  z)  are  given  off  from  each  side  of  the 
arterial   trunk  near  its  origin;  and  the  longitudinal   partition,  above 
spoken  of,  is  so  placed  that  both  these  branches  fall  upon  one  side  of  it, 
and  are  both,  consequently,  given  off  from  that 
division  of  the  artery  which  is  connected  with 
the  right  side  of  the  heart. 

The  first  portion  of  the  arterial  trunk  is  also 
divided  into  two  parallel  vessels  of  nearly  simi- 
lar curvature,  which  join  each  other  a  short 
distance  beyond  the  origin  of  the  pulmonary 
branches.  The  left  lateral  division  of  the  arte- 
rial trunk  is  the  commencement  of  the  aorta  (i ); 

HE  ART  still  far-  while  its  riSht  lateral  ^vision  is  the  trunk  of 
ther  developed.  - 1.  Aorta,  the  pulmonary  artery  (2),  giving  off  the  right 
2  Pulmonary  artery.  3,  3.  anc]  jeft  pulmonary  branches  (s,  a),  at  a  short 

Pulmonary      branches.       4.  ....  m.  ,.  „  ,. 

Ductus  arteriosus.  distance  from  its  origin.     That  oortion  of  the 


Fi 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


803 


Fig.  313. 


HEART  OF  INFANT,  showing 
the  mode  of  disappearance  of  the 
arterial  duct  after  birth. — 1.  Aorta. 
2.  Pulmonary  artery.  3,  3.  Pulmo- 
nary branches.  4.  Ductus  arterio- 
fcus  becoming  obliterated. 


pulmonary  trunk  (4)  which  is  beyond  the  origin  of  the  pulmonary 
branches,  and  which  communicates  freely  with  the  aorta,  is  the  Ductus 
arteriosus. 

The  ductus  arteriosus  is  at  first  as  large  as  the  pulmonary  trunk 
itself;  and  nearly  the  whole  of  the  blood  coming  from  the  right  ven- 
tricle, passes  through  the  arterial  duct, 
and  enters  the  aorta  without  going  to  the 
lungs.  But  as  the  lungs  become  devel- 
oped, the  pulmonary  branches  increase  in 
proportion  to  the  pulmonary  trunk  and  to 
the  ductus  arteriosus.  At  the  termination 
of  fetal  life  in  man,  the  ductus  arteriosus 
is  about  as  large  as  either  one  of  the  pul- 
monary branches  ;  and  a  considerable  por- 
tion of  the  blood,  therefore,  coming  from 
the  right  ventricle,  still  passes  onward  to 
the  aorta  without  being  distributed  to  the 
lungs. 

But  at  the  period  of  birth,  the  lungs 
enter  upon  the  performance  of  the  func- 
tion of  respiration,  and  immediately  re- 
quire a  greater  supply  of  blood.  The 
right  and  left  pulmonary  branches  then  enlarge,  so  as  to  become  the 
two  principal  divisions  of  the  pulmonary  trunk.  (Fig.  313.)  The  ductus 
arteriosus  at  the  same  time  contracts  to  such  an  extent  that  its  cavity 
is  obliterated ;  and  it  is  finally  converted  into  an  impervious  cord, 
which  remains  until  adult  life,  running  from  the  point  of  bifurcation  of 
the  pulmonary  artery  to  the  under  side  of  the  arch  of  the  aorta.  The 
obliteration  of  the  arterial  duct  is  complete,  at  latest,  by  the  tenth 
week  after  birth.  (Guy.) 

The  two  auricles  are  separated  from  the  two  ventricles  by  transverse 
septa  which  grow  from  the  internal  surface  of  the  cardiac  walls ;  but 
these  septa  remaining  incomplete,  the  auriculo-ventricular  orifices  con- 
tinue pervious,  and  allow  the  passage  of  the  blood  from  the  auricles  to 
the  ventricles. 

The  interventricular  septum,  or  that  which  separates  the  two  ven- 
tricles from  each  other,  is  completed  at  an  early  date ;  but  the  inter- 
auricular  septum,  or  that  situated  between  the  two  auricles,  remains 
incomplete  for  a  long  time,  being  perforated  by  an  oval-shaped  opening, 
the  foramen  ovate,  allowing,  at  this  situation,  a  free  passage  from  the 
right  to  the  left  side  of  the  heart.  The  existence  of  the  foramen  ovale 
and  of  the  ductus  arteriosus  gives  rise  to  a  peculiar  crossing  of  the 
streams  of  blood  in  passing  through  the  heart,  which  is  characteristic 
of  foetal  life,  and  which  may  be  described  as  follows : 

The  two  venae  cavse  in  the  foetus  do  not  open  into  the  right  auricle  on 
the  same  plane  or  in  the  same  direction  ;  for  while  the  superior  vena 
cava  is  situated  anteriorly,  and  is  directed  downward  and  forward,  the 


804 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


Fig.  314. 


inferior  is  situated  posteriorly,  and  passes  into  the  auricle  in  a  direction 
from  right  to  left,  transversely  to  the  axis  of  the  heart.  A  nearly  ver- 
tical curtain  or  valve  at  the  same  time  projects  behind  the  orifice  of  the 
superior  vena  cava  and  in  front  of  the  orifice  of  the  inferior.  This  cur- 
tain is  formed  by  the  lower  and  right  hand  edge  of  the  septum  of  the 
auricles,  which,  as  above  mentioned,  is  incomplete  at  this  time,  and  which 
terminates  inferiorly  and  toward  the  right  in  a  crescentic  border,  leaving 
an  oval  opening,  the  foramen  ovale.  The  stream  of  blood,  coming  from 
the  superior  vena  cava,  falls  in  front  of  this  curtain,  and  passes  down- 
ward, through  the  auriculo-ventricular  orifice,  into  the  right  ventricle. 
But  the  inferior  vena  cava,  being  farther  back  and  directed  transversely, 
opens,  properly  speaking,  not  into  the  right  auricle,  but  into  the  left ; 
for  its  stream  of  blood,  falling  behind  the  curtain  above  mentioned, 
passes  across,  through  the  foramen  ovale,  into  the  cavity  of  the  left  auri- 
cle. This  direction  of  the  current 
of  blood,  coming  from  the  inferior 
vena  cava,  is  further  secured  by  a 
special  membranous  valve,  which 
exists  at  this  period,  termed  the 
Eustachian  value.  This  valve, 
which  is  very  thin  and  transparent 
(Fig.  314, /),  is  attached  to  the  an- 
terior border  of  the  orifice  of  the 
inferior  vena  cava,  and  terminates 
by  a  crescentic  edge,  directed  to- 
ward the  left ;  thus  standing  as  an 
incomplete  membranous  partition 
between  the  cavity  of  the  inferior 
vena  cava  and  that  of  the  right 
auricle.  A  bougie,  placed  in  the 
inferior  vena  cava,  as  shown  in  Fig. 
314,  lies  quite  behind  the  Eusta- 
chian valve,  and  passes  through 
the  foramen  ovale,  into  the  left 
auricle. 

The  two  streams  of  blood,  there- 
fore, coming  from  the  superior  and 
inferior  venae  cavse,  cross  each  other 
upon  entering  the  heart.  This 
crossing  does  not  take  place  in  the 
cavity  of  the  right  auricle  ;  but,  owing  to  the  position  and  direction  of 
the  two  veins,  the  stream  coming  from  the  superior  vena  cava  enters  the 
right  auricle,  while  that  from  the  inferior  passes  almost  directly  into 
the  left. 

It  also  appears,  from  the  relative  position  of  the  aorta,  pulmonary 
artery,  and  ductus  arteriosus,  at  this  time,  that  the  arteria  innominata, 
together  with  the  left  carotid  and  left  subclavian  arteries,  are  given  off 


HEART  OF  THE  HUMAN  F<ETITS,  at 
the  end  of  the  sixth  month  ;  from  a  specimen 
in  the  author's  possession. — a.  Inferior  vena 
cava.  ft.  Superior  vena  cava.  c.  Cavity  of 
the  right  auricle,  laid  open  from  the  front. 
d.  Appendix  auricularis.  e.  Cavity  of  the 
right  ventricle,  also  laid  open.  /.  Eustachian 
valve.  The  bougie  which  is  placed  in  the  in. 
ferior  vena  cava,  can  be  seen  passing  behind 
the  Eustachian  valve,  just  below  the  point 
indicated  by  /,  then  crossing  behind  the 
cavity  of  the  right  auricle,  through  the 
foramen  ovale,  to  the  left  side  of  the  heart. 


DEVELOPMENT    OF    THE    VASCULAR    SYSTEM. 


805 


Fig.  315. 


Diagram  of  the    CIRCULATION 

THROUGH   THE    FtETAL    HEART,. 

— a.  Superior  vena  cava.  b.  Inferior 
vena  cava.  c,  c,  c,  c.  Arch  of  the  aorta 
and  its  branches.  d.  Pulmonary 
artery. 


from  the  arch  of  the  aorta,  before  its  junction  with  the  ductus  arteriosus ; 
and  this  arrangement  causes  the  blood  of  the  two  venae  cavae,  not  only 
to  enter  the  heart  in  different  directions,  but  also  to  be  distributed,  after 
leaving  the  ventricles,  to  different  parts  of  the  body.  (Fig.  315.)  The 
blood  of  the  superior  vena  cava  passes 
through  the  right  auricle  downward  into 
the  right  ventricle,  thence  through  the 
pulmonary  artery  and  ductus  arteriosus, 
into  the  thoracic  aorta ;  while  the  blood 
of  the  inferior  vena  cava,  entering  the 
left  auricle,  passes  into  the  left  ventricle, 
thence  into  the  arch  of  the  aorta,  and  is 
distributed  to  the  head  and  upper  extre- 
mities. The  two  streams,  therefore,  in 
passing  through  the  heart,  cross  each 
other  both  behind  and  in  front.  The 
venous  blood,  returning  from  the  head 
and  upper  extremities  by  the  superior 
vena  cava,  passes  through  the  thoracic 
and  abdominal  aorta  and  the  umbilical 
arteries,  to  the  lower  part  of  the  body, 
and  to  the  placenta ;  while  that  returning 
from  the  placenta,  by  the  inferior  vena 

cava,  is  distributed  to  the  head,  and  upper  extremities,  through  the 
vessels  given  off  from  the  arch  of  the  aorta. 

This  division  of  the  streams  of  blood,  during  a  certain  period  of  foetal 
life,  is  so  complete  that  Reid,1  on  injecting  the  inferior  vena  cava  with 
red,  and  the  superior  with  yellow,  in  a  human  foetus  of  seven  months, 
found  that  the  red  injection  had  passed  through  the  foramen  ovale  into 
the  left  auricle  and  ventricle  and  the  arch  of  the  aorta,  and  had  filled 
the  vessels  of  the  head  and  upper  extremities  ;  while  the  yellow  had 
passed  into  the  right  ventricle,  pulmonary  artery,  ductus  arteriosus,  and 
thoracic  aorta,  with  only  a  slight  admixture  of  red  at  the  posterior  part 
of  the  right  auricle.  All  the  branches  of  the  thoracic  and  abdominal 
aorta  were  filled  with  yellow,  while  the  whole  of  the  red  had  passed  to 
the  upper  part  of  the  body. 

We  have  repeated  this  experiment  several  times  on  the  foetal  pig, 
when  about  one-half  and  three-quarters  grown,  first  taking  the  precau- 
tion to  wash  out  the  heart  and  large  vessels  with  a  watery  injection, 
immediately  after  the  removal  of  the  foetus,  and  before  the  blood  had 
been  allowed  to  coagulate.  The  injections  used  were  blue  for  the  supe- 
rior vena  cava,  and  yellow  for  the  inferior.  The  two  syringes  were 
managed,  at  the  same  time,  by  the  right  and  left  hands ;  their  nozzles 
being  held  in  place  b}'  the  fingers  of  an  assistant.  When  the  points  of 
the  syringes  were  introduced  into  the  veins,  at  equal  distances  from  the 


Edinburgh  Medical  and  Surgical  Journal,  1835,  vol.  xliii.  p.  11. 


80(3     DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 

heart,  and  the  two  injections  made  with  equal  rapidity,  it  was  found 
that  the  admixture  of  the  colors  was  so  slight,  that  at  least  nineteen- 
tvventieths  of  the  yellow  injection  had  passed  into  the  left  auricle,  and 
nineteen-twentieths  of  the  blue  into  the  right.  The  pulmonary  artery 
and  ductus  arteriosus  contained  a  similar  proportion  of  blue,  and  the 
arch  of  the  aorta  of  yellow.  In  the  thoracic  and  abdominal  aorta,  how- 
ever, there  was  always  an  admixture  of  the  two  colors,  generally  in 
about  equal  proportions.  This  may  be  owing  to  the  smaller  size  of  the 
head  and  upper  extremities  in  the  pig,  as  compared  with  those  of  the 
human  foetus,  which  would  prevent  their  receiving  all  the  blood  coming 
from  the  left  ventricle ;  or  to  some  difference  in  the  manipulation  of 
these  experiments,  in  which  it  is  not  always  easy  to  imitate  exactly 
the  force  and  rapidity  of  the  different  currents  of  blood  in  the  living 
bod}'.  These  results,  however,  leave  no  doubt  of  the  fact,  that,  up  to 
an  advanced  stage  of  foetal  life,  by  far  the  greater  portion  of  the  blood 
coming  from  the  inferior  vena  cava  passes  through  the  foramen  ovale, 
into  the  left  side  of  the  heart;  while  by  far  the  greater  portion  of  that 
coming  from  the  head  and  upper  extremities  passes  into  the  right  side 
of  the  heart,  and  thence  outward  by  the  pulmonary  trunk  and  ductus 
"arteriosus.  Toward  the  latter  periods  of  gestation,  this  division  of  the 
venous  currents  becomes  less  complete,  owing  to  the  following  causes. 

First,  the  lungs  increasing  in  size,  the  two  pulmonary  arteries,  as  well 
as  the  pulmonary  veins,  enlarge  in  proportion ;  and  a  greater  quantity 
of  the  blood  coming  from  the  right  ventricle,  instead  of  going  onward 
through  the  ductus  arteriosus,  passes  to  the  lungs,  and,  returning  thence 
by  the  pulmonary  veins  to  the  left  auricle  and  ventricle,  joins  the  stream 
passing  out  by  the  arch  of  the  aorta. 

Secondly,  the  Eustachian  valve  diminishes  in  size.  This  valve,  which 
is  very  large  at  the  end  of  the  sixth  month,  subsequently  becomes 
atrophied  to  such  an  extent  that,  at  the  end  of  gestation,  it  has  either 
disappeared,  or  is  reduced  to  the  condition  of  a  narrow  membranous 
ridge,  which  can  exert  no  influence  on  the  current  of  the  blood.  Thus, 
the  cavity  of  the  inferior  vena  cava,  at  its  upper  extremity,  ceases  to 
be  separated  from  that  of  the  right  auricle  ;  and  a  passage  of  blood  from 
one  to  the  other  may  more  readily  take  place. 

Thirdly,  the  foramen  ovale  becomes  partially  closed  by  a  valve  which 
passes  across  its  orifice  from  behind  forward.  This  valve,  which  begins 
to  be  formed  at  a  very  early  period,  is  the  valve  of  the  foramen  ovale. 
It  consists  of  a  thin,  fibrous  sheet,  which  grows  from  the  posterior  sur- 
face of  the  auricular  cavity,  a  little  to  the  left  of  the  foramen  ovale,  and 
projects  into  the  left  auricle,  presenting  a  thin  crescentic  border,  at- 
tached, b}'  its  two  extremities,  to  the  auricular  septum  upon  the  left 
side.  The  valve  does  not  at  first  interfere  with  the  flow  of  blood  from 
right  to  left,  since  its  edge  hangs  loosely  into  the  cavity  of  the  left 
auricle.  It  only  opposes  regurgitation  from  left  to  right. 

But  as  gestation  advances,  while  the  walls  of  the  heart  continue  to 
enlarge,  and  its  cavities  expand  in  every  direction,  the  fibrous  bundles, 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM.     807 

forming  the  valve,  do  not  elongate  in  proportion.  The  valve,  accord- 
ing^, becomes  drawn  downward  more  closely  toward  the  foramen  ovale. 
It  thus  comes  in  contact  with  the  edges  of  the  inter-auricular  septum, 
and  unites  with  its  substance  ;  the  adhesion  taking  place  first  at  the 
lower  and  posterior  portion,  and  proceeding  gradually  upward  and  for- 
ward, so  that  the  passage  from  the  right  auricle  to  the  left  becomes  con- 
stantly more  oblique  in  direction. 

At  the  same  time  there  is  an  alteration  in  the  position  of  the  inferior 
vena  cava.  This  vessel,  which  at  first  looked  transversely  toward  the 
foramen  ovale,  becomes  directed  more  obliquely  forward ;  and  thus,  the 
Eustachian  valve  having  nearly  disappeared,  a  part  of  the  blood  of  the 
inferior  vena  cava  enters  the  right  auricle,  while  the  remainder  still 
passes  through  the  equally  oblique  opening  of  the  foramen  ovale. 

At  birth  a  change  takes  place,  by  which  the  foramen  ovale  is  com- 
pletely occluded,  and  all  the  blood  coming  through  the  inferior  vena 
cava  is  turned  into  the  right  auricle. 

The  change  depends  upon  the  commencement  of  respiration.  When 
this  occurs,  a  much  larger  quantity  of  blood  is  sent  to  the  lungs,  and 
of  course  returns  from  them  to  the  left  auricle.  The  left  auricle, 
being  thus  filled  with  blood  from  the  lungs,  no  longer  admits  the 
entrance  of  a  further  quantity  from  the  right  auricle  through  the  fora- 
men ovale ;  and  the  valve  of  the  foramen,  pressed  backward  against  the 
edges  of  the  septum,  becomes  after  a  time  adherent  throughout,  and 
thus  obliterates  the  opening.  The  cutting  off  of  the  placental  circula- 
tion diminishes  at  the  same  time  the  quantity  of  blood  arriving  at  the 
heart  by  the  inferior  vena  cava.  It  is  evident  that  the  same  quantity 
of  blood  which  previously  returned  from  the  placenta  by  the  inferior 
vena  cava  on  the  right  side  of  the  inter-auricular  septum,  now  returns 
from  the  lungs,  by  the  pulmonary  veins,  upon  the  left  side  of  the  same 
septum  ;  and  it  is  owing  to  all  these  circumstances  combined,  that,  while 
before  birth  a  portion  of  the  blood  always  passed  from  the  right  auricle 
to  the  left  through  the  foramen  ovale,  no  such  passage  takes  place  after 
birth,  since  the  pressure  is  then  equal  on  both  sides  of  the  auricular 
septum. 

The  foetal  circulation  is  then  replaced  by  the  adult  circulation,  repre- 
sented in  Fig.  316. 

That  portion  of  the  inter-auricular  septum,  originally  occupied  by  the 
foramen  ovale,  is  accordingly  constituted,  in  the  adult  condition,  by  the 
valve  of  the  foramen  ovale,  which  has  become  adherent  to  the  edges  of 
the  septum.  The  septum  in  the  adult  heart  is,  therefore,  thinner  at  this 
spot  than  elsewhere ;  and  presents,  on  the  side  of  the  right  auricle,  an 
oval  depression,  termed  the  fossa  ovalis,  which  indicates  the  site  of  the 
original  foramen  ovale.  The  fossa  ovalis  is  surrounded  by  a  slightly 
raised  ring,  the  annulus  ovalis,  representing  the  curvilinear  edge  of  the 
original  inter-auricular  septum. 

The  foramen  ovale  is  sometimes  completely  obliterated  within  a  few 
days  after  birth,  but  often  remains  partially  pervious  for  several  weeks 


808 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


or  months.  We  have  a  specimen,  taken  from  a  child  one  year  and  nine 
months  old,  in  which  the  opening  is  still  very  distinct ;  and  it  is  not 
unfrequent  to  find  a  small  aperture  existing  even  in  adult  life.  In  these 

Fig.  316. 


Diagram  of  the  ADULT  CIRCULATION  THROUGH  THE  HEART.— a,  a.  Superior  and 
inferior  venae  cavse.  b.  Right  ventricle,  c.  Pulmonary  artery,  dividing  into  right  and  left 
branches,  d.  Pulmonary  vein.  e.  Left  ventricle.  /.  Aorta. 

instances,  although  the  adhesion  and  solidification  of  the  inter-auricular 
septum  may  not  be  complete,  yet  no  admixture  of  blood  takes  place 
between  the  right  and  left  sides  of  the  heart ;  since  the  direction  of  the 
passage  is  always  very  oblique,  and  its  valvular  arrangement  prevents 
any  regurgitation  from  left  to  right.  The  complete  filling  of  the  left 
auricle  with  arterial  blood,  returning  from  the  lungs,  also  opposes  a 
complete  obstacle  to  the  entrance  of  venous  blood  from  the  right 
auricle. 


CHAPTEK  XVIII. 

DEVELOPMENT    OF    THE    BODY  AFTER    BIRTH. 

THE  newly-born  infant  is  still  far  from  having  arrived  at  a  state  of 
complete  development.  The  changes  through  which  it  has  passed  while 
in  the  foetal  condition  are  followed  by  others  during  the  periods  of 
infancy,  childhood,  and  adolescence.  The  anatomy  of  the  organs,  both 
internal  and  external,  their  physiological  functions,  and  even  the  morbid 
derangements  to  which  they  are  subject,  continue  to  undergo  gradual 
and  progressive  alterations,  throughout  the  entire  course  of  subsequent 
life.  The  history  of  development  extends,  properly  speaking,  from  the 
earliest  organization  of  the  embryonic  tissues  to  the  complete  formation 
of  the  adult  body.  The  period  of  birth  marks  only  a  single  epoch  in  a 
constant  series  of  changes,  some  of  which  have  preceded,  while  many 
others  are  to  follow. 

The  weight  of  the  newly-born  infant  is  about  seven  pounds.  The 
middle  point  of  the  body  is  nearly  at  the  umbilicus,  the  head  and  upper 
extremities  being  still  large,  in  proportion  to  the  lower  extremities  and 
the  pelvis.  The  abdomen  is  larger  and  the  chest  smaller,  in  proportion, 
than  in  the  adult.  The  lower  extremities  are  still  partially  curved  in- 
ward, so  that  the  soles  of  the  feet  look  obliquely  toward  each  other, 
instead  of  being  directed  horizontally  downward,  as  at  a  subsequent 
period.  Both  the  arms  and  the  legs  are  curled  upward  and  forward 
over  the  chest  and  the  abdomen,  and  all  the  joints  are  in  a  semi-flexed 
position. 

The  process  of  respiration  is  imperfectly  performed  for  some  time 
after  birth.  The  expansion  of  the  pulmonary  vesicles,  and  the  changes 
in  the  circulatory  apparatus  which  take  place  at  the  time  of  birth,  far 
from  being  instantaneous,  are  always  more  or  less  gradual  in  character, 
and  require  an  interval  of  several  days  for  their  completion.  Respira- 
tion seems  to  be  accomplished,  during  this  period,  to  a  considerable  ex- 
tent through  the  skin,  whicli  is  remarkably  soft,  vascular,  and  ruddy. 
The  animal  heat  is  less  actively  generated  than  in  the  adult,  and  re- 
quires to  be  sustained  by  careful  protection,  and  by  contact  with  the 
body  of  the  mother.  The  young  infant  sleeps  during  the  greater  part 
of  the  time ;  and  even  when  awake  exhibits  comparatively  few  mani- 
festations of  intelligence  or  perception.  The  special  senses  of  sight 
and  hearing  are  dull  and  inexcitable,  and  even  consciousness  seems 
present  only  to  a  limited  extent.  Voluntary  motion  and  sensation  are 
52  '  (  809  ) 


810          DEVELOPMENT    OF    THE    BODY    AFTER    BIRTH. 

nearly  absent ;  and  the  almost  constant  irregular  movements  of  the 
limbs,  observable  at  this  time,  are  mainly  automatic.  Nearly  all  the 
nervous  phenomena  presented  by  the  newly-born  infant,  are  of  a  similar 
nature.  The  motions  of  its  hands  and  feet,  the  act  of  suckling,  and  even 
its  cries  and  the  contortions  of  its  face,  are  reflex  in  their  origin,  and  do 
not  indicate  the  existence  of  active  volition,  or  distinct  perception  of 
external  objects.  There  is  at  first  but  little  nervous  connection  with 
the  external  world,  and  the  system  is  almost  exclusively  occupied  with 
the  functions  of  nutrition  and  respiration. 

The  difference  in  organization  between  the  newly-born  infant  and 
the  adult  may  be  represented,  to  some  extent,  by  the  following  list, 
which  gives  the  relative  weight  of  the  most  important  internal  organs 
at  the  period  of  birth  and  in  adult  age ;  the  weight  of  the  entire  body 
being  reckoned,  in  each  case,  as  1000.  The  relative  weight  of  the  adult 
organs  has  been  calculated  from  the  estimates  of  Cruveilhier,  Solly,  and 
Wilson,  that  of  the  organs  in  the  foetus  at  term  from  our  own  observa- 
tions. 

Foetus  at  term.  Adult. 

Weight  of  the  entire  body      .        .         .  1000.00  1000.00 

"       encephalon       .         .         .  148.00  23.00 

"       liver        ....  37.00  29.00 

"       heart       ....  7.77  4.17 

"           "       kidneys    ....  6.00  4.00 

"       supra-renal  capsules         .  1.63  0.13 

"       thyroid  gland  .         .         .  0.60  0.51 

"       thymus  gland  .         .         .  3.00  0.00 

It  appears  that  most  of  the  internal  organs  diminish  in  relative  size 
after  birth,  owing  principally  to  the  increased  development  of  the  osse- 
ous and  muscular  systems,  both  of  which  are  in  an  imperfect  condition 
throughout  intra-uterine  life,  but  come  into  activity  during  childhood 
and  youth. 

The  remains  of  the  umbilical  cord  begin  to  wither  within  the  first  day 
after  birth,  and  become  completely  desiccated  by  about  the  third  day. 
A  superficial  ulceration  then  takes  place  at  the  point  of  its  attachment, 
and  it  is  separated  and  thrown  off  within  the  first  week.  After  the 
separation  of  the  cord,  the  umbilicus  becomes  completely  cicatrized  by 
the  tenth  or  twelfth  day.  (Guy.) 

An  exfoliation  and  renovation  of  the  cuticle  take  place  over  the  whole 
body  soon  after  birth.  According  to  Kolliker,  the  eyelashes,  and  pro- 
bably all  the  hairs  of  the  body  and  head,  are  thrown  off  and  replaced 
by  new  ones  within  the  first  year. 

The  teeth  in  the  newly-born  infant  are  but  partially  developed,  being 
still  inclosed  in  their  follicles  and  concealed  beneath  the  gums.  They 
are  twenty  in  number,  namely,  two  incisor,  one  canine,  and  two  molar 
teeth  on  each  side  of  each  jaw.  At  birth  there  is  a  thin  layer  of  den- 
tine and  enamel  covering  their  upper  surfaces,  but  the  body  of  the  tooth 
and  its  fangs  are  formed  subsequently  by  progressive  elongation  and 


DEVELOPMENT    OF    THE    BODY    AFTER    BIRTH.          811 

ossification  of  the  tooth-pulp.  The  fully-formed  teeth  emerge  from  the 
gums  in  the  following  order.  The  central  incisors  in  the  seventh  month 
after  birth ;  the  lateral  incisors  in  the  eighth  month ;  the  anterior  molars 
at  the  end  of  the  first  year;  the  canines  at  a  year  and  a  half;  and  the 
second  molars  at  two  years  (Kblliker).  The  eruption  of  the  teeth  in 
the  lower  jaw  generally  precedes  by  a  short  time  that  of  the  correspond- 
ing teeth  in  the  upper  jaw. 

During  the  seventh  year  a  change  begins  to  take  place  by  which  the 
first  set  of  teeth  are  thrown  off  and  replaced  by  the  second  or  permanent 
set,  which  are  different  in  number,  size,  and  shape  from  the  preceding. 
The  anterior  permanent  molar  tooth  first  shows  itself  just  behind  the 
posterior  temporary  molar,  on  each  side.  This  happens  at  about  six 
and  a  half  years  after  birth.  At  the  end  of  the  seventh  year  the  middle 
incisors  are  thrown  off  and  replaced  by  corresponding  permanent  teeth, 
of  larger  size.  At  the  eighth  year  a  similar  exchange  takes  place  in  the 
lateral  incisors.  In  the  ninth  and  tenth  years,  the  anterior  and  second 
molars  are  replaced  by  the  anterior  and  second  permanent  bicuspid 
teeth.  In  the  twelfth  year,  the  canine  teeth  are  changed.  In  the  thir- 
teenth year  the  second  permanent  molars  show  themselves ;  and  from 
the  seventeenth  to  the  twenty-first  year,  the  third  molars,  or  "  wisdom 
teeth,"  emerge  from  the  gums,  at  the  posterior  extremities  of  the  dental 
arch.  (Wilson.)  The  jaw,  therefore,  in  the  adult  condition,  contains 
three  teeth  on  each  side  more  than  in  childhood,  making  in  all  thirty- 
two  permanent  teeth ;  namely,  on  each  side,  above  and  below,  two 
incisors,  one  canine,  two  bicuspids,  and  three  permanent  molars. 

The  generative  apparatus,  which  is  still  inactive  at  birth,  begins  to 
enter  upon  a  condition  of  functional  activity  from  the  fifteenth  to  the 
twentieth  year.  The  entire  configuration  of  the  body  alters  at  this 
period,  and  the  distinction  between  the  sexes  becomes  more  marked. 
The  beard  is  developed  in  the  male ;  and  in  the  female  the  breasts  as- 
sume the  size  and  form  characteristic  of  the  condition  of  puberty.  The 
voice,  which  is  shrill  and  sharp  in  infancy  and  childhood,  becomes  deeper 
in  tone,  and  the  countenance  assumes  a  more  sedate  expression.  After 
this  period,  the  muscular  system  increases  still  further  in  size  and 
strength,  and  the  consolidation  of  the  skeleton  also  continues  ;  the  bony 
union  of  its  various  parts  not  being  entirely  accomplished  until  the 
twenty-fifth  or  thirtieth  year.  Finally,  all  the  different  organs  of  the 
body  arrive  at  the  adult  condition,  and  the  entire  process  of  develop- 
ment is  then  complete. 


INDEX. 


A  BDOMEN,  movement  of,  in  inspira- 
A        tion,  276 
Abdominal  plates,  725 
Abdominal  pregnancy,  711 
Abdominal  respiration,  276 
Abducens  nerve,  538 
Absorption,  189 

by  bloodvessels,  194 

by  lacteals,  19(3 

of  fat,  192 

of  liquids  by  animal  substances,  359, 
365 

of  oxygen  in  respiration,  281 
Absorption-bands,  207 
Accommodation,  of  the  eye,  for  vision  at 

different  distances,  629 
Acid,  carbonic,  60,  128,  129,  130,  283,  296, 
744 

lactic,  118,  158 

cholic,  104,  105 

glycocholic,  104 

taurocholic,  105 

hippuric,  111 

meconic,  142 

oxalic,  393 

uric,  111,  385 

phosphoric,  51 

Acid  and  alkaline  animal  fluids,  50 
Acid  fermentation  of  urine,  393 
Acidity,  of  gastric  juice,  158 

of  urine,  382 
Action  of  arrest,  568,  571 
Adipose  tissue,  72 

digestion  of,  168,  185 
Adult  circulation,  320,  794 

establishment  of,  807 
Air,  quantity  of,  used  in  respiration,  280 

alterations  of,  in  respiration,  280 
Air-cells,  of  lungs,  274 
Air-chamber,  in  fowl's  egg,  691 
Ala  cinerea,  506,  557 
Albumen,  86 

vegetable,  87 

in  milk,  118 

in  saliva,  141 

in  the  blood,  259 

in  urine,  385,  389 

of  the  egg,  how  produced,  690,  721 
Albuininose,  87,  160 

produced  in  digestion,  160,  168 

in  the  blood-plasma,  259 

interference  with  Trommer's  test,  87 

with  iodine-test  for  starch,  88 
Albuminous  matters,  79 
Alimentary  canal,  131 

development  of,  727,  775 
Alkalies,  effect  of,  on  urine,  386 
Alkaline  carbonates,  51 


Alkaline  fluids,  of  the  animal  system,  50 
Alkaline  phosphates,  49 
Alkaline  fermentation,  of  the  urine,  394 
Alkalescence,  of  the  blood,  50,  51,  260 
Allantois,  739 

formation  of,  741 

in  fowl's  egg,  742 

function  of,  743 

in  fcetal  pig,  755 

Ammonio-magnesian  phosphate,  in   de- 
composing urine,  395 
Ammonium  carbonate,  in  decomposing 

urine,  394 
Amnion,  739 

formation  of,  740 

enlargement  of,  745 

contact  of,  with  chorion,  746 
Amniotic  fluid,  746 
Amniotic  folds,  746 
i  Amoeba,  255 
Amoeba  princeps,  256 
!  Amoeboid  movements  of  -white  globules 

of  the  blood,  255,  256 
Amphioxus,  251 
Amphiuma   tridactylum,  blood-globules 

of,  252 

Ampullre,  of  the  semi-circular  canals,  656 
Analysis,  of  animal  fluids,  35,  36 
Animal  charcoal,  as  a  decolorizer,  94 
Animal  functions,  25 
Animal  heat,  300 

quantity  of,  produced,  302 

mode  of  generation  of,  305 

normal  variations  of,  303 

local  production  of,  307 
Animalcules,  infusorial,  676 
Annulus  ovalis,  807 
Anterior  columns  of  spinal  cord,  435,445, 

450 

Anterior  pyramids,  438 
Anus,  formation  of,  727,  779 

imperforate,  776 
Aorta,  development  of,  796 
Aphasia,  485 

Appetite,  disturbed  by  anxiety,  171 
Aquatic  respiration,  272 
Aqueous  humor,  612 
Arbor  vitse  uterina,  693 
Arch  of  aorta,  formation  of,  796 
Arches,  cervical,  795 
Area  pellucida,  724 
Area  vasculosa,  742 
Arrest,  action  of,  568,  571 
Arteries,  330 

pulsation  of,  331 

movement  of  blood  in,  330,  338 

omphalo-mesenteric,  792 

vertebral,  79_',  795 

(813) 


814 


INDEX. 


Arteries,  umbilical,  793 
Arterial  pressure,  338 
Arterial  system,  330 

development  of,  795 
Articulation,  conditions  of,  485,  509,  545, 

579 

Arytenoid  cartilages,  278 
Asphyxia,  281 
Ataxia,  locomotor,  466 
Attitude,  4G4 
Auditory  apparatus,  649 
Auditory  nerve,  551 
Auditory  hairs,  656 
Auriculo-ventricular  valves,  320 
Axis  cylinder,  403 
Azygous  veins,  formation  of,  799 


BACTERIUM  TEKMO,  83,  680 
Batrachians,  red  blood-globules  of, 

252 
Bile,  201 

physical  characters  of,  205 

spectrum  of,  207 

composition  of,  211 

quantity  of,  218,  219 

reactions  of,  with  gastric  juice,  159, 
222 

functions  of,  221 

alteration  and  reabsorption  of,  in  in- 
testine, 220,  223 

secretion  of,  in  the  foetus,  777 
Bile-test,  Gmelin's,  98 
Biliary  matters,  in  urine,  388 
Biliary  salts,  106,  211 
Bilifulvine,  98 
Biliphseine,  98 
Bilirubine,  98,  206 
Biliverdine,  98,  206 
Binocular  vision,  637 

Bladder,  urinary,  closure  and  evacuation 
of,  468 

formation  of,  in  foetus,  779 
Blastoderm,  723,  730 

folds  of  the,  731 
Blind  spot,  of  the  retina,  620 
Blood,  243 

red  globules  of,  243 

spectrum  of,  248,  250 

diagnosis  of,  253 

white  globules  of,  254 

plasma,  257 

coagulation  of,  260 

quantity  of,  267 

alterations  of,  in  respiration,  293 

temperature  of,  300,  308 

cooling  of,  in  lungs  and  skin,  308 

circulation  of,  318 

occurrence  of,  in  the  urine,  392 
Blood-stains,  recognition  of,  253 
Bones,  composition  of,  45 

ossification  of,  45,  773 

of  the  middle  ear,  6^0 
Brain,  of  reptile,  436 

of  bird,  437 

of  quadruped,  437 

of  man,  433,  441,  471 

fissures  and  convolutions  of,  472 

rapidity  of  nervous  action  in,  430 

remarkable  cases  of  injury  to,  479 

of  idiots,  481 

development  of,  769 


Branchiae,  272 

Bread,  119 

Broad  ligaments,  of  uterus,  formation  of, 

789 

Bronchi,  division  of,  273 
Bronchial  tubes,  ultimate,  273 
Brunner's  glands,  180 
Butter,  119 
Butyrine,  119  „ 


pANAL,  medullary,  725,  736,  769 
\J     Canal  of  Schlemm,  609 
Canals,  semicircular,  655 

of  Cuvier,  797 
Cane  sugar,  67 
Capillary  bloodvessels,  343 

inosculation  of,  345 

motion  of  blood  in,  346 
Capillary  circulation,  343 

causes  of,  348 

rapidity  of,  349 

local  variations  in,  351 

peculiarities    of,   in  different   parts, 

353 
Capsule,  internal,  475 

external,  476 

Caput  coli,  formation  of,  776 
Carbo-hydrates,  55 
Carbonate,  lime,  46 

ammonium,    in   decomposing  urine, 

394 

Carbonates,  alkaline,  51 
Carbonic  acid,  60, 128, 129, 130, 283,  287, 291 

in  the  breath,  283 

in  the  blood,  296 

origin  of,  297 

mode  of  production  of,  298 

daily  quantity  of,  283 

exhaled  by  the  skin,  285 

by  the  egg,  during  incubation,  744 

absorbed  by  vegetables,  60,  131,  270 
Cardiac  circulation,  in  adult,  320,  808 

in  the  foetus,  803 
Carnivorous  animals,  respiration  of,  286 

urine  of,  52,  112 

Carotid  arteries,  formation  of,  795 
Caseine,  88 
Catalytic  action,  81 
Catoptric  images,  in  the  eye,  632 
Cellulose,  of  starch,  56 
Centre,  nervous,  definition  of,  415 
Cereal  grains,  composition  of,  119 
Cerebellum,  493 

effects  of  injury  to,  494 

function  of,  499 

development  of,  770 
Cerebral  ganglia,  437,  476,  491 
Cerebral  vesicles,  769 
Cerebrine,  103 
Cerebro-spinal  system,  432 

development  of,  769 
Cerebrum,  471 

development  of,  770 
Cervical  arches,  795 
Cervical  fissures,  780 
Cervix  uteri,  693 

in  the  foetus,  789 
Chalazae,  of  fowl's  egg,  690 
Cheese,  118 

Chest,  movements  of,  in  respiration,  276 
Chiasma,  of  optic  nerves,  516 


INDEX. 


815 


Chick,  development  of,  729 
Chloride,  potassium,  49,  384 
Chloride,  sodium,  47,  384 
Chlorophylle,  101 
Cholepyrrhine,  98 
Cholesterine,  76 
Chondrine,  91 

Chorda  dorsalis,  725,  734,  736,  772 
Chorda  tympani,  549 

influence  of,  on   circulation  in  sub- 
maxillary  gland,  550 

on  the  sense  of  taste,  550 
Chordae  vocales,  movement  of,  in  respira- 
tion, 277 

action  of,  in  vocalization,  565 

obstruction  of  glottis  by,  after  section 

of  the  pneumogastric  nerves,  563 
Chorion,  746 

villosities  of,  747 

source  of  vascularity  of,  748 

union  of,  with  decidua,  753 
Choroid  coat,  of  the  eye,  610 
Chyle,  73,  192,  367 

absorption  of,  192 

in  the  lacteals,  197 

in  the  blood,  199 
Chyme,  169 
Cicatricula,  689,  729 

segmentation  of,  730 
Ciliary  muscle,  610,  634 
Ciliary  nerves,  583 
Circulation,  318 

in  the  heart,  318 

in  the  arteries,  330 

in  the  veins,  340 

in  the  capillaries,  343 

rapidity  of,  350 

local  variations  of,  351 

peculiarities  of,  in  different  parts,  353 

placenta!,  759,  793 

vitelline,  791 

adult,  794 
Circulatory  apparatus,  318 

development  of,  791 
Claustrum,  476 
Clot,  formation  of,  262 
Coagulation,  81 

of  fibrine,  81,  86,  258 

of  albumen,  86 

of  milk,  118 

of  pancreatine,  175 

of  pty  aline,  141,  142 

of  blood,  260 
Cochlea,  660 
Cold,  resistance  to,  by  animals,  300,  314 

effect  of,  when  long  continued,  312 
Collagen,  91 
Coloring  matters,  94 

of  the  blood,  95 

of  the  skin,  97 

of  bile,  98,  99,  206 

of  urine,  99 

of  the  corpus  luteum,  100 

of  green  plants,  101 

Commissure,    gray,  of  the   spinal  cord, 
435 

white,  of  the  spinal  cord,  435,  445 

transverse,  of  the  cerebrum,  477 

of  the  cerebellum,  494,  500 
Composition,  of  Fehling's  liquor,  64 

of  different  articles  of  food,  118 

of  the  daily  ration  of  food,  125 


Composition,  of  saliva,  141 

of  human  parotid  saliva,  144 

of  gastric  juice,  157 

of  pancreatic  juice,  173 

of  intestinal  juice,  183 

of  bile,  211 

of  the  red  blood-globules,  247 

of  blood-plasma,  257 

of  cutaneous  perspiration,  316 

of  lymph,  367 

of  lymph  and  chyle,  369 

of  the  urine,  378 

Congenital  diaphragmatic  hernia,  779 
Congenital  inguinal  hernia,  788 
Congenital  umbilical  hernia,  777 
Contraction,  of  stomach  during  digestion, 
167 

of  the  blood-clot,  261 

of   the    diaphragm    and    intercostal 
muscles  in  respiration,  275 

of  the  posterior  crico-arytenoid  mus- 
cles, 278 

of  the  ventricles  of  the  heart,  324 

of  the  muscles  after  death,  419 

of  the  sphincter  ani,  467 

of  the  rectum,  467 

of  the  urinary  bladder,  468 

of  the  pupil,  under  the  influence  of 

light,  400,  518,  524,  611,  634 
Convolutions,  of  the  human  brain,  475 
Cooking,  effect  of,  on  albuminous  matters, 
82 

on  meat,  121 

on  vegetables,  123 
Cord,  spinal,  433,  443 

umbilical,  763 
Cornea,  609 

Corpora  striata,  437,  476 
Corpora  Wolffiana,  784 
Corpus  callosum,  47" 
Corpus  dentatum,  493 
Corpus  geniculatum,  internum  and  ex- 

ternum,  516 
Corpus  luteum,  713 

of  menstruation,  713 

of  pregnancy,  717 
Cbrti,  organ  of,  662 
Cranial  nerves,  511 

classification  of,  513 

general  arrangement  and  origin  of, 

579 

Creatine,  106 
Creatinine,  107,  382 
Cremaster  muscle,  787 
Crossed  action,  of  spinal  cord,  454 

of  optic  nerves,  521 

of  optic  tubercles,  522 

of  the  oculomotorius  nerves,  523 

of  the  facial  nerves,  546 
Crossing,  of  fibres  in  medulla  oblongata, 
439,  455 

of  sensitive  fibres  in  spinal  cord,  455 

of  fibres  of  optic  nerves,  516 

of  streams  of  blood  in  the  foetal  heart, 

803 

Crystalline  lens,  613 
Crystallizable  nitrogenous  matters,  102 
Crystals,  of  stearine,  70 

of  palmitine,  71 

of  cholesterine,  77 

of  sodium  glycocholate,  105 

of  sodium  taurocholate,  106 


816 


INDEX. 


Crystals,  of  biliary  matters,  from  small 
intestine,  217 

of  creatine,  107 

of  creatinine,  107 

of  urea,  109 

of  sodium  urate,  382 

of  uric  acid,  385 

of  lime  oxalate,  394 

of   ammonio-magnesian    phosphate. 

396 

Cumulus  proligerus,  706 
Cupola,  of  the  cochlea,  660 
Cuticle,  exfoliation  of,  after  birth,  810 
Cuvier,  canals  of,  797 
Cysticercus  cellulose,  673 


DEATH,   a  necessary  consequence  of 
life,  668 
Decidua,  750 

vera,  751 

reflexa,  751 

union  of,  with  chorion,  753 

vera  and  reflexa,  contact  of,  765 
Decussation,  of  cerebro-spinal  nerve  fi- 
bres, 433 

of  anterior  columns  of  spinal  cord, 
444,  445 

of  anterior  pyramids,  439,  454,  503 

of  sensitive  fibres  in  the  spinal  cord, 
455 

of  optic  nerves,  440,  519 

of  the  patheticus  nerves,  525 

of  the  facial  nerves,  546 
Degeneration,  fatty,  of  the  decidua,  766 

of  the  uterine  muscular  fibres,  after 

delivery,  767 
Deglutition,  151,  508,  579 

retarded  by  division  of  Steno's  duct, 
148 

reflex  action  of,  508,  555,  566 
Dentition,  first,  810 

second,  811 

Deposits,  iu  the  urine,  390 
Descent,  of  the  testicles,  786 

of  the  ovaries,  788 

Development,   of  the  impregnated  egg, 
721,  745 

of  allantois,  740,  741 

of  chorion,  746 

of  decidua,  750 

of  placenta,  793 

of  nervous  system,  769 

of  eye,  771 

of  ear,  772 

of  skeleton,  772 

of  limbs,  773 

of  integument,  774 

of  alimentary  canal,  775 

of  urinary  passages,  779 

of  liver,  778 

of  face,  780 

of  Wolffian  bodies,  784 

of  kidneys,  785 

of  internal  organs  of  generation,  785 

of  circulatory  apparatus,  791 

of  arterial  system,  795 

of  venous  system,  797 

of  hepatic  circulation,  799 

of  the  heart,  802 

of  the  body  after  birth,  809 
Dextrine,  59 


Diabetes,  242 

in  the  fetus,  778 
Diaphragm,  action  of,  275 

formation  of,  779 

Diaphragmatic  hernia,  congenital,  779 
j  Diagnosis,  of  blood,  253 
I  Diastase,  59,  142 
I  Dichroism,  of  bile,  206 
|  Dicrotic  pulse,  335 
Diet,  influence  of,  on  nutrition,  116 

on  the  products  of  respiration,  2P6 

on  formation  of  urea,  110 

on  formation  of  sodium  urate,  111 
Digestion,  131 

of  starch,  60,  149,  150,  175 

of  fats,  168,  175 

of  sugar,  184 

of  albuminous  matters,  160,  168.  177 

of  meat,  168 

of  milk,  169 

of  vegetable  tissues,  169 

time  required  for,  170 
Digestive  apparatus,  of  fowl,  132 

of  ox,  133 

of  man,  134 
Dilator  pupillse,  611 
Direct  and  indirect  vision,  628 
Discus  proligerus,  706 
Distance  and  solidity,  appreciation  of,  640 
Diurnal  variation,  in  exhalation  of  car- 
bonic acid,  283 

in  production  of  urea,  109 

in  density  and  acidity  of  the  urine,  376 
Dorsal  plates,  724,  732 
Double  vision,  639,  640 
Ductus  arteriosus,  802,  803 
Ductus  cochlearis,  661 
Ductus  venosus,  799,  800 
Duodenal  fistula,  217 
Duodenal  glands,  180 
Duration,  of  luminous  impulses  necessary 
for  sight,  644 

of  musical  sounds  necessary  for  hear- 
ing, 666 


EAR,  external,  649 
middle,  649 

internal,  654 

development  of,  772 
Earthy  phosphates,  46 

in  urine,  47,  383,  390,  395 
Egg,  685 

contents  of,  386 

where  formed,  687 

pre-existence  of,  in  ovary,  703 

development  of,  at  puberty,  704 

ripening  and  discharge  of,  705,  707 

impregnation  of,  698 

development  of,  after  impregnation, 
721 

attachment    of,    to  uterine    mucous 
membrane,  753 

discharge  of,  at  delivery,  765 

condition  of,  in  fcetus  at  term,  790 
,  as  food,  122 
Elasticine,  92 
Embryo,  formation  of,  721 

position  of,  in  the  fowl's  egg,  733 
Embryonic  spot,  724 
Emulsion  of  fats,  68 

by  pancreatic  juice,  176 


INDEX. 


817 


Encephalon,  471 
Endolymph,  658 
Endosmosis,  360 
Endosmonjeter,  361 
Entozoa,  672 

encysted  and  sexless,  673 
reproduction  of,  674,  675 
Epilepsy,  from  injury  of  the  spinal  cord, 

461 

Epidermis,  exfoliation  of,  after  birth,  810 
Epididymis,  698 

formation  of,  787 

Epithelium,  of  salivary  glands,  139 
in  saliva,  141 

of  gastric  follicles,  153,  154 
of  intestine,  during  digestion,  193 
of  the   membranous   labyrinth,  656, 

657 

of  the  ductus  cochlearis,  662 
Equilibrium,  sense  of,  659 
Eustachian  tube,  654 
Eustachian  valve,  804 
Evacuation,  of  the  rectum  and  bladder, 

467 

Excrementitious  substances,  374 
Excretine,  188 
Excretion,  374 

Exfoliation,  of  cuticle  after  birth,  810 
Exhalation,  from  the  lungs,  43,  288 
from  the  skin,  43,  316 
from  the  fowl's  egg,  during  incuba- 
tion, 743 
Exhaustion,  of  muscles  and  nerves,  by 

repeated  irritation,  420 
Exosmosis,  361 
Experiments  on  living  animals,  26 

direct  and  indirect  results  of,  28 
Expiration,  movements  of,  276 
Eye,  608 

inflammation  of,  after  division  of  tri- 

geminus  nerve,  536 
development  of,  771 


FACE,  motor  nerve  of,  539 
sensitive  nerve  of,  526 

development  of,  780 
Facial  paralysis,  541,  543 
Fallopian  tubes,  692 

formation  of,  786,  789 
Farinaceous  substances,  55 

digestion  of,  60,  149,  150,  175 
Fat,  68 

absorption  of,  192 

emulsion  of,  68,  175 

decomposition  of,  in  the  blood,  199 

necessary,   as  an   ingredient    of  the 

food,  115 
Fatty  degeneration,  of  the  decidua,  766 

of  uterine  muscular  fibres,  after  de- 
livery, 767 
Feces,  187 

Fecundation,  of  the  egg,  698,  711 
Fehling's  test  for  glucose,  64 
Female  generative  organs,  685 

development  of,  788 
Fenestra  rotunda,  655 
Fenestra  ovalis,  655 
Fermentation,  64 

of  bread,  120 

of  saccharine  urine,  386 

acid,  of  urine,  393 


Fermentation,  alkaline,  of  urine,  394 
Fibrine,  85 

of  the  blood,  257 

coagulation  of,  86,  258,  261 

disappearance  of  in  liver  and  kidneys, 
266 

usefulness  of,  266 
Fibrinogen,  265 
I  Fibrino-plastic  matter,  265 
1  Fifth  pair  of  cranial  nerves,.  526 
!  Fissure,  frontal,  488 

of  Kolando,  473 

of  Sylvius,  472 

parietal,  473 

|  Fissure  of  the  palate,  783 
!  Fissures,  cervical,  7&0 
I  Fistula,  gastric,  156 

pancreatic,  172 

duodenal,  217 
Fixation,  point  of,  in  vision  with  both 

eyes,  638 

Fluorescence,  of  the  bile,  206 
Fcetus,  development  of,  769 
Follicles,  salivary,  139 

gastric,  152 

of  Lieberkuhn,  180 

Graafian,  687 

uterine,  750 
Food,  113 

daily  quantity  of,  124 

effect  of  cooking  on,  121,  123 
Foramen  ovale,  803 

valve  of,  806 

closure  of,  807 
Force,  nervous,  rapidity  of  transmission 

of,  425 

Fossa  ovalis,  807 
Fovea  centralis,  623- 
Functions,  25 

animal,  32 

vegetative,  31 

of  the  teeth,  136 

of  saliva,  147 

of  gastric  juice,  160,  166" 

of  pancreatic  juice,  174 

of  intestinal  juice,  184 

of  bile,  221 

of  perspiration,  317 

of  the  crystalline  lens,  614 

of  the  semicircular  canals,  65& 

of  the  cochlea,  QQ3- 


GALVANISM,  action  of,  on   muscles, 
II         418 

on  nerves,  419 
Ganglia,  cerebral,  437,  476,  491 

spinal,  446,  583 

of  the  sympathetic  system,  583 
Ganglion,  Gasserian,  528 

geniculatum,  548 

impar,  585 

jugular,  557 

ophthalmic,  583 

otic,  584 

petrosal,  553 

semilunar,  585 

sphenopalatine,  584 

spiral,  663 

submaxillary,  584 

Ganglionic  system  of  nerves,  432,  582 
Gasserian  ganglion,  528 


818 


INDEX. 


Gastric  fistula,  156 

Gastric  follicles,  152,  153,  154 

Gastric  juice,  152 

mode  of  obtaining,  157 

composition  of,  157 

action  of,  on  the  food,  159,  166 

mode  of  secretion  of,  161 

daily  quantity  of,  164 

reabsorption  of,  170 
Gelatine,  35 

source  of,  91 

eft'ect  of  feeding  animals  on,  117 
Generation,  668 

spontaneous,  670 

of  infusoria,  679 

of  entozoa,  672 

sexual,  682 
Germ,  682 

Germinal  membrane,  723 
Germinative  vesicle,  686 

disappearance  of,  in  mature  egg,  721 
Germinative  spot,  686 
Gills,  272 
Glands,  of  Brunner,  180 

salivary,  138 

peptic,  155 

of  small  intestine,  190 

lymphatic,  356 

Glandulse,  agminatse  and  solitariae,  190 
Globules,  red,  of  the  blood,  243 

appearance  of,  under  the  microscope, 
244 

mutual  adhesion  of,  245 

action  of  water  on,  246 

composition  of,  247 

size  of,  in  different  animals,  250 

function  of,  254,  294 
Globules,  white,  of  the  blood,  254 

amoeboid  movements  of,  255 
Globules,  of  lymph,  369 
Glomeruli,  of   the  Wolffian  bodies   and 

kidneys,  784 

Glosso-pharyngeal  nerve,  553 
Glottis,  movements  of,  in  respiration,  277 

in  vocalization,  565 
Glottis,  closure  of,  after  division  of  the 

pneumogastric  nerves,  563 
Glucose,  62 

formation  of,  in  the  liver,  232 

detection  of,  in  the  urine,  386 
Gluten,  in  wheat,  flour,  86 
Glycerine,  69,  231 
Glycine,  104 

Glycocholate,  sodium,  104 
Glycocholic  acid,  104 
Glycogen,  61,  228 

conversion  of,  into  sugar,  232 
Glycogenic  function  of  liver,  228 

'  in  the  foetus,  778 
Gmelin's  bile-test,  98 
Graafian  follicles,  687 

structure  of,  706 

rupture  of,  in  ovulation,  707 

in  menstruation,  710 

condition  of,  in  foetus  at  term,  790 
Granulose,  of  starch  grains,  56 
Gray  substance,  of  the  nervous  system, 

400,  413 

Groove,  medullary,  724,  732,  736,  769 
Gubernarulum  testis,  787 
Gustatory  nerves,  533,  554,  601 


HAIES,  auditory,  656 
Hairs,  formation  of,  in  foetus,  774 

exfoliation   of,  during    intra-uterino 
life,  778 

exfoliation  of,  after  birth,  810 
Hare-lip,  783 

Headache,  pathology  of,  531 
Hearing,  sense  of,  648 

organ  of,  649 
Heart,  318 

of  mammalians,  319 

of  man,  319 

circulation  of  blood  through,  320 

sounds  of,  322 

movements  of,  324 

impulse  of,  326 

development  of,  802 
Heat,  vital,  of  animals,  300 

of  plants,  301 

how  produced,  305 
Hemaphaaine,  99 
Hematoidine,  98 
Hemianassthesia,  492 
Hemiplegia,  457,  45S,  492 

with  aphasia,  486 
Hemispheres,  cerebral,  436,  471 

cases  of  injury  to,  479 

effect  of  removal  of,  482 

effect  of  disease  of,  481 

functions  of,  479 

centres  of  motion  in,  487 

development  of,  770 
Hemoglobine,  95 

spectrum  of,  248,  250 
Hemorrhage,  arrest  of,  by  coagulation  of 
fibrin e,  266 

from  the  placenta,  in  parturition,  765 
Hepatic  circulation,  201 

development  of,  799 
Herbivorous  animals,  respiration  of,  286 

urine  of,  52,  112 
Hernia,  congenital,  diaphragmatic,  779 

inguinal,  788 

umbilical,  777 
Hibernation,  311 

respiration  in,  282 

production  of  heat  in,  305 
Hippurate,  sodium,  111 
Hippuric  acid,  111 
Honey,  composition  of,  67 
Hydrobilirubine,  99 

Hydrocarbonaceous    proximate     princi- 
ples, 55 

source  and  destination  of,  78 
Hygroscopicity,  of  albuminous  matters,  80 
Hyperaesthesia,  after    injury    to    spinal 

cord,  456 
Hypoglossal  nerve,  574 


TDIOTS,  brain  of,  481 

1     Images,  catoptric,  in  the  eye,  632 

Images,  negative,  646 

Im perforate  anus,  776 

Impregnation,  of  the  egg,  698,  711 

of  the  female,  700 
Impulse,  of  the  heart,  326 
Incisor  teeth,  136,  138 
Incus,  650 

Infant,  newly  born,  condition  of,  809 
Infusoria,  676 

reproduction  of,  679 


INDEX. 


819 


Inguinal  hernia,  congenital,  788 
Inorganic  proximate  principles,  40 

source  and  destination  of,  54 
Inosculation,  of  veins,  341 

of  capillaries,  345 

of  nerves,  405,  406 
Inspiration,  movements  of,  275,  278 
Instinct,  nature  of,  501 
Integument,  respiration  by,  285,  809 

development  of,  774 
Intellectual  powers,  484 
Intestine,  of  fowl,  132 

of  man,  134 

secretions  of,  180 

digestion  in,  184 

epithelium  of,  193 

development  of,  727,  775 
Intestinal  juice,  180 
Iodine,  action  of,  on  starch,  58 

in  the  urine,  389 
Iris,  610 

movements  of,  400,  518,  524,  611,  G34 

formation  of,  772 
Iron,  in  hemoglobine,  96 

in  the  food,  97 

in  melanine,  98 
Irritability,  nervous,  417 

muscular,  418 
Island  of  Keil,  473 


TACOBSON,  nerve  of,  553 
U   Jaundice,  yellow  color  of  urine  in,  388 
Judgment,  484 
Jugular  ganglion,  557 


TfERATINE,  92 

IV  Kidneys,  circulation  in,  352,  353 

elimination  of  medicinal  substances 
by,  389 

development  of,  785 


T  ABYRINTH,  654 

JJ     Laeteals,  197 

Lactic  acid,  in  souring  milk,  118 

in  gastric  juice,  158 
Lactose,  66 

Lamina,  spiral,  of  the  cochlea,  661 
Language,  articulate,  485,  509,  545,  579 
Large  intestine,  186 

development  of,  775,  776 
Larynx,  action  of,  in  respiration,  277 

in  vocalization,  565 

nerves  of,  557,  558 

Layers,   blastoclermic,   external  and  in- 
ternal, 723,  730 

intermediate,  734 
Lecithine,  102 
Legumine,  89 
Lens,  crystalline,  613 
Leucine,  104 

Lieberkiikn,  follicles  of,  180,  181 
Ligament,  broad,  of  the  uterus,  789 

round,  of  the  uterus,  789 

round,  of  the  liver,  801 

of  the  ovary,  789 
Limbs,  formation  of,  727,  773 
Lime  carbonate,  46 

oxalate,  394 


Lime  phosphate,  43 

Line  of  direct  vision,  628 

Lingual  nerve,  530,  532 

Liver,  201 

secretion  of  bile  in,  216 
formation  of  glycogen  in,  228 
production  of  sugar  in,  232 
development  of,  778,  799 

Liver-cells,  202 

Liver-sugar,  formation  of,  232 

accumulation  of,  after  death,  234 
proportion  of,  during  life,  236 
production  of,  in  the  foetus,  778 

Lobules,  of  the  liver,  201 
of  the  lung,  273 

Locomotion,  464 

Locomotor  ataxia,  466 

Lungs,  structure  of,  272,  273 
development  of,  779 

Luteine,  100 

Lymph,  367 

Lymph-globules,  369 

Lymphatic  system,  354 


MACULA  AUDITIVA,  656 
Macula  lutea,  623 
Magnesium  phosphate,  46 
Male  organs  of  generation,  695 

development  of,  786 
Malleus,  650 
Mastication,  136,  533,  579 

unilateral,  in  rumination,  145 

retarded  by  suppression  of  saliva,  148 
Meat,  as  food,  121 
Meconic  acid,  142 
Meconium,  777 
Medulla  oblongata,  439,  440,  502 

reflex  action  of,  505,  507 

development  of,  770 
Medullary  canal,  725,  736,  769 
Medullary  groove,  724,  732,  736,  769 
Medullary  layer,  of  nerve  fibres,  402 
Melanine,  97 
Membrana  basilaris,  661 
Membrana  granulosa,  706 
Membrana  tympani,  649 
Membrane,  pupillary,  772 
Membranous  labyrinth,  655 
Memory,  484 
Menobranchus,  blood-globules  of,  252 

gills  of,  272 

spermatozoa  of,  696 
Menstruation,  708 

corpus  luteum  of,  713 
Mesenteric  glands,  358 
Metalbumen,  259,  264 
Micropyle,  685,  699 
Middle  ear,  649 

bones  of,  650 
Milk,  73,  118 
Milk-sugar,  66 

conversion  of,  into  lactic  acid,  118 
Molar  teeth,  137,  138 
Motor  nerve  fibres,  409 
Mouth,  134 

development  of,  780,  782 
Movements,  of  bacterium  cells,  84,  680 

of  stomach,  166 

of  intestine,  191 

of  white  blood-globules,  255,  256 

of  chest,  in  respiration,  275 


820 


INDEX. 


Movements  of  glottis,  in  respiration,  277 

of  the  heart,  324 

of  spermatozoa,  096 

of  the  iris,  400,  518,  524,  611,  634 

of  the  foetus  in  utero.  764 

of  the  newly-born  infant,  810 
Mucosine,  90 
Mucous  membrane,  of  stomach,  152 

of  intestine,  180,  189 

of  the  uterus,  693,  750 
Mucus,  in  the  urine,  392 
Muscles,  irritability  of,  419 
Musical  notes,  production  and  perception 

of,  665 

Myeline-forms,  102 
Myopic  eye,  636 
Myosiue,  90 


NAILS,  development  of,  774 
Negative  images,  646 
Nerve,  abducens,  538 

auditory,  551 

facial,  539 

great  superficial  petrosal,  548 

glossopharyngeal,  553 

hypoglossal,  574 

lingual,  530,  532 

oculomotorius,  522 

olfactory,  513 

optic,  516 

patheticus,  524 

pneumogastric,  557 

small  superficial  petrosal,  549 

spinal  accessory,  571 

stapedius,  549 

sympathetic,  582 

trigeminus,  526 
Nerve  cells,  413 
Nerve  fibres,  400 

medullated,  402 

non-medullated,  404 

division  of,  406,  407 

termination  of,  408 

sensitive  and  motor,  409 

effect  of  division  on,  410 

union  and  regeneration  of,  411 

connection  of,  with  nerve  cells,  414 
Nerves,  405 

spinal,  434,  445 

cranial,  511,  579 
Nervous  force,  419 

nature  of,  423 

rapidity  of  transmission  of,  425 
Nervous  irritability,  417 

duration  of,  after  death,  419 

exhausted  by  excitement,  420 
Nervous  system,  399 

development  of,  769 
Nervous  tissue,  two  kinds  of,  400 
Network,  capillary,  346 
Nitrogen,   a  constituent  of   albuminous 

rnatters,  79 
Non-nitrogenous    proximate    principles, 

55 
Nucleus,  caudate,  476 

lenticular,  476 

olivary,  504 

of  the  abducens  and  facial  nerves,  538 

of  the  auditory  nerve,  551 

of  the  glossopharyngeal  nerve,  553 

of  the  hypoglossal  nerve,  574 


Nucleus  of  the  oculomotorius  and  path* 

ticus  nerves,  522 
of  the  optic  nerve,  516 
of  the  pneumogastric  nerve,  557 
of  the  spinal  accessory,  571 
of  the  trigeiniuus,  526 

Nutrition,  33 


OBLITERATION,  of  ductus  venosus, 
801 

of  ductus  arteriosus,  803 

of  foramen  ovale,  807 
Oculomotorius  nerve,  522 
(Esophagus,  134 

paralysis   of,   after  division   of    the 

pneumogastric  nerves,  566 
(Estruation,  phenomena  of,  708 
Oleaginous  substances,  68 

importance  of,  as  ingredients  of  the 
food,  115, 116 

in  the  blood,  199,  260 
Oleine,  70 

Olfactory  apparatus,  604 
Olfactory  bulb,  514 
Olfactory  ganglia,  436 
Olfactory  lobes,  515 
Olfactory  nerves,  513 
Olfactory  tubercle,  514 
Olivary  bodies,  439,  504 
Omphalo-mesenteric  vessels,  792,  799 
Ophthalmic  ganglion,  583 
Ophthalmoscope,  615 
Optic  ganglia,  436 
Optic  nerves,  516 

decussation  of,  519 

crossed  action  of,  521 

physiological  properties  of,  620,  626 

development  of,  771 
Optic  thalami,  437,  476 

development  of,  769 
Optic  tract,  516 
Optic  tubercles,  436 
Ora  serrata,  616 
Organ  of  Corti,  662 
Organs,  25 
Organization,  of  the   animal  solids  and 

fluids,  34 

Origin,  of  plants  and  animals,  667 
Ossicles,  auditory,  650 
Ossification,  of  the  skeleton,  45,  773 
Otic  ganglion,  584 
Otoconia,  657 
Ovarian  pregnancy,  711 
Ovaries,  683 

of  tsenia,  683 

of  frog,  687 

of  fowl,  689 

of  human  female,  692 

development  of,  785,  788 

condition  of,  in  fcetus  at  term,  790 
Oviducts,  687 

Oviparous  and  viviparous  animals,  703 
Ovulation,  703,  710 
Ovum,  683,  685 

Oxalic  acid,  produced  in  urine,  393 
Oxygen,  absorbed  in  respiration,  281 

solution  of,  in  the  blood,  248,  254,  294 

absorption  of,  by  the  tissues,  295 

exhalation  of,  by  plants,  60,  131,  270 

absorption    of,    by  the    fowl's    egg. 
during  incubation,  744 


INDEX. 


821 


pACINIAN  bodies,  407 
JT    Pain,  sensations  of,  597 
Palate,  formation  of,  783 
Palmitine,  70 
Pancreas,  172 
Pancreatic  juice,  171 

mode  of  obtaining,  172 

composition  of,  173 

action  of,  on  starch  and  fat,  175 

on  albuminous  matters,  177 

daily  quantity  of,  179 
Pancreatiue,  89 

in  pancreatic  juice,  174 
Paralysis,  muscular,  422 

nervous,  423 

after  division  of  anterior  spinal  nerve 
root,  447 

direct,  after  lateral  injury  of  spinal 
cord,  455 

crossed,  after  lateral  injury  of  brain, 
455 

various  forms  of,  457 

facial,  543 

glosso-labio-laryngeal,  510 

of  motor  nerves,  by  woorara,  422 

of  voluntary  motion  and  sensation  by 
destruction  of  tuber  annulare,  502 

of  larynx,  pharynx,  and  oesophagus, 
by  division  of  the  pneumogastric 
nerves,  564,  566 

of  muscular  coat  of  stomach,  569 

of  the  external  muscles  of  the  eye- 
ball, 523 

of  levator  palpebrse  superioris,  523 

of  the  muscles  of  mastication,  533 

of  the  sphincter  ani,  468 

of  the  urinary  bladder,  470 
Paraplegia,  457 

reflex  action  of  the  spinal  cord  in, 

463 

Parasites,  internal,  672 
Parotid  saliva,  143,  144     . 
Parturition,  765 
Par  vagum,   see  Pneumogastric  Nerve, 

557 

Patheticus  nerve,  524 
Pelvis,  development  of,  596 
Pepsine,  59 

in  gastric  juice,  158 
Pepsine  cells,  155 
Peptic  glands,  155 
Perception,  of  sensations,  483,  501 
Perilymph,  655 
Periodical  ovulation,  703,  710 
Peristaltic  action,  of  stomach,  166 

of  intestine,  191 

of  oviduct,  688,  689 

Personal  error,  in  the  observation  of  phe- 
nomena, 431 
Perspiration,  316 

function  of,  in  regulating  tempera- 
ture, 317 

Petrosal  ganglion,  553 
Petrosal  nerve,  548,  549 
Pettenkofer's  test  for  bile,  212 
Peyer's  patches,  190 
Pharynx,  action  of,  in  swallowing,  555 
Phenomena,  vital,  29 
Phonation,  509 

Phosphate,  amrnonio-mapnesian,  in   de- 
composing urine,  395 

lime,  44 


Phosphates,  alkaline,  49,  51,  383 

earthy,  46,. 47,  260,  383,  390,  395 
Phosphorized  fat,  102 
Phosphorus,  not  a  proximate  principle, 
35 

a  constituent  of  lecithine,  103 

oxidation  of,  in  the  body,  51,  103 
Physiology,  definition  of,  25 

method  of  study  of,  26,  31 
Placenta,  755 

formation  of,  757 

foetal  tufts  of,  758 

maternal  sinuses  of,  759 

injection   of,  from  uterine  bloodves- 
sels, 760 

function  of,  761 

separation  of,  in  delivery,  765 
Placental  circulation,  793 
Plasma,  of  the  blood,  243,  257 
Plasmine,  264 
Plates,  dorsal,  724 

abdominal,  725 

Plexus,  capillary,  152,  189,  190,  194,  202, 
274,  346 

peripheral,  of  nerves,  406 

laryngeal,  558 

cesophageal,  559 

pulmonary,  559 

solar,  585 
Pneumogastric  nerve,  557 

physiological  properties  of,  559 

connection  of,  with  respiration,  560 

with  phonatiou,  565 

with  deglutition,  566 

with  the  stomach  and  digestion,  568 

influence  of,  on  the  heart,  569 
Point  of  distinct  vision,  629 
Point  of  fixation,  in  vision  with  both  eyes, 

638 

Polarity,  of  nerve  fibres  in  action,  424 
Polarized  light,  rotation  of,   by  organic 

fluids,  59 

Pons  Varolii,  439,  500 
Portal  blood,  temperature  of,  308 
Portal  vein,  distribution  of,  in  the  liver, 
201,  202 

evelopment  of,  800 
Posterior  columns  of  the  spinal  cord,  435, 

445,  449,  453,  465 
Potassium  chloride,  49,  384 
Potassium  sulphate,  52,  53,  384 
Potassium  urate,  382 
Presbyopic  eye,  635 
Pressure,  arterial,  338 
Primitive  trace,  724 
Primitive  vertebrae,  735,  772 
Protagon,  102 

Proteus  anguinus,  blood-globules  of,  252 
Proximate  principles,  33 

definition  of,  35 

mode  of  extraction  of,  36 

varying  proportion  of,  37 

classification  of,  38 
Ptyaline,  89,  141,  142 
Puberty,  signs  of,  704 
Pulsation,  of  heart,  322 

of  arteries,  330 
Pulse,  arterial,  330 

dicrotic,  335 
Pupil,  action  of,  400,  518,  524,  611,  634, 

588 
Pupillary  membrane,  772 


822 


INDEX. 


Pus,  in  the  urine,  393 
Putrefaction,  82 

arrested  by  gastric  juice,  161 
Pyramids,  anterior,    of  medulla  oblon- 
gata,  438 

decussatiou  of,  439,  455 


QUANTITY,  daily,  of  air  used  in  res- 
piration, 280 

of  albuminous  matter,   starch,  and 
fat  in  the  food,  128 

of  bile,  219 

of  biliary  acids,  106 

of  carbonic  acid  exhaled,  283 

of  creatinine,  108 

of  earthy  posphates  in  the  urine,  47 

of  feces,  187 

of  fluids  secreted    and  reabsorbed, 
373 

of  food,  124 

of  gastric  juice,  164 

of  lime  phosphate,  in  the  urine,  46 

of  lymph  and  chyle,  371 

of  magnesium  phosphate,  in  the  urine, 
46 

of  materials  absorbed  and  discharged, 
397 

of  mineral  matter  introduced  and  dis- 
charged, 114 

of  oxygen  consumed,  281 

of  pancreatic  juice,  179 

of  perspiration,  316 

of  saliva,  146 

of  sodium  chloride  discharged,  49 

of  sodium  and  potassium  phosphates, 
in  the  urine,  51 

of  sodium  and  potassium  sulphates, 
in  the  urine,  53 

of  solid  matters,  in  the  urine,  377 

of  urea,  109 

of  urine,  376 

Quantity,  entire,  of  blood  in  the  body, 
267 

of  iron  in  the  blood,  96 

of  lime  phosphate  in  the  body,  44 

of  sodium  chloride  in  the  body,  47 

of  sulphur  in  the  albuminous  ingre- 
dients of  the  body,  63 


RABBIT,  brain  of,  437 
Rapidity,  of  movements  of  respira- 
tion, 279 

of  the  arterial  current,  338 

of  the  venous  current,  349 

of  the  circulation  in  general,  350 

of  nervous  action,  425 
Reactions,  of  the  bile,  205 

of  fat,  68 

of  gastric  juice,  157 

of  intestinal  juice,  184 

of  milk,  118 

of  pancreatic  juice,  173 

of  saliva,  141 

of  starch,  58 

of  sugar,  62 

of  urine,  384 
Reasoning  powers,  484 
Rectum,  134 

evacuation  of,  467 

development  of,  776 


Red  globules  of  the  blood,  243 
Reflex  action,  416 

of  the  spinal  cord,  459 

of  the  brain,  485 

of  tubercula  quadrigemina,  518,  522 

of  tuber  annulare,  500 

of  medulla  oblongata,  507 
Refraction,   of  light,  by  the  crystalline 

lens,  613 

Regeneration,   of   divided    nerve  fibres, 
411 

of  the  uterine  tissues,  after  pregnan 

cy,  766,  768 
Reil,  island  of,  473 
Rennet,  118,  133 
Reproduction,  667 

by  generation,  668 
Resinous  matters,  of  the  bile,  105 
Respiration,  270 

in  vegetables,  270 

organs  of,  271 

by  gills,  272 

by  lungs,  272 

by  the  skin,  285,  809 

movements  of,  275 

thoracic,  276 

abdominal,  276 

internal  phenomena  of,  280,  293 

in  the  newly-born  infant,  809 
Respiratory  movements,  of  the  chest,  275 

of  the  abdomen,  276 

of  the  glottis,  277 

after  division  of  the  pneumogastric 
nerves,  560,  563 

after  injury  of  the  spinal  cord,  458 
Restiform  bodies,  494 
Retina,  616 

Rhythm,  of  the  heart's  action,  328 
Round  ligament,  of  the  uterus,  789 

of  the  liver,  801 

Ruminating  animals,  stomach  of,  133 
Rumination,  movements  of,  133,  145 
Rutting  condition,  of  the  lower  animals, 
708 


QACCHARINE  SUBSTANCES,  61 
U        in  the  liver,  232 
in  the  blood,  240 
in  the  urine,  240,  386 
Saccharomyces  cerevisise,  65 
Saccharose,  67 

Sacculus.  of  the  internal  ear,  655 
Saliva,  138 

composition  of,  141 

different  kinds  of,  143 

secretion  of,  145 

daily  quantity  of,  146 

physiological  action  of,  147 
Salivary  glands,  138 
Salivary  tubes,  139 
Salts,  biliary,  104,  105 

of  the  blood,  260 

of  the  urine,  386 
Saponification,  of  fat,  69 
Scala  tympani,  661 
Scala  vestibuli,  661 
Schlemm,  canal  of,  609 
Sclerosis,   of   posterior   columns  of  the 

spinal  cord,  466 

Sclerotic  coat,  of  the  eyeball,  609 
Secretion,  of  saliva,  145 


INDEX. 


823 


Secretion  of  gastric  juice,  161 
of  intestinal  juice,  180 

of  pancreatic  juice,  179 

of  bile,  216 

of  perspiration,  316 

of  ineconium,  bile,  and  gastric  juice 

in  the  foetus,  777,  778 
Segmentation,  of  the  vitellus,  722 

of  the  cicatricula,  730 
Semicircular  canals,  655 
Seminal  fluid,  695 
Sensation,  409 

dependence  of,  on  the  tuber  annulare, 
500 

channels    of    transmission    for,     in 
spinal  cord,  452,  455 

loss  of,  in  paraplegia  and  hemiplegia, 

457,  458,  492 
Sensations,  of  touch,  593 

of  temperature,  597 

of  pain,  597 
Sense,  of  taste,  600 

of  smell,  604 

of  sight,  607 

of  hearing,  618 
Senses,  the,  593 

mode  of  action  of,  598 
Sensibility,  general,  593 

of  different  regions,  595 

of  nerves  to  electric  current,  419 

of  posterior  spinal  nerve  roots,  448 

of  posterior  and  lateral  columns  of 
the  spinal  cord,  449,  450 

of  the  facial  nerve,  547 

of  the  hypoglossal  nerve,  578 

of  the  spinal  accessory  nerve,  572 

stereoscopic,  642 
Seriue,  259 

Serum,  of  the  blood,  252 
Sexes,  distinctive  characters  of,  684 

union  of,  700 
Sexual  generation,  683 
Shock,  nervous,  420 
Sight,  sense  of,  607 

organ  of,  608 

physiological  conditions  of,  627 
Single  and  double  vision,  639 
Sinuses,  vascular,   of  the  placenta,  758, 

759 

Skeleton,  ossification  of,  45,  772 
Skin,  perspiratory  secretion  of,  316 

respiration  by,  285,  809 

development  of,  774 
Smell,  sense  of,  604 

nerves  of,  513,  605 
Sodium  biphosphate,  382 

carbonate,  51 

chloride,  47,  384 

glycocholate,  104 

hippurate,  111 

phosphate,  49 

sulphate,  52,  384 

sulphocyanide,  141,  142 

taurocholate,  105 

urate,  111,  382,  391 

Solar  plexus,  of  sympathetic  nerve,  585 
Solid  bodies,  vision  of,  with   two   eyes, 

640 
Sound,  how  produced,  649 

how  perceived,  657 
Sounds,  of  the  heart,  322 

vocal,  565,  566,  573 


Special  senses,  599 
Species,  668 

continuation  of,  669 
Specific  gravity,  of  the  saliva,  144 

of  gastric  juice,  157 

of  bile,  205 

of  the  blood,  243 

of  lymph,  367 

of  the  urine,  376 
Spectrum,  of  bile,  207 

of  chlorophylle,  210 

of  Pettenkofer's  test,  213,  214,  215 

of  blood,  248,  250 
Spermatozoa,  695 

formation  of,  697 

entrance  of,  into  the  egg,  699 
Sphincter  aui,  467 
Sphincter  vesicse,  468 
Sphincter  pupillse,  611 
Sphygmograph,  331 
Spina  bifida,  773 
Spinal  accessory  nerve,  571 
Spinal  column,  formation  of,  726,  735 
Spinal  cord,  433,  443 

commissures  of,  435 

anterior,  lateral,  and  posterior  col- 
umns of,  435 

origin  of  nerves  from,  434,  445 

gray  substance  of,  443 

white  substance  of,  445 

sensibility  and  excitability  of,  449 

transmission  of  nervous  impulses  in, 
429,  449,  452 

crossed  action  of,  454 

reflex  action  of,  459 

protective  action  of,  463 

influence  of,  on  sphincters,  467 

development  of,  726 
Spinal  nerves,  origin  of,  434,  445 

transmission  of  motor  and  sensitive 

impulses  in,  447 
Spiral  ganglion,  of  the   cochlear  nerve, 

663 

Spiral  lamina,  of  the  cochlea,  661 
Spontaneous  generation,  670 
Stapedius  muscle,  652 
Starch,  55 

action  of  saliva  on,  142 

digestion  of,  60,  149,  150,  175 
Stearine,  70 
Stercorine,  188 
Stereoscope,  642 
Stereoscopic  sensibility,  642 
Stomach,  133,  134,  152 

digestion  in,  150, 166 

influence  of  pneumogastric  nerve  on, 
568 

formation  of,  775 

Strabismus,  from   paralysis  of  oculomo- 
torius  nerve,  523 

of  abducens  nerve,  539 
Striated  bodies,  437 
Strychnine,  effect  of,  on  the  spinal  cord, 

461 

Sublingual  saliva,  143 
Submaxillary  ganglion,  of   the   sympa- 
thetic, 584 
Submaxillary  gland,  140 

influence  of  nerves  on  the  circulation 

in,  550,  591 

Submaxillary  saliva,  143 
Sugar,  61 


824 


INDEX. 


Sugar,  varieties  of,  62 

tests  for,  62 

fermentation  of,  64 

source  and  destination  of,  67,  68 

production  of,  in  liver,  232 

discharge  of,  by  the  urine,  240,  386 
Sulphates,  alkaline,  52,  53 

in  the  urine,  384 

Sulpho-cyanide,  sodium,  in  saliva,  141, 142 
Sulphur,  in  albuminous  matters,  53 

in  biliary  matters,  105 

in  excretine,  188 

in  the  feces,  224 

oxidation  of,  in  the  body,  53 
Swallowing,  151,  508,  579 

retarded  by  suppression  of  the  saliva, 
148 

by    division    of   the    pneumogastric 
nerves,  566 

reflex  action  of,  508,  555,  566 
Sympathetic  nerve,  582 

physiological  properties  of,  585 

influence  of,  on  movement  and  sensi- 
bility, 586 

on  the  special  senses,  586 

on  the  circulation,  589 

on  the  temperature  of  parts,  590 

on  reflex  actions,  592 


mACTILE  corpuscle,  407,  408,  594 
1     Tactile   sensibility,    of   different  re- 
gions, 595 
Tadpole,  development  of,  724 

transformation  of,  into  frog,  728 
Tsenia,  674 

single  articulation  of,  683 
Tapeworm,  674 

production  of,  from  cysticercus,  675 
Taste,  600 

nerves  of,  533,  554,  601 

conditions  of,  603 

injury  of,  by  paralysis  of  facial  nerve, 

550 

Taurine,  105 

Tauro-cholate,  sodium,  105,  106 
Tauro-cholic  acid,  105 
Teeth,  136,  138 

first  and  second  sets  of,  810,  811 
Temperature,  animal,  300,  308 

in  different  species,  301 

of  the  blood  in  different  organs,  308 

regulation  of,  311 

elevation    of,    after  division   of   the 
sympathetic  nerve,  590 

sensations  of,  597 
Tensor  tympani,  651 
Terminal  bulb,  of  a  sensitive  nerve,  408, 

594 
Termination,  peripheral,  of  nerve  fibres, 

406,  407,  408 
Tests,  for  starch,  58 

for  sugar,  62,  386 

for  bile,  98,  211,  212 

for  sulpho-cyanides,  142 
Testicles,  683 

periodical  activity  of,  in  fish,  700 

development  of,  785 

descent  of,  786 
Tetanus,  pathology  of,  461 
Thalami,  optic,  437,  441,  476,  491 
formation  of,  769 


Thaumatrope,  643 
Thoracic  duct,  197,  198 
Thoracic  respiration,  276 
Tic  douloureux,  532 
Tongue,  601 

motor  nerve  of,  574 

sensitive  nerve  of,  532,  554 
Toothache,  532 
Touch,  sensations  of,  593 
Trace,  primitive,  724 
Tract,  optic,  516 

Transmission,  of  nerve  force,  rapidity  of, 
425 

in  motor  nerves,  428 

in  sensitive  nerves,  429 

in  the  spinal  cord,  429 

in  the  brain,  420 
Transudation,  359,  365 
Trichina  spiralis,  675 
Tricuspid  valve,  320 
Trigeminus  nerve,  526 
Trommer's  test  for  glucose,  62 

in  the  urine,  63 

interfered  with  by  albuminose,  87 
Tubal  pregnancy,  711 
Tube,  Eustachian,  654 
Tuber  annulare,  439,  499 

action  of,  500 
Tubercula  bigemina,  517 
Tubercula  quadrigemina,  436,  516 

reflex  action  of,  518 

crossed  action  of,  521 

development  of,  770 
Tubes,  Fallopian,  692 

salivary,  139 
Tubules,  gastric,  152 

uterine,  750 

Tufts,  placental,  757,  758,  759 
Tunica  vaginalis    testis,    formation    of, 

788 
Tympanum,  of  the  ear,  649 


UMBILICAL  CORD,  763 
separation  of,  after  birth,  810 
Umbilical  hernia,  777 
Umbilical  vesicle,  738,  745,  776 
Umbilical  veins,  formation  of,  794 

obliteration  of,  801 
Urachus,  780 
Urate,  sodium,  111,  382 
Urates,  deposits  of,  in  the  urine,  390 
Urea,  108,  379 

daily  quantity  of,  109 

conversion  of,  into  ammonium   car- 
bonate, 108,  394 
Uric  acid,  111 

deposited  from  urine,  385,  392 
Urine,  374 

general  character  of,  52,  112,  374 

physical  properties  of,  376 

composition  of,  378 

ingredients  of,  379 

reactions  of,  384 

interference  of,  with  Trommer's  test, 
63 

abnormal  ingredients  of,  386 

deposits  in,  390 

acid  fermentation  of,  393 

alkaline  fermentation  of,  394 
Urinary  bladder,  closure  and  evacuation 
Of,  468 


INDEX. 


825 


Urinary  bladder,  development  of,  779 

Urobiline,  99 

Urochrome,  99 

Urohematine,  99 

Urosaciue,  99 

Urosine,  99 

Uterus,  692,  693 

mucous  membrane  of,  750 
changes  in,  after  impregnation,  751 
regeneration  of,  after  delivery,  766 
development  of,  789 
position  of,  at  birth,  790 

Uterus  bicornis,  789 

Utricle,  of  the  internal  ear,  655 


yALVE,  Eustachian,  804 
V     of  the  foramen  ovale,  806 

of  Vieussens,  525 
Valves,  of  the  heart,  320,  323 

of  the  veins,  342 

of  the  lymphatics,  355,  370 
Valvulse  conniventes,  135 

formation  of,  776 
Vasa  deferentia,  698 

formation  of,  786,  787 
Vascular  system,  development  of,  791 
Vapor,  watery,  exhalation  of,  43 

from  the  lungs,  288 

from  the  skin,  316 

Vegetable  food,  necessary  to  man,  114 
Vegetables,  as  food,  122 

production  of  organic  matter  in,  60 

production  of  fat  in,  69 

green  coloring  matter  of,  101 

absorption  of  carbonic  acid  and  ex- 
halation of  oxygen  by,  60,  131,  270 

respiration  in,  270 

production  of  heat  in,  301,  302 
Vegetative  functions,  31 
Veins,  340 

motion  of  the  blood  in,  341 

action  of  the  valves  of,  342 

rapidity  of  blood-current  in,  313 

omphalo-mesenteric,  792 

umbilical,  794 

vertebral,  797 

Vena   azygos,  major  and  minor,  forma- 
tion of,  799 

Venje  cavse,  formation  of,  797,  798 
Venous  system,  development  of,  797 
Ventricles,  of  the  heart,  situation  of,  319 

action  of,  320 

muscular  fibres  of,  328 
Vernix  caseosa,  774 
Vertebral  arteries,  792,  795 
Vertebral  veins,  797 
Vertebrae,  primitive,  735 

permanent,  formation  of,  737,  772 
Vesicle,  umbilical,  738,  745,  776 
Vesicles,  adipose,  72 

cerebral,  769 


Vesicles,  pulmonary,  274 

seminal,  698 
Vesiculfe  seminales,  698 

formation  of,  787 
Vestibule,  of  the  internal  ear,  654 
Vieussens,  valve  of,  525 
Villi,  of  stomach,  152 

of  intestine,  189,  194 

of  chorion,  747 
Visceral  folds,  781 
Vision,  sense  of,  607 

acuteness  of,  626 

field  of,  627 

line  of  direct,  628 

point  of  distinct,  629 

erect,  638 

binocular,  639 
Vital  phenomena,  29 
Vitellus,  685,  686 

segmentation  of,  722 

formation  of,  in  foetus,  790 
Vitelline  circulation,  791 
Vitelline  membrane,  685 
Vitelline  spheres,  722 
Vitreous  body,  of  the  eye,  612 
Voice,  formation  of,  in  the  larynx,  565 

loss  of,  after  division  of  the  pneumo- 
gastric  nerves,  566 

of  the  spinal  accessory  nerves,  573 
Volition,  seat  of,  in  the  tuber  annulare, 

501 
Vomiting,  how  produced,  556 


WATER,  as  a  proximate  principle,  40 
proportion    of,   in    the    tissues    and 

fluids,  41 
probable  formation  of,  in  the  system, 

42 
discharge  of,  from  the  body,  43,  288, 

316 
Weight  of  organs,    comparative,  in  the 

foetus  at  term  and  adult,  810 
Wheaten  bread,  composition  of,  121 
White  globules  of  the  blood,  254 
amoeboid  movements  of,  255 
sluggish  movement  of,  in  the  circula- 
tion, 348 
White  substance  of  the  nervous  system, 

409 
Wolflfian  bodies,  784 

atrophy  and  disappearance  of,  785 
Woorara,   action   of,    on   motor    nerves, 
422 


YEAST-FUNGUS,  65 
Yolk,  686,  689,  729 

17  ON  A  pellucida,  685 


53 


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ANATOMY. 

ANATOMICAL  ATLAS.  By  SMITH  and  HOENER.  One  imp.  8vo.  vol.  with  600  illustrations.  Cloth  $4  50 

BELLAMY'S  SURGICAL  ANATOMY.  One  vol.  12mo.  with  illustrations.  Cloth 2  25 

GRAY'S  ANATOMY,  DESCRIPTIVE  AND  SURGICAL.  In  one  imperial  octavo  volume,  new 

edition.  Over  900  pages,  and  465  cuts.  Cloth,  $6 ;  leather 700 

GREEN'S  PATHOLOGY  AND  MORBID  ANATOMY.  One  handsome  octavo  volume,  cloth 2  50 

HEATH'S  PRACTICAL  ANATOMY.  One  volume,  royal  12mo.  of  572  pages,  and  247  illustrations. 

Cloth,  $3.50 ;  leather 4  00 

MACLISE'S  SURGICAL  ANATOMY.  One  imperial  quarto  volume,  68  colored  plates,  containing 

190  figs.  Cloth 14  00 

WILSON'S  HUMAN  ANATOMY.  In  one'Svo.  volume  of  600  pp.  and  397  cuts.  Cloth,  $4;  leather  5  00 

PHYSIOLOGY. 

CARPENTER'S  HUMAN  PHYSIOLOGY.    In  one  handsome  8vo.  volume  of  900  pages,  and  many 

illustrations.    Cloth,  $5.50 ;  leather 6  50 

D ALTON'S  HUMAN  PHYSIOLOGY.    Sixth  revised  and  enlarged  edition  (now  ready).    In  one  8ro. 

volume  of  830  pages  and  316  illustrations.    Cloth,  $       ;  leather 

KIRKES'S  PHYSIOLOGY.    A  new  American  from  the  eighth  London  edition,  in  one  large  12mo. 

vol.  containing  250  illustrations.    Cloth,  $3.25  ;  leather ' 3  75 

MARSHALL'S  PHYSIOLOGY.    One  large  8vo.  volume  of  1026  pages,  and  122  illustrations    Cloth, 

$6.50;  leather 7  50 

CHEMISTRY. 

ATTFIELD'S  CHEMISTRY,  GENERAL  MEDICAL  AND  PHARMACEUTICAL.    Fifth  edition, 

revised  by  the  Author.  In  one  large  12mo.  volume.  Cloth,  $2.75 ;  leather 3  25 

BLOXAM'S  CHEMISTRY,  INORGANIC  AND  ORGANIC.  In  one  large  octavo  volume,  with  about 

300  illustrations.  Cloth,  $4 ;  leather 5  00 

BOWMAN'S  PRACTICAL  CHEMISTRY.  In  one  vol.  12mo.  of  351  pp.,  cuts.  Cloth 2  25 

MEDICAL  CHEMISTRY  "  «  «  "  225 

FOWNES'  MANUAL  OF  ELEMENTARY  CHEMISTRY.  From  the  10th  English  edition.  In  one 

12mo.  volume  of  650  pages.  Cloth,  $2.75 ;  leather 3  25 

GALLOWAY'S  MANUAL  OF  QUALITATIVE  ANALYSIS.  From  5th  English  edition.  In  one 

volume,  12mo.  Cloth '. 2  50 

ODLING'S  CHEMISTRY  FOR  MEDICAL  STUDENTS.  In  one  12mo.  volume.  Cloth.... 200 

WOHLER'S  OUTLINES  OF  ORGANIC  CHEMISTRY.  In  one  12mo.  volume.  Cloth 3  00 

PHARMACY. 

ELLIS' MEDICAL  FORMULARY.    Twelfth  edition.    In  one  8vo.  volume  of  376  pages.    Cloth....      300 
GRIFFITHS'  UNIVERSAL  FORMULARY.    Third  edition,  revised  by  J.  M.  Maisch.    In  one  hand- 
some octavo  volume  of  about  800  pages.    Cloth,  $4.50 ;  leather 5  50 

PARRISH'S  PHARMACY.   Fourth  edition,  thoroushly  revised.    In  one  8vo.  volume  of  977  pages, 

and  280  illustrations.    Cloth,$5.50;   leather 650 

MATERIA  MEDICA  AND  THERAPEUTICS. 

PEREIRA'S  MATERIA  MEDICA.  In  one  imperial  octavo  volume  of  1040  pages,  and  236  illustra- 
tions. Cloth,$7;  leather 8  00 

STILLES  THERAPEUTICS.  Fourth  edition,  thoroughly  revised  and  improved.  In  two  handsome 

octavo  volumes.  Cloth,  $10 ;  leather 12  OQ 

PRACTICE  OF  MEDICINE. 

FLINT'S  PRINCIPLES  AND  PRACTICE  OF  MEDICINE.    Fourth  edition,  thoroughly  revised. 

In  one  imperial  octavo  volume  of  about  1100  pa^ea.  Cloth,  $6;  leather 7  00 

HARTSHORNE'S  ESSENTIALS  OF  THE  PRINCIPLES  AND  PRACTICE  OF  MEDICINE. 

Fourth  edition.  In  one  royal  12mo.  volume,  with  about  100  illust.  Cloth,  $2.63;  half  bound..  288 
WATSON  ON  THE  PRINCIPLES  AND  PRACTICE  OF  MEDICINE.  From  the  fifth  English 

edition.  In  two  handsome  8vo.  vols.,  many  illustrations.  Cloth,  $9;  leather 1100 

BUMSTEAD  ON  VENEREAL.  Third  edition.  In  one  large  8vo.  volume.  Cloth,  $5;  leather 6  00 

BLANDFORD  ON  INSANITY  AND  ITS  TREATMENT,  with  an  Appendix.  By  Dr.  ISAAC  RAT. 

In  one  8vo.  volume.    Cloth 3  25 

CULLERIER'S  ATLAS  OF  VENEREAL  DISEASES.   Imperial  quarto  vol.    26  colored  plates.  Cloth    17  00 
FLINT   ON   PHYSICAL   EXPLORATION    OF   THE   CHEST.     Second  edition.    In  One  octavo 

volume  of  595  pages.    Cloth ; 4  50 

FLINT  ON  PHTHISIS.    A  new  work.    In  one  handsome  8vo.  vol.    (Preparing.) 

FLINT  ON  DISEASES  OF  THE  HEART.    Second  edition.    In  one  octavo  volume  of  550  pages. 

Cloth 4  00 

LINCOLN'S  ELECTRO-THERAPEUTICS.     In  one  handsome  12mo.  vol.  Cloth 1  50 

WILSON  ON  DISEASES  OF  THE  SKIN.    Seventh  edition.    In  one  handsome  octavo  volume  of 

800  pages.    Cloth 5  00 

PLATES  to  ditto.    8vo.    Cloth,  $5.50.    Text  and  plates  in  one  volume.    Cloth 1000 


LEADING  MEDICAL  TEXT-BOOKS-Qontinued. 

DISEASES  OF  WOMEN  AND  CHILDREN. 

BARNES  ON  THE  DISEASES  OF  WOMEN.     In  one  handsome  octavo  volume  of  about  800 

pages,  with  169  illustrations.  Cloth,  $5;  leather $6  00 

HODGE  ON  DISEASES  OF  WOMEN.  Second  edition.  In  one  handsome  octavo  volume  of 

531  pages  and  many  illustrations.  Cloth 4  50 

THOMAS  ON  THE  DISEASES  OF  WOMEN.  Fourth  edition.  In  one  handsome  octavo 

volume  of  about  800  pages,  and  186  illustrations.  Cloth,  $5;  leather 6  00 

WEST  ON  DISEASES  OF  FEMALES.  Third  edition.  In  one  8vo.  volume  of  550  pages.  Cloth, 

$3.75  ;  leather 4  7."> 

CONDIE  ON  DISEASES  OF  CHILDREN.  Sixth  edition.  In  one  large  Svo.  volume  of  nearly 

800  pages.  Cloth,  $.3.25  ;  leather 6  2.3 

SMITH  ON  DISEASES  OF  CHILDREN.  Second  edition.  In  one  large  octavo  volume  of  741 

pages.  Illustrations.  Cloth,  $5 ;  leather 6  00 

WEST  ON  DISEASES  OF  INFANCY  AND  CHILDHOOD.  From  5th  English  edition.  In  one 

Svo.  vol.  of  650  pages.     Cloth,  $1.50  ;  leather 5  50 

OBSTETBICS. 

CHURCHILL  ON  THE  THEORY  AND  PRACTICE  OF  MIDWIFERY.    From  the  4th  English 

edition.  In  one  large  Svo.  volume  of  700  pages,  and  194  illustrations.  Cloth,  $4 ;  leather  5  00 
HODGE'S  OBSTETRICS.  In  one  large  quarto  volume  of  550  pages,  with  many  plates  and 

cuts.  Cloth 14  00 

IRISHMAN'S  SYSTEM  OF  MIDWIFERY.  In  one  large  octavo  volume  of  over  700  pages,  with 

182  illustrations.  Cloth,  $o ;  leather  600 

RAMSBOTHAM'S  MIDWIFERY.  In  one  imperial  octavo  volume  of  650  pages,  many  plates 

and  cuts.  Leather 7  00 

SWAYNE'S  OBSTETRIC  APHORISMS.  From  the  5th  English  edition.  In  one  small  12mo. 

volume.     Cloth 1  2.3 

SURGERY, 

ASH  HURST'S  PRINCIPLES  AND  PRACTICE  OF  SURGERY.     In  one  large  octavo  volume 

of  1000  pages,  and  550  illustrations.  Cloth,  $6.50  ;  leather 7  50 

BRYANT'S  PRACTICE  OF  SURGERY.  In  one  handsome  Svo.  volume  of  over  1000  pages, 

and  many  illustrations.  Cloth,  $6.25  ;  leather 7  2.5 

DRUITT'S  SURGERY.  From  the  8th  English  edition.  In  one  handsome  octavo  volume  of  about 

700  pages,  and  432  illustrations.  Cloth,  $4  ;  leather 500 

ERICHSEN'S  SCIENCE  AND  ART  OF  SURGERY.  From  the  6th  English  edition.  In  two 

large  octavo  volumes  of  over  1700  pages,  with  more  than  700  illustrations.     Cloth,  $') ; 

leather  11  00 

GROSS'  SYSTEM  OF  SURGERY.  Fifth  and  enlarged  edition.  In  two  imperial  octavo  vols. 

of  over  2200  pages,  and  1403  illustrations.     Leather 15  00 

MILLER'S  PRINCIPLES  OF  SURGERY.    In  one  large  Svo.  volume,  with  240  illustrations. 

Cloth 3  75 

MILLER'S  PRACTICE  OF  SURGERY.  la  one  large  Svo.  vol.,  with  364  illustrations.  Cloth  3  75 
HAMILTON  ON  FRACTURES  AND  DISLOCATIONS.  Fifth  and  revised  edition.  In  one 

handsome  octavo  volume  of  831  pages,  and  344  illustrations.     Cloth,  $5.75;  leather 6  75 

OPHTHALMOLOGY. 

LAWRENCE  &  MOON'S  OPHTHALMIC  SURGERY.      Second  edition.      In  one  Svo.  volume. 

Cloth 2  75 

LAWSON  ON  INJURIES  OF  THE  EYE.  In  one  octavo  vol.,  many  illustrations.  Cloth....  3  50 
WELLS  ON  DISEASES  OF  THE  EYE.  Second  revised  and  enlarged  edition.  In  one  large 

octavo  volume  of  over  750  pages,  and  many  illustrations.    Plates.     Cloth,  $5  ;  leather. , . .      6  00 

JTJRISPBUDENCE. 

TAYLOR'S  MANUAL  OF  MEDICAL  JURISPRUDENCE.  Seventh  American  edition.  Edited 
by  John  J.  Reese,  M.D.  In  one  large  octavo  volume  of  nearly  900  pages.  Cloth,  $5; 
leather 6  00 

TAYLOR'S  PRINCIPLES  AND  PRACTICE  OF  MEDICAL  JURISPRUDENCE.  Second  edition. 

In  two  large  octavo  volumes.  Cloth,  $10;  leather 12  00 

TAYLOR  ON  POISONS.  Third  edition.  In  one  Svo.  volume  of  850  pages,  and  many  illus- 
trations. Cloth,  $5.50;  leather 6  5) 

DICTIONARIES  AND  MANUALS. 

DUNGLISON'S  MEDICAL  LEXICON.     A  new  and  revised  edition.     Edited  by  Richard  J. 

Dunglison,  M.D.  In  one  royal  octavo  volume  of  over  1100  pages.  Cloth,  $6.50;  leather  7  50 
HOBLYN'S  MEDICAL  DICTIONARY.  In  one  handsome  12mo.  volume  of  over  500  pages. 

Cloth,  $1.50;  leather 2  00 

HARTSHORNE'S  CONSPECTUS  OF  THE  MEDICAL  SCIENCES.  Second  and  revised  edition. 

In  one  large  12mo.  volume  of  over  1000  page,,  and  477  illustrations.  Cloth,  $1.25 ;  leather  5  00 
LUDLOW'S  MANUAL  OF  EXAMINATIONS.  Third  edition.  In  one  large  12mo.  volume, 

many  cuts.  Cloth,  $3.25  ;  leather 3  75 

NEILL  &  SMITH'S  COMPENDIUM  OF  THE  MEDICAL  SCIENCES.  In  one  handsome  octavo 

volume  of  about  1000  pages,  with  374  illustrations.  Cloth,  $t ;  leather 4  75 

TANNER'S  MANUAL  OF  CLINICAL  MEDICINE.  From  the  second  English  edition.  In  one 

12mo.  vol.  of  375  pages.    Cloth I  50 


HENRY  C.  LEA— Philadelphia. 


O. 

(LATE  LEA  &  BLANCHARD'S) 


OIF 

MEDICAL  AND  SURGICAL  PUBLICATIONS. 


In  asking  the  attention  of  the  profession  to  the  works  advertised  in  the  following 
pages,  the  publisher  would  state  that  no  pains  are  spared  to  secure  a  continuance  of 
the  confidence  earned  for  the  publications  of  the  house  by  their  careful  selection  and 
accuracy  and  finish  of  execution. 

The  printed  prices  are  those  at  which  books  can  generally  be  supplied  by  booksellers 
throughout  the  United  States,  who  can  readily  procure  for  their  customers  any  works 
not  kept  in  stock.  Where  access  to  bookstores  is  not  convenient,  books  will  be  sent 
by  mail  post-paid  on  receipt  of  the  price,  but  no  risks  are  assumed  either  on  the 
money  or  the  books,  and  no  publications  but  my  own  are  supplied.  Gentlemen  will 
therefore  in  most  cases  find  it  more  convenient  to  deal  with  the  nearest  bookseller. 

An  ILLUSTRATED  CATALOGUE,  of  64  octavo  pages,  handsomely,  printed,  will  be  for- 
warded by  mail,  post-paid,  on  receipt  of  ten  cents. 

HENRY  C.  LEA. 

Nos.  706  and  708  SANSOM  ST.,  PHILADELPHIA,  September,  1875. 


ADDITIONAL  INDUCEMENT  FOR  SUBSCRIBERS  TO 

THE  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES. 


THEEE  MEDICAL  JOURNALS,  containing  over  2000  LAEGE  PAGES, 
Free  of  Postage,  for  SIX  DOLLAES  Per  Annum, 


TERMS  FOR  1875: 


THE  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES,  and  )  Five  Dollars  per  annum, 
THE  MEDICAL  NEWS  AND  LIBRARY,  both  free  of  postage,  j  in  advance. 


THE  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES,  published  quar-  "]   q-    -r\  -\-\ 

terly  (llnO  pages  per  annum),  with 

THE  MEDICAL  NEWS  AND  LIBRARY,  monthly  (384  pp.  per  annum),  and   }•  per  annum, 
THE    MONTHLY    ABSTKACT    OF    MEDICAL    SCIENCE  (592  pages  per   |   ina(jvan, 

annum), 

SEPARATE  SUBSCRIPTIONS  TO 

THE  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES,  when  not  paid  for  in  advance, 

Five  Dollars. 

THE  MEDICAL  NEWS  AND  LIBRARY,  free  of  postage,  in  advance,  One  Dollar. 
THE  MONTHLY  ABSTRACT  OF  MEDICAL  SCIENCE,  free  of  postage,  in  advance,  Two 

Dollars  and  a  Half. 

It  is  manifest  that  only  a  very  wide  circulation  can  enable  so  vast  an  amount  of 
valuable  practical  matter  to  be  supplied  at  a  price  so  unprecedentedly  low.  The  pub- 
lisher, therefore,  has  much  gratification  in  stating  that  the  very  great  favor  with  which 
these  periodicals  are  regarded  by  the  profession  promises  to  render  the  enterprise  a 
permanent  one,  and  it  is  with  especial  pleasure  that  he  acknowledges  the  valuable 
assistance  spontaneously  rendered  by  so  many  of  the  old  subscribers  to  the  "JOUR- 
NAL," who  have  kindly  made  known  among  their  friends  the  advantages  thus  offered, 
and  have  induced  them  to  subscribe.  Relying  upon  a  continuance  of  these  friendly 
exertions,  he  hopes  to  be  able  to  maintain  the  unexampled  rates  at  which  these  works 


(For  "THE  OBSTETRICAL  JOURNAL,"  see  p.  22.) 


2          HENRY  C.  LEA'S  PUBLICATIONS  —  (Am.  Journ.  Med.  Sciences). 

are  now  offered,  and  to  succeed  in  his  endeavor  te  place  upon  the  table  of  every 
reading  practitioner  in  the  United  States  the  equivalent  of  three  large  octavo  volumes, 
at  the  comparatively  trifling  cost  of  Six  DOLLARS  per  annum. 

These  periodicals  are  universally  known  for  their  high  professional  standing  in  their 
several  spheres. 

I. 

THE  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES, 
EDITED  BY  ISAAC  HAYS,  M.D., 

is  published  Quarterly,  on  the  first  of  January,  April,  July,  and  October.  Each  num- 
ber contains  nearly  three  hundred  large  octavo  pages,  appropriately  illustrated  wher- 
ever necessary.  It  has  now  been  issued  regularly  for  over  FIFTY  years,  during  nearly 
the  whole  of  which  time  it  has  been  under  the  control  of  the  present  editor.  Through- 
out this  long  period,  it  has  maintained  its  position  in  the  highest  rank  of  medical 
periodicals  both  at  home  and  abroad,  and  has  received  the  cordial  support  of  the  en- 
tire profession  in  this  country.  Among  its  Collaborators  will  be  found  a  large  number 
of  the  most  distinguished  names  of  the  profession  in  every  section  of  the  United 
States,  rendering  the  department  devoted  to 

ORIGINAL     COMMUNICATIONS 

full  of  varied  and  important  matter,  of  great  interest  to  all  practitioners.  Thus,  during 
1874,  articles  have  appeared  in  its  pages  from  nearly  one  hundred  gentlemen  of  the 
highest  standing  in  the  profession  throughout  the  United  States.* 

Following  this  is  the  "REVIEW  DEPARTMENT,"  containing  extended  and  impartial 
reviews  of  all  important  new  works,  together  with  numerous  elaborate  "ANALYTICAL 
AND  BIBLIOGRAPHICAL  NOTICES"  of  nearly  all  the  medical  publications  of  the  day. 

This  is  followed  by  the  "QUARTERLY  SUMMARY  OF  IMPROVEMENTS  AND  DISCOVERIES 
IN  THE  MEDICAL  SCIENCES,"  classified  and  arranged  under  different  heads,  presenting 
a  very  complete  digest  of  all  that  is  new  and  interesting  to  the  physician,  abroad  as 
well  as  at  home. 

Thus,  during  the  year  1874,  the  "JOURNAL"  furnished  to  its  subscribers  85  Orig- 
inal Communications,  113  Reviews  and  Bibliographical  Notices,  and  305  articles  in 
the  Quarterly  Summaries,  making  a  total  of  about  FIVE  HUNDRED  articles  emanating 
from  the  best  professional  minds  in  America  and  Europe. 

That  the  efforts  thus  made  to  maintain  the  high  reputation  of  the  "JOURNAL"  are 
successful,  is  shown  by  the  position  accorded  to  it  in  both  America  and  Europe  as  a 
national  exponent  of  medical  progress:  — 


America  continues  to  take  a  great  place  in  this 
class  of  journals  (quarterlies),  at,  the  head  of  which 
the  great  work  of  Dr.  Hays,  the  American  Journal 
of  the  Medical  Sciences,  still  holds  its  ground,  as  our 
quotations  have  often  proved.  —  Dublin  Med.  Press 
uitd  Circular,  Jan.  31,  1872. 

Of  English  periodicals  the  Lancet,  and  of  American 
the  Am.  Journal  of  the  Medical  Sciences,  are  to  be 
regarded  as  necessities  to  the  reading  practitioner.  — 
Ji  Y.  Medical  Gazette,  Jan.  7,  1871. 

The  American  Journal  of  the  Medical  Sciences 


rowed  matter  it  contains,  and  has  established  for 
itself  a  reputation  in  every  country  where  medicine 
is  cultivated  as  a  science. — Brit,  and  For.  Med.-Chi- 
rurg.  Review,  April,  1S71. 

This,  if  not  the  best,  is  one  of  the  best-conducted 
medical  quarterlies  in  the  English  language,  and  the 
present  number  is  not  by  any  means  inferior  to  its 
predecessors. — London  Lancet,  Aug.  23,  1873. 

Almost  the  only  one  that  circulates  everywhere, 
all  over  the  Union  and  in  Europe. — London  Medical 
Times,  Sept.  5,  1868. 


yields  to  none  in  the  amount  of  original  and  bor- 

And  that  it  was  specifically  included  in  the  award  of  a  medal  of  merit  to  the  Pub- 
lisher in  the  Yienna  Exhibition"  in  1873. 

The  subscription  price  of  the  "  AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES"  has 
never  been  raised  during  its  long  career.  It  is  still  FIVE  DOLLARS  per  annum  ;  and 
when  paid  for  in  advance,  the  subscriber  receives  in  addition  the  "MEDICAL  NEWS  AND 
..LIBRARY,"  making  in  all  about  1500  large  octavo  pages  per  annum,  free  of  postage. 

II. 

THE  MEDICAL  NEWS  AND  LIBRARY 

is  a  monthly  periodical  of  Thirty-two  large  octavo  pages,  making  384  pages  per 
annum.  Its  "NEWS  DEPARTMENT"  presents  the  current  information  of  the  day,  with 
Clinical  Lectures  and  Hospital  Gleanings;  while  the  "LIBRARY  DEPARTMENT"  is  de- 
voted to  publishing  standard  works  on  the  various  branches  of  medical  science,  paged 

*  Communications  are  invited  from  gentlemen  in  all  parts  of  the  country.  Elaborate  articles  inserted 
<by  the  Editor  are  paid  for  by  the  Publisher. 


HENRY  C.  LEA'S  PUBLICATIONS— (Am.  Journ.  Med.  Sciences).         3 

separately,  so  that  they  can  be  removed  and  bound  on  completion.  In  this  manner 
subscribers  have  received,  without  expense,  such  works  as  "  WATSON'S  PKACTICE," 
"  TODD  AND  BOWMAN'S  PHYSIOLOGY,"  "WEST  ON  CHILDREN,"  "  MALGAIGNE'S  SUR- 
GERY," &c.  &c.  With  Jan.  1875,  was  commenced  the  publication  of  Dr.  WILLIAM 
STOKES'S  new  work  on  FEVER  (see  p.  14),  rendering-  this  a  very  desirable  time  for  new 
subscriptions. 

As  stated  above,  the  subscription  price  of  the  "  MEDICAL  NEWS  AND  LIBRARY"  is 
ONE  DOLLAR  per  annum  in  advance ;  and  it  is  furnished  without  charge  to  all  advance 
paying  subscribers  to  the  ''AMERICAN  JOURNAL  OF  THE  MEDICAL  SCIENCES." 

III. 

THE  MONTHLY  ABSTRACT  OF  MEDICAL  SCIENCE, 

The  publication  in  England  of  Banking's  "  HALF-YEARLY  ABSTRACT  OF  THE  MEDI- 
CAL SCIENCES"  having  ceased  with  the  volume  for  January,  1874,  its  place  has  been 
supplied  in  this  country  by  a  monthly  "ABSTRACT"  containing  forty-eight  large  octavo 
pages  each  month,  thus  furnishing  in  the  course  of  the  year  about  six  hundred  pages, 
the  same  amount  of  matter  as  heretofore  embraced  in  the  Half-Yearly  Abstract. 
As  the  discontinuance  of  the  "Ranking"  arose  from  the  multiplication  of  journals 
appearing  more  frequently  and  presenting  the  same  character  of  material,  it  has  been 
thought  that  this  plan  of  monthly  issues  will  better  meet  the  wants  of  subscribers, 
who  will  thus  receive  earlier  intelligence  of  the  improvements  and  discoveries  in  the 
medical  sciences.  The  aim  of  the  MONTHLY  ABSTRACT  will  be  to  present  a  careful 
condensation  of  all  that  is  new  and  important  in  the  medical  journalism  of  the  world, 
and  all  the  prominent  professional  periodicals  of  both  hemispheres  will  be  at  the  dis- 
posal of  the  Editors. 

Subscribers  desiring  to  bind  the  ABSTRACT  will  receive,  on  application  at  the  end 
of  each  year,  a  cloth  cover,  gilt  lettered,  for  the  purpose,  or  it  will  be  sent  free  by 
mail  on  receipt  of  the  postage,  which,  under  existing  laws,  will  be  six  cents. 

The  subscription  to  the  "  MONTHLY  ABSTRACT,"  free  of  postage,  is  Two  DOLLARS 
AND  A  HALF  a  year,  in  advance. 

As  stated  above,  however,  it  will  be  supplied  in  conjunction  with  the  "AMERICAN 
JOURNAL  OF  THE  MEDICAN  SCIENCES"  and  the  "MEDICAL  NEWS  AND  LIBRARY,"  making 
in  all  about  rJ VENTY-ONE  HUNDRED  pages  per  annum,  the  whole  free  of  postage,  for 
Six  DOLLARS  a  year,  in  advance. 

The  first  volume  of  the  "  MONTHLY  ABSTRACT,"  from  July  to  December,  1874,  can 
be  had  by  those  who  desire  to  have  complete  sets,  if  early  application  be  made,  for 
$1  50,  forming  a  handsome  octavo  volume  of  300  pages,  cloth. 

In  this  effort  to  bring  so  large  an  amount  of  practical  information  within  the  reach 
of  every  member  of  the  profession,  the  publisher  confidently  anticipates  the  friendly 
aid  of  ail  who  are  interested  in  the  dissemination  of  sound  medical  literature.  He 
trusts,  especially,  that  the  subscribers  to  the  "AMERICAN  MEDICAL  JOURNAL"  will  call 
the  attention  of  their  acquaintances  to  the  advantages  thus  offered,  and  that  he  will 
be  sustained  in  the  endeavor  to  permanently  establish  medical  periodical  literature 
on  a  footing  of  cheapness  never  heretofore  attempted. 

PEEMIUM  POR  NEW  SUBSOKIBEES  TO  TEE  "  JOUKNAL," 

Any  gentleman  who  will  remit  the  amount  for  two  subscriptions  for  1875,  one  of 
which  must  be  for  a  new  subscriber,  will  receive  as  a  PREMIUM,  free  by  mail,  a  copy  of 
"FLINT'S  ESSAYS  ON  CONSERVATIVE  MEDICINE"  (for  advertisement  of  which  see  p.  15), 
or  of  "STURGES'S  CLINICAL  MEDICINE"  (see  p.  14),  or  of  the  new  edition  of  "SWAYNE'S 
OBSTETRIC  APHORISMS"  (see  p.  24),  or  of  "TANNER'S  CLINICAL  MANUAL"  (see  p.  5), 
or  of  "  CHAMBERS'S  RESTORATIVE  MEDICINE"  (see  p.  16),  or  of  "  WEST  ON  NERVOUS. 
DISORDERS  OF  CHILDREN"  (see  page  21). 

%*  Gentlemen  desiring  to  avail  themselves  of  the  advantages  thus  offered  will  do 
well  to  forward  their  subscriptions  at  an  early  day,  in  order  to  insure  the  receipt  of 
complete  sets  for  the  year  1875,  as  the  constant  increase  in  the  subscription  list 
almost  always  exhausts  the  quantity  printed  shortly  after  publication. 

10^*  The  safest  mode  of  remittance  is  by  bank  check  or  postal  money  order,  drawn 
to  the  order  of  the  undersigned.  Where  these  are  not  accessible,  remittances  for  the 
"JOURNAL"  may  be  made  at  the  risk  of  the  publisher,  by  forwarding  in  REGISTERED 
letters.  Address, 

HENRY  C.  LEA, 
Nos.  706  and  708  SANSOM  ST.,  PHILADELPHIA,  PA. 


u.  IAEA'S 


ruBLicATiONS  —  (JJictionames). 


J^UNGLISON  (ROBLEY),  M.D., 

Late  Professor  of  Institutes  of  Medicine  in  Jefferson  Medical  College,  Philadelphia. 

MEDICAL  LEXICON;  A  DICTIONARY  OP  MEDICAL  SCIENCE:  Con- 
taining a  concise  explanation  of  the  various  Subjects  and  Terms  of  Anatomy,  Physiology, 
Pathology,  Hygiene,  Therapeutics,  Pharmacology,  Pharmacy,  Surgery,  Obstetrics,  Medical 
Jurisprudence,  and  Dentistry.  Notices  of  Climate  and  of  Mineral  Waters;  Formulae  for 
Officinal,  Empirical,  and  Dietetic  Preparations;  with  the  Accentuation  and  Etymology  of 
the  Terms,  and  the  French  and  other  Synonymes ;  so  as  to  constitute  a  French  as  well  as 
English  Medical  Lexicon.  A  New  Edition.  Thoroughly  Revised,  and  very  greatly  Mod- 
ified and  Augmented.  By  RICHARD  J.  DUNGLISON,  M.D.  In  one  very  large  and  hand- 
some royal  octavo  volume  of  over  1100  pages.  Cloth,  $6  50;  leather,  raised  bands,  $7  50. 
(Just  Issued.) 

The  object  of  the  author  from  the  outset  has  not  been  to  make  the  work  a  mere  lexicon  or 
dictionary  of  terms,  but  to  afford,  under  each,  a  condensed  view  of  its  various  medical  relations, 
and  thus  to  render  the  work  an  epitome  of  the  existing  condition  of  medical  science.  Starting 
with  this  view,  the  immense  demand  which  has  existed  for  the  work  has  enabled  him,  in  repeated- 
revisions,  to  augment  its  completeness  and  usefulness,  until  at  length  it  has  attained  the  position 
of  a  recognized  and  standard  authority  wherever  the  language  is  spoken. 

Special  pains  have  been  taken  in  the  preparation  of  the  present  edition  to  maintain  this  en- 
viable reputation.  During  the  ten  years  which  have  elapsed  since  the  last  revision,  the  additions 
to  the  nomenclature  of  the  medical  sciences  have  been  greater  than  perhaps  in  any  similar  period 
of  the  past,  and  up  to  the  time  of  his  death  the  author  labored  assiduously  to  incorporate  every- 
thing requiring  the  attention  of  the  student  or  practi'ioner.  Since  then,  the  editor  has  been 
equally  industrious,  so  that  the  additions  to  the  vocabulary  are  more  numerous  than  in  any  pre- 
vious revision.  Especial  attention  has  been  bestowed  on  the  accentuation,  which  will  be  found 
marked  on  every  word.  The  typographical  arrangement  has  been  much  improved,  rendering 
reference  much  more  easy,  and  every  care  has  been  taken  with  the  mechanical  execution.  The 
work  has  been  printed  on  new  type,  small  but  exceedingly  clear,  with  an  enlarged  page,  so  that 
the  additions  have  been  incorporated  with  an  increase  of  but  little  over  a  hundred  pages,  and 
the  volume  now  contains  the  matter  of  at  least  four  ordinary  octavos. 


A  book  well  known  to  our  readers,  and  of  which 
every  American  ought  to  be  proud.  When  the  learned 
author  of  the  work  passed  away,  probably  all  of  us 
fen  ml  lest  the  book  should  net  maintain  its  place 
iu  the  advancing  science  whose  terms  it  defines.  For- 
tnna-tely,  Dr.  Kichard  J.  Dunglison,  having  assisted  his 
father  iu  the  revision  of  several  editions  of  the  work, 
and  having  been,  therefore,  trained  in  the  methods  and 
imbued  with  the  spirit  of  the  book,  has  been  able  to 
edit  it,  not  in  the  patchwork  manner  so  dear  to  the 
heart  of  book  editors,  so  repulsive  to  the  taste  of  intel- 
ligent book  readers,  but  to  edit  it  as  a  work  of  the  kind 
should  be  edited — to  carry  it  on  steadily,  without  jar 
or  interruption,  along  the  grooves  of  thought  it  has 
travelled  during  its  lifetime.  To  show  the  magnitude 
of  the  task  which  Dr.  Dunglison  has  assumed  and  car- 
ried through,  it  is  only  necessary  to  state  that  more 
than  six  thousand  new  subjects  have  been  added  in  the 
present  edition.  Without  occupying  more  space  with  the 
theme,  we  congratulate  the  editor  on  the  successful 
completion  of  his  labors,  and  hope  he  may  reap  the  well- 
earned  reward  of  profit  and  honor. — Ph-da.  Med.  Times. 
Jan.  3, 1874. 


About  the  first  book  purchased  by  the  medical  stu- 
dent is  the  Medical  Dictionary.  The  lexicon  explana- 
tory of  technical  terms  is  simply  a  sine  qua  non.  In  a 
science  so  extensive,  and  with  such  collaterals  as  medi- 
cine, it  is  as  much  a  necessity  also  to  the  practising 
physician.  To  meet  the  wants  of  students  and  most 
physicians,  the  dictionary  must  be  condensed  while 
comprehensive,  and  practical  while  perspicacious.  Jt 
was  because  Dunglison's  met  these  indications  that  it 
became  at  once  the  dictionary  of  general  use  wherever 
medicine  was  studied  in  the  English  language.  In  no 
i';L-iiier  revision  have  tlie  alterations  and  additions  been 
s<  >  great.  More  than  six  thousand  new  subjects  and  terms 
have  been  added.  The  chief  terms  have  been  set  in  black 
letter,  while  the  derivatives  follow  in  small  caps;  an 
arrangement  which  greatly  facilitates  reference.  WTe 
may  safely  confirm  the  hope  ventured  by  the  editor 
'•  that  the  work,  which  possesses  for  him  a  filial  as  well 
as  an  individual  interest,  will  be  found  worthy  a  con- 
tinuance of  the  position  so  long  accorded  to  it  as  a  I  references. — London  Medical  Gazette. 
standard  authority." — Cincinnati  Clinic,  Jan.  10,  1874.  | 


We  are  glad  to  see  a  new  edition  of  this  invaluable 
work,  and  to  find  that  it  has  been  so  thoroughly  revised, 
and  so  greatly  improved.  The  dictionary,  iu  its  pre- 
sent form,  is  a  mtdical  library  in  itself,  and  one  of 
which  every  physician  should  be  possessed.—  A".  1".  Med. 
Journal,  Feb.  1874. 

With  a  history  of  forty  years  of  unexampled  success 
and  universal  indorsement  by  the  medical  profession  of 
the  western  continent,  it  would  be  presumption  in  any 
living  medical  American  to  essay  its  review.  No  re- 
viewer, however  able,  can  add  to  its  fame;  no  captious 
critic,  however  caustic,  can  remove  a  single  stone  from 
its  firm  and  enduring  foundatipn.  It  is  destined,  as  a 
colossal  monument,  to  perpetuate  the  solid  and  richly 
deserved  fame  of  Kobley  Dunglison  to  coming  genera- 
tions. The  large  additions  made  to  the  vocabulary,  we 
think,  will  be  welcomed  by  the  profession  as  supplying 
the  want  of  a  lexicon  fully  up  with  the  march  of  sci- 
ence, which  has  been  increasingly  felt  for  some  years 
past.  The  accentuation  of  terms  is  very  complete,  and, 
as  far  as  we  have  been  able  to  examine  it,  very  excel- 
lent. WTe  hope  it  may  be  the  means  of  securing  greater 
uniformity  of  pronunciation  among  medical  men.  —  At- 
lanta Med.  and  Surg.  Journ.,  Feb.  1874. 


It  would  be  mere  waste  of  words  in  us  to  express 
our  admiration  of  a  work  which  is  so  universally 
and  deservedly  appreciated.  The  most  admirable 
work  of  its  kind  in  the  English  language.  —  Glasgow 
Medical  Journal,  January,  1866. 

A  work  to  which  there  is  no  equal  in  the  English 
language.  —  Edinburgh  Medical  Journal. 

Few  works  of  the  class  exhibit  a  grander  monument 
i)f  patient  research  and  of  scientific  lore.  The  extent 
of  the  sale  of  this  lexicon  is  sufficient  to  testify  to  its 
asefulness,  and  to  the  great  service  conferred  by  Dr. 
Robley  Dunglison  on  the  profession,  and  indeed  on 
ithers,  by  its  issue.  —  London  Lancet,  May  13,  1865. 

It  has  the  rare  merit  that  it  certainly  has  no  rival 
in  the  English  language  for  accuracy  and  extent  of 


fJOBLYN  (RICHARD  D.),  M.D. 


A  DICTIONARY  OF  THE  TERMS  USED  IN  MEDICINE  AND 

THE  COLLATERAL  SCIENCES.     Revised,  with  numerous  additions,  by  ISAAC   HATS, 
M.D.,  Editor  of  the  "American  Journal  of  the  Medical  Sciences."     In  one  large  royal 
12mo.  volume  of  over  500  double-columned  pages;  cloth,  $1  50  ;  leather,  $2  00. 
It  is  the  best  book  of  definitions  we  have,  and  ought  always  to  be  aponthe  •Indent's  table.— Southern 
.Med.  and  Surg.  Journal. 


HENRY  0.  LEA'S  PUBLICATIONS — (Manuals). 


WEILL  (JOHN],  M.D.,    and      &MITH  (FRANCIS  G.),  M.D., 

Prof,  of  the  Institutes  of  Medicine  hi  the  Univ.  of  Penna. 

AN    ANALYTICAL    COMPENDIUM   OF   THE   VARIOUS 

BRANCHES  OF  MEDICAL  SCIENCE;  for  the  Use  and  Examination  of  Students.  A 
new  edition,  revised  and  improved.  In  one  very  large  and  handsomely  printed  royal  12mo. 
volume,  of  about  one  thousand  pages,  with  374  wood  cuts,  cloth,  $4;  strongly  bound  in 
leather,  with  raised  bands,  $4  75. 


The  Compend  of  Drs.  Neill  and  Smith  is  incompara- 
bly tke  most  valuable  work  of  its  class  ever  published 
*.n  this  country.  Attempts  have  been  made  in  various 
ijnarters  to  squeeze  Anatomy,  Physiology,  Surgery, 
the  Practice  of  Medicine,  Obstetrics,  Materia  Medica, 
*nd  Chemistry  into  a  single  manual;  but  the  opera- 
tion has  signally  failed  in  the  hands  of  all  up  to  the 
advent  of  "Neill  and  Smith's"  volume,  which  is  quite 
».  miracle  of  success.  The  outlines  of  the  whole  are 
:«,dffiirably  drawn  and  illustrated,  and  the  authors 
are  eminently  entitled  to  the  grateful  consideration 
of  the  student  of  every  class. — N.  0.  Med.  and  Surg. 
Journal. 

There  are  but  few  students  or  practitioners  of  me- 
dicine unacquainted  with  the  former  editions  of  this 
anassnming  though  highly  instructive  work.  The 
whole  science  of  medicine  appears  to  have  been  sifted, 
»s  the  gold-bearing  sands  of  El  Dorado,  and  the  pre- 


cious facts  treasured  up  in  this  little  volume.  A  com- 
plete portable  library  so  condensed  that  the  student 
may  make  it  his  constant  pocket  companion. —  West- 
ern Lancet. 

In  the  rapid  course  of  lectures,  where  work  for  the 
students  is  heavy,  and  review  necessary  for  an  exa- 
mination, a  compend  is  not  only  valuable,  but  it  is 
almost  a  sine  qua  non.  The  one  before  us  is,  in  most 
of  the  divisions,  the  most  unexceptionable  of  all  books 
of  the  kind  that  we  know  of.  Of  course  it  is  useless 
for  us  to  recommend  it  to  all  last  course  students,  but 
there  is  a  class  to  whom  we  very  sincerely  commend 
tnis  cheap  book  as  worth  its  weight  in  silver— that 
class  is  the  graduates  in  medicine  of  more  than  ten 
years'  standing,  who  have  not  studied  medicine 
since.  They  will  perhaps  find  out  from  it  that  the 
science  is  not  exactly  now  what  it  was  when  they 
left  it  off.— The  Stethoscope. 


IffARTSHORNE  (HENRY],  M.  D., 

Professor  of  Hygiene  in  the  University  of  Pennsylvania. 

A   CONSPECTUS    OF   THE    MEDICAL   SCIENCES;   containing 

Handbooks  on  Anatomy,  Physiology,  Chemistry,  Materia  Medica,  Practical  Medicine 
Surgery,  and  Obstetrics.  Second  Edition,  thoroughly  revised  and  improved.  In  one  large 
royal  12mo.  volume  of  more  than  1000  closely  printed  pages,  with  477  illustrations  on 
wood.  Cioth,  $4  25;  leather,  $5  00.  (Lately  Issued.) 

The  favor  with  which  this  work  has  been  received  has  stimulated  the  author  in  its  revision  to 
render  it  in  every  way  fitted  to  meet  the  wants  of  the  student,  or  of  the  practitioner  desirous  to 
refresh  his  acquaintance  with  the  various  departments  of  medical  science.  The  various  sections  have 
been  brought  up  to  a  level  with  the  existing  knowledge  of  the  day,  while  preserving  the  condensa- 
tion of  form  by  which  so  vast  an  accumulation  of  facts  have  been  brought  within  so  narrow  a 
eompnss.  The  series  of  illustrations  has  been  much  improved,  while  by  the  use  of  a  smaller  type 
the  additions  have  been  incorporated  without  increasing  unduly  the  size  of  the  volume. 

The  work  before  us  has  already  successfully  assert- |  and  the  clear  and  instructive  illustrations  in  some 
ed  its  claim  to  the  confidence  and  favor  of  the  profes-  parts  of  the  work.— American  Journ.  of  Pharmacy 
siou  ;  it  but  remains  for  us  to  say  that  in  the  present  j  Philadelphia,  July,  1874. 

The  volume  will  be  found  useful,  not  only  to  stu- 
dents, but  to  many  others  who  may  desire  to  refresh 
their  memories  with  the  smallest  possible  expendi- 
ture of  time.—  N.  Y.  Med.  Journal,  Sept.  1874. 

The  student  will  find,this  the  most  convenient  and 
useful  book  of  the  kind  on  which  he  can  lay  his 
hand.— Pacific  Med.  and  Surg.  Journ.,  Aug.  1874. 


edition  the  whole  work  has  been  fully  overhauled 
and  brought  up  to  the  present  status  of  the  science. — 
Atlanta  Med.  and  Surg.  Journal,  Sept.  1874. 

The  work  is  intended  as  an  aid  to  the  medical  stu- 
dent, and  as  such  appears  to  admirably  fulfil  its  ob- 
ject by  its  excellent  arrangement,  the  full  compilation 
of  facts,  the  perspicuity  and  terseness  of  language, 


fUDLOW  (J.L.),  M.D. 
A   MANUAL   OF   EXAMINATIONS   upon   Anatomy,   Physiology, 

Surgery,  Practice  of  Medicine,  Obstetrics,  Materia  Medica,  Chemistry,  Pharmacy,  and 
Therapeutics.  To  which  is  added  a  Medical  Formulary.  Third  edition,  thoroughly  revised 
and  greatly  extended  and  enlarged.  With  370  illustrations.  In  one  handsome  royal 
12mo.  volume  of  816  large  pages,  cloth,  $3  25;  leather,  $3  75. 

The  arrangement  of  this  volume  in  the  form  of  question  and  answer  renders  it  especially  suit- 
fcbla  for  the  office  examination  of  students,  and  for  those  preparing  for  graduation. 


WANNER  (THOMAS  HA  WKES),  M.  D.,  frc. 

A  MANUAL  OF  CLINICAL  MEDICINE  AND  PHYSICAL  DIAG- 
NOSIS. Third  American  from  the  Second  London  Edition.  Revised  and  Enlarged  by 
TILBURY  Fox,  M.  D.,  Physician  to  the  Skin  Department  in  University  College  Hospital, 
Ac.  In  one  neat  volume  small  12mo.,  of  about  375  pages,  cloth,  $1  50. 

***  By  reference  to  the  "  Prospectus  of  Journal"  on  page  3,  it  will  be  seen  that  this  work  is 
offered  as  a  premium  for  procuring  new  subscribers  to  the  "AMERICAN  JOURNAL  OP  THE  MEDICAL 
SCIENCES." 


Taken  as  a  whole,  it  is  the  most  compact  vade  me- 
cum  for  the  use  of  the  advanced  student  and  junior 
practitioner  with  which  we  are  acquainted. — Boston 
Med.  and  Surg.  Journal,  Sept.  22,  1870. 

It  contains  so  much  that  is  valuable,  presented  in 
so  attractive  a  form,  that  it  can  hardly  be  spared 
even  in  the  presence  of  more  full  and  complete  works. 
Its  convenient  size  makes  it  a  valuable  companion 
to  the  country  practitioner,  and  if  conitantly  car- 
ried by  him,  would  often  render  him  good  service, 
and  relieve  many  a  doubt  and  perplexity. — Leaven- 


The  objections  commonly,  and  justly,  urged  against 
the  general  run  of  "compends,"  "conspectuses,"  and 
other  aids  to  indolence,  are  not  applicable  to  this  little 
volume,  which  contains  in  concise  phrase  just  those 
practical  details  that  are  of  most  use  in  daily  diag- 
nosis, but  which  the  young  practitioner  finds  it  diffi- 
cult to  carry  always  in  his  memory  without  some 
quickly  accessible  means  of  reference.  Altogether, 
the  book  is  one  which  we  can  heartily  commend  to 
those  who  have  not  opportunity  for  extensive  read- 
ing, or  who,  having  read  much,  still  wish  an  occa- 
sional practical  reminder. — N.  T.  Med.  Gazette,  NOT. 


HENRY  C.  LEA'S  PUBLICATIONS — (Anatomy). 


(HENRY),  F.R.S., 

Lecturer  on  Anatomy  at  St.  George's  Hospital,  London. 

ANATOMY,   DESCRIPTIVE    AND    SURGICAL.      The  Drawings  by 

H.  V.  CARTER,  M.  D.,  late  Demonstrator  on  Anatomy  at  St.  George's  Hospital ;  the  Dissec- 
tions jointly  by  the  AUTHOR  and  DR.  CARTER.  A  new  American,  from  the  fifth  enlarged 
and  improved  London  edition.  In  one  magnificent  imperial  octavo  volume,  of  nearly  906 
pages,  with  465  large  and  elaborate  engravings  on  wood.  Price  in  cloth,  $6  00  ;  lea- 
ther, raised  bands,  $7  00.  (Just  Issued.) 

The  author  has  endeavored  in  this  work  to  cover  a  more  extended  range  of  subjects  than  is  cus- 
tomary in  the  ordinary  text-books,  by  giving -not  only  the  details  necessary  for  the  student,  but 
also  the  application  of  those  details  in  the  practice  of  medicine  and  surgery,  thus  rendering  it  both 
a  guide  for  the  learner,  and  an  admirable  work  of  reference  for  the  active  practitioner.  The  en  - 
gravings  form  a  special  feature  in  the  work,  many  of  them  being  the  size  of  nature,  nearly  all 
original,  and  having  the  names  of  the  various  parts  printed  on  the  body  of  the  cut,  in  place  of 
figures  of  reference,  with  descriptions  at  the  foot.  They  thus  form  a  complete  and  splendid  series, 
which  will  greatly  assist  the  student  in  obtaining  a  clear  idea  of  Anatomy,  and  will  also  serve  to 
refresh  the  memory  of  those  who  may  find  in  the  exigencies  of  practice  the  necessity  of  recalling 
the  details  of  the  dissecting  room;  while  combining,  as  it  does,  a  complete  Atlas  of  Anatomy,  with 
a  thorough  treatise  on  systematic,  descriptive,  and  applied  Anatomy,  the  work  will  be  found  of 
essential  use  to  all  physicians  who  receive  students  in  their  offices,  relieving  both  preceptor  and 
pupil  of  much  labor  in  laying  the  groundwork  of  a  thorough  medical  education. 

Notwithstanding  the  enlargement  of  this  edition,  it  has  been  kept  at  its  former  very  moderate 
price,  rendering  it  one  of  the  cheapest  works  now  before  the  profession. 


The  illustrations  are  beautifully  executed,  and  ren- 
der this  work  an  indispensable  adjunct  to  the  library 
of  the  surgeon.  This  remark  applies  with  great  force 


From  time  to  time,  as  successive  editions  have  ap- 
peared, we  have  had  much  pleasure  in  expressing 
the  general  judgment  of  the  wonderful  excellence  of 


to  those  surgeons  practising  at  a  distance  from  our  j  Gray's  Anatomy. — Cincinnati  Lancet,  July,  1870. 
large  cities,  as  the  opportunity  of  refreshing  their        Altogether,  it  is  unquestionably  the  most  complete 


and  serviceable  text-book  in  anatomy  that  has  evov 
been  presented  to  the  student,  and  forms  a  striking 
contrast  to  the  dry  and  perplexing  volumes  on  the 
same  subject  through  which  their  predecessors  strug- 
gled in  days  gone  by. — N.  Y.  Med.  Record,  June  15, 
1870. 

To  commend  Gray's  Anatomy  to  the  medical  pro- 
fession is  almost  as  much  a  work  of  supererogation 
as  it  would  be  to  give  a  favorable  notice  of  the  Bible 
in  the  religious  press.  To  say  that  it  is  the  most 
complete  and  conveniently  arranged  text-book  of  its 
kind,  is  to  repeat  what  each  generation  of  students 
has  learned  as  a  tradition  of  the  elders,  and  verified 
by  personal  experience. — N  Y.  Med.  Gazette,  Dec. 
17,1870. 


memory  by  actual  dissection  is  not  always  attain- 
able.— Canada  Med.  Journal,  Aug.  1870. 

The  work  is  too  well  known  and  appreciated  by  the 
profession  to  need  any  comment.  No  medical  man 
can  afford  to  be  without  it,  if  its  only  merit  were  to 
serve  as  a  reminder  of  that  which  so  soon  becomes 
forgotten,  when  not  called  into  frequent  use,  viz.,  the 
relations  and  names  of  the  complex  organism  of  the 
human  body.  The  present  edition  is  much  improved. 
—California  Med.  Gazette,  July,  1870. 

Gray's  Anatomy  has  been  so  long  the  standard  of 
perfection  with  every  student  of  anatomy,  that  we 
need  do  no  more  than  call  attention  to  the  improve- 
ment in  the  present  edition. — Detroit  Review  of  Med. 
and  Pharm.,  Aug.  1870. 

VMITH  (HENRY H.),  M.D.,         and  JJORNER  (  WILLIAM  E.},M.D., 

Prof,  of  Surgery  in  the  Univ.  of  Penna.,  &c.  LateProf.  of  Anatomy  in  the  Univ.  ofPenna.,  Ac. 

AN    ANATOMICAL    ATLAS,  illustrative  of  the   Structure  of  the 

Human  Body.     In  one  volume,  large  imperial  octavo,  cloth,  with  about  six  hundred  and 

fifty  beautiful  figures.     $4  50. 

The  plan  of  this  Atlas,  which  renders  it  so  pecn- 1  the  kind  that  has  yet  appeared ;  and  we  must  add, 
liarly  convenient  for  the  student,  and  its  superb  ar-  |  the  very  beautiful  manner  in  which  it  is  "got  up," 
tistical  execution,  have  been  already  pointed  out.  We  !  is  so  creditable  to  the  country  as  to  be  flattering  to 
must  congratulate  the  student  upon  the  completion    our  national  pride. — American  Medical  Journal. 
of  this  Atlas,  as  it  is  the  most  convenient  work  of  I 

VHARPEY  (  WILJjIAM],  M.D.,     and       Q  VAIN  (JONES  fr  RICHARD). 
HUMAN  ANATOMY.  Revised,  with  Notes  and  Additions,  by  JOSEPH 

LEIDT,  M.  D.,  Professor  of  Anatomy  in  the  University  of  Pennsylvania.     Complete  in  two 
large  octavo  volumes,  of  about  1300  pages,  with  511  illustrations;  cloth,  $6  00. 
The  very  low  price  of  this  standard  work,  and  its  completeness  in  all  departments  of  the  subject, 
should  command  for  it  a  place  in  the  library  of  all  anatomical  students. 


fTO DOES  (RICHARD  M.},  M.D., 

Late  Demonstrator  of  Anatomy  in  the  Medical  Department  of  Harvard  University. 

PRACTICAL  DISSECTIONS.     Second  Edition,  thoroughly  revised.     In 

one  neat  royal  12mo.  volume,  half-bound,  $2  00. 

The  object  of  this  work  is  to  present  to  the  anatomical  student  a  clear  and  concise  description 
of  that  which  he  is  expected  to  observe  in  an  ordinary  couise  of  dissections.  The  author  has 
endeavored  to  omit  unnecessary  details,  and  to  present  the  subject  in  the  form  which  many  years' 
experience  has  shown  him  to  be  the  most  convenient  and  intelligible  to  the  student.  In  the 
revision  of  the  present  edition,  he  has  sedulously  labored  to  render  the  volume  more  worthy  of 
the  favor  with  which  it  has  heretofore  been  received. 


HOENER'S  SPECIAL  ANATOMY  AND  HISTOLOGY.  I      In  2  vols.  8vo.,  of  over  1000  pages,  with  more  tha» 
Eighth  edition,  extensively  revised  and  modified.  1     300  wood-cuts;  cloth,  $6  00. 


HBNRY  C.  LEA'S  PUBLICATIONS— (Anatomy). 


\XTILSON  (ERASMUS),  F.R.S. 

A  SYSTEM  OF  HUMAN  ANATOMY,  General  and  Special.    Edited 

by  W.  H.  GOBRECHT,  M.  D.,  Professor  of  General  and  Surgical  Anatomy  in  the  Medical  Col- 
lege of  Ohio.  Illustrated  with  three  hundred  and  ninety-seven  engravings  on  wood.  In 
one  large  and  handsome  octavo  volume,  of  over  600  large  pages;  cloth,  $4  00;  leather, 
$5  00. 

The  publisher  trusts  that  the  well-earned  reputation  of  this  long-established  favorite  will  be 
more  than  maintained  by  the  present  edition.  Besides  a  very  thorough  revision  by  the  author,  it 
has  been  most  carefully  examined  by  the  editor,  and  the  efforts  of  both  have  been  directed  to  in- 
troducing everything  which  increased  experience  in  its  use  has  suggested  as  desirable  to  render  it 
a  complete  text-book  for  those  seeking  to  obtain  or  to  renew  an  acquaintance  with  Human  Ana- 
tomy. The  amount  of  additions  which  it  has  thus  received  may  be  estimated  from  the  fact  that 
i,he  present  edition  contains  over  one-fourth  more  matter  than  the  last,  rendering  a  smaller  type 
9>n<l  an  enlarged  page  requisite  to  keep  the  volume  within  a  convenient  size.  The  author  has  not 
only  thus  added  largely  to  the  work,  but  he  has  also  made  alterations  throughout,  wherever  there 
appeared  the  opportunity  of  improving  the  arrangement  or  style,  so  as  to  present  every  fact  in  its 
taost  appropriate  manner,  and  to  render  the  whole  as  clear  and  intelligible  as  possible.  The  editor 
lj.aa  exercised  the  utmost  caution  to  obtain  entire  accuracy  in  the  text,  and  has  largely  increased 
the  number  of  illustrations,  of  which  there  are  about  one  hundred  and  fifty  more  in  this  edition 
than  in  the  last,  thus  bringing  distinctly  before  the  eye  of  the  student  everything  of  interest  or 
Importance. 

fJEATH  (CHRISTOPHER),  F.'R.  C.  S.t 

Teacher  of  Operative  Surgery  in  University  College,  London. 

PRACTICAL   ANATOMY:   A   Manual   of  Dissections.     From  the 

Second  revised  and  improved  London  edition.  Edited,  with  additions,  by  W.  W.  KKSN, 
M.  D.,  Lecturer  on  Pathological  Anatomy  in  the  Jefferson  Medical  College,  Philadelphia. 
In  one  handsome  royal  12ino.  volume  of  578  pages,  with  247  illustrations.  Cloth,  $3  50  j 
leather,  $4  00.  (Lately  Published.) 

lining  its  hold  upon  the  slippery  slopes  of  anatomy. 

-St.  Louis  Med.  and  Surg.  Journal,  Mar.  10,  1871. 
It  appears  to  us  certain  that,  as  a  guide  in  dissec- 

,ion,  and  as  a  work  containing  facts  of  anatomy  in 

brief  and  easily  understood  form,    this   manual   is 


}>r.  Keen,  the  American  editor  of  this  work,  in  his 
preface,  says:  "In  presenting  this  American  edition 
«f  •  Heath's  Practical  Anatomy,'  I  feel  that  I  have 
keon  instrumental  in  supplying  a  want  long  felt  for 
a  real  dissector's  manual,"  and  this  assertion  of  its 

editor  we  deem  is  fully  justified,  after  an  examina-  j  ^plete.  This  work  contains,  also,  very  perfect 
tion  of  its  contents,  for  it  is  really  an  excellent  worft.  |  nustrations  of  parts  which  can  thus  be  more  easily 
Indeed,  we  do  not  hesitate  to  say,  the  best  of  its  class 
with  which  we  are  acquainted  ;  resembling  Wilson 
In  terse  aud  clear  description,  excelling  most  of  the 
ao-called  practical  anatomical  dissectors  in  the  scope 
<?f  the  subject  aud  practical  selected  matter.  .  .  . 
In  reading  this  work,  one  is  forcibly  impressed  with 
Uie  great  pains  the  author  takes  to  impress  the  sub- 
ject upon  the  mind  of  the  student.  He  is  full  of  rare 
e.ud  pleasing  little  devices  to  aid  memory  in  main- 


inderstood  and  studied;  in  this  respect  it  compares 
'avorably  with  works  of  much  greater  pretension. 
Such  manuals  of  anatomy  are  always  favorite  works 
with  medical  students.  We  would  earnestly  recom- 
mend this  one  to  their  attention;  it  has  excellences 
which  make  it  valuable  as  a  guide  in  dissecting,  as 
well  as  in  studying  anatomy. — Buffalo  Medical  and 
Surgical  Journal,  Jan.  1871. 


f>ELLAMY(E.),  F.R.C.S. 

THE  STUDENT'S  GUIDE  TO  SURGICAL  ANATOMY:  A  Text- 

Book  for  Students  preparing  for  their  Pass  Examination.    With  engravings  on  wood.    In. 
ono  handsome  royal  12nio.  volume.     Cloth,  $2  25.     (Just  Issued.) 


We  welcome  Mr.  Bellamy's  work,  as  a  contribu- 
tion to  the  study  of  regional  anatomy,  of  equal  value 
to  the  student  and  the  surgeon.  It  is  written  in  a 
clear  and  concise  style,  and  its  practical  suggestions 
add  largely  to  the  interest  attachiug  to  its  technical 
details  —Chicago  Med.  Examiner,  March  1,  1874. 

We  cordially  congratulate  Mr.  Bellamy  upon  hav- 
ing produced  it. — Med.  Times  and  Qaz. 


We  cannot  too  highly  recommend  it. — Student's 
Journal. 

Mr.  Bellamy  has  spared  no  pains  to  produce  a  real- 
ly reliable  student's  guide  to  surgical  anatomy — one 
which  all  candidates  for  surgical  degrees  may  con- 
sult with  advantage,  and  which  posseses  much  ori- 
ginal matter — Mad.  Press  and  Circular. 


MACLISE  (JOSEPH). 

SURGICAL  ANATOMY.     By  JOSEPH  MACLISE,  Surgeon.    In  one 

volume,  very  large  imperial  quarto ;  with  68  large  and  splendid  plates,  drawn  in  the  best 
style  and  beautifully  colored,  containing  190  figures,  many  of  them  the  size  of  life;  together 
with  copious  explanatory  letter-press.  Strongly  and  handsomely  bound  in  cloth.  Price 
$14  00. 

We  know  of  no  work  on  surgical  anatomy  which 
nan  compete  with  it. — Lancet. 

The  work  of  Maclise  on  surgical  anatomy  is  of  the 


feighest  value.  In  some  respects  it  is  the  best  publi- 
cation of  its  kind  we  have  seen,  and  is  worthy  of  a 
place  in  the  library  of  any  medical  man,  while  the 
student  could  scarcely  make  a  better  investment  than 
t  h  is. — The  Western  Journal  of  Medicine  and  Siirgery. 
No  such  lithographic  illustrations  of  surgical  re- 


$ions  have  hitherto,  we  think,  been  given.  While 
bhe  operator  is  shown  every  vessel  and  nerve  where 
in  operation  is  contemplated,  the  exact  anatomist  is 
refreshed  by  those  clear  and  distinct  dissections, 
which  every  one  must  appreciate  who  has  a  particle 
of  enthusiasm.  The  English  medical  press  has  quits 
exhausted  the  words  of  praise,  in  recommending  this 
admirable  treatise, — Boston  Med.  and  Surg.  Journ. 


fJARTSHORNE  (HENRY),  M.D., 

•*•-*•  Professor  of  Hygiene,  etc  ,  in  the  Univ.  ofPenna. 

HANDBOOK  OF   ANATOMY  AND   PHYSIOLOGY.     Second  Edi- 
tion, revised.   In  ane  ro.yal  12mo.  volume,  with  220  wood-cuts;  cloth,  $1  75.  (Just  Issued.) 


HENRY  C.  LEA'S  PUBLICATIONS — (Physiology). 


MARSHALL  (JOHN),  F.  R.  S., 

fLuL  Professor  of  Surgery  in  University  College,  London,  &c. 

OUTLINES  OF  PHYSIOLOGY,  HUMAN  AND  COMPARATIVE. 

With  Additions  by  FRANCIS  GURNEY  SMITH,  M.  D.,  Professor  of  the  Institutes  of  Medi- 
cine in  the  University  of  Pennsylvania,  &c.     With  numerous  illustrations.     In  one  large 
and  handsome  octavo  volume,  of  1026  pages,  cloth,  $6  50 ;  leather,  raised  bands,  $7  50. 
In  fact,  in  every  respect,  Mr.  Marshall  has  present- ,  tive,  with  which  we  are  acquainted.     To  speak  ol 

this  work  in  the  terms  ordinarily  used  on  snch  occa- 
sions would  not  be  agreeable  to  ourselves,  and  would 
fail  to  do  justice  to  its  author.  To  write  such  a  boofc 
requires  a  varied  and  wide  range  of  knowledge,  con- 
siderable power  of  analysis,  correct  judgment,  ski}.} 


ed  us  with  a  most  complete,  reliable,  and  scientific 
work,  and  we  feel  that  it  is  worthy  our  warmest 
commendation. — St.  Louis  Med.  Reporter,  Jan.  1869. 


We  doubt  if  there  is  in  the  English  language  any 
compend  of  physiology  more  useful  to  the  student 
than  this  work.— St.  Louis  Med.  and  Surg.  Journal, 
Jan.  1869. 

It  quite  fulfils,  in  our  opinion,  the  author's  design 
of  making  it  truly  educational  in  its  character— which 


in  arrangement,  and  conscientious  spirit. — London 
Lancet,  Feb.  22,  1868. 


rp^,^r^^ 


asked.— Am.  Journ.  Med.  Sciences,  Jan.  1869. 

We  may  now  congratulate  him  on  having  com- 
pleted the  latest  as  well  as  the  best  summary  of  mod- 
ern physiological  science,  both  human  and  compara- 


joyed  the  highest  reputation  as  a  teacher  of  physiol- 
ogy, possessing  remarkable  powers  of  clear  exposition 
and  graphic  illustration.  We  have  rarely  the  plea- 
sure of  being  able  to  recommend  a  text-book  so  unre- 
servedly as  this.— British  Med.  Journal,  Jar .  25, 1868. 


CARPENTER  (WILLIAM  B.),  M.D.,  F.R.S., 

V/  Examiner  in  Physiology  and  Comparative  Anatomy  in  the  University  of  London. 

PRINCIPLES  OF  HUMAN  PHYSIOLOGY;  with  their  chief  appli- 
cations to  Psychology,  Pathology,  Therapeutics,  Hygiene  and  Forensic  Medicine.  A  ne^ 
American  from  the  last  and  revised  London  edition.  With  nearly  three  hundred  illustrations. 
Edited,  with  additions,  by  FRANCIS  GTJRNEY  SMITH,  M.  D.,  Professor  of  the  Institutes  o! 
Medicine  in  the  University  of  Pennsylvania,  &c.  In  one  very  large  and  beautiful  octavo 
volume,  of  about  900  large  pages,  handsomely  printed;  cloth,  $5  50  ;  leather,  raised  bands, 
$6  50. 


With  Dr.  Smith,  we  confidently  believe  "that  the 
present  will  more  than  sustain  the  enviable  reputa- 
tion already  attained  by  former  editions,  of  being 
one  of  the  fullest  and  most  complete  treatises  on  the 
subject  in  the  English  language."  We  know  of  none 
from  the  pages  of  which  a  satisfactory  knowledge  of 
the  physiology  of  the  human  organism  can  be  as  well 
obtained,  none  better  adapted  for  the  use  of  such  as 
take  up  the  study  of  physiology  in  its  reference  to 
the  institutes  and  practice  of  medicine. — Am.  Jour. 
Med.  Sciences. 


We  doubt  not  it  is  destined  to  retain  a  strong  hold 
on  public  favor,  and  remain  the  favorite  text-book  ia 
our  colleges. —  Virginia  Medical  Journal. 

.  The  above  is  the  title  of  what  is  emphatically  the 
great  work  on  physiology ;  and  we  are  conscious  that 
it  would  be  a  useless  effort  to  attempt  to  add  any- 
thing to  the  reputation  of  this  invaluable  work,  and 
can  only  say  to  all  with  whom  our  opinion  has  any 
influence,  that  it  is  our  authority.— Atlanta  Med.. 
Journal. 


T>T  THE  SAME  AUTHOR. 

PRINCIPLES  OF  COMPARATIVE  PHYSIOLOGY.    New  Ameri- 
can, from  the  Fourth  and  Revised  London  Edition.     In  one  large  and  handsome  octavo 
volume,  with  over  three  hundred  beautiful  illustrations.    Pp.  752.    Cloth,  $5  00. 
As  a  complete  and  condensed  treatise  on  its  extended  and  important  subject,  this  work  becomes 
a  necessity  to  students  of  natural  science,  while  the  very  low  price  at  which  it  is  offered  places  it 
within  the  reach  of  all. 


JTIRKES  (  WILLIAM  SENHOUSE),  M.D. 

A  MANUAL  OF  PHYSIOLOGY.     Edited  by  W.  MORRANT  BAKER, 

M.D.,  F.R.C.S.  A  new  American  from  the  eighth  and  improved  London  edition.  With 
about  two  hundred  and  fifty  illustrations.  In  one  large  and  handsome  royal  12mo.  vol- 
ume. Cloth,  $3  25;  leather,  $3  75.  (Lately  Issued.) 

Kirkes'  Physiology  has  long  been  known  as  a  concise  and  exceedingly  convenient  text-book, 
presenting  within  a  narrow  compass  all  that  is  important  for  the  student.  The  rapidity  with 
which  successive  editions  have  followed  each  other  in  England  has  enabled  the  editor  to  keep  it 
thoroughly  on  a  level  with  the  changes  and  new  discoveries  made  in  the  science,  and  the  eighth 
edition,  of  which  the  present  is  a  reprint,  has  appeared  so  recently  that  it  may  be  regarded  as 
the  latest  accessible  exposition  of  the  subject. 


On  the  whole,  there  is  very  little  in  the  book 
which  either  the  student  or  practitioner  will  nottind 
of  practical  value  and  consistent  -with  our  present 
knowledge  of  this  rapidly  changing  science  ;  and  we 
have  no  hesitation  in  expressing  our  opinion  that 
this  eighth  edition  is  one  of  the  best  handbooks  on 
physiology  which  we  have  in  our  language. — N.  Y. 
Med.  Record,  April  15,  1873. 

This  volume  might  well  be  used  to  replace  many 
of  the  physiological  text-books  in  use  in  this  coun- 
try. It  represents  more  accurately  than  the  works 
of  Dalton  or  Flint,  the  present  state  of  our  knowl- 
edge of  most  physiological  questions,  while  it  is 
much  less  bulky  and  far  more  readable  than  the  lar- 


ger text-books  of  Carpenter  or  Marshall.  The  book 
is  admirably  adapted  to  be  placed  in  the  hands  of 
students. — Boston  Med.  and  Surg.  Journ.,  April  10, 
1873. 

In  its  enlarged  form  it  is,  in  our  opinion,  etill  the 
best  book  on  physiology,  most  useful  to  the  student. 
—Phila.  Med.  Timed,  Aug.  30,  1873. 

This  is  undoubtedly  the  best  work  for  students  of 
physiology  extant. — Cincinnati  Med.  News,  Sept.  '73. 

It  more  nearly  repi'esents  the  present  condition  of 
physiology  than  any  other  text-book  on  the  subject. — 
Detroit  Rev.  of  Med.  Pharm.,  Nov.  1873. 


HENRY  C.  LEA'S  PUBLICATIONS— (Physiology).  9 

f)ALTON  (J.  (7.),  M.D., 

-U  Professor  of  Physiology  in  the  College  of  Physicians  and  Surgeons,  New  York,  &c. 

A  TREATISE  ON  HUMAN  PHYSIOLOGY.    Designed  for  the  use 

of  Students  and  Practitioners  of  Medicine.  Sixth  edition,  thoroughly  revised  and  enlarged, 
with  three  hundred  and  sixteen  illustrations  on  wood.  In  one  very  beautiful  octavo  vol- 
ume, of  over  800  pages.  (Nearly  Ready.) 

From  the  Preface  to  the  Sixth  Edition. 

In  the  present  edition  of  this  book,  while  every  part  has  received  a  careful  revision,  the  ori- 
ginal plan  of  arrangement  has  been  changed  only  so  far  as  was  necessary  for  the  introduction  of 
new  material.  Although  the  whole  field  of  physiology  has  been  cultivated,  of  late  years,  with 
unusual  industry  and  success,  perhaps  the  most  important  advances  have  been  made  in  the  two 
departments  of  Physiological  Chemistry  and  the  Nervous  System.  The  number  and  classification 
of  the  proximate  principles,  more  especially,  and  their  relation  to  each  other  in  the  process  of 
nutrition,  have  become,  in  many  respects,  better  understood  than  formerly  ;  though  it  is  evident 
that  this  fundamental  part  of  physiology  is  to  receive,  in  the  future,  modifications  and  additions 
of  the  most  valuable  kind. 

The  additions  and  alterations  in  the  text,  requisite  to  present  concisely  the  growth  of  positive 
physiological  knowledge,  have  resulted  in  spite  of  the  author's  earnest  efforts  at  condensation, 
in  an  increase  of  fully  fifty  per  cent,  in  the  matter  of  the- work.  A  change,  however,  in  the  ty- 
pographical arrangement  has  accommodated  these  additions  without  undue  enlargement  in  the 
bulk  of  the  volume. 

The  new  chemical  notation  and  nomenclature  are  introduced  into  the  present  edition,  as  hav- 
ing now  so  generally  taken  the  place  of  the  old,  that  no  confusion  need  result  from  the  change. 
The  centigrade  system  of  measurements  for  length,  volume,  and  weight,  is  also  adopted,  these 
measurements  being  at  present  almost  universally  employed  in  original  physiological  investiga- 
tions and  their  published  accounts.  Temperatures  are  given  in  degrees  of  the  centigrade  s  ale, 
usually  accompanied  by  the  corresponding  degrees  of  Fahrenheit's  scale,  inclosed  in  brackets. 
NEW  YORK,  September,  1875. 

A  few  notices  of  the  previous  edition  are  subjoined. 


The  fifth  edition  of  this  truly  valuable  work  on 
Human  Physiology  comes  to  us  with  many  valuable 
Improvements  and  additions.  As  a  text-book  of 
physiology  the  work  of  Prof.  Dalton  has  long  been 
well  known  as  one  of  the  best  which  could  be  placed 
In  the  hands  of  student  or  practitioner.  Prof.  Dalton 
has,  in  the  several  editions  of  his  work  heretofore 
published,  labored  to  keep  step  with  the  advancement 
5a  science,  and  the  last  edition  shows  by  its  improve- 
ments on  former  ones  that  he  is  determined  to  main- 
tain the  high  standard  of  his  work.  We  predict  for 
the  present  edition  increased  favor,  though  this  work 
has  long  been  the  favorite  standard. — Buffalo  Med. 
and  Surg.  Journal,  April,  1872. 

An  extended  notice  of  a  work  so  generally  and  fa- 
vorably known  as  this  is  unnecessary.  It  is  justly 
regarded  as  one  of  the  most  valuable  text-books  on 
the  subject  in  the  English  language. — St.  Louit  Med. 
Archives,  May,  1872. 

We  know  no  treatise  in  physiology  so  clear,  com- 
plete, well  assimilated,  and  perfectly  digested,  as 
Dalton's.  He  never  writes  cloudily  or  dubiously,  or 
in  mere  quotation.  He  assimilates  all  his  material, 
and  from  it  constructs  a  homogeneous  transparent 


irgument,  which  is  always  honest  and  well  informed, 
ind  hides  neither  truth,  ignorance,  nor  doubt,  so  far 
is  either  belongs  to  the  subject  in  hand. — Brit.  Med. 
Journal,  March  23,  1872. 

Dr.  Dalton's  treatise  is  well  known,  and  by  many 
highly  esteemed  in  thiscountry.  It  is,  indeed,  a  good 
elementary  treatise  on  the  subject  it  professes  to 
teach,  and  may  safely  be  put  into  the  hands  of  Eng- 
lish students.  It  has  one  great  merit — it  is  clear,  and, 
on  the  whole,  admirably  illustrated.  The  part  we 
have  always  esteemed  most  highly  is  that  relating 
to  Embryology.  The  diagrams  given  of  the  various 
stages  of  development  give  a  clearer  view  of  the  sub- 
ject than  do  those  in  general  use  in  this  country  ;  and 
the  text  may  be  said  to  be,  upon  the  whole,  equally 
clear. — London  Med.  Times  and  Gazette,  March  23, 
1872. 

Professor  Dalton  is  regarded j  ustly  as  the  authority 
in  this  country  on  physiological  subjects,  and  the 
fifth  edition  of  his  valuable  work  fully  justifies  the 
exalted  opinion  the  medical  world  has  of  his  labors. 
This  last  edition  is  greatly  enlarged. — Virginia  Clin- 
ical Record,  April,  1872. 


J)UNGLISON  (ROBLEY),  M.D., 

Professor  of  Institutes  of  Medicine  in  Jefferson  Medical  College,  Philadelphia. 

HUMAN  PHYSIOLOGY.     Eighth  edition.     Thoroughly  revised  and 

extensively  modified  and  enlarged,  with  five  hundred  and  thirty-two  illustrations.     In  two 
large  and  handsomely  printed  octavo  volumes  of  about  1500  pages,  cloth,  $7  00. 


TEHMANN  (C.  6?.). 

PHYSIOLOGICAL  CHEMISTRY.  Translated  from  the  second  edi- 
tion by  GEORGE  E.  DAY,  M.  D.,  P.  R.  S.,  Ac.,  edited  by  R.  E.  ROGERS,  M.  D.,  Professor  of 
Chemistry  in  the  Medical  Department  of  the  University  of  Pennsylvania,  with  illustrations 
selected  from  Funke's  Atlas  of  Physiological  Chemistry,  and  an  Appendix  of  plates.  Com- 
plete in  two  large  and  handsome  octavo  volumes,  containing  1200  pages,  with  nearly  two 
hundred  illustrations,  cloth,  $6  00. 


THE  SAME  AUTHOR. 

MANUAL  OF  CHEMICAL  PHYSIOLOGY.     Translated  from  the 

German,  with  Notes  and  Additions,  by  J.  CHESTON  MORRIS,  M.  D.,  with  an  Introductory 
Essay  on  Vital  Force,  by  Professor  SAMUEL  JACKSON,  M.  D.,  of  the  University  of  Pennsyl- 
vania. With  illustrations  on  wood.  In  one  very  handsome  octavo  volume  of  336  pages, 
oloth,  $2  25. 


10 


HENRY  C.  LEA'S  PUBLICATIONS — (Chemistry). 


A  TTFIELD  (JOHN),  Ph.  D., 

"^  Professor  of  Practical  Chemistry  to  the  Pharmaceutical  Society  of  Great  Britain,  Ac. 

CHEMISTRY,   GENERAL,  MEDICAL,  AND  PHARMACEUTICAL  ; 

including  the  Chemistry  of  the  U.  S.  Pharmacopoeia.  A  Manual  of  the  General  Principles 
of  the  Science,  and  their  Application  to  Medicine  and  Pharmacy.  Fifth  Edition,  revised 
by  the  author.  In  one  handsome  royal  12mo.  volume ;  cloth,  $2  75 ;  leather,  $3  25. 
(Lately  Issued.) 


No  other  American  publication  with  which  we  are 
acquainted  covers  the  same  ground,  or  does  it  so  well. 
In  addition  to  an  admirable  expose"  of  th«  facts  and 
principles  of  general  elementary  chemistry,  the  au- 
thor has  presented  us  with  a  condensed  mass  of  prac- 
tical matter,  just  such  as  the  medical  student  and 
practitioner  needs. — Cincinnati  Lancet,  Mar.  1874. 

We  commend  the  work  heartily  as  one  of  the  best 
text-books  extant  for  the  medical  student. — Detroit 
Rev.  of  Med.  and  Pharm.,  Feb.  1872. 

The  best  work  of  the  kind  in  the  English  language. 
— N.  T.  Psychological  Journal,  Jan.  1872. 

The  work  is  constructed  with  direct  reference  to 
the  wants  of  medical  and  pharmaceutical  students; 
and,  although  an  English  work,  the  points 'of  differ- 
ence' between  the  British  and  United  States  Pharma- 
copoeias are  indicated,  making  it  as  useful  here  as  in 
England.  Altogether,  the  book  is  one  we  can  heart- 
ily recommend  to  practitioners  as  well  as  students. 
— N.  Y.  Med.  Journal,  Dec.  1871. 

It  differs  from  other  text-books  in  the  following 
particulars:  first,  in  the  exclusion  of  matter  relating 
to  compounds  which,  at  present,  are  only  of  interest 
to  the  scientific  chemist;  secondly,  in  containing  the 
chemistry  of  every  substance  recognized  officially  or 
in  general,  as  a  remedial  agent.  It  will  be  found  a 
most  valuable  book  for  pupils,  assistants,  and  others 


engaged  in  medicine  and  pharmacy,  and  we  heartily 
commend  it  to  our  readers. — Canada  Lancet,  Oct. 
1871. 

When  the  original  English  edition  of  this  work  was 
published,  we  had  occasion  to  express  our  high  ap- 
preciation of  its  worth,  and  also  to  review,  in  con- 
siderable detail,  the  main  features  of  the  book.  As 
the  arrangement  of  subjects,  and  the  main  part  of 
the  text  of  the  present  edition  are  similar  to  the  for- 
mer publication,  it  will  be  needless  for  us  to  go  over 
the  ground  a  second  time  ;  we  may,  however,  call  at- 
tention to  a  marked  advantage  possessed  by  the  Ame- 
rican work— we  allude  to  the  introduction  of  the 
chemistry  of  the  preparations  of  the  United  States 
Pharmacopoeia,  as  well  as  that  relating  to  the  Britisli 
authority.  —  Canadian  Pharmaceutical  Journal, 
Nov.  1871. 

Chemistry  has  borne  the  name  of  being  ahard  sub- 
ject to  master  by  the  student  of  medicine,  am), 
chiefly  because  so  much  of  it  consists  of  compounds 
only  of  interest  to  the  scientific  chemist ;  in  this  work 
such  portions  are  modified  or  altogether  left  out,  and 
in  the  arrangement  of  the  subject-matter  of  the  work, 
practical  utility  is  sought  after,  and  we  think  fully 
attained.  We  commend  it  for  its  clearness  and  ord&r 
to  both  teacher  and  pupil. — Oregon  Med.  and  Surg. 
Reporter,  Oct.  1871. 


F 


OWNES  (GEORGE),  Ph.D. 


A  MANUAL  OF  ELEMENTARY  CHEMISTRY;   Theoretical  and 

Practical.    With  one  hundred  and  ninety-seven  illustrations.    A  new  American,  from  the 
tenth  and  revised  London  edition.     Edited  by  ROBERT  BRIDGES,  M.  D.     In  one  large 
royal  12mo.  volume,  of  about  850  pp.,  cloth,  $2  75  ;  leather,  S3  25.      (Lately  Issued.) 
This  work  is  so  well  known  that  it  seems  almost    other  work  that  has  greater  claims  on  the  physician, 

superfluous  for  us  to  speak  about  it.     It  has  been  a    pharmaceutist,  or  student,  than  this.     We  cheerfully 

favorite  text-book  with  medical  students  for  years,    recommend  it  as  the  best  text-book  on  elementary 

and  its  popularity  has  in  no  respect  diminished,    chemistry,  and  bespeak  for  it  the  careful  attention 

Whenever  we  have  been  consulted  by  medical  stu- 

dents,  as  has  frequently  occurred,  what  treatise  on 

chemistry  they  should  procure,  we  have  always  re- 

commend^d  Fownes',  for  we  regarded  it  as  the  best. 


'  students  of  pharmacy. — Chicago  Pharmacist,  Aug. 


There  is  no  work  that  combines  so  many  excellen 


Here  is  a  new  edition  which  has  been  long  watched 
for  by  eager  teachers  of  chemistry.     In  its  new  garb, 


ces.      It  is  of  convenient  size,  not  prolix,  of  plain    and  under  the  editorship  of  Mr.  Watts,  it  has  resumed 
perspicuous  diction,   contains   all    the  most  recent   its  old  place  as  the  most  successful  of  text-books.— 
discoveries,  and  is  of  moderate  price.— Cincinnati,  Indian  Medical.  Gazette,  Jan.  1,  1869 
Med.  Repertory,  Aug.  1869.  It  wm  continae?  as  heretofore)  to  boid  the  flr8t  raa)t 

Large  additions  have  been  made,  especially  in  the    %s   a  text-book  for  students  of  medicine.— Chtcnpe 
department  of  organic  chemistry,  and  we  know  of  no    Wed.  Examiner,  Aug.  1869. 


0 


DLTNG  ( WILLIAM), 

Lecturer  on  Chemistry  at  St.  Bartholomew's  Hospital,  Ac. 

A  COURSE  OF  PRACTICAL  CHEMISTRY,  arranged  for  the  Use 

of  Medical  Students.    With  Illustrations.    Prom  the  Fourth  and  Revised  London  Edition. 
In  one  neat  royal  12mo.  volume,  cloth,  $2. 


riALLOWAY  (ROBERT),  F.C.S., 

Prof,  of  Applied  Chemistry  in  the  Royal  College  of  Science  for  Ireland,  &c. 

A  MANUAL  OF  QUALITATIVE  ANALYSIS.  From  the  Fifth  Lon- 
don Edition.  In  one  neat  royal  12mo.  volume,  with  illustrations,-  cloth,  $2  50.  (Ju& 
Issued.) 

The  success  which  has  carried  this  work  through  repeated  editions  in  England,  and  its  adoption 
as  a  text-book  in  several  of  the  leading  institutions  in  this  country,  show  that  the  author  has  suo- 
oeeded  in  the  endeavor  to  produce  a  sound  practical  manual  and  book  of  reference  for  the  che- 
mical student. 


Prof.  Galloway's  books  are  deservedly  in  high 
esteem,  and  this  American  reprint  of  the  fifth  edition 
(1869)  of  his  Manual  of  Qualitative  Analysis,  will  be 
acceptable  to  many  Amer^pan  students  to  whom  the 
English  edition  is  not  accessible.—  Am.  Jour,  of  Sci- 
tnc6  and  Arts,  Sept.  1872. 


We  regard  this  volume  as  a  valuable  addition  to 
the  chemical  text-books,  and  as  particularly  calcu- 
lated to  instruct  the  student  in  analytical  researches 
of  the  inorganic  compounds,  the  important  vegetable 
acids,  and  of  compounds  and  various  secretions  and 
excretions  of  animal  origin. — Am.  Journ. 
Sept.  1873. 


HENRY  C.  LEA'S  PUBLICATIONS— (  Chemistry). 


11 


T>LOXAM  (C.  L.}, 

•*-*  Professor  of  Chemistry  in  King's  College,  London. 

CHEMISTRY,  INORGANIC  AND  ORGANIC.  From  the  Second  Lon- 
don Edition.  In  one  very  handsome  octavo  volume,  of  700  pages,  with  about  300  illustra- 
tions. Cloth,  $4  00 ;  leather,  $5  00.  (Lately  Issued.) 

It  has  been  the  author's  endeavor  to  produce  a  Treatise  on  Chemistry  sufficiently  comprehen- 
sive for  those  studying  the  science  as  a  branch  of  £,  neral  education,  and  one  which  a  student 
may  use  with  advantage  in  pursuing  his  chemical  stud  s  at  one  of  the  colleges  or  medical  schools. 
The  special  attention  devoted  to  Metallurgy  and  some  other  branches  of  Applied  Chemistry  renders 
the  work  especially  useful  to  those  who  are  being  educated  for  employment  in  manufacture. 

We  have  in  this  work  a  complete  aud  most  excel-    experiment  have  been  worked  up  with  especial  care, 
lent  text-book  for  the  use  of  schools,  and  can  heart- 
ily recommend  it  as  such. — Boston  Med.  and  Surg. 
Journ.,  May  28,  1874. 

Of  all  the  numerous  works  upon  elementary  chem- 
istry that  have  been  published  within  the  last  few 
years,  we  can  point  to  none  that,  in  fulness,  accuracy, 
and  simplicity,  can  surpass  this;  while,  in  the  num- 
ber and  detailed  descriptions  of  experiments,  as  also 
in  the  profuseness  of  its  illustrations,  we  believe  it 
stands  above  any  similar  work  publ  ished  in  this  coun- 
try  The  statements  made  are  clear  and  con- 
cise, and  every  step  proved  by  an  abundance  of  ex- 
periments, which  excite  our  admiration  as  much  by 
their  simplicity  as  by  their  direct  conclusiveness.— 
Chicago  Med.  Examiner,  Nov.  15,  1873. 

It  is  seldom  that  in  the  same  compass  so  complete 
and  interesting  a  compendium  of  the  leading  facts  of 
chemistry  is  offered. — Druggists'  Circular,  Nov.  '73. 


The  above  is  the  title  of  a  work  which  we  can  most 
conscientiously  recommend  to  students  of  chemistry. 
It  is  as  easy  as  a  work  on  chemistry  could  be  made, 
at  the  same  time  that  it  presents  a  full  account  of  that 
Rcience  as  it  now  stands.  We  have  spoken  of  the 
workasadmirably  adapted  to  the  wants  of  students  ; 
it  is  quite  as  well  suited  to  the  requirements  of  prac- 
titioners who  wish  to  review  their  chemistry,  or  have 
occasion  to  refresh  their  memories  on  any  point  re- 
lating to  it.  In  a  word,  it  is  a  book  to  be  read  by  all 
who  wish  to  know  what  is  the  chemistry  of  the  pre- 
sent day. — American  Practitioner,  Nov.  1873. 

Among  the  various  works  upon  general  chemistry 
issued,  we  know  of  none  that  will  supply  the  average 
wants  of  the  student  or  teacher  better  than  this. — 
Indiana,  Jour n.  of  Med.,  Nov.  1873. 

We  cordially  welcome  this  American  reprint  of  a 
work  which  has  already  won  for  itself  so  substantial 
a  reputation  in  England.  Professor  Bloxam  has  con- 
densed into  a  wonderfully  small  com  >ass  all  the  im- 
portant principles  and  facts  of  chemical  science. 
Thoroughly  imbued  with  an  enthusiastic  love  for  the 
science  he  expounds,  he  has  stripped  it  of  ail  need- 
less technicalities,  and  rounded  out  its  hard  outlines 
by  a  fulness  of  illustration  that  cannot  fail  to  attract 
and  delight  the  student.  The  details  of  illustrative 


and  many  of  the  experiments  described  ai-e  both  nex 
aud  striking.  —Detroit  Rev.  of  Med.  and  Pharm., 
Nov.  1873. 

One  of  the  best  text-books  of  chemistry  yet  pub- 
lished.— Chicago  Med.  Journ.,  Nov.  1873. 

This  is  an  excellent  work,  well  adapted  for  the  be- 
ginner and  the  advanced  student  of  chemistry. — Am. 
Journ.  of  Pharm.,  Nov.  1873. 

Probably  the  most  valuable,  and  at  the  same  time 
practical,  text-book  on  general  chemistry  extant  in 
our  language. — Kansas  City  Med.  Journ.,  Dec.  1873. 

Prof.  Bloxam  possesses  pre-eminently  the  inestima- 
ble gift  of  perspicuity.  It  is  a  pleasure  to  read  his 
books,  for  he  is  capable  of  making  very  plain  what 
other  authors  frequently  have  left  very  obscure. — 
Va.  Clinical  Record,  Nov.  1873. 


It  would  be  difficult  for  a  practical  chemist  and 
teacher  to  find  any  material  fault  with  this  most  ad- 
mirable treatise.  The  author  has  given  us  almost  a 
cyclopedia  within  the  limits  of  aconvenient  volume, 
and  has  done  so  without  penning  the  useless  para- 
graphs too  commonly  making  up  a  great  part  of  the 
bulk  of  many  cumbrous  works.  The  progressive  sci- 
entist is  not  disappointed  when  he  looks  for  the  record 
of  new  and  valuable  processes  and  discoveries,  while 
the  cautious  conservative  does  not  find  its  pages  mo- 
nopolized by  uncertain  theories  and  speculations.  A 
peculiar  point  of  excellence  is  the  crystallized  form  of 
expression  in  which  great  truths  are  expressed  in 
very  short  paragraphs.  One  is  surprised  at  the  brief 
space  allotted  to  an  important  topic,  and  yet,  after 
reading  it,  he  feels  that  little,  if  any  more,  should 
have  been  said.  Altogether,  it  is  seldom  you  see  a 
text-book  so  nearly  faultless.—  Cincinnati  Lancet, 
Nov.  1873. 

Professor  Bloxam  has  given  us  a  most  excellent 
and  useful  practical  treatise.  His  666  pages  are 
crowded  with  facts  and  experiments,  nearly  all  well 
chosen,  ajid  many  quite  new,  even  to  scientific  men. 
.  .  .  It  is  astonishing  how  much  information  he  often 
conveys  in  a  few  paragraphs.  We  might  quote  fifty 
instances  of  this. — Chemical  News. 


IXTOHLER  AND  FITTIG. 

OUTLINES  OF  ORGANIC  CHEMISTRY.  Translated  with  Ad- 
ditions from  the  Eighth  German  Edition.  By  IRA  REMSEN,  M.D.,  Ph.D.,  Professor  of 
Chemistry  and  Physics  in  Williams  College,  Mass.  In  one  handsome  volume,  royal  12mo. 
of  550  pp.,  cloth,  $3. 

As  the  numerous  editions  of  the  original  attest,  this  work  is  the  leading  text-book  and  standard 
Authority  throughout  Germany  on  its  important  and  intricate  subject — a  position  won  for  it  by 
the  clearness  and  conciseness  which  are  its  distinguishing  characteristics.  The  translation  has 
been  executed  with  the  approbation  of  Profs.  Wohler  and  Fittig,  and  numerous  additions  and 
alterations  have  been  introduced,  so  as  to  render  it  in  every  respect  on  a  level  with  the  most 
advanced  condition  of  the  science. 

JgOWMAN  (JOHN  E.),M.  D. 

PRACTICAL  HANDBOOK  OF  MEDICAL  CHEMISTRY.    Edited 

by  C.  L.  BLOXAM,  Professor  of  Practical  Chemistry  in  King's  College,  London.      Sixth 
American,  from  the  fourth  and  revised  English  Edition.     In  one  neat  volume,  royal  12mo., 
pp.  351,  with  numerous  illustrations,  cloth,  $2  25. 
J£Y  THE  SAME  AUTHOR.     (Lately  Issued.)       

INTRODUCTION   TO   PRACTICAL  CHEMISTRY,  INCLUDING 

ANALYSIS.  Sixth  American,  from  the  sixth  and  revised  London  edition.  With  numer- 
ous illustrations.  In  one  neat  vol.,  royal  12mo.,  cloth,  $2  25. 


KBTAPP'S  TECHNOLOGY  ;  or  Chemistry  Applied  to 
tse  Art*,  and  to  Manufactures.  With  American 
additions,  by  Prof.  WALTER  B.  JOHHSOS.  In.  two 


very  handsome  octavo  volumes,  with  600  wood 
engravings,  cloth,  $6  00. 


12       HENRY  0.  LEA'S  PUBLICATIONS — (Mat.  Med.  and  Therapeutics}.     . 

PARRISH  (EDWARD], 

Late  Professor  of  Materia  Medica  in  the  Philadelphia  College  of  Pharmacy. 

A  TREATISE  ON  PHARMACY.    Designed  as  a  Text-Book  for  the 

Student,  and  as  a  Guide  for  the  Physician  and  Pharmaceutist.  With  many  Formulae  and 
Prescriptions.  Fourth  Edition,  thoroughly  revised,  by  THOMAS  S.  WIEGAND.  In  one 
handsome  octavo  volume  of  977  pages,  with  280  illustrations;  cloth,  $5  50;  leather,  $6  50. 
(Just  Issued.) 

The  delay  in  the  appearance  of  the  new  U.  S.  Pharmacopoeia,  and  the  sudden  death  of  the  au 
thor,  have  postponed  the  preparation  of  this  new  edition  beyond  the  period  expected.  The  notes 
and  memoranda  left  by  Mr.  Parrish  have  been  placed  in  the  hands  of  the  editor,  Mr.  Wiegand, 
who  has  labored  assiduously  to  embody  in  the  work  all  the  improvements  of  pharmaceutical  sci- 
ence which  have  been  introduced  during  he  last  ten  years.  It  is  therefore  hoped  that  the  new 
edition  will  fully  maintain  the  reputation  which  the  volume  has  heretofore  enjoyed  as  a  standard 
text-book  and  work  of  reference  for  all  engaged  in  the  preparation  and  dispensing  of  medicines. 
Of  Dr  Parrish's  great  work  on  pharmacy  it  only  an  honored  place  on  our  own  bookshelves. — Dublin 
remains  to  be  said  that  the  editor  has  accomplished  j  Med.  Prexs  and  Circular,  Aug.  12,  1S74. 
his  work  so  well  as  to  maintain  in  this  fourth  edi-  We  expressed  our  Opin5on  of  a  former  edition  in 
tion,  the  high  standard  of  excellence  which  it  bad  terms  of  unquallfied  pralRe  and  we  are  in  no  ,nood 
attained  in  previous  editions,  under  the  editorship  of ,  to  detract  from  tnat  opinlon  in  reference  to  the  pre- 


its  accomplished  author.     This  has  not  been  accom 


seat  edition,  the  preparation  of  which  has  fallen  into 


plished  without  much  labor,  and  many  additions  and  competem  hands.  It  is  a  book  with  which  uopharma- 
improvemeuts,  involving  changes  in  the  arrangement  1  cist  cau  dispense,  and  from  which  no  physician  can 
of  the  several  parts  of  the  work,  and  the  addition  o\  fail  to  derive  mnch  informa,ion  of  THiue  10  him  in 
much  new  matter.  With  the  modifications  thus  et  practjce,— Pacific  Mtd.  and  Sura.  Journ.,  June  '74. 
fected  it  constitutes,  as  now  presented,  a  compendium  j 
of  the  science  and  art  indispensable  to  the  pharma-  |  With  these  few  remarks  we  heartily  commend  the 


cist,  and  of  the  utmost  value  to  every  practitioner 
of  medicine  desirous  of  familiarizing  himself  with 
the  pharmaceutical  preparation  of  the  articles  which 
he  prescribes  for  his  patients. — Chicago  Med.  Journ., 
July,  1874. 

The  work  is  eminently  practical,  and  has  the  rare 
merit  of  being  readable  and  interesting,  while  it  pre- 
serves a  striciJy  scientific  character.  The  whole  work 
reflects  the  greatest  credit  on  author,  editor,  and  pub- 
lisher It  will  convey  some  idea  of  i  he  liberality  which 
has  been  bestowed  upon  its  production  when  we  men- 
tion that  there  are  no  less  than  2SO  carefully  executed 
illustrations.  In  conclusion,  we  heartily  recommend 
the  work,  not  only  to  pharmacists,  but  also  to  the 
multitude  of  medical  practitioners  who  are  obliged 
to  compound  their  own  medicines.  It  will  ever  hold 


work,  and  have  no  doubt  that  it  will  maintain  its 
old  reputation  as  a  text  book  for  the  student,  and  a 
work  of  reference  for  the  more  experienced  physi- 
cian and  pharmacist . —  Chicago  Med.  Examiner, 
June  1-3,  1874. 

Perhaps  one,  if  not  the  most  important  book  upon 
pharmacy  which  has  appeared  in  the  English  lan- 
guage has  emanated  from  the  transatlantic  press. 
"Parrish's  Pharmacy'' is- 
side  of  the  water,  and  tin 

useful  work  never  becomes  merely  local  in  ics  fame. 
Thanks  to  the  judicious  editing  of  Mr.  Wiegaiid,  the 
posthumous  edition  of  "Parrish"  has  been  saved  to 
the  public  with  all  the  mature  experience  of  its  au- 
thor, an.i  perhaps  none  the  worse  for  a  dash  of  aew 
blood.— Lond.  Pharm.  Journal,  Oct.  17,  1874. 


a  well-known  work  on  this 
fact  shows  us  that  a  really 


&TILLE  (ALFRED),  M.D., 

*3  Professor  of  Theory  and  Practice  of  Medicine  in  the  University  of  Penna. 

THERAPEUTICS  AND  MATERIA  MEDICA;  a  Systematic  Treatise 

on  the  Action  and  Uses  of  Medicinal  Agents,  including  their  Description  and  History. 

Fourth  edit.,  revised  and  enlarged.      In  two  large  and  handsome  8vo.  vols.  of  about  2000 

pages.      Cloth,  $10;  leather,  $12.      (Now Ready.) 

The  care  bestowed  by  the  author  on  the  revision  of  this  edition  has  kept  the  work  out  of  the 
market  for  nearly  two  years,  and  has  increased  its  size  about  two  hundred  and  fifty  pages.  Not" 
withstanding  this  enlargement,  the  price  has  been  kept  at  the  former  very  moderate  rate.  A  few 
notices  of  former  editions  are  subjoined. 


Dr.  iSlille's  splendid  work  on  therapeutics  and  ma- 
teria  medica. — London  Med.  Times,  April  8,  1865. 

Dr.  Still6  stands  to-day  one  of  the  best  and  most 
honored  representatives  at  home  and  abroad,  of  Ame- 
rican medicine ;  and  these  volumes,  a  library  in  them- 
selves, a  treasure-house  for  every  studious  physician, 
assure  his  fame  even  had  he  done  nothing  more. — The 
Western  Journal  of  Medicine,  Dec.  1868. 

We  regard  this  work  as  the  best  one  on  Materia 
Medica  in  the  English  language,  and  as  such  it  de- 
serves the  favor  it  has  received. — Am.  Journ.  Medi- 
cal Sciences,  July  1868. 

We  need  not  dwell  on  the  merits  of  the  third  edition 
of  this  magnificently  conceived  work.  It  is  the  work 
on  Materia  Medica,  in  which  Therapeutics  are  prima- 
rily considered — the  mere  natural  history  of  drugs 


abroad  its  reputation  as  a  standard  treatise  on  Materin 
Medica  is  securely  established.  It  is  second  to  no 
work  on  the  subject  in  the  English  tongue,  and,  in- 
deed, is  decidedly  superior,  in  some  respects,  to  any 
other. — Pacific  Med.  and  Surg  Journal,  July,  1S68, 

Stille~'s  Therapeutics  is  incomparably  the  best  work 
on  the  subject.— N.  Y.  Med.  Gazette,  Sept.  26,  1868. 

Dr.  Still's  work  is  becoming  the  best  known  of  any 
of  our  treatises  on  Materia  Medica.  .  .  .  One  of  the 
most  valuable  works  in  the  language  on  the  subjects 
of  which  it  treats.— jy.  Y.  Med.  Journal,  Oct.  1868. 

The  rapid  exhaustion  of  two  editions  of  Prof.  Stille'n 
scholarly  work,  and  the  consequent  necessity  for  & 
third  edition,  is  sufficient  evidence  of  the  high  esti- 
mate placed  upon  it  by  the  profession.  It  is  no  exag- 
geration to  say  that  there  is  no  superior  work  upon 


briefly  disposed  of.     To  medical  practitioners  I  the  subject  in  the  English  language.     The  present 
this  Is  a  very  valuable  conception.     It  is  wonderful  \  edition  is  fully  up  to  the  most  recent  advance  in  the 

' 


how  much  of  the  riches  of  the  literature  of  Materia 
Medica  has  been  condensed  into  this  book.  The  refer- 
ences alone  would  make  it  worth  possessing.  But  it 
is  not  a  mere  compilation.  The  writer  exercises  a 
#ood  judgment  of  his  own  on  the  great  doctrines  and 
points  of  Therapeutics.  For  purposes  of  practice, 

Still6's  book  is  almost  unique  as  a  repertory  of  in-  for  itself.  As  a  work  of  great  research,  and  scholar- 
formation,  empirical  and  scientific,  on  the  actions  and  |  ship,  it  is  safe  to  say  we  have  nothing  superior.  It  i» 
uses  of  medicines. — London  Lancet,  Oct.  31,  1868.  exceedingly  full,  and  the  busy  practitioner  will  find 
Through  the  former  editions,  the  professional  world  '  ample  suggestions  upon  almost  every  important  point 
is  well  acquainted  with  this  work.  At  home  and  j  of  therapeutics. — Cincinnat i  Lancet,  Aug.  1868. 


science  and  art  of  therapeutics. — Leavenworth  Medi- 
cal Herald,  Aug  1868. 

The  work  of  Prof.  Still6  has  rapidly  taken  a  high 
place  in  professional  esteem,  and  to  say  that  a  third 
edition  is  demanded  and  now  appears  before  us,  suffi- 
ciently  attests  the  firm  position  this  treatise  has  made 


HENRY  C.  LEA'S  PUBLICATIONS — {Mat.  Med.  and  Therapeutics).       13 

/GRIFFITH  (ROBERT  E.),  M.D. 

A  UNIVERSAL  FORMULARY,  Containing  the  Methods  of  Prepar- 
ing and  Administering  Officinal  and  other  Medicines.    The  whole  adapted  to  Physician*  and 
Pharmaceutists.     Third  edition,  thoroughly  revised,  with  numerous  additions,  bj  JOHN  M. 
MAISCH,  Professor  of  Materia  Medica  in  the  Philadelphia  College  of  Pharmacy.   In  one  large 
andhandsome  octavo  volume  of  aboutSOO  pages,  cloth,  $4  50  ;  leather,  $5  50.    (Just  Issued.) 
This  work  has  long  been  known  for  the  vast  amount  of  information  which  it  presents  in  a  con- 
densed form,  arranged  for  easy  reference.      The  new  edition  has  received  the  most  careful  revi- 
sion at  the  competent  hands  of  Professor  Maisch,  who  has  brought  the  whole  up  to  the  standard  of 
the  most  recent  authorities.     More  than  eighty  new  headings  of  remedies  have  been  introduced, 
the  entire  work  has  been  thoroughly  remodelled,  and  whatever  has  seemed  to  be  obsolete  has  been 
omitted.     As  a  comparative  view  of  the  United  States,  the  British,  the  German,  and  the  French 
Pharmacopoeias,  together  with  an  immense  amount  of  unofficinal  formulas,  it  affords  to  the  prac- 
titioner and  pharmaceutist  an  aid  in  their  daily  avocations  not  to  be  found  elsewhere,  while  three 
indexes,  one  of  "Diseases  and  their  Remedies,"  one  of  Pharmaceutical  Names,  and  a  General 
Index,  afford  an  easy  key  to  the  alphabetical  arrangement  adopted  in  the  text. 


The  young  practitioner  will  find  the  work  invalu- 
able in  suggesting  eligible  modes  of  administering 
many  remedies. — Am.  Journ.  of  Pharm.,  Feb.  1874. 

Our  copy  of  Griffith's  Formulary,  after  long  use, 
first  in  the  dispensing  shop,  and  afterwards  in  our 
medical  practice,  had  gradually  fallen  behind  in  the 
onward  march  of  materia  medica,  pharmacy,  and 
therapeutics,  until  we  had  ceased  to  consult  it  as  a 
daily  book  of  reference.  So  completely  has  Prof. 
Maisch  reformed,  remodelled,  and  rejuvenated  it  in 
the  new  edition,  we  shall  gladly  welcome  it  back  to 
our  table  again  beside  Duuglison,  Webster,  and  Wood 
&  Bache.  The  publisher  could  not  have  been  more 
fortunate  in  the  selection  of  an  editor.  Prof.  Maisch 
is  eminently  the  man  for  the  work,  and  he  has  done 
it  thoroughly  and  ably.  To  enumerate  the  altera- 
tions, amendments,  and  additions  would  be  an  end- 
less task;  everywhere  we  are  greeted  with  the  evi- 
dences of  his  labor.  Following  the  Formulary,  is  an 
addendum  of  useful  Recipes,  Dietetic  Preparations, 
List  of  Incompatibles,  Posological  table,  table  of 
Pharmaceutical  Names,  Officinal  Preparations  and 
Directions,  Poisons.  Antidotes  and  Treatment,  and 
copious  indices,  which  afford  ready  access  to  all  parts 
of  the  work.  We  unhesitatingly  commend  the  book 
as  being  the  best  of  its  kind,  within  our  knowledge. 
— Atlanta  Med.  and  Surg.  Journ.,  Feb.  1874. 


To  the  druggist  a  good  formulary  is  simply  indis- 
pensable, and  perhaps  no  formulary  has  been  more 
extensively  used  than  the  well-known  work  before 
us.  Many  physicians  have  to  officiate,  also,  as  drug- 
gists. This  is  true  especially  of  the  country  physi- 
cian, and  a  work  which  shall  teach  him  the  means 
by  which  to  administer  or  combine  his  remedies  in 
the  most  efficacious  and  pleasant  manner,  will  al- 
ways hold  its  place  upon  his  shelf.  A  formulary  of 
this  kind  is  of  benefit  also  to  the  city  physician  in 
largest  practice.— Cincinnati  Vlinic,  Feb.  21,  1874. 

The  Formulary  has  already  proved  itself  accepta- 
ble to  the  medical  profession,  and  we  do  not  hesitate 
to  say  that  the  third  edition  is  much  improved,  and 
of  greater  practical  value,  in  consequence  of  the  care- 
ful revision  of  Prof  Maisch.— Chicago  Med.  Exam- 
iner, March  15,  1874. 

A  more  complete  formulary  than  it  is  in  its  pres- 
ent form  the  pharmacist  or  physician,  could  hardly 
desire.  To  the  first  some  such  work  is  indispensa- 
ble, and  it  is  hardly  less  essential  to  the  practitioner 
who  compounds  his  own  madiciaes.  Much  of  what 
is  contained  in  the  introduction^ought  to  be  com- 
mitted to  memory  by  every  student  of  inedijiae. 
As  a  help  to  physiciaus  it  will  be  found  invaluable, 
and  doubtless  will  make  its  way  into  libraries  not 
already  supplied  with  a  standard  work  of  the  kind. 
—  The  American  Practitioner,  Louisville,  July,  '74. 


E. 


'LLIS  (BENJAMIN],  M.D. 

THE  MEDICAL  FORMULARY:  being  a  Collection  of  Prescriptions 

derived  from  the  writings  and  practice  of  many  of  the  most  eminent  physicians  of  America 
and  Europe.  Together  with  the  usual  Dietetic  Preparations  and  Antidotes  for  Poisons.  The 
whole  accompanied  with  a  few  brief  Pharmaceutic  and  Medical  Observations.  Twelfth  edi- 
tion, carefully  revised  and  much  improved  by  ALBERT  H.  SMITH,  M.D.  In  one  volume  8v@. 
of  376  pages,  cloth,  $3  00. 


iEREIRA  (JONATHAN),  M.D.,  F.R.S.  and  L.S. 

MATERIA  MEDICA  AND  THERAPEUTICS;  being  an  Abridg- 
ment of  the  late  Dr.  Pereira's  Elements  of  Materia  Medica,  arranged  in  conformity  with 
the  British  Pharmacopoeia,  and  adapted  to  the  use  of  Medical  Practitioners,  Chemists  and 
Druggists,  Medical  and  Pharmaceutical  Students,  &c.  By  F.  J.  FARRE,  M.D.,  Senior 
Physician  to  St.  Bartholomew's  Hospital,  and  London  Editor  of  the  British  Pharmacopoeia ; 
assisted  by  ROBEHT  BENTLEY,  M.R.C.S.,  Professor  of  Materia  Medica  and  Botany  to  the 
Pharmaceutical  Society  of  Great  Britain;  and  by  ROBERT  WARINGTON,  F.R.S.,  Chemical 
Operator  to  the  Society  of  Apothecaries.  With  numerous  additions  and  references  to  the 
United  States  Pharmacopoeia,  by  HORATIO  C.  WOOD,  M.D.,  Professor  of  Botany  in  the 
University  of  Pennsylvania.  In  one  large  and  handsome  octavo  volume  of  1040  closety 
printed  pages,  with  236  illustrations,  cloth,  $7  00;  leather,  raised  bands,  $8  00. 


DDNGLISON'S  NEW  REMEDIES,  WITH  FORMULA 
FOR  THEIR  PREPARATION  AND  ADMINISTRA- 
TION. Seventh  edition,  with  extensive  additions. 
One  vol.  8vo.,  pp.  770;  cloth.  $4  00. 

EOYLE'S  MATERIA  MEDICA  AND  THERAPEU- 
TICS. Edited  by  JOSEPH  CAKSON,  M.  D.  With 
ninety-eight  illustrations.  1  vol.  8vo.,  pp.  700, 
cloth.  $3  00. 

CARSON'S  SYNOPSIS  OF  THE  LECTURES  ON  MA- 
TERIA MEDICA  AND  PHARMACY,  delivered  in 
the  University  of  Pennsylvania.  Fourth  and  re- 
vised edition.  Cloth,  $3. 


'HRISTISON'S  DISPENSATORY.  With  copious  ad 
^U.irttifi,  and  9.1 3  lar««  wood-«n«rravin«s  Bv  R. 
EGLESFELD  GRIFFITH,  M.  D.  One  vol.  8vo.,  pp.  1000 ; 
cloth.  $4  00. 

CARPENTER'S  PRIZE  ESSAY  ON  THE  USE  OP 
ALCOHOLIC  LIQUORS  IN  HEALTH  AND  DISEASE.  New 
edition,  with  a  Preface  by  D.  F.  CONDIE.  M.D.,  and 
explanations  of  scientific  words.  In  one  neat  12mo. 
volume,  pp.  178,  cloth.  60  cents. 

DE  JONGH  ON  THE  THREE  KINDS  OF  COD-LIVEB 
OIL,  with  their  Chemical  and  Therapeutic  Pro- 
perties. 1  vol.  12rno.,  cloth.  75  cents. 


14 


HENRY  C.  LEA'S  PUBLICATIONS — (Pathology -,  <£<?.). 


flENWICK  (SAMUEL],  M.D., 

-*-  Assistant  Physician  to  the  London  Hospital. 

THE  STUDENT'S  GUIDE  TO  MEDICAL  DIAGNOSIS.     From  the 

Third  Revised  and  Enlarged  English  Edition.     With   eighty-four  illustrations  on  wood. 

In  one  very  handsome  volume,  royal  ]2mo.,  cloth,  $2  25.     (J^(,st  Issued.} 

The  very  great  success  which  this  work  has  obtained  in  England,  shows  that  it  has  supplied  an 
admitted  want  among  elementary  books  for  the  guidance  of  students  and  junior  practitioners. 
Taking  up  in  order  each  portion  of  the  body  or  class  of  disease,  the  author  has  endeavored  to 
present  in  simple  language  the  value  of  symptoms,  so  as  to  lead  the  student  to  a  correct  appreci- 
ation of  the  pathological  changes  indicated  by  them.  The  latest  investigations  have  been  care- 
fully introduced  into  the  present  edition,  so  that  it  may  fairly  be  considered  as  on  a  level  with 
the  most  advanced  condition  of  medical  science. 

Of  the  many  guide-books  on  medical  diagnosis,  |  else,  practical  manner,  well  calculated  to  assist  the 


claimed  to  be  written  for  the  special  instruction  of 
students,  this  is  the  best.  The  author  is  evidently  a 
well-read  and  accpmplished  physician,  and  he  knows 
how  to  'each  practical  medicine.  The  charm  of  sim- 
plicity is  not  the  least  interesting  feature  in  the  man- 
ner in  which  Dr.  Fenwick  conveys  instruction.  There 
are  few  books  of  this  size  on  practical  medicine  that 
contain  so  much  and  convey  it  so  well  as  the  volume 
before  us.  It,  is  a  book  we  can  sincerely  recommend 
to  the  student  for  direct  instruction,  and  to  the  prac- 
titioner as  a  ready  and  useful  aid  to  his  memory. — 
Am.  Jo  urn.  of  Syphilography,  Jan.  1874. 

It  covers  the  ground  of  medical  diagnosis  in  a  con- 


student  in  forming  a  correct,  thorough,  and  system- 
atic method  of  examination  and  diagnosis  of  disease. 
The  illustrations  are  numerous,  and  finely  executed. 
Those  illustrative  of  the  microscopic  appearance  of 
morbid  tissue,  &c.,  are  especially  clear  and  distinct.. 
— Chicago  Med.  Examiner,  Nov.  1£73. 

So  far  superior  to  any  offered  to  students  that  the 
colleges  of  this  country  should  recommend  it  to  their 
respective  classes. — 27.  0.  Med.  and  Surg.  Journ., 
March,  1874. 

This  little  book  ought  to  be  in  the  possession  of 
every  medical  student. — Boston  Medical  and  Surg. 
Journ.,  Jan.  15,  1874. 


SCREEN  (T.  HENRY),  M.D., 

Lecturer  on  Pathology  and  Morbid  Anatomy  at  Charing-Gross  Hospital  Medical  School. 

PATHOLOGY  AND  MORBID  ANATOMY.  With  numerous  Illus- 
trations on  Wood.  In  one  very  handsome  octavo  volume  of  over  250  pages,  cloth,  $2  50. 
(Lately  Published.) 

We  have  been  very  much  pleased  by  our  perusal  of    thology  and  morbid  anatomy.  The  author  shows  that 
this  little  volume.   It  is  the  only  one  of  the  kind  with    he  has  been  not  only  a  student  of  the  teachings  of  his 
which  we  are  acquainted,  and  practitioners  as  well 
as  students  will  find  it  a  very  useful  guide ;  for  the 
information  is  up  to  the  day,  well  and  compactly  ar- 
ranged, without  being  at  all  scanty. — London  Lan- 
cet, Oct.  7,  1871. 

It  embodies  in  a  comparatively  small  space  a  clear 
statement  of  the  present  state  of  our  knowledge  of  pa- 


zonfrtres  in  this  branch  of  science,  but  a  practical 
and  conscientious  laborer  in  the  post-mortem  cham- 
ber. The  work  will  provea  useful  one  to  the  great 
mass  of  students  and  practitioners  whose  time  for  de- 
votion to  this  class  of  studies  is  limited.—  Am.  Journ, 
of  Syphilography,  April,  1872. 


GLUGE'S  ATLAS  OF  PATHOLOGICAL  HISTOLOGY. 
Translated,  with  Notes  and  Additions,  by  JOSEPH 
LEIDT,  M.  D.  In  one  volume,  very  large  imperial 
quarto,  with  320  copper-plate  figures,  plain  and 
colored,  cloth.  $4  00. 

JONES  AND  SIEVEKING'S  PATHOLOGICAL  ANA- 
TOMY. With  397  wood-cuts.  1  vol.  Svo.,  of  nearly 
750  pages,  cloth.  $3  50. 

HOLLAND'S  MEDICAL  NOTES  AND  .REFLEC- 
TIONS. 1  vol.  8vo.,  pp.  500,  cloth.  $3  50. 

WHATTO  OBSERVE  ATTHE  BEDSIDE  AND  AFTEE 
DEATH  IN  MEDICAL  CASES.  Published  under  the 
authority  of  the  London  Society  for  Medical  Obser- 
vation. From  the  second  London  edition.  1  vol. 
royal  12mo.,  cloth.  $1  00. 


LA  ROCHE  ON  YELLOW  FEVER,  considered  in  its 
Historical,  Pathological,  Etiological,  and  Therapeu- 
tical Relations.  In  two  large  and  handsome  octavo 
volumes  of  nearly  1500  pages,  cloth.  $7  00. 

LAYCOCK'S  LECTURES  ON  THE  PRINCIPLES 
AND  METHODS  OF  MEDICAL  OBSERVATION  AND  RE- 
SEARCH. For  the  use  of  advanced  students  and 
junior  practitioners.  In  one  very  neat  royal  12mo. 
volume,  cloth.  $1  00. 

BARLOW'S  MANUAL  OF  THE  PRACTICE  OP 
MEDICINE.  With  Additions  by  D.  F.  CONDIE, 
M.  D.  1  vol.  8vo.,  pp.  600,  cloth.  $2  50. 

TODD'S  CLINICAL  LECTURES  ON  CERTAIN  ACUTE 
DISEASES.  In  one  neat  octavo  volume,  of  320  pages, 
cloth.  $2  60. 


&TURGES  (OCTAVIUS],  M.D.  Cantab., 

*-J  Fellow  of  the  Royal  College  of  Physicians,  &c.  &c. 

AN   INTRODUCTION   TO    THE    STUDY   OP   CLINICAL   MED- 

ICINE.     Being  a  Guide  to  the  Investigation  of  Disease,  for  the  Use  of  Students.     In  one 
handsome  12mo.  volume,  cloth,  $1  25.      (Just  Issued.) 


D 


AVIS  (NATHAN  S.}, 

Prof,  of  Principles  and  Practice  of  Medicine,  etc.,  in  Chirago  Med.  College. 

CLINICAL  LECTURES  ON  VARIOUS    IMPORTANT   DISEASES; 

being  a  collection  of  the  Clinical  Lectures  delivered  in  the  Medical  Wards  of  Mercy  Hos- 
pital, Chicago.  Edited  by  FRANK  H.  DAVIS,  M.D.  Second  edition,  enlarged.  In  one 
handsome  royal  12mo.  volume.  Cloth,  $1  75.  (Now  Ready.) 


&TOKES  (WILLIAM],  M.D.,  D.C.L.,  F.R.S., 

'A3  Reyius  Professor  of  Physic  in  the  Univ.  of  Dublin,  &c. 

LECTURES  ON  FEVER,  delivered  in  the  Theatre  of  the  Meath  Hos- 
pital and  County  of  Dublin  Infirmary.  Edited  by  JOHN  WILLIAM  MOORE,  M.D  ,  Assistant 
Physician  to  the  Cork  Street  Fever  Hospital.  In  one  neat  octavo  volume.  (Preparing.) 

j^*^  To  appear  in  the  "  MEDICAL  NEWS  AND  LIBRARY"  for  1875. 


HENRY  C.  LEA'S  PUBLICATIONS — (Practice  of  Medicine). 


15 


F 


rLINT  (AUSTIN],  M.D., 

Professor  of  the  Principles  and  Practice  of  Medicine  in  Bellevue  Med.  College,  N.  T. 


A   TREATISE    ON    THE    PRINCIPLES    AND    PRACTICE    OF 

MEDICINE  ;  designed  for  the  use  of  Students  and  Practitioners  of  Medicine.     Fourth 
edition,  revised  and  enlarged.    In  one  large  and  closely  printed  octavo  volume  of  about  1 100 
pages;  cloth,  $6  00  ;  or  strongly  bound  in  leather,  with  raised  bands,  $7  00.     (.Just  Issued.) 
By  common  consent  of  the  English  and  American  medical  press,  this  work  has  been  assigned 
to  the  highest  position  as  a  complete  and  compendious  text-book  on  the  most  advanced  condition 
of  medical  science.     At  the  very  moderate  price  at  which  it  is  offered  it  will  be  found  one  of  the 
cheapest  volumes  now  before  the  profession.     A  few  notices  of  previous  editions  are  subjoined. 


Admirable  and  unequalled.  —  Western  Journal  of 
Medicine,  Nov.  1869. 

Dr.  Flint's  work,  though  claiming  no  higher  title 
than  that  of  a  text-book,  is  really  more.  He  is  a  man 
of  large  clinical  experience,  and  his  book  is  fnll  of 
such  masterly  descriptions  of  disease  as  can  only  be 
drawn  by  a  man  intimately  acquainted  with  their 
various  forms.  It  is  not  so  long  since  we  had  the 
pleasure  of  reviewing  his  first  edition,  and  we  recog- 
nize a  great  improvement,  especially  in  the  general 
part  of  the  work.  It  is  a  work  which  we  can  cordially 
recommend  to  our  readers  as  fully  abreast  of  the  sci- 
ence of  the  day. — Edinburgh  Me.d.  Journal,  Oct.  '69. 

One  of  the  best  works  of  the  kind  for  the  practi- 
tioner, and  the  most  convenient  of  all  for  the  student. 
—Am.  Journ.  Med.  Sciences,  Jan.  1869. 

This  work,  which  stands  pre-eminently  as  the  ad- 
vance standard  of  medical  science  up  to  the  present 
time  in  the  practice  of  medicine,  has  for  its  author 
one  who  is  well  and  widely  known  as  one  of  the 
leading  practitioners  of  this  continent.  In  fact,  it  is 
•eldora  that  any  work  is  ever  issued  from  the  press 
more  deserving  of  universal  recommendation. — Do- 
minion Med.  Journal,  May,  1869. 

The  third  edition  of  this  most  excellent  book  scarce- 
ly needs  any  commendation  from  us.  The  volume, 
as  it  stands  now,  is  really  a  marvel :  first  of  all,  it  is 


sxcellently  printed  and  bound  —  and  we  encounter 
that  luxury  of  America,  the  ready-cut  pages,  which 
the  Yankees  are  'cute  enough  to  insist  upon — nor  are 
these  by  any  means  trifles  ;  but  the  contents  of  the 
book  are  astonishing.  Not  only  is  it  wonderful  that 
iny  one  man  can  have  grasped  in  his  mind  the  whole 
scope  of  medicine  with  that  vigor  which  Dr.  Flint 
shows,  but  the  condensed  yet  clear  way  in  which 
this  is  done  is  a  perfect  literary  triumph.  Dr.  Flint 
is  pre-eminently  one  of  the  strong  men,  whose  right 
to  do  this  kind  of  thing  is  well  admitted  ;  and  we  say 
10  more  than  the  truth  when  we  affirm  that  he  is 
very  nearly  the  only  living  man  that  could  do  it  with 
mch  results  as  the  volume  before  us. — The  London 
Practitioner,  March,  1869. 

This  is  in  some  respects  the  best  text-book  of  medi- 
cine in  our  language,  and  it  is  highly  appreciated  on 
the  other  side  of  the  Atlantic,  inasmuch  as  the  first, 
edition  was  exhausted  in  a  few  months.  The  second 
sdition  was  little  more  than  a  reprint,  but  the  present 
has,  as  the  author  says,  been  thoroughly  revised. 
Much  valuable  matter  has  been  added,  and  by  mak- 
ing the  type  smaller,  the  bulk  of  the  volume  is  not 
much  increased.  The  weak  point  in  many  American 
works  is  pathology,  but  Dr.  Flint  has  taken  peculiar 
pains  on  this  point,  greatly  to  the  value  of  the  book. 
—London  Med.  Times  and  Gazette,  Feb.  6,  1869. 


T>Y  THE  SAME  AUTHOR. 

ESSAYS    ON    CONSERVATIVE   MEDICINE    AND    KINDRED 

TOPICS.     In  one  very  handsome  royal  12ino.  volume.     Cloth,  $1  38.     (Just  Issued.") 

CONTENTS, 

I.  Conservative  Medicine.  II.  Conservative  Medicine  as  applied  to  Therapeutics.  III.  Con- 
servative Medicine  as  applied  to  Hygiene.  IV.  Medicine  in  the  Past,  the  Present,  and  the  Fu- 
ture. V.  Alimentation  in  D  sease.  VI.  Tolerance  of  Disease.  VII.  On  the  Age  cy  of  the 
Mind  in  Etiology,  Prophylaxis,  and  Therapeutics.  VIII.  Divine  design  as  exemplified  in  the 
Natural  History  of  Disease. 

"ATSON  (THOMAS],  M.  D.,  &c, 

LECTURES     ON    THE     PRINCIPLES    AND    PRACTICE    OF 

PHYSIC.  Delivered  at  King's  College,  London.  A  new  American,  from  the  Fifth  re- 
vised and  enlarged  English  edition.  Edited,  with  additions,  and  several  hundred  illustra- 
ations,  by  HENRY  HARTSHORNE,  M.D.,  Professor  of  Hygiene  in  the  University  of  Pennsylv- 
nia.  In  two  large  and  handsome  Svo.vols.  Cloth,  $9  00  ;  leather,  $11  00.  (Lately  Published.) 


W: 


It  is  a  subject  for  congratulation  and  for  thankful- 
ness that  Sir  Thomas  Watson,  during  a  period  of  com- 
parative leisure,  after  a  long,  laborious,  and  most 
honorable  professional"  career,  while  retaining  full 
possession  of  his  high  mental  faculties,  should  have 
employed  the  opportunity  to  submit  his  Lectures  to 
a  more  thorough  revision  than  was  possible  during 
the  earlier  and  busier  period  of  his  life.  Carefully 
passing  in  review  some  of  the  most  intricate  and  im- 
portant pathological  and  practical  questions,  there- 
suits  of  his  clear  insight  and  his  calm  judgment  are 
now  recorded  for  the  benefit  of  mankind,  in  language 
which,  for  precision,  vigor,  and  classical  elegance,  has 
rarely  been  equalled,  and  never  surpassed  The  re- 
vision has  evidently  been  most  carefully  done,  and 
the  results  appear  in  almost  every  page. — Brit.  Med. 
Journ.,  Oct.  14,  1871. 

The  lectures  are  so  well  known  and  so  justly 
appreciated,  that  it  is  scarcely  necessary  to  do 
more  than  call  attention  to  the  special  advantages 
of  the  last  over  previous  editions.  The  author's 


rare  combination  of  great  scientific  attainments  com- 
bined with  wonderful  forensic  eloquence  has  exerted 
extraordinary  influence  over  the  last  two  generations 
of  physicians.  His  clinical  descriptions  of  most  dis- 
eases have  never  been  equalled  ;  and  on  this  score 
at  least  his  work  will  live  long  in  the  future.  The 
work  will  be  sought  by  all  who  appreciate  a  great 
book. — Amer.  Journ.  of  Syphilography,  July,  1872. 
We  are  exceedingly  gratified  at  the  reception  of 
this  new  edition  of  Watson,  pre-eminently  the  prince 
of  English  authors,  on  "Practice."  We,  who  read 
the  first  edition  shall  never  forget  the  great  pleasure 
and  profit  we  derived  from  its  graphic  delineations 
of  disease,  its  vigorous  style  and  splendid  English. 
Maturity  of  years,  extensive  observation,  profound 
research,  and  yet  continuous  enthusiasm,  have  com- 
bined to  give  us  in  this  latest  edition  a  model  of  pro- 
fessional excellence  in  teaching  with  rare  beauty  in 
the  mode  of  communication.  But  this  classic  needs 
no  eulogium  of  ours. — Chicago  Med.  Journ.,  July, 
1872. 


D 


UNGLISON,  FORBES,  TWEEDIE,  AND  CONOLLY. 

THE  CYCLOPAEDIA  OF   PRACTICAL  MEDICINE:   comprising 

Treatises  on  the  Nature  and  Treatment  of  Diseases,  Materia  Medica  and  Therapeutics, 
Diseases  of  Women  and  Children,  Medical  Jurisprudence,  <fcc.  <fec.  In  four  large  super-royal 
octavo  volumes,  of  3254  double-columned  pages,  strongly  and  handsomely  bound  in  leather, 
$15  j  cloth,  $J1. 


16  HENRY  C.  LEA'S  PUBLICATIONS — (Practice  of  Medicine). 

fTARTSHORNE  (HENRY),  M.D., 

•*-*•  Professor  of  Hygiene  in  the  University  of  Pennsylvania. 

ESSENTIALS  OF  THE  PRINCIPLES  AND  PRACTICE  OF  MEDI- 

CINE.  A  handy-book  for  Students  and  Practitioners.  Fourth  edition,  revised  and  im- 
proved. With  about  one  hundred  illustrations.  In  one  handsome  royal  12mo.  volume, 
of  about  550  pages,  cloth,  $2  63  ;  half  bound,  $2  88.  (Just  Ready.) 

The  thorough  manner  in  which  the  author  has  labored  to  fully  represent  in  this  favorite  hand- 
book the  most  advanced  condition  of  practical  medicine  is  shown  by  the  fact  that  the  present 
edition  contains  more  than  250  additions,  representing  the  investigations  of  172  authors  not  re- 
ferred to  in  previous  editions.  Notwithstanding  an  enlargement  of  the  page,  the  size  has  been 
increased  by  sixty  pages.  A  number  of  illustrations  have  been  introduced  which  it  is  hoped 
will  facilitate  the  comprehension  of  details  by  the  reader,  and  no  effort  has  been  spared  to  make 
the  volume  worthy  a  continuance  of  the  very  great  favor  with  which  it  has  hitherto  been  received. 
The  work  is  brought  fully  up  with  all  the  recent  j  Without  doubt  the  best  hook  of  tLekind  published 
advances  in  medicine,  is  admirably  condensed,  and  in  the  English  language. — St.  Louis  Mtd.  andSurg. 
yet  sufficiently  explicit  for  all  the  purposes  intended,  Journ.,  Nov.  1874. 


thus  making  it  by  far  the  be?t  work  of  its  character 
ever  published.— Cincinnati  Clinic,  Oct.  24,  1874. 

We  have  already  had  occasion  to  notice  the  previ- 
ous editions  of  this  work.  It  is  excellent  of  its  kind. 
The  author  has  given  a  very  careful  revision,  in  view 
of  the  rapid  progress  of  medical  science.—  N.  Y.  Med. 
Journ.,  JNTov.  1874. 


As  a  handbook,  which  clearly  sets  forth  the  ESSEN- 
TIALS Of  the  PRINCIPLES  AND  PRACTICE  OF  MEDICINE,  W8 

do  not  know  of  its  equal.—  Va.  Mc.d.  Monthly. 

As  a  brief,  condensed,  but  comprehensive  hand- 
book, it  cannot  be  improved  upon. — Chicago  Med. 
Examiner,  Nov.  35,  1874. 


f>AVY(F.  W.),M.D.,F.R.S., 

-*•  Senior  Asst.  Physician  to  and  Lecturer  on  Physiology,  at  Guy's  Hospital,  Ac. 

A  TREATISE  ON  THE    FUNCTION  OF  DIGESTION;  its  Disor- 

ders  and  their  Treatment.     From  the  second  London  edition.     In  one  handsome  volume, 
small  octavo,  cloth,  $2  00. 
T>J  THE  SAME  AUTHOR.    (Just  Ready. 

A  TREATISE  ON  FOOD  AND  DIETETICS,  PHYSIOLOGI- 
CALLY AND  THERAPEUTICALLY  CONSIDERED.  In  one  handsome  octavo  volume 
of  nearly  600  pages,  cloth,  $4  75. 

SUMMARY  OF  CONTENTS. 

Introductory  Remarks  on  the  Dynamic  Relations  of  Food — On  the  Origination  of  Food — The 
Constituent  Relations  of  Food — Alimentary  Principles,  their  Classification,  Chemical  Relations, 
Digestion,  Assimilation,  and  Physiological  Uses — Nitrogenous  Alimentary  Principles — Non-Ni- 
trogenous Alimentary  Principles — The  Carbo-Hydrates — The  Inorganic  Alimentary  Principles — 
Alimentary  Substances — Animal  Alimentary  Substances — Vegetable  Alimentary  Substances — 
Beverages — Condiments — The  Preservation  of  Food — Principles  of  Dietetics — Practical  Dietetics 
— Diet  of  Infants — Diet  for  Training — Therapeutic  Dietetics — Dietetic  Preparations  for  the  Inva- 
lid— Hospital  Dietaries. 

riHAMBERS  (T.  K.},  M.D.   (Now  Ready.} 

V^  Consulting  Physician  to  St.  Mary  n  Hospital,  London,  &c. 

A  MANUAL  OF  DIET  AND  REGIMEN  IN  HEALTH  AND  SICK- 

NESS.     In  one  handsome  octavo  volume.     Cloth,  $2  75. 

The  aims  of  this  handbook  are  purely  practical,  and  therefore  it  has  not  been  thought  right 
to  increase  its  size  by  the  addition  of  the  chemical,  botanical,  and  industrial  learning  which 
rapidly  collects  round  the  nucleus  of  every  nrticle  interesting  as  an  eatable.  Space  has  been 
thus  gained  for  a  full  discussion  of  many  matters  connecting  food  and  drink  with  the  daily  cur- 
rent of  social  life,  which  the  position  of  the  author  as  a  practising  physician  has  led  him  to 
believe  highly  important  to  the  present  and  future  of  our  race. — Preface. 

SUMMARY     OF      CONTENTS. 

PARTl.  General  Dietetics.  CHAP.  I.  Theories  of  Dietetics.  II.  On  the  Choice  of  Food.  III. 
On  the  Preparation  of  Food.  IV.  On  Digestion  and  Nutrition. 

PART  II.  Special  Dietetics  of  Health.  CHAP.  I.  Regimen  of  Infancy  and  Motherhood.  II. 
Regimen  of  Childhood  and  Youth.  III.  Commercial  Life.  IV.  Literary  and  Professional  Life. 
V.  Noxious  Trades.  VI.  Athletic  Training.  VII.  Hints  for  Healthy  Travellers.  VIII.  Effects 
of  Climate.  IX.  Starvation,  Poverty,  and  Fasting.  X.  The  Decline  of  Life.  XI.  Alcohol. 

PART  III.  Dietetics  in  Sickness.  CHAP.  I.  Dietetics  and  Regimen  in  Acute  Fevers.  II.  The 
Diet  and  Regimen  of  certain  other  Inflammatory  States.  III.  The  Diet  and  Regimen  of  Weak 
Digestion.  IV.  Gout  and  Rheumatism.  V.  Gravel,  Stone,  Albuminuria,  and  Diabetes.  VI. 
Deficient  Evacuation.  VII.  Nerve  Disorders.  VIII.  Scrofula,  Rickets,  and  Consumption.  IX. 
Diseases  of  Heart  and  Arteries. 

T)Y  THE  SAME  AUTHOR.     (Lately  Published.) 

RESTORATIVE  MEDICINE.   An  Harveian  Annual  Oration.   With 

Two  Sequels.     In  one  very  handsome  volume,  small  12mo.,  cloth,  $1  00. 


TyRINTON  (WILLIAM),  M.D.,  F.R.S. 
-^LECTURES  ON  THE  DISEASES  OF  THE  STOMACH;   with  an 

Introduction  on  its  Anatomy  and  Physiology.  From  the  second  and  enlarged  London  edi- 
tion. With  illustrations  on  wood  In  one  handsome  octavo  volume  of  about  300  pages 
cloth,  $3  25. 


HENRY  C.  LEA'S  PUBLICATIONS. 


(AUSTIN),  M.D., 

Professor  of  the  Principles  and  Practice  of  Medicine  in  Bellevue  Hospital  Med.  College,  N.  T. 

A  PRACTICAL  TREATISE  ON  THE  DIAGNOSIS,  PATHOLOGY, 

AND  TREATMENT  OF  DISEASES  OF  THE  HEART.     Second  revised  and  enlarged 
edition.     In  one  octavo  volume  of  550  pages,  with  a  plate,  cloth,  $4. 

Dr.  Flint  chose  a  difficult  subjectfor  his  researches,  i  able  for  purposes  of  illustration,  in  connection  with 
and  has  shown  remarkable  powers  of  observation    cases  which  have  been  reported  by  other  trustworthy 


and  reflection,  as  well  as  great  industry,  in  his  treat- 
ment of  it.  His  book  must  be  considered  the  fullest 
aud  clearest  practical  treatise  on  those  subjects,  and 
should  be  in  the  hands  of  all  practitioners  and  stu- 
dents. It  is  a  credit  to  American  medical  literature. 
— Amer.  Journ.  of  the  Med.  Sciences,  July,  1860. 

We  question  the  fact  of  any  recent  American  author 
In  our  profession  being  more  extensively  known,  or 
more  deservedly  esteemed  in  this  country  than  Dr. 


observers.—  Brit,  and  For.  Med.-Chirurg.  Review. 

In  regard  to  the  merits  of  the  work,  we  have  no 
hesitation  in  pronouncing  it  full,  accurate,  aud  judi- 
cious. Considering  the  present  state  of  science,  such 
a  work  was  much  needed.  It  should  be  in  the  hands 
of  every  practitioner. — Chicago  Med.  Journ. 

With  more  than  pleasure  do  we  hail  the  advent  of 
this  work,  for  it  fills  a  wide  gap  on  the  list  of  text- 


Flint.  We  willingly  acknowledge  his  success,  more  j  books  for  our  schools,  and  is,  for  the  practitioner,  the 
particularly  in  the  volume  on  diseases  of  the  heart,  most  valuable  practical  work  of  its  kind.—  N.  0.  Med. 
jn  making  an  extended  personal  clinical  study  avail-  I  News. 


>Y  THE  SAME  AUTHOR. 

A  PRACTICAL  TREATISE  ON7  THE  PHYSICAL  EXPLORA- 
TION OF  THE  CHEST  AND  THE  DIAGNOSIS  OF  DISEASES  AFFECTING  THE 
RESPIRATORY  ORGANS.  Second  and  revised  edition.  In  one  handsome  octavo  volume 
of  595  pages,  cloth,  $4  50. 

which  pervades  his  whole  work  lend  an  additional 


Dr.  Flint's  treatise  is  one  of  the  most  trustworthy 
guides  which  we  can  consult.  The  style  is  clear  and 
distinct,  and  is  also  concise,  being  free  from  that  tend- 
ency to  over-refinement  and  unnecessary  minuteness 
which  characterizes  many  works  on  the  same  sub- 
ject.— Dublin  Medical  Press,  Feb.  6,  1867. 

The  chapter  on  Phthisis  is  replete  with  interest ; 
and  his  remarks  on  the  diagnosis,  especially  in  the 
early  stages,  are  remarkable  for  their  acumen  and 
great  practical  value.  Dr.  Flint's  style  is  ciear  and 
elegant,  and  the  tone  of  freshness  and  originality 


force  to  its  thoroughly  practical  character,  which 
cannot  fail  to  obtain  for  it  a  place  as  a  standard  work 
on  diseases  of  the  respiratory  system. — London 
Lancet,  Jan.  IP,  1867. 

This  is  an  admirable  book.  Excellent  in  detail  and 
execution,  nothing  better  could  be  desired  by  the 
practitioner.  Dr.  Flint  enriches  his  subject  with 
much  solid  and  not  a  little  original  observation.— 
Ranking' s  Abstract,  Jan.  1867. 


gY  THE  SAME  AUTHOR. 

A  PRACTICAL  TREATISE    ON  PHTHISIS—  DIAGNOSIS,  PROG- 

NOSIS, AND  TREATMENT.     IN  A  SERIES  OF  CLINICAL  STUDIES.     A  new  work, 
in  preparation  for  early  publication.     In  one  handsome  octavo  volume. 
A  brief  table  of  contents  is  subjoined:  — 

CHAP.  I.   Morbid   Anatomy.     II.    Etiology.     III.    Symptomatic  Events  and  Complications. 
IV.  Fatality  and  Prognosis.     V.  Treatment.     VI.   Physical  Signs  and  Diagnosis. 

PULLER  (HENRY  WILLIAM],  M.  D., 

Physician  to  St.  George's  Hospital,  London. 

ON  DISEASES  OF  THE   LUNGS   AND   AIR-PASSAGES.     Their 

Pathology,  Physical  Diagnosis,  Symptoms,  and  Treatment.     From  the  second  and  revised 
English  edition.     In  one  handsome  octavo  volume  of  about  500  pages,  cloth,  $3  50. 


(c.  j.  B.}, 

Senior  Consulting  Physician  to  the  Hospital  for  Consumption,  Brompton,  and 

(CHARLES  T.},  M.D., 

Physician  to  the  Hospital  for  Consumption. 

PULMONARY  CONSUMPTION;  Its  Nature,  Yarieties,  and  Treat- 

ment.     With  an  Analysis  of  One  Thousand  Cases  to  exemplify  its  duration.     In  one  neat 
octavo  volume  of  about  350  pages,  cloth,  $250.      (Lately  Published.} 


He  can  still  speak  from  a  more  enormous  experi- 
ence, and  a  closer  study  of  the  morbid  processes  in- 
volved in  tuberculosis,  than  most  living  men.  He 
owed  it  to  himself,  and  to  the  importance  of  the  sub- 
ject, to  embody  his  views  in  a  separate  work,  and 
we  are  glad  that  he  has  accomplished  this  duty. 


After  all,  the  grand  teaching  which  Dr  Williams  has 
for  the  profession  is  to  be  found  in  his  therapeutical 
chapters,  and  in  the  history  of  individual  cases  ex- 
tended, by  dint  of  care,  over  ten,  twenty,  thirty,  and 
aven  forty  years.— London  Lancet,  Oct.  21, 1871. 


LA  ROCHE  ON  PNEUMONIA.     1  vol.  8vo.,  cloth, 

of  500  pages.     Price  $3  00. 
SMITH  ON  CONSUMPTION ;  ITS  EARLY  AND  RE- 

MEDIABLE  STAGES.     1  vol.  8vo.,  pp.  254.     $2  25. 


WALSHE  ON  THE  DISEASES  OF  THE  HEART  AND 
GREAT  VESSELS.  Third  American  edition.  In 
1  vol.  8vo.,  420  pp.,  cloth.  $3  00. 


FOX  ( WILSON),  M.D., 

•*-  Holme  Prof,  of  Clinical  Med.,  University  Coll.,  London. 

THE  DISEASES  OF  THE  STOMACH:  Being  the  Third  Edition  of 

the  "Diagnosis  and  Treatment  of  the  Varieties  of  Dyspepsia."     Revised  and  Enlarged. 
With  illustrations.     In  one  handsome  octavo  volume,  cloth,  $2  00.     (Now  Ready.) 
Dr.  Fox  has  put  forth  a  volume  of  uncommon  ex-  I  rank  among  works  that  treat  of  the  stomach.— Am- 
cellence,  which  we  feel  very  sure  will  take  a  high  |  Practitioner,  March,  1873. 


18 


HENRY  C.  LEA'S  PUBLICATIONS — (Practice  of  Medicine). 


•*-b 

A 


OBERTS  (  WILLIAM],  M.  D., 

Lecturer  on  Medicine  in  the  Manchester  School  of  Medicine,  &c. 

PRACTICAL  TREATISE    ON  URINARY  AND   RENAL   DIS- 

EASES, including  Urinary  Deposits.  Illustrated  by  numerous  cases  and  engravings.  Sec- 
ond American,  from  the  Second  Revised  and  Enlarged  London  Edition.  In  one  large 
and  handsome  octavo  volume  of  616  pages,  with  a  colored  plate  ;  cloth,  $4  50.  (Lately 
Published.) 

The  author  has  subjected  this  work  to  a  very  thorough  revision,  and  has  sought  to  embody  in 
it  the  results  of  the  latest  experience  and  investigations.  Although  every  effort  has  been  made 
to  keep  it  within  the  limits  of  its  former  size,  it  has  been  enlarged  by  a  hundred  pages,  many 
new  wood-cuts  have  been  introduced,  and  also  a  colored  plate  representing  the  appearance  of  the 
different  varieties  of  urine,  while  the  price  has  been  retained  at  the  former  very  moderate  rate. 

diseases  we  have  examined.    It  is  peculiarly  adapted 
to  the  wants  of  the  majority  of  American  practition- 


The plan,  it  will  thus  be  seen,  is  very  complete, 
and  the  manner  in  which  it  has  been  carried  out  is 
in  the  highest  degree  satisfactory.  The  character* 
of  the  different  deposits  are  very  well  described,  and 
the  microscopic  appearances  they  present  are  illus- 
trated by  numerous  well  executed  engravings.  It 
only  remains  to  us  to  strongly  recommend  to  our 
readers  Dr.  Roberts's  work,  as  containing  an  admira- 
ble r<'xum6  of  the  present  state  of  knowledge  of  uri- 
nary diseases,  and  as  a  safe  and  reliable  guide  to  the 
clinical  observer. — Edin.  Med.  Jour. 

The  most  complete  and  practical  treatise  upon  renal 


ers  from  its  clearness  and  simple  announcement  of  the 
facts  in  relation  to  diagnosis  and  treatment  of  urinary 
disorders,  and  contains  in  condensed  form  the  investi- 
gations of  Bence  Jones,  Bird,  Beale,  Hassall,  Prout, 
and  a  host  of  other  well-known  writers  upon  this  sub- 
ject. The  characters  of  urine,  physiological  and  pa- 
thological, as  indicated  to  the  naked  eye  as  well  as  by 
microscopical  and  chemical  investigations,  are  con- 
cisely represented  both  by  description  and  by  well 
executed  engravings. — Cincinnati  Journ.  of  Med. 


B 


ASSAM  (W.R.),  M.D., 

Senior  Physician  to  the  Westminster  Hospital,  &c. 

RENAL  DISEASES :  a  Clinical  Guide  to  their  Diagnosis  and  Treatment. 

With  illustrations.     In  one  neat  royal  12mo.  volume  of  304  pages,  cloth,  $2  00. 

ieUll*  of  larger  books  here  acquire  a  new  interest 
from  the  author's  arrangement.  This  part  of  the 
book  is  full  of  good  work. — Brit,  and  For.  Medico- 
Jhirurgival  Review,  July,  1870. 


The  chapters  on  diagnosis  and  treatment  are  very 
good,  and  the  student  and  young  practitioner  will 
find  them  full  of  valuable  practical  hints.  The  third 
part,  on  the  urine,  is  excellent,  and  we  cordially 
recommend  its  perusal.  The  author  has  arranged 
his  matter  in  a  somewhat  novel,  and,  we  think,  use- 
ful form.  Here  everything  can  be  easily  found,  and, 
what  is  more  important,  easily  read,  for  all  the  dry 


The  easy  descriptions  and  compact  modes  of  state- 
ment render  the  book  pleasing  and  convenient. — Am. 
Journ.  Med.  Sciences,  July,  1870. 


INCOLN  (D.  F.).  M.D., 

Physician  to  the  Department  of  Nervous  Diseases,  Boston  Dispensary. 

ELECTRO  THERAPEUTICS  ;  A.  Concise  Manual  of  Medical  Electri- 

city.     In  one  very  neat  royal  12mo.  volume,  cloth,  with  illustrations,  $1  50.      (Just  Ready.) 


The  work  is  convenient  in  size,  its  descriptions  of 
methods  and  appliances  are  sufficiently  complete  for 
the  general  practitioner,  and  the  chapters  on  Electro- 
physiology  and  diagnosis  are  well  written  and  read- 
able. For  those  who  wish  a  handy-book  of  directions 
for  the  employment  of  galvanism  in  medicine,  this 
will  serve  as  a  very  good  and  reliable  guide. — New 
Remedies,  Oct.  1874. 

It  is  a  well  written  work,  and  calculated  to  meet 
the  demands  of  the  busy  practitioner.  It  contains 
the  latest  researches  in  this  important  branch  of  med- 
icine.— Peninsular  Journ.  of  Med.,  Oct.  1874. 

Eminently  practical  in  character.  It  will  amply 
repay  any  one  for  a  careful  perusal. — Leavenworth 
Med.  Herald,  Oct.  1874. 


This  little  hook  is,  considering  its  size,  one  of  the 
very  best  of  the  English  treatises  on  its  subject  that 
has  come  to  our  notice,  possessing,  among  others,  the 
rare  merit  of  dealing  avowedly  and  actually  with 
principles,  mainly,  rather  than  with  practical  details, 
thereby  supplying  a  real  want,  instead  of  helping 
merely  to  flood  the  literary  market  Dr.  Lincoln's 
style  is  usually  remarkably  clear,  and  the  whole 
book  is  readable  and  interesting. — Boston  Med.  and 
Surg.  Journ.,  July  23,  1874. 

We  have  here  in  a  small  compass  a  great  deal  of 
valuable  information  upon  the  subject  of  Medical 
Electricity. — Canada  Med.  and  Surg.  Journ..  Nov. 
1874. 


TEE  (HENRY). 

Prof,  of  Surgery  at  the  Riyal  College  of  Surgeons  of  England,  etc. 

LECTURES  ON  SYPHILIS  AND  ON  SOME  FORMS  OF  LOCAL 

DISEASE  AFFECTING  PRINCIPALLY  THE  ORGANS  OF  GENERATION.     In  one 
handsome  octavo  volume. 

c  o  isr  T  IE  nxr  T  s . 

LECTURES  I.,  II.,  III.  General. — IV.  Treatment  of  Syphilis — V.  Treatment  of  Particular 
and  Modified  Syphilitic  Affections — VI.  Second  Stage  of  Lues  Venerea;  Treatment — VII.  Lo- 
cal Suppurating  Venereal  bore  ;  Syphilization  ;  Lymphatic  Absorption  ;  Physiological  Absorp- 
tion ;  Twofold  Inoculation — VIII.  Urethral  Discharges  :  different  kinds;  Treatment;  Conclu- 
sions of  Hunter  and  Ricord — IX.  Prostatic  Discharges — X.  Lymphatic  Absorption  continued  ; 
Local  Affections  ;  Warts  and  Excrescences. 


DIPHTHERIA  ;  its  Nature  and  Tr<>at  nent,  with  an 
account  of  the  History  of  its  Prevalence  in  vari- 
ous Countries.  By  D.  D.  SLADK,  M.D.  Second  and 
revised  edition.  In  one  neat  royal  12mo.  volume, 
cloth,  $1  25. 

LECTURES  ON  THE  STUDY  OF  FEVER.  By  A. 
HUDSON,  M.D.,  M.R.I.A.,  Physician  to  the  Meath 
Hospital.  In  one  vol.  8vo.,  cloth,  $2  50. 


A  TREATISE  ON  FEVER.  By  ROBERT  D.  LYONS, 
K  C  C.  In  one  octavo  volume  of  362  pages,  cloth, 
$2  25. 

CLINICAL  OBSERVATIONS  ON  FUNCTIONAL 
NERVOUS  DISORDERS  ByC.  HANDFIELD  JONKS, 
M.D.,  Physician  to  St.  Mary's  Hospital,  &c.  Sec- 
ond American  Edition.  In  one  handsome  octavo 
volume  of  348  pages,  cloth,  $3  25.  ; 


HENRY  C.  LEA'S  PUBLICATIONS — (  Venereal  Diseases,  etc.). 


19 


~DUMSTEAD  (FREEMAN  J.},  M.D., 

•*-*        Professor  of  Venereal  Diseases  at  the  Col.  of  Phys.  and  Surgr.,  New  York,  &c. 

THE  PATHOLOGY  AND  TREATMENT  OF  VENEREAL  DIS- 

EASES.  Including  the  results  of  recent  investigations  upon  the  subject.  Third  edition, 
revised  and  enlarged,  with  illustrations.  In  one  large  and  handsome  octavo  volume  of 
over  700  pages,  cloth,  $5  00  ;  leather,  $6  00. 

In  preparing  this  standard  work  again  for  the  press,  the  author  has  subjected  it  to  a  very 
thorough  revision.  Many  portions  have  been  rewritten,  and  much  new  matter  added,  in  order  to 
bring  it  completely  on  a  level  with  the  most  advanced  condition  of  syphilography,  but  by  careful 
compression  of  the  text  of  previous  editions,  the  work  has  been  increased  by  only  sixty-four  pages. 
The  labor  thus  bestowed  upon  it,  it  is  hoped,  will  insure  for  it  a  continuance  of  its  position  as  a 
complete  and  trustworthy  guide  for  the  practitioner. 

It  is  the  most  complete  book  with  which  we  are  ac- 
quainted in  the  language.  The  latest  views  of  the 
best  authorities  are  put  forward,  and  the  information 
IR  well  arranged — a  great  point  for  the  student,  and 


more  for  the  pi-actitioner.  The  subjects  of  vis- 
C' -val  syphilis,  syphilitic  affections  of  the  eyes,  and 
t '•!'.:  treatment  of  syphi/is  by  repeated inoculat'ons,  are 
very  fully  discussed. — London  Lancet,  Jan.  7,  1871. 

Dr.  Bumstead's  work  is  already  so  universally 
known  as  the  best  treatise  in  the  English  language  on 
venereal  diseases,  that  it  may  seem  almost  superflu- 
ous to  say  more  of  it  than  that  a  new  edition  has  been 
Issued.  But  the  author's  industry  has  rendered  this 
new  edition  virtually  a  new  work,  and  so  merits  as 


much  special  commendation  as  if  its  predecessors  had 
not  been  published.  As  a  thoroughly  practical  book 
on  a  class  of  diseases  which  form  a  large  share  of 
nearly  every  physician's  practice,  the  volume  before 
us  is  by  far  the  best  of  which  we  have  knowledge. — 


N.  Y.  Medical  Gazette,  Jan.  28,  1871. 

It  is  rare  in  the  history  of  medicine  to  find  any  one 
book  which  contains  all  that  a  practitioner  needs  to 
know;  while  the  possessor  of  "Bumstead  on  Vene- 
real" has  no  occasion  to  look  outside  of  its  covers  for 
anything  practical  connected  with  (he  diagnosis,  his- 
tory, or  treatment  of  these  affections.—  N.  Y.  Medical 
Journal,  March,  1871. 


rtULLERIER  (A.},  and 

*~S        Surgeon  to  the  Hdpital  du  Midi. 


ftUMSTEAD  (FREEMAN  J.}, 

•*-*       Professor  of  Venerea  I  Diseases  in  the  College  of 
Physicians  and  Surgeons,  N.  Y. 

AN  ATLAS  OF  VENEREAL  DISEASES.     Translated  and  Edited  by 

FREEMAN  J.  BUMSTEAD.  In  one  large  imperial  4to.  volume  of  328  pages,  double-columns, 
with  26  plates,  containing  about  150  figures,  beautifully  colored,  many  of  them  the  size  of 
life;  strongly  bound  in  cloth,  $17  00  ;  also,  in  five  parts,  stout  wrappers  for  mailing,  at  $3 
per  part. 

Anticipating  a  very  large  sale  for  this  work,  it  is  offered  at  the  very  low  price  of  THREE  DOL- 
LARS a  Part,  thus  placing  it  within  the  reach  of  all  who  are  interested  in  this  department  of  prac- 
tice.    Gentlemen  desiring  early  impressions  of  the  plates  would  do  well  to  order  it  without  delay. 
A  specimen  of  the  plates  and  text  sent  free  by  mail,  on  receipt  of  25  cents. 

which  for  its  kind  is  more  necessary  for  them  to  have. 
-California  Med.  Gazette,  March,  1869. 

The  most  splendidly  illustrated  work  in  the  lan- 
guage, and  in  our  opinion  far  more  useful  than  the 
French  original. — Am.  Journ.  Med.  Sciences,  Jan. '69. 

The  fifth  and  concluding  number  of  this  magnificent 
work  has  reached  us,  and  we  have  no  hesitation  in 
saying  that  its  illustrations  surpass  those  of  previous 
numbers. — Boston  Med.  and  Surg.  Journal,  Jan.  14, 
1869. 

Other  writers  besides  M.  Cullerier  have  given  us  a 
good  account  of  the  diseases  of  which  he  treats,  but 
no  one  has  furnished  us  with  such  a  complete  series 
of  illustrations  of  the  venereal  diseases.  There  is, 
however,  an  additional  interest  and  value  possessed 
by  the  volume  before  us  ;  for  it  is  an  American  reprint 
and  translation  of  M.  Cullerier's  work,  with  inci- 
dental remarks  by  one  of  the  most  eminent  American 
syphilographers,  Mr.  Bumstead.  —  Brit,  and  For. 
Medico-Chir.  Review,  July,  1869. 


We  wish  for  once  that  our  province  was  not  restrict- 
•d  to  methods  of  treatment,  that  we  might  say  some- 
thing of  the  exquisite  colored  plates  in  this  volume. 
—London  Practitioner,  May,  1869. 

As  a  whole,  it  teaches  all  that  can  be  taught  by 
means  of  plates  and  print. — London  Lancet,  March 
13,  186S. 

Superior  to  anything  of  the  kind  ever  before  issued 
on  this  continent. — Canada  Med.  Journal,  March,  '69. 

The  practitioner  who  desires  to  understand  this 
branch  of  medicine  thoroughly  should  obtain  this, 
the  most  complete  and  best  work  ever  published. — 
Dominion  Med.  Journal,  May,  1869. 

This  is  a  work  of  master  hands  on  both  sides.  M. 
CuHerier  is  scarcely  second  to,  we  think  we  may  truly 
«ay  is  a  peer  of  the  illustrious  and  venerable  Ricord, 
frVnle  in  this  country  we  do  not  hesitate  to  say  that 
Dr.  Bumstead,  as  an  authority,  is  without  a  rival 
A..SUI ing  our  readers  that  these  illustrations  tell  the 
•wholo  history  of  venereal  disease,  from  its  inception 
to  its  end,  we  do  not  know  a  single  medical  work, 


(BERKELEY], 

Surgeon  to  the  Lock  Hospital,  London. 

ON  SYPHILIS  AND  LOCAL 

one  handsome  octavo  volume  ;  cloth,  $3 
Bringing,  as  it  does,  the  entire  literature  of  the  dis- 
ease down  to  the  present  day,  and  giving  with  great 
ability  the  results  of  modern  research,  it  is  in  every 
respect  a  most  desirable  work,  and  one  which  should 
find  a  place  in  the  library  of  every  surgeon. — Cali- 
fornia Med.  Gazette,  June,  1869. 

Considering  the  scope  of  the  book  and  the  careful 
attention  to  the  manifold  aspects  and  details  of  its 
subject,  it  is  wonderfully  concise.  All  these  qualities 
render  it  an  especially  valuable  book  to  the  beginner, 


CONTAGIOUS  DISORDERS.    In 

25. 

to  whom  we  would  most  earnestly  recommend  its 
study  ;  while  it  is  no  less  useful  to  the  practitioner.— 
St.  Louis  Med.  and  Surg.  Journal,  May,  1869. 

The  most  convenient  and  ready  book  of  i-eference 
we  have  met  with.— A1'.  Y.  Med.  Record,  May  1,1869. 

Most  admirably  arranged  for  both  student  and  prac- 
titioner, no  other  work  on  the  subject  equals  it ;  it  i» 
more  simple,  more  easily  studied. — Buffalo  Med.  and 
Surg.  Journal,  March,  1869. 


M.D. 


A  COMPLETE  TREATISE  ON  VENEREAL  DISEASES.    Trans- 

lated from  the  Second  Enlarged  German  Edition,  by  FREDERIC  R.  STURGIS,  M.D     In  one 
octavo  volume,  with  illustrations.     (Preparing.) 


HENRY  C.  LEA'S  PUBLICATIONS — (Diseases  of  the  Skin). 


WILSON  (ERASMUS),  F.R.S. 

ON  DISEASES  OF  THE  SKIN.     With  Illustrations  on  wood.    Sev- 

enth  American,  from  the  s\xth  and  enlarged  English  edition.     In  one  large  octavo  volume 
of  over  800  pages,  $5. 

A  SERIES  OF  PLATES  ILLUSTRATING  "WILSON  ON  DIS- 
EASES OF  THE  SKIN;"  consisting  of  twenty  beautifully  executed  plates,  of  which  thir- 
teen are  exquisitely  colored,  presenting  the  Normal  Anatomy  and  Pathology  of  the  Skin, 
and  embracing  accurate  representations  of  about  one  hundred  varieties  of  disease,  most  of 
them  the  size  of  nature.  Price,  in  extra  cloth,  $5  50. 

Also,  the  Text  and  Plates,  bound  in  one  handsome  volume.     Cloth,  $10. 


No  one  treating  skin  diseases  should  be  without 
a  copy  of  this  standard  work. — Canada  Lancet. 

We  can  safely  recommend  it  to  the  profession  at 
the  best  work  on  the  subject  now  in  existence  ir 
the  English  language. — Medical  Times  and  Gazette 

Mr.  Wilson's  volume  is  an  excellent  digest  of  the 
actual  amount  of  knowledge  of  cutaneous  diseases  : 
it  includes  almost  every  fact  or  opinion  of  importanc€ 
connected  with  the  anatomy  and  pathology  of  the 
skin. — British  and  Foreign  Medical  Review. 

Such  a  work  as  the  one  before  us  is  a  most  capital 


ind  acceptable  help.  Mr.  Wilson  has  long  been  held 
is  high  authority  in  this  department  of  medicine,  and 
his  book  on  diseases  of  the  skin  has  long  been  re- 
jarded  as  one  of  the  best  text-books  extant  on  the 
subject.  The  present  edition  is  carefully  prepared, 
ind  brought  up  in  its  revision  to  the  present  time.  In 
his  edition  we  have  also  included  the  beautiful  series 
of  plates:  illustrative  of  the  text,  and  in  the  last  edi- 
tion published  separately.  There  are  twenty  of  these 
plates,  nearly  all  of  them  colored  to  nature,  and  ex- 
hibiting with  great  fidelity  the  various  groups  of 
diseases. — Cincinnati  Lancet. 


F  THE  SAME  AUTHOR.  

THE  STUDENT'S  BOOK  OF  CUTANEOUS 

EASES  OP  THE  SKIN. 


MEDICINE  and  Dis- 

In  one  very  handsome  royal  12mo.  volume.   $3  50. 


TtfELIGAN  (J.MOORE},  M.D.,  M.R.I. A. 

A    PRACTICAL    TREATISE    ON    DISEASES    OF    THE    SKIN. 

Fifth  American,  from  the  second  and  enlarged  Dublin  edition  by  T.  W.  Belcher,  M.B. 
In  one  neat  royal  12mo.  volume  of  462  pages,  cloth,  $2  25. 


Fully  equal  to  all  the  requirements  of  students  and 
young  practitioners. — Dublin  Med.  Press. 

Of  the  remainder  of  the  work  we  have  nothing  be- 
yond unqualified  commendation  to  offer.  It  is  so  far 
the  most  complete  one  of  its  size  that  has  appeared, 
and  for  the  student  there  can  be  none  which  can  com- 
pare with  it  in  practical  value.  All  the  late  disco- 
veries in  Dermatology  have  been  duly  noticed,  and 
Y  THE  SAME  AUTHOR. 


their  value  justly  estimated;  in  a  word,  the  work  is 
fully  up  to  the  times,  and  is  thoroughly  stocked  with 
most  valuable  information. — New  York  Med.  Record, 
Jan.  15,  1867. 

The  most  convenient  manual  of  diseases  of  the 
skin  that  can  be  procured  by  the  student. — Chicago 
Med.  Journal,  Dec.  1866. 


ATLAS   OF   CUTANEOUS   DISEASES.     In  one  beautiful   quarto 

volume,  with  exquisitely  colored  plates,  &c.,  presenting  about  one  hundred  varieties  of 
disease.     Cloth,  $5  50. 

The  diagnosis  of  eruptive  disease,  however,  under  I  inclined  to  consider  it  a  very  superior  work,  corn- 
all  circumstances,  is   very  difficult.     Nevertheless,  |  bining  accurate  verbal  description  with  sound  view* 


Dr.  Neligau  has  certainly,  "as  far  as  possible,"  given 
a  faithful  and  accurate  representation  of  this  class  of 
diseases,  and  there  can  be  no  doubt  that  these  plates 
will  be  of  great  use  to  the  student  and  practitioner  in 
drawing  a  diagnosis  as  to  the  class,  order,  and  species 
to  which  the  particular  case  may  belong.  While 


looking  over  the 
examine  also  the 


Atlas"  we  have  been  induced  to 
'Practical  Treatise,"  and  we  are 


of  the  pathology  and  treatment  of  eruptive  diseases. 
—  Glasgow  Med.  Journal. 

A  compend  which  will  very  much  aid  the  practi- 
tioner in  this  difficult  branch  of  diagnosis.  Taken 
with  the  beautiful  plates  of  the  Atlas,  which  are  re- 
markable for  their  accuracy  and  beauty  of  coloring, 
it  constitutes  a  very  valuable  addition  to  the  library 
of  a  practical  man. — Buffalo  Med.  Journal. 


pflLLIER  (THOMAS],  M.D., 

Physician  to  the  Skin  Department  of  University  College  Hospital,  &c . 

HAND-BOOK  OF  SKIN  DISEASES,  for  Students  and  Practitioners. 

Second  American  Edition.     In  one  royal  12mo.  volume  of  358  pp.     With  Illustrations. 
Cloth,  $2  25. 


We  can  conscientiously  recommend  it  to  the  stu- 
dent; the  style  is  clear  and  pleasant  to  read,  the 
matter  is  good,  and  the  descriptions  of  disease,  with 
the  modes  of  treatment  recommended,  are  frequently 
illustrated  with  well-recorded  cases. — London  Med. 
Times  and  Gazette,  April  1,  1865. 


It  is  a  concise,  plain,  practical  treatise  on  the  vari- 
ous diseases  of  the  skin  ;  just  such  a  work,  indeed, 
as  was  much  needed,  both  by  medical  students  and 
practitioners.  —  Chicago  Medical  Examiner,  May, 
1865. 


A  NDERSON  (McCALL],  M.D., 

•^*~  Physician  to  the  Dispensary  for  Skin  Diseases,  Glasgow,  &c. 

ON  THE  TREATMENT  OF  DISEASES  OF  THE  SKIN.     With  an 

Analysis  of  Eleven  Thousand  Consecutive  Cases.  In  one  vol.  8vo.   $1.   (Lately  Published.) 

GUERSANT'S  SURGICAL  DISEASES  OF  INFANTS  I  DT5WEES  ON  THE  PHYSICAL  AND  MEDICAL 
AND  CHILDREN.  Translated  by  R.  J.  DUNGLI-  TREATMENT  OF  CHILDREN.  El  wventh  edition. 
BOX,  M.D.  1  vol.  8vo.  Cloth,  $2  50.  1  TO!.  8vo.  of  548  pages.  Cloth,  $2  80. 


HENRY  C.  LEA'S  PUBLICATIONS — (Diseases  of  Children).  21 

GMITH(J.  LEWIS],  M.  D., 

O  Professor  of  Morbid  Anatomy  in  the  Bellevue  Hospital  Med.  College,  N.  T. 

A  COMPLETE  PRACTICAL  TREATISE  ON  THE  DISEASES  OP 

CHILDREN.     Second  Edition,  revised  and  greatly  enlarged.     In  one  handsome  octavo 
volume  of  742  pages,  cloth,  $5;  leather,  $6.     (Lately  Published.) 
FROM  THE  PREFACE  TO  THE  SECOND  EDITION. 

In  presenting  to  the  profession  the  second  edition  of  his  work,  the  author  gratefully  acknow- 
ledges the  favorable  reception  accorded  to  the  first.  He  has  endeavored  to  merit  a  continuance 
of  this  approbation  by  rendering  the  volume  much  more  complete  than  before.  Nearly  twenty 
additional  diseases  have  been  treated  of,  among  which  may  be  named  Diseases  Incidental  to 
Birth  Rachitis,  Tuberculosis,  Scrofula,  Intermittent,  Remittent,  and  Typhoid  Fevers,  Chorea, 
and  the  various  forms  of  Paralysis.  Many  new  formulae,  which  experience  has  shown  to  be 
useful,  have  been  introduced,  portions  of  the  text  of  a  less  practical  nature  have  been  con- 
densed, and  other  portions,  especially  those  relating  to  pathological  histology,  have  been 
rewritten  to  correspond  with  recent  discoveries.  Every  effort  has  been  made,  however,  to  avoid 
an  undue  enlargement  of  the  volume,  but,  notwithstanding  this,  and  an  increase  in  the  size  of 
the  page,  the  number  of  pages  has  been  enlarged  by  more  than  one  hundred. 

227  WEST  49TH  STREET,  NEW  YORK,  April,  1872. 

The  work  will  be  found  to  contain  nearly  one-third  more  matter  than  the  previous  edition,  and 
It  is  confidently  presented  as  in  every  respect  worthy  to  be  received  as  the  standard  American 
text-book  on  the  subject. 

Eminently  practical  as  well  as  judicious  in  its 
teachings.— Cincinnati  Lancet  and  Obs.,  July,  1S72. 

A  standard  work  that  leaves  little  to  be  desired.— 
Indiana  Journal  of  Medicine,  July,  1872. 

We  know  of  no  book  on  this  subject  that  we  can 
more  cordially  recommend  to  the  medical  student 
and  the  practitioner. — Cincinnati  Clinic,  June  29,  '72. 


We  regard  it  as  superior  to  any  other  single  work 
on  the  diseases  of  infancy  and  childhood. — Detroit 
Rev.  of  Med.  and  Pharmacy,  Aug.  1872. 

We  confess  to  increased  enthusiasm  in  recommend- 
ing this  second  edition.—  St.  Louis  Med.  and  Surg. 
Journal,  Aug.  1872. 


rtONDIE  (D.  FRANCIS),  M.D. 

A  PRACTICAL  TREATISE  ON  THE  DISEASES  OF  CHILDREN. 

Sixth  edition,  revised  and  augmented.     In  one  large  octavo  volume  of  nearly  800  closely- 
printed  pages,  cloth,  $5  25  ;  leather,  $6  25. 


The  present  edition,  which  is  the  sixth,  is  fully  up 
to  the  times  in  the  discussion  of  all  those  points  in  the 
pathology  and  treatment  of  infantile  diseases  which 
kave  been  brought  forward  by  the  Germa  u  and  French 


teachers.  As  a  whole,  however,  the  work  is  the  best 
American  one  that  we  have,  and  in  its  special  adapta- 
tion to  American  practitioners  it  certainly  has  no 
equal.—  New  York  Med.  Record,  Marci  2,  1868. 


TXTEST  (CHARLES],  M.D., 

Physician  to  the  Hospital  for  Sick  Children,  &c. 

LECTURES  ON   THE   DISEASES   OP   INFANCY  AND  CHILD- 
HOOD.    Fifth  American  from  the  sixth  revised  and  enlarged  English  edition.     In  one  large 
and  handsome  octavo  volume  of  678  pages.     Cloth,  $4  50  ;  leather,  $5  50.     (Just  Issued.) 
The  continued  demand  for  this  work  on  both  sides  of  the  Atlantic,  and  its  translation  into  Ger- 
man, French,  Italian,  Danish,  Dutch,  and  Russian,  show  that  it  fills  satisfactorily  a  want  exten- 
sively felt  by  the  profession.     There  is  probably  no  man  living  who  can  speak  with  the  authority 
derived  from  a  more  extended  experience  than  Dr.  West,  and  his  work  now  presents  the  results  of 
nearly  2000  recorded  cases,  and  600  post-mortem  examinations  selected  from  a.mong  nearly  40,000 
cases  which  have  passed  under  bis  care.     In  the  preparation  of  the  present  edition  he  has  omitted 
much  that  appeared  of  minor  importance,  in  order  to  find  room  for  the  introduction  of  additional 
matter,  and  the  volume,  while  thoroughly  revised,  is  therefore  not  increased  materially  in  size. 

Of  all  the  English  writers  on  the  diseases  of  chil-  I  living  authorities  in  the  difficult  department  of  medi- 
dren,  there  is  no  one  so  entirely  satisfactory  to  us  as  |  cal  science  in  which  he  is   most  widely  known. — 
Dr.  West.    For  years  we  have  held  his  opinion  as  I  Boston  Med.  and  Surg.  Journal. 
judicial,  and  have  regarded  him  as  one  of  the  highest  | 


DF  THE  SAME  AUTHOR.    (Lately Issued.) 

ON  SOME  DISORDERS  OF  THE  NERVOUS  SYSTEM  IN  CHILD- 

HOOD;  being  the  Lumleian  Lectures  delivered  at  the  Royal  College  of  Physicians  of  Lon- 
don, in  March,  1871.     In  one  volume,  small  12mo.,  cloth,  $1  00. 

J3MITH  (E USTA  CE),  M.  D^~ 

Physician  to  the  Northwest  London  Free  Dispensary  for  Sick  Children. 

A  PRACTICAL  TREATISE  ON   THE  WASTING   DISEASES  OF 

INFANCY  AND  CHILDHOOD.     Second  American,  from  the  second  revised  and  enlarged 
English  edition.     In  one  handsome  octavo  volume,  cloth,  $2  50.     (Lately  Issued.) 


This  is  in  every  way  an  admirable  book.  The 
modest  title  which  the  author  has  chosen  for  it  scarce- 
ly conveys  an  adequate  idea  of  the  many  subjects 
upon  which  it  treats.  Wasting  is  so  constant  an  at- 
tendant upon  the  maladies  of  childhood,  that  a  trea- 
tise upon  the  wasting  diseasesof  childrenmust  neces 
garily  embrace  the  consideration  of  many  affections 
of  which  it  is  a  symptom  ;  and  this  is  excellently  well 
done  by  Dr.  Smith.  The  book  might  fairly  be  de- 


scribed as  a  practical  handbook  of  the  common  dis- 
eases of  children,  so  numerous  are  the  affections  con- 
sidered either  collaterally  or  directly.  We  are 
acquainted  with  no  safer  guide  to  the  treatment  of 
children's  diseases,  and  few  works  give  the  insight 
into  the  physiological  and  other  peculiarities  of  chil- 
dren that  Dr.  Smith's  book  does.— Brit.  Med.  Journ., 
April  8,  1871. 


22 


HENRY  C.  LEA'S  PUBLICATIONS — (Diseases  of  Women). 


mRE  OBSTETRICAL  JOURNAL.     (Free  of  postage  for  1875.) 

THE    OBSTETRICAL   JOURNAL   of  Great   Britain   and  Ireland; 

Including  MIDWIFERY,  and  the  DISEASES  OF  WOMEN  AND  INFANTS.  With  an  American 
Supplement,  edited  by  WILLIAM  F.  JENKS,  M.D.  A  monthly  of  about  80  octavo  pages, 
very  handsomely  printed.  Subscription,  Five  Dollars  per  annum.  Single  Numbers,  50 
cents  each. 

Commencing  with  April,  1873,  the  Obstetrical  Journal  consists  of  Original  Papers  by  Brit- 
ish and  Foreign  Contributors  ;  Transactions  of  the  Obstetrical  Societies  in  England  and  abroad  ; 
Reports  of  Hospital  Practice;  Reviews  and  Bibliographical  Notices;  Articles  and  Notes,  Edito- 
rial, Historical,  Forensic,  and  Miscellaneous;  Selections  from  Journals;  Correspondence,  Ac. 
Collecting  together  the  vast  amount  of  material  daily  accumulating  in  this  important  and  ra- 
pidly improving  department  of  medical  science,  the  value  of  the  information  which  it  pre- 
sents to  the  subscriber  may  be  estimated  from  the  character  of  the  gentlemen  who  have  already 
promised  their  support,  including  such  names  as  those  of  Drs.  ATTHILL,  ROBERT  BARNES,  HENRY 
BENNET,  THOI^AS  CHAMBERS,  FLEETWOOD  CHURCHILL,  MATTHEWS  DUNCAN,  GRAILY  HEWITT, 
BRAXTON  HICKS,  ALFRED  MEADOWS,  W.  LEISHMAN,  ALEX.  SIMPSON,  TYLER  SMITH,  EDWARD  J. 
TILT,  SPENCER  WELLS,  &c.  <fcc. ;  in  short,  the  representative  men  of  British  Obstetrics  and  Gynae- 
cology. 

In  order  to  render  the  OBSTETRICAL  JOURNAL  fully  adequate  to  the  wants  of  the  American 
profession,  each  number  contains  a  Supplement  devoted  to  the  advances  made  in  Obstetrics  and 
Gynaecology  on  this  side  of  the  Atlantic.  This  portion  of  the  Journal  is  under  the  editorial 
charge  of  Dr.  WILLIAM  F.  JENKS,  to  whom  editorial  communications,  exchanges,  books  for  re- 
view, Ac.,  may  be  addressed,  to  the  care  of  the  publisher. 

**.*  Complete  sets  from  the  beginning  can  no  longer  be  furnished,  but  subscriptions  can  com- 
mence with  January,  1875,  or  with  Vol.  II.,  April,  1874. 


fTHOMAS  (T.  GAILLARD),M.J)., 

Professor  of  Obstetrics,  &c.,  in  the  College  of  Physicians  and  Surgeons,  N.  T.,  &c. 

A  PRACTICAL  TREATISE  ON  THE  DISEASES  OF  WOMEN.   Fourth 

edition,  enlarged  and  thoroughly  revised.     In  one  large  and  handsome  octavo  volume  of 
800  pages,  with  191  illustrations.     Cloth,  $5  00;  leather,  $6  00.      (Now  Ready.) 
The  author  has  taken  advantage  of  the  opportunity  afforded  by  the  call  for  another  edition  of 
this  work  to  render  it  worthy  a  continuance  of  the  very  remarkable  favor  with  which  it  has  been 
received.     Every  portion  has  been  subjected  to  a  conscientious  revision,  and  no  labor  has  been 
spared  to  make  it  a  complete  treatise  on  the  most  advanced  condition  of  its  important  subject. 

A  few  notices  of  the  previous  editions  are  subjoined  : — 

No  general  practitioner  can  afford  to  be  without 
it.—  St.  Louis  Mud.  and  Surg.  Journal,  May,  1872. 


Professor  Thomas  fairly  took  the  Profession  of  the 
United  States  by  storm  when  his  book  first  made  its 
appearance  early  in  IS'.iS.  Its  reception  was  simply 
enthusiastic,  notwithstanding  a  few  adverse  criti- 
cisms from  our  transatlantic  brethren,  the  first  large 
edition  was  rapidly  exhausted,  and  in  six  mouths  a 
second  one  was  issued,  and  in  two  years  a  third  one 
was  announced  and  published,  and  we  are  now  pro- 
mised the  fourth.  The  popularity  of  this  work  was 
not  ephemeral,  and  its  success  was  unprecedented  in 
the  annals  of  American  medical  literature.  Six  years 
is  a  long  period  in  medical  scientific  research,  but 
Thomas's  work  on  "Diseases  of  Women"  is  still  the 
leading  native  production  of  the  United  States.  The 
order,  the  matter,  the  absence  of  theoretical  disputa- 
tU-eness,  the  fairness  of  statement,  and  the  elegance 
of  diction,  preserved  throughout  the  entire  range  of 
the  book,  indicate  that  Professor  Thomas  did  not 
overestimate  his  powers  when  he  conceived  the  idea 
and  executed  the  work  of  producing  a  new  treatise 
upon  diseases  of  women. — PROF.  PALLEX,  in  Louis- 
mile  Med.  Journal,  Sept.  1874. 

Briefly,  we  may  say  that  we  know  of  no  book 
which  so  completely  and  concisely  represents  the 
present  state  of  gynaecology;  none  so  full  of  well- 
digested  and  reliable  teaching  ;  none  which  bespeaks 
an  author  more  apt  in  research  and  abundant  in  re- 
sources.— N.  Y.  Med.  Record,  May  1,  1872. 


Its  able  author  need  not  fear  comparison  between 
it  and  any  similar  work  in  tlie  English  language; 
nay  more,  as  a  text-hoek  for  students  and  as  a  guide 
for  practitioners,  we  believe  it  is  unequalled.  If 
either  student  or  practitioner  can  get  but  ^ne  book 
on  diseasesof  women, that  hook  should  be  "Thomas." 
—Amer.  Jour.  Med.  Sciences,  April,  '  872 

To  students  we  unhesitatingly  recommend  it  as 
the  best  text-book  on  diseases  of  females  extant.— 
Sf.  Louis  Med.  Reporter,  June,  1869. 

Of  all  the  army  of  books  that  nave  appeared  of  late 
years, on  the  diseases  of  the  uterus  and  its  appendages, 
we  know  of  none  that  is  so  clear,  comprehensive,  and 
practical  as  this  of  Dr.  Thomas',  or  one  that  we  should 
more  emphatically  recommend  to  the  young  practi- 
tioner, as  his  guide.— California  Med.  Gazette)  June, 
1869. 

It  would  he  superfluous  to  give  an  extended  review 
of  what  is  now  firmly  established  as  the  American 
text-hook  of  Gynaecology.— N.  Y.  Med.  Gazette,  July 
17,  1869. 

This  is  a  new  and  revised  edition  of  a  work  which 
we  recently  noticed  at  some  length,  and  earnestly 


We  shou.d  not  be  doing  onr  duty  to  the  profession  i  g^****  *'  tt^on  "pace""?  tT^'K. 


r^n-er^^^ 

^0?e^^^ 

__i :»„!.:„„: ,  „  „„  j ;  „  „  r»r.   Th/\ma  c'o  •nr^flr  u  ,s   I    LanCet,  AUK.   1OD9. 


no  hesitation  in  recommending  Dr.  Thomas's  work  as 
one  of  the  most  complete  of  its  kind  ever  published. 
It  should  be  in  the  possession  of  every  practitioner 
for  reference  and  for  study.— London  Lancet,  April 
27,  1872. 

We  are  free  to  say  that  we  regard  Dr.  Thomas  the 
best  American  authority  on  diseases  of  women. — 
Cincinnati  Lancet  and' Observer,  May,  1S72. 


Lancet,  Aug. 

It  is  so  short  a  time  since  we  gave  a  full  review  of 
the  first  edition  of  this  book,  that  we  deem  it  only 
necessary  now  to  call  attention  to  the  second  appear- 
ance of  the  work.  Its  success  has  been  remarkable, 
and  we  can  only  congratulate  the  author  on  the 
brilliant  reception  his  book  has  received.—/?".  Y.-Med. 
Journal,  April,  1869. 


HENRY  C.  LEA'S  PUBLICATIONS — (Diseases  of  Women). 


TTODGE  (HUGH  Z/.),  M.D., 

•O-  Emeritus  Professor  of  Obstetrics,  Ac.,  in  the  University  of  Pennsylvania. 

ON  DISEASES  PECULIAR  TO  WOMEN;  including  Displacements 

of  the  Uterus.     With  original  illustrations.     Second  edition,  revised  and  enlarged.     ID 
one  beautifully  printed  octavo  volume  of  531  pages,  cloth,  $4  50. 


From  PROF.  W.  H.  BTPORD,  of  the  Riish  Medical 
College,  Chicago. 

The  book  bears  the  impress  of  a  master  hand,  and 
must,  as  its  predecessor,  prove  acceptable  to  the  pro- 
fession. In  diseases  of  women  Dr.  Hodge  has  estab- 
lished a  school  of  treatment  that  has  become  world- 
wide in  fame. 

Professor  Hodge's  work  is  truly  an  original  one 
from  beginning  to  end,  consequently  no  one  can  pe- 
ruse its  pages  without  learning  something  new.  The 
book,  which  is  by  no  means  a  large  oue,  is  divided  into 
two  grand  sections,  so  to  speak  :  first,  that  treating  of 
the  nervous  sympathies  of  the  uterus,  and,  secondly, 


chat  which  speaks  of  the  mechanical  treatment  of  dis- 
placements of  that  organ.  He  is  disposed,  as  a  non- 
Seliever  In  the  frequency  of  inflammations  of  the 
uterus,  to  take  strong  ground  against  many  of  the 
highest  authorities  iu  this  branch  of  medicine,  and 
the  arguments  which  he  offers  in  support  of  his  posi- 
tion are.  to  say  the  least,  well  put.  Numerous  wood- 
cuts adorn  this  portion  of  the  work,  and  add  incalcu- 
lably to  the  proper  appreciation  of  the  variously 
shaped  instruments  referred  to  by  our  author.  As  s 
contribution  to  the  study  of  women's  diseases,  it  i«  o* 
great  value,  and  is  abundantly  able  to  stand  on  its 
own  merits.— .V.  Y.  Medical  Record,  Sept.  15,  1868. 


W 


•EST  (CHARLES),  M.D. 

LECTURES  ON  THE  DISEASES  OF  WOMEN.    Third  American, 

from  the  Third  London  edition.     In  one  neat  octavo  volume  of  about  550  pages,  cloth, 
$3  75  ;  leather,  $4  75. 

seeking  truth,  and  one  that 


As  a  writer.  Dr.  West  stands,  in  our  opinion,  se- 
eoud  only  to  Watson,  the  "Macaulay  of  Medicine;' 
he  possesses  that  happy  faculty  of  clothing  instruc- 
tion in  easy  garments ;  combining  pleasure  with 
profit,  he  leads  his  pupils,  in  spite  of  the  ancient  pro- 
verb, along  a  royal  road  to  learning.  His  work  is  one 
which  will  not  satisfy  the  extreme  on  either  side,  but 
It  is  one  that  will  please  the  great  majority  wko  are 


0 , ill  convince  the  student 

that  he  has  committed  himself  to  a  candid,  safe,  and 
valuable  guide.— jr.  A.  Med.-Chirurg  Review. 

We  have  to  say  of  it,  briefly  and  decidedly,  that  it 
is  the  best  work  on  the  subject  in  any  language,  and 
that  it  stamps  Dr.  West  as  the  facile  princeps  of 
British  obstetric  authors.— Edinburgh  Med. 


PARNES  (ROBERT],  M.D.,  F.R.  C.P., 

•*-*  Obstetric  Physician  to  St.  Thomas'*  Hospital,  Ac. 

A  CLINICAL  EXPOSITION  OF  THE  MEDICAL  AND  SURGI- 
CAL DISEASES  OF  WOMEN.  In  or,«  hnmlsome  octavo  volume  of  about  800  pages,  with 
169  illustrations.  Cloth,  $5  00,  leather,  $6  00.  (Just  Issued.} 

The  very  complete  scope  of  this  volume  and  the  manner  in  which  it  has  been  filled  out,  may 
be  seen  by  the  subjoined  Summary  of  Contents. 

INTRODUCTION.  CHAPTER  I.  Ovaries  ;  Corpus  Luteum.  II.  Fallopinn  Tubes.  III.  Shape  of 
Uterine  Cavity.  IV.  Structure  of  Uterus.  V.  The  Vagina.  VI.  Examinations  and  Diagnosis. 
VII.  Significance  of  Leucorrhoea.  VIII.  Discharges  of  Air.  IX.  Watery  Discharges.  X.  Puru- 
lent Discharges.  XI.  Hemorrhagic  Discharges.  XII  Significance  of  Pain.  XIII.  Significance 
of  Dyspareunia.  XIV.  Significance  of  Sterility.  XV.  Instrumental  Diagnosis  and  Treatment. 
XVI.  Diagnosis  by  the  Touch,  the  Sound,  the' Speculum.  XVII.  Menstruation  and  its  Disor- 
ders. XVIII.  Amenorrhcea.  XIX.  Amenorrhcea  (continued).  XX.  Dysuienorrhoea.  XXI. 
Ovarian  Dysmenorrhoea,  Ac.  XXII.  Inflammatory  Dysmenorrhoea.  XXIII.  Irregularities  of 
Change  of  Life.  XXIV.  Relations  between  Menstruation  and  Diseases.  XXV.  Disorders  of  Old 
Age.  XXVI.  Ovary,  Absence  and  Hernia  of.  XXVII.  Ovary,  Hemorrhage,  Ac.,  of.  XXVIII. 
Ovary,  Tubercle,  Cancer,  Ac.,  of.  XXIX.  Ovarian  Cystic  Tumors.  XXX.  Dermoid  Cvsts  of 
Ovary.  XXXI.  Ovarian  Tumors,  Prognosis  of.  XXXII.  Diagnosis  of  Ovarian  Tumors.  XXXIII. 
Ovarian  Cysts,  Treatment  of.  XXXIV.  Fallopian  Tubes.  Diseases  of.  XXXV.  Broad  Liga- 
ments, Diseases  of.  XXXVI.  Extra-uterine  Gestation.  XXXVII.  Special  Pathology  of  Ute 
rus.  XXXVIII.  General  Uterine  Pathology.  XXXIX.  Alterations  of  Blood  Supply.  XL. 
Metritis,  Endometritis,  Ac.  XLI.  Pelvic  Cellulitis  and  Peritonitis,  Ac.  XLII.  Haematocele,  Ac 
XLIII.  Displacements  of  Uterus.  XLIV.  Displacements  (continued).  XLV.  Retroversion  and 
Retroflexion.  XLVI.  Inversion.  XLVII.  Uterine  Tumors.  XLVIII.  Polypus  Uteri.  XLIX. 
Polypus  Uteri  (continued).  L.  Cancer.  LI.  Diseases  of  Vagina.  LIT.  Diseases  of  the  Vulva. 

mas,  and  Peaslee,  as  if  these  eminent  men  were  his 


Embodying  the  long  experience  and  personal  obser- 
vation of  one  of  the  greatest  of  living  teachers  in  dis- 
eases of  women,  it  seems  pervaded  by  the  presence 
of  the  author,  who  speaks  directly  to  the  reader,  and 
speaks,  too,  as  one  having  authority.  And  yet,  not- 
withstanding this  distinct  personality,  there  is  noth- 
ing narrow  as  to  time,  place,  or  individuals,  in  the 
views  presented,  and  in  the  instructions  given  ;  Dr. 
Barnes  has  been  an  attentive  student,  not  only  of  Eu- 
ropean, but  also  of  American  literature,  pertaining  to 
diseases  of  females,  and  enriched\his  own  experience 
by  treasures  thence  gathered  ;  he  seems  as  familiar, 
for  example,  with  the  writings  of  Sims,  Emmet,  Tho- 


countrymen  and  colleagues,  and  gives  them  a  credit 
which  must  be  gratifying  to  every  American  physi- 
cian.— Am.  Journ.  Med.  Set.,  April,  1874. 

Throughout  the  whole  book  it  is  impossible  not  to 
feel  that  the  author  has  spontaneously,  conscientious- 
ly, and  fearlessly  performed  his  task.  He  goes  direct 
to  the  point,  and  does  not  loiter  on  the  way  to  gossip 
or  quarrel  with  other  authors.  Dr.  Barnes's  book 
will  be  eagerly  read  all  over  the  world,  and  will 
everywhere  be  admired  for  its  comprehensiveness, 
honesty  of  purpose,  and  ability.  —  The  Obstet.  Journ. 
of  Great  Britain  and  Ireland,  March,  1874. 


CHURCHILL  ON  THE  PUERPERAL  FEVER  AND 
OTHER  DISEASES  PECULIAR  TO  WOMEN.  1  vol. 
Svo.,  pp.  450,  cloth.  $2  50. 

MEIGS  ON  WOMAN:  HER  DISEASES  AND  THEIR 
REMEDIES.  A  Series  of  Lectures  to  his  Class. 
Fourth  and  Improved  Edition.  1  vol.  Svo.,  over 
700  pages,  cloth,  $5  00  ;  leather,  *6  00. 

MEIGS  ON  THE  NATURE,  SIGNS,  AND  TREAT- 
MENT OF  CHILDBED  FEVER.  1  vol.  8vo.,  pp 
3SS,  cloth.  $2  00. 


ASHWELL'S  PRACTICAL  TREATISE  ON  THE  DIS- 
EASES PECULIAR  TO  WOMEN.  Third  American, 
from  the  Third  and  revised  London  edition.  1  vol. 
8vo.,  pp.  528,  cloth.  $3  50. 

DEWEES'S  TREATISE  ON  THE  DISEASES  OF  FE- 
MALES. With  illustrations.  Eleventh  Edition, 
with  the  Author's  last  improvements  and  correc- 
tions. In  one  octavo  volume  of  536  pages,  with 
plates,  cloth.  $3  00. 


HENRY  C.  LEA'S  PUBLICATIONS — (Midwifery). 


fTODGE  (HUGH  L.},  M.D., 

•*--*-  Emeritus  Professor  of  Midwifery,  &c.,  in  the  University  of  Pennsylvania,  Ac. 

THE  PRINCIPLES  AND  PRACTICE  OF  OBSTETRICS.  Illus- 
trated with  large  lithographic  plates  containing  one  hundred  and  fifty-nine  figures  from 
original  photographs,  and  with  numerous  wood-cuts.  In  one  large  and  beautifully  printed 
quarto  volume  of  550  double-columned  pages,  strongly  bound  in  cloth,  $14. 


The  work  of  Dr.  Hodge  is  something  more  than  a 
simple' presentation  of  his  particular  views  in  the  de- 
partment of  Obstetrics;  it  is  something  more  than  an 
ordinary  treatise  on  midwifery;  it  is,  in  fact,  a  cyclo- 
paedia of  midwifery.  He  has  aimed  to  embody  in  a 
single  volume  the  whole  science  and  art  of  Obstetrics. 
An  elaborate  text  is  combined  with  accurate  and  va- 
ried pictorial  illustrations,  so  that  no  fact  or  principle 
Is  left  unstated  or  unexplained. — Am.  Med.  Times, 
Sept.  8,  1864. 

We  should  like  to  analyze  the  remainder  of  this 
excellent  work,  but  already  has  this  review  extended 
beyond  our  limited  space.  We  cannot  conclude  this 
aotice  without  referring  to  the  excellent  finish  of  the 
work.  In  typography  it  is  not  to  be  excelled ;  the 
paper  is  superior  to  what  is  usually  afforded  by  our 
American  cousins,  quite  equal  to  the  best  of  English 

books.      The  engravings  and  lithographs   are  most j —0 t 

beautifully  executed. ^  The  Work  recommends  itself  instructive,  and  in  the  main,  we  believe"  correct. "The 

great  attention  which  the  author  has  devoted  to  the 


for  its  originality,  and  is  in  every  way  a  most  valu- 
able addition  to  those  on  the  subject  of  obstetrics.-- 
Canada  Med.  Jorirnal,  Oct.  1864. 
It  is  very  large,  profusely  and  elegantly  illustrated, 


We  have  examined  Professor  Hodge's  work  with 
great  satisfaction ;  every  topic  is  elaborated  most 
fully.  The  views  of  the  author  are  comprehensive, 
and  concisely  stated.  The  rules  of  practice  are  judi- 
cious, and  will  enable  the  practitioner  to  meet  every 
emergency  of  obstetric  complication  with  confidence. 
— Chicago  Med.  Journal,  Aug.  1864. 

More  time  than  we  have  had  at  our  disposal  since 
we  received  the  great  work  of  Dr.  Hodge  is  necessary 
to  do  it  justice.  It  is  undoubtedly  by  far  the  most 
original,  complete,  and  carefully  composed  treatise 
on  the  principles  and  practice  of  Obstetrics  which  has 
ever  been  issued  from  the  American  press. — Pacific 
Med.  and  Surg.  Journal,  July,  1864. 

We  have  read  Dr.  Hodge's  book  with  great  plea- 
sure, and  have  much  satisfaction  in  expressing  our 
commendation  of  it  as  a  whole.  It  is  certainly  highly 


mechanism  of  parturition,  taken  along  with  the  con- 
clusions at  which  he  has  arrived,  point,  we  think, 
conclusively  to  the  fact  that,  in  Britain  at  least,  the 


and  is  fitted  to  take  its  place  near  the  works  of  great ;  doctrines  of  Naegele  have  been  too  blindly  received. 


obstetricians.    Of  the  American  works  on  the  subject 


—Glasgow  Med.  Joiirnal,  Oct.  1864. 


It  is  decidedly  the  best.— Edinb.  Med.  Jour.,  Dec.  '64. 

#*#  Specimens  of  the  plates  and  letter-press  will  be  forwarded  to  any  address,  free  by  mail, 
en  receipt  of  six  cents  in  postage  stamps. 

BANNER  (THOMAS  H.},  M.  D. 
ON  THE  SIGNS  AND  DISEASES  OF  PREGNANCY.     First  American 

from  the  Second  and  Enlarged  English  Edition.     With  four  colored  plates  and  illustrations 
on  wood.     In  one  handsome  octavo  volume  of  about  500  pages,  cloth,  $4  25. 


The  very  thorough  revision  the  work  has  undergone 
has  added  greatly  to  its  practical  value,  and  increased 
materially  its  efficiency  as  a  guide  to  the  student  and 
to  the  young  practitioner.—  Am.  Journ.  Med.  Sci., 
April,  1868. 

With  the  immense  variety  of  subjects  treated  of 
and  the  ground  which  they  are  made  to  cover,  the  im- 
possibility  of  giving  an  extended  review  of  this  truly 
remarkable  work  must  be  apparent.  We  have  not  a 
single  fault  to  find  with  it,  and  most  heartily  com- 
mend it  to  the  careful  study  of  every  physician  who 
would  not  only  always  be"  sure  of  his  diagnosis  of 


pregnancy,  but  always  ready  to  treat  all  the  nume- 
rous ailments  that  are,  unfortunately  for  the  civilized 
women  of  to-day,  so  commonly  associated  with  the 
function.—^.  T.  Med.  Record,  March  1U,  1S68. 

We  recommend  obstetrical  students,  young  and 
old,  to  hav*  this  volume  in  their  collections.  It  con- 
tains not  on!  j 
and  diseases  of  pregnancy, 
much  interesting  relative  matter  that  is  not  to  be 
found  in  any  other  work  that  we  can  name.  —  Edin- 
burgh Med  Journal,  Jan.  1868. 


a  fair  statement  of  the  signs,  symptoms, 
f    renanc,  but  comprises  in  addition 


Sf WAYNE  (JOSEPH  GRIFFITHS),  M.  D., 

Physician- Accoucheur  to  the  British  General  Hospital,  &c. 

OBSTETRIC  APHORISMS  FOR  THE  USE  OF  STUDENTS  COM- 

MENCING  MIDWIFERY  PRACTICE.  Second  American,  from  the  Fifth  and  Revised 
London  Edition,  with  Additions  by  E.  R.  HUTCHINS,  M.  D.  With  Illustrations.  In  one 
neat  12mo.  volume.  Cloth,  $1  25.  (Lately  Issued.) 

*  ,.*  See  p.  3  of  this  Catalogue  for  the  terms  on  which  this  work  is  offered  as  a  premium  to 
subscribers  to  the  "  AMERICAN  JOURNAL  OP  THE  MEDICAL  SCIENCES." 

It  is  really  a  capital  little  compendium  of  the  sub-    answers   the  purpose.     It  is  not  only  valuable  for 


ject,  and  we  recommend  young  practitioners  to  buy  it 
and  carry  it  with  them  when  called  to  attend  cases  of 
labor.  They  can  while  away  the  otherwise  tedious 
hours  of  waiting,  and  thoroughly  fix  in  their  memo- 
ries the  most  important  practical  suggestions  it  con- 
tains. The  American  editor  has  materially  added  by 
his  notes  and  the  concluding  chapters  to  the  com- 
pleteness and  general  value  of  the  book. — Chicago 
Med.  Journal,  Feb.  1870. 

The  manual  before  us  containsin  exceedingly  small 
compass — small  enough  to  carry  in  the  pocket — about 
all  there  is  of  obstetrics,  condensed  into  a  nutshell  of 
Aphorisms.  The  illustrations  are  well  selected,  and 
serve  as  excellent  reminders  of  the  conduct  of  labor — 
regular  and  difficult. — Cincinnati  Lancet,  April,  '70. 

TMs  is  a  mostadmirable  little  work,  and  completely 


young  beginners,  but  no  one  who  is  not  a  proficient 
in  the  art  of  obstetrics  should  be  without  it,  because 
it  condenses  all  that  is  necessary  to  know  for  ordi- 
nary midwifery  practice.  We  commend  the  book 
most  favorably. — St.  Louis  Med.  and  Surg.  Journal, 
Sept.  10,  1870. 

A  studied  perusal  of  this  little  book  has  satisfied 
us  of  its  eminently  practical  value.  The  object  of  the 
work,  the  author  says,  in  his  preface,  is  to  give  the 
student  a  few  brief  and  practical  directions  respect- 
ing the  management  of  ordinary  cases  of  labor  ;  and 
also  to  point  out  to  him  in  extraordinary  cases  when 
and  how  he  may  act  upon  his  own  responsibility,  and 
when  he  ought  to  send  for  assistance.—^.  Y.  Medical 
Journal,  May,  1870. 


VfTINCKEL  (F.), 

Professor  and  Director  of  the  Gyncecological  Clinic  in  the  University  of  Rostock. 

A  COMPLETE  TREATISE  ON  THE  PATHOLOGY  AND  TREAT- 
MENT OF  CHILDBED,  for  Students  and  Practitioners.  Translated,  with  the  consent  of 
the  author,  from  the  Second  German  Edition,  by  JAMES  READ  CHADWICK,  M  D.  In  one 
octavo  volume.  (Preparing.) 


HENRY  C.  LEA'S  PUBLICATIONS— (Midwifery). 


25 


^EISHMAN  (WILLIAM],  M.D., 

'  Regius  Professor  of  Midwifery  in  the  University  of  Glasgow,  &c. 

A  SYSTEM  OF  MIDWIFERY,  INCLUDING  THE  DISEASES  OF 

PREGNANCY  AND  THE  PUERPERAL  STATE.  In  one  large  and  very  handsome  oc- 
tavo volume  of  over  700  pages,  with  one  hundred  and  eighty-two  illustrations.  Cloth, 
$5  00  ;  leather,  $6  00.  (Lately  Published.) 


This  is  one  of  a  most  complete  and  exhaustive  cha- 
racter. We  have  gone  carefully  through  it,  and  there 
Is  no  subject  in  Obstetrics  which  ha>  not- been  con- 
sidered well  and  fully.  The  result  is  a  work,  not 
only  admirable  as  a  text-book,  but  valuable  as  a  work 
of  reference  to  the  practitioner  in  the  various  emer- 
gencies of  obstetric  practice.  Take  it  all  in  all,  we 
have  no  hesitation  in  saying  that  it is  in  our  judgment 
the  best  English  work  on  the  subject. — London  Lan- 
cet, Aug.  23,  1873. 

The  work  of  Leishman  gives  an  excellent  view  of 
modern  midwifery,  and  evinces  its  author's  extensive 
acquaintance  with  British  and  foreign  literature  ;  and 
not  only  acquaintance  with  it,  but  wholesome  diges- 
tion and  sound  judgment  of  it.  He  has,  withal,  a 
manly,  free  style,  and  can  state  a  difficult  and  Compli- 
cated matter  with  remarkable  clearness  and  brevity. 
—Kdin.  Med.  Journ.,  Sept.  1873. 

The  author  has  succeeded  in  presenting  to  the  pro- 
fession an  admirable  treatise,  especially  in  its  practi- 
cal aspects  ;  one  which  is,  iu  general,  clearly  written, 
and  sound  in  doctrine,  and  one  which  cannot  fail  to 
add  to  his  already  high  reputation.  In  concluding 
our  examination  of  this  work,  we  cannot  avoid  again 
saying  that  Dr.  Leishman  has  fully  accomplished 
that  difficult  task  of  presenting  a  good  text-book  upon 
obstetrics.  We  know  none  better  for  the  use  of  the  stu- 
dent or  junior  practitioner.—  Am.  Practitioner,  Mar. 
1874. 

It  proposes  to  offer  to  practitioners  and  students 


"A  Complete  System  of  the  Midwifery  of  the  Present 
Day,"  and  well  redeems  the  promise.  In  all  that 
relates  to  the  subject  of  labor,  the  teaching  is  admi- 
rably clear,  concise,  and  practical,  representing  not 
alone  British  practice,  but  the  contributions  of  Con- 
tinental and  American  schools. — N.  T.  Med.  Record, 
March  2,  1874. 

The  work  of  Dr.  Leishman  is,  in  many  respects, 
not  only  the  best  treatise  on  midwifery  that  we  have 
seen,  but  one  of  the  best  treatises  on  any  medical  sub- 
ject that  has  been  published  of  late  years. — Lond. 
Practitioner,  Feb.  187-4. 

It  was  written  to  supply  a  desideratum,  and  we  will 
be  much  surprised  if  it  does  not  fulfil  the  purpose  of 
its  author.  Taking  it  as  a  whole,  we  know  of  no 
work  on  obstetrics  by  an  English  author  in  which  the 
student  and  the  practitioner  will  find  the  information 
so  clear  and  so  completely  abreast  of  the  present  state 
of  our  knowledge  on  the  subject.—  Glasgow  Med. 
Journ.,  Aug.  1873. 

Dr.  Leishman's  System  of  Midwifery,  which  has 
only  just  been  published,  will  go  far  to  supply  the 
want  which  has  so  long  been  felt,  of  a  really  good 
modern  English  text-book.  Although  large,  as  is  in- 
evitable in  a  work  on  so  extensive  a  subject,  it  is  so 
well  and  clearly  written,  that  it  is  never  wearisome 
to  read.  Dr.  Leishman's  work  may  be  confidently 
recommended  as  an  admirable  text-book,  and  is  sure 
to  be  largely  used.— Lond.  Med.  Record,  Sept.  1873. 


ffAMSBOTHAM  (FRANCIS  H.),  M.D. 

THE  PRINCIPLES  AND  PRACTICE  OF  OBSTETRIC  MEDI- 
CINE AND  SURGERY,  in  reference  to  the  Process  of  Parturition.  A  new  and  enlarged 
edition,  thoroughly  revised  by  the  author.  With  additions  by  W.  V.  KEATING,  M.  D., 
Professor  of  Obstetrics,  &c.,  in  the  Jefferson  Medical  College,  Philadelphia.  In  one  large 
and  handsome  imperial  octavo  volume  of  650  pages,  strongly  bound  in  leather,  with  raised 
bands  ;  with  sixty-four  beautiful  plates,  and  numerous  wood-cuts  in  the  text,  containing  in 
all  nearly  200  large  and  beautiful  figures.  $7  00. 


We  will  only  add  that  the  student  will  learn  from 
it  all  he  need  to  know,  and  the  practitioner  will  find 
it,  as  a  book  of  reference,  surpassed  by  none  other. — 
Stethoscope. 

The  character  and  merits  of  Dr.  Ramsbotham's 
work  are  so  well  known  and  thoroughly  established, 
that  comment  is  unnecessary  and  praise  superfluous. 
The  illustrations,  which  are  numerous  and  accurate, 
are  executed  in  the  highest  style  of  art.  We  cannot 
too  highly  recommend  the  work  to  our  readers. — St. 
Louis  Med.  and  Surg.  Journal. 


To  the  physician' s  library  it  is  indispensable,  while 
to  the  student,  as  a  text-book,  from  which  to  extract 
the  material  for  laying  the  foundation  of  an  education 
on  obstetrical  science,  it  has  no  superior.— Ohio  Med. 
and  Surg.  Journal. 

When  we  call  to  mind  the  toil  we  underwent  in 
acquiring  a  knowledge  of  this  subject,  we  cannot  but 
envy  the  student  of  the  present  day  the  aid  which 
this  work  will  afford  him.—  Am.  Jour,  of  the  Med. 
Sciences. 


rjHURCHILL  (FLEETWOOD),  M.D.,  M.R.I. A. 

ON  THE  THEORY  AND  PRACTICE  OF  MIDWIFERY.     A  new 

American  from  the  fourth  revised  and  enlarged  London  edition.  With  notes  and  additions 
by  D.  FRANCIS  CONDIE,  M.  D.,  author  of  a  "Practical  Treatise  on  the  Diseases  of  Chil- 
dren," <fcc.  With  one  hundred  and  ninety-four  illustrations.  In  one  very  handsome  octavo 
volume  of  nearly  700  large  pages.  Cloth,  $4  00;  leather,  $5  00. 


These  additions  render  the  work  still  more  com- 
plete and  acceptable  than  ever ;  and  we  can  com- 
mend it  to  the  profession  with  great  cordiality  and 
pleasure. — Qinnnnati  Lancet. 

Few  work?  on  this  branch  of  medical  science  are 
equal  to  it,  certainly  none  excel  it,  whether  in  regard 
to  theory  or  practice — Brit.  Am.  Journal. 

No  treatise  on  obstetrics  with  which  we  are  ac- 


quainted can  compare  favorably  with  this,  in  re' 
spect  to  the  amount  of  material  which  has  been  gath- 
ered from  every  source. — Boston  Med.  and  Siirg 
Journal . 

There  is  no  better  text-book  for  students,  or  work 
of  reference  and  study  for  the  practising  physician 
than  this.  It  should  adorn  and  enrich  every  medical 
library. — Chicago  Med.  Journal. 


MONTGOMERY'S  EXPOSITION  OF  THE  SIGNS  i  aiQBY'S  SYSTEM  OF  MIDWIFERY,.  With  Notes 
AND  SYMPTOMS  OF  PREGNANCY.  With  two  and  Additional  Illustrations.  Second  American 
exquisite  colored  plates,  and  numerous  wood-cats.  '  edition.  One  volume  octavo,  cloth,  422  pages. 
In  1vol.  8vo.,  of  nearly  600  pp.,  cloth.  $375.  1  $260. 


26 


HENRY  C.  LEA'S  PUBLICATIONS — (Surgery). 


flROSS  (SAMUEL  D.),  M.D., 

"  Professor  of  Surgery  in  the  Jefferson  Medical  College  of  Philadelphia. 

A  SYSTEM  OF  SURGERY:   Pathological,  Diagnostic,  Therapeutic, 

and  Operative.     Illustrated  by  upwards  of  Fourteen  Hundred  Engravings.     Fifth  edition, 
carefully  revised,  and  improved.    In  two  large  and  beautifully  printed  imperial  octavo  vol- 
umes of  about  2300  pages,  strongly  bound  in  leather,  with  raised  bands,  $15.    ( Just  Issued.) 
The  continued  favor,  shown  by  the  exhaustion  of  successive  large  editions  of  this  great  work, 
proves  that  it  has  successfully  supplied  a  want  felt  by  American  practitioners  and  students.    In  the 
present  revision  no  pains  have  been  spared  by  the  author- to  bring  it  in  every  respect  fully  up  to 
the  day.     To  effect  this  a  large  part  of  the  work  has  been  rewritten,  and  the  whole  enlarged  by 
nearly  one-fourth,  notwithstanding  which  the   price  has  been  kept  at  its  former  very  moderate 
rate.     By  the  use  of  a  close,  though  very  legible  type,  an  unusually  large  amount  oi  matter  ie 
condensed  in  its  pages,  the  two  volumes  containing  as  much  as  four  or  five  ordinary  octavos. 
This,  combined  with  the  most  careful  mechanical  execution,  and  its  very  durable  binding,  renders 
it  one  of  the  cheapest  works  accessible  to  the  profession.     Every  subject  properly  belonging  to  the 
domain  of  surgery  is  treated  in  detail,  so  that  the  student  who  possesses  this  work'  may  be  said  to 
have  in  it  a  surgical  library.     A  few  notices  of  the  previous  edition  are  subjoined  : — 

It  must  long  remain  the  most  comprehensive  work 
on  this  important  part  of  medicine. — Boston  Medical 
and  Stirgical  Journal,  March  23,  1865. 

We  have  compared  it  with  most  of  our  standard 
works,  such  as  those  of  Erichsen,  Miller,  Fergusson, 
Syme,  and  others,  and  we  must,  in  justice  to  our 
author,  award  it  the  pre-eminence.  As  a  work,  com- 
plete in  almost  every  detail,  no  matter  how  minute 
or  trifling,  and  embracing  every  subject  known  in 
the  principles  and  practice  of  surgery,  we  believe  it 
stands  without  a  rival.  Dr.  Gross,  in  his  preface,  re- 
marks "my  aim  has  been  to  embrace  the  whole  do- 
main of  surgery,  and  to  allot  to  every  subject  its 
legitimate  claim  to  notice;"  and,  we  assure  our 
readers,  he  has  kept  his  word.  It  is  a  work  which 
we  can  most  confidently  recommend  to  our  brethren, 
for  its  utility  is  becoming  the  more  evident  the  longer 
It  is  upon  the  shelves  of  our  library. — Canada  Med. 
Journal,  September,  1865. 

The  first  two  editions  of  Professor  Gross'  System  of 
Surgery  are  so  well  known  to  the  profession,  and  so 
highly  prized,  that  it  would  be  idle  for  us  to  speak  in 
praise  of  this  work.—  Chicago  Medical  Journal, 
September,  1865. 

We  gladly  indorse  the  favorable  recommendation 
of  the  work,  both  as  regards  matter  and  style,  which 
we  made  when  noticing  its  first  appearance.—  British 
and  Foreign  Medico- Chirurgical  Review,  Oct.  1865. 

The  most  complete  work  that  has  yet  issued  from 
the  press  on  the  science  and  practice  of  surgery.— 
London  Lancet. 

This  system  of  surgery  is,  we  predict,  destined  to 
take  a  commanding  position  in  our  surgical  litera- 
ture, and  be  the  crowning  glory  of  the  author's  well 
earned  fame.  As  an  authority  on  general  surgical 
subjects,  this  work  is  long  to  occupy  a  pre-eminent 
place,  not  only  at  home,  but  abroad.  We  have  no 

DY  THE  SAME  AUTHOR. 

A   PRACTICAL    TREATISE    ON    FOREIGN    BODIES   IN   THE 

AIR-PASSAGES.     In  1  vol.  8vo.,  with  illustrations,  pp.  468,  cloth,  $2  75. 


hesitation  in  pronouncing  it  without  a  rival  in  onr 
language,  and  equal  to  the  best  systems  of  surgery  in 
any  language.—^.  Y.  Med.  Journal. 

Not  only  by  far  the  best  text-book  on  the  subject, 
as  a  whole,  within  the  reach  of  American  students, 
but  one  which  will  be  much  more  than  ever  likely 
to  be  resorted  to  and  regarded  as  a  high  authority 
abroad. — Am.  Journal  Med.  Sciences,  Jan.  1865. 

The  work  contains  everything,  minor  and  major, 
operative  and  diagnostic,  including  mensuration  and 
examination,  venereal  diseases,  and  uterine  manipu- 
lations and  operations.  It  is  a  complete  Thesaurus 
of  modem  surgery,  where  the  student  and  practi- 
tioner shall  not  seek  in  vain  for  what  they  desire.— 
San  Francisco  Med.  Press,  Jan.  1865. 

Open  it  where  we  may,  we  find  sound  practical  in- 
formation conveyed  in  plain  language.  'This  book  i» 
no  mere  provincial  or  even  national  system  of  sur- 
gery, but  a  work  which,  while  very  largely  indebted 
to  the  past,  has  a  strong  claim  on  the  gratitude  of  tha 
future  of  surgical  science. — Edinburgh  Med.  Journal, 
Jan.  1865. 

A  glance  at  the  work  is  sufficient  to  show  that  the 
author  and  publisher  have  spared  no  labor  in  making 
it  the  most  complete  "System  of  Surgery"  ever  pub- 
lished in  any  country. — St.  Louis  Med.  and  Surg. 
Journal,  April,  1865. 

A  system  of  surgery  which  we  think  unrivalled  in 
our  language,  and  which  will  indelibly  associate  his 
name  with  surgical  science.  And  what,  in  our  opin- 
ion, enhances  the  value  of  the  work  is  that,  while  the 
practising  surgeon  will  find  all  that  he  requires  in  it, 
it  is  at  the  same  time  one  of  the  most  valuable  trea- 
tises which  can  b£  put  into  the  hands  of  the  student 
seeking  to  know  the  principles  and  practice  of  this 
branch  of  the  profession  which  he  designs  subse- 
quently to  follow. — The  Brit.  Am.Journ.,  Montreal. 


SKET'S    OPERATIVE  SURGERY.     In  1   vol.   8vo. 

cloth,  of  over  650  pages  ;  with  about  100  wood-cuts. 

$3  25. 
COOPER'S  LECTURES  ON  THE  PRINCIPLES  AND 

PRACTICE  OF  SURGERY.  In  1  vol.  8vo.  cloth,  750  p.  $2.  j 


GIBSON'S  INSTITUTES  AND  PRACTICE  OF  SUB- 
GERY.  Eighth  edition,  improved  and  altered.  With 
thirty-four  plates.  In  two  handsome  octavo  vol- 
umes, about  1000 pp., leather, raised  bandt.  $6  60. 


M 


ILL  EH  (JAMES), 

Late  Professor  of  Surgery  in  the  University  of  Edinburgh,  &c. 

PRINCIPLES  OF  SURGERY.     Fourth  American,  from  the  third  and 

revised  Edinburgh  edition.  In  one  large  and  very  beautiful  volume  of  700  pages,  with 
two  hundred  and  forty  illustrations  on  wood,  cloth,  $3  76. 

DY  THE  SAME  AUTHOR. 

THE   PRACTICE   OF   SURGERY.    Fourth  American,  from  the  last 

Edinburgh  edition.  Revised  by  the  American  editor.  Illustrated  by  three  hundred  and 
sixty-four  engravings  on  wood.  In  one  large  octavo  volume  of  nearly  700  pages,  cloth, 
$3  75.  

UARGENT  (F.  W.),  M.D. 
®      ON  BANDAGING  AND    OTHER   OPERATIONS   OF   MINOR 

SURGERY,  New  edition,  with  an  additional  chapter  on  Military  Surgery.  One  handsome 
royai  12mo.  volume,  of  nearly  400  pages,  with  184  wood-cuts.  Cloth,  $1  76. 


HENRY  C.  LEA'S  PUBLICATIONS — (Surgery). 


27 


ASHHURST  (JOHN,  Jr.),  M.D., 

Surgeon  to  the  Episcopal  Hospital,  Philadelphia. 

THE   PRINCIPLES   AND    PRACTICE   OF   SURGERY.     In  one 

very  Large  and  handsome  octavo  volume  of  about  1000  pages,  with  nearly  550  illustrations, 
cloth,  $6  50;  leather,  raised  bands,  $7  50.      (Lately  Published.) 

The  object  of  the  author  has  been  to  present,  within  as  condensed  a  compass  as  possible,  a 
complete  treatise  on  Surgery  in  all  its  branches,  suitable  both  as  a  text-book  for  the  student  and 
a  work  of  reference  for  the  practitioner.  So  much  has  of  late  years  been  done  for  the  advance- 
ment of  Surgical  Art  and  Science,  that  there  seemed  to  be  a  want  of  a  work  which  should  present 
the  latest  aspects  of  every  subject,  and  which,  by  its  American  character,  should  render  accessible 
to  the  profession  at  large  the  experience  of  the  practitioners  of  both  hemispheres.  This  has  been 
the  aim  of  the  author,  and  it  is  hoped  that  the  volume  will  be  found  to  fulfil  its  purpose  satisfac- 
torily. The  plan  and  general  outline  of  the  work  will  be  seen  by  the  annexed 

CONDENSED  SUMMARY  OF  CONTENTS. 

CHAPTER  I.  Inflammation.  II.  Treatment  of  Inflammation.  III.  Operations  in  general: 
Anaesthetics.  IV.  Minor  Surgery.  V.  Amputations.  VI.  Special  Amputations.  VII.  Effects 
of  Injuries  in  General  :  Wounds.  VIII.  Gunshot  Wounds.  IX.  Injuries  of  Bloodvessels.  X. 
Injuries  of  Nerves,  Muscles  and  Tendons,  Lymphatics,  Bursae,  Bones,  and  Joints.  XI.  Fractures. 
XII.  Special  Fractures.  XIII.  Dislocations.  XIV.  Effects  of  Heat  and  Cold.  XV.  Injuries 
of  the  Head.  XVI.  Injuries  of  the  Back.  XVII.  Injuries  of  the  Face  and  Neck.  XVIII. 
Injuries  of  the  Chest.  XIX.  Injuries  of  the  Abdomen  and  Pelvis.  XX.  Diseases  resulting  from 
Inflammation.  XXI.  Erysipelas.  XXII.  Pyaemia.  XXIII.  Diathetic  Diseases:  Struma  (in- 
eluding  Tubercle  and  Scrofula);  Rickets.  XXIV.  Venereal  Diseases  ;  Gonorrhoea  and  Chancroid. 
XXV.  Venereal  Diseases  continued  :  Syphilis.  XXVI.  Tumors.  XXVII.  Surgical  Diseases  of 
Skin,  Areolar  Tissue,  Lymphatics,  Muscles,  Tendons,  and  Bursae.  XXVIII.  Surgical  Disease 
of  Nervous  System  (including  Tetanus).  XXIX.  Surgical  Diseases  of  Vascular  System  (includ- 
ing Aneurism).  XXX.  Diseases  of  Bone.  XXXI.  Diseases  of  Joints.  XXXII.  Excisions. 
XXXIII.  Orthopaedic  Surgery.  XXXIV.  Diseases  of  Head  and  Spine.  XXXV.  Diseases  of  the 
Eye.  XXXVI.  Diseases  of  the  Ear.  XXXVII.  Diseases  of  the  Face  and  Neck.  XXXVIII. 
Diseases  of  the  Mouth,  Jaws,  and  Throat.  XXXIX.  Diseases  of  the  Breast.  XL.  Hernia.  XLI. 
Special  Hernias.  XLII.  Diseases  of  Intestinal  Canal.  XLIII.  Diseases  of  Abdominal  Organs, 
and  various  operations  on  the  Abdomen.  XLIV.  Urinary  Calculus.  XLV.  Diseases  of  Bladder 
and  Prostate.  XLVI.  Diseases  of  Urethra.  XLVII.  Diseases  of  Generative  Organs.  INDEX. 


Its  author  has  evidently  tested  the  writings  and 
experiences  of  the  past  and  present  in  the  crucible 
of  a  careful,  analytic,  and  honorable  mind,  and  faith- 
fully endeavored  to  bring  his  work  up  to  the  level  of 
the  highest  standard  of  practical  surgery.  He  is 
frank  and  definite,  and  gives  us  opinions,  and  gene- 
rally sound  ones,  instead  of  a  mere  resume  of  the 
opinions  of  others.  He  is  conservative,  but  not  hide- 
bound by  authority.  His  style  is  clear,  elegant,  and 
scholarly.  The  work  is  an  admirable  tex-tbook,  and 
a  useful  book  of  reference  It  is  a  credit  to  American 
professional  literature,  and  one  of  the  first  ripe  fruits 
of  the  soil  fertilized  by  the  blood  of  our  late  unhappy 
war.—  N.  Y.  Med.  Record,  Feb.  1,  1872. 


Indeed,  the  work  as  a  whole  must  be  regarded  as 
an  excellent  and  concise  exponent  of  modern  sur- 
gery, and  as  such  it  will  be  found  a  valuable  text- 
book for  the  student,  and  a  useful  book  of  reference 
for  the  general  practitioner. — N.  Y.  Med.  Journal, 
Feb.  1872. 

It  gives  us  great  pleasure  to  call  the  attention  of  the 
profession  to  this  excellent  work.  Our  knowledge  of 
its  talented  and  accomplished  author  led  us  to  expect 
from  him  a  very  valuable  treatise  upon  subjects  to 
which  he  has  repeatedly  given  evidence  of  having  pro- 
fitably devoted  much  time  and  labor,  and  we  are  in  no 
way  disappointed.— Phila.  Med.  Times,  Feb.  1, 1872. 


pIRRIE  (  WILLIAM),  F.  R.  S.  E., 

•*-  Professor  of  Surgery  in  the  University  of  Aberdeen. 

THE  PRINCIPLES  AND  PRACTICE  OF  SURGERY.    Edited  by 

JOHN  NEILL,  M.  D.,  Professor  of  Surgery  in  the  Penna.  Medical  College,  Surgeon  to  the 
Pennsylvania  Hospital,  &c.  In  one  very  handsome  octavo  volume  of  780  pages,  with  316 
illustrations,  cloth,  $3  75. 


TJAMILTON  (FRANK  H.},  M.D., 

Professor  of  Fractures  and  Dislocations,  &c.,  in  Bellevue  Hosp.  Med.  College,  New  York. 

A  PRACTICAL  TREATISE  ON  FRACTURES  AND  DISLOCA- 
TIONS. Fourth  edition,  thoroughly  revised.  In  one  large  and  handsome  octavo  volume 
of  nearly  800  pages,  with  several  hundred  illustrations.  Cloth,  $5  75;  leather,  $6  75. 


It  is  not,  of  course,  our  intention  to  review  in  ex- 
Censo,  Hamilton  on  "Fractures  and  Dislocations." 
Eleven  years  ago  such  review  might  not  have  been 
out  of  place  ;  to-day  the  work  is  an  authority,  so  well, 
so  generally,  and  so  favorably  known,  that  it  only 
remains  for  the  reviewer  to  say  that  a  new  edition  is 
just  out,  and  it  is  better  than  either  of  its  predeces- 
sors.— Cincinnati  Clinic,  Oct.  14,  1871. 

Undoubtedly  the  best  work  on  Fractures  and  Dis- 
locations in  the  English  language.— Cincinnati  Med. 
Repertory,  Oct.  1871. 

We  have  once  more  before  us  Dr. .Hamilton's  admi- 


rable treatise,  which  we  have  always  considered  the 
most  complete  and  reliable  work  on  the  subject.  As 
a,  whole,  the  work  is  without  an  equal  in  the  litera- 
ture of  the  profession. — Boston  Med.  and  Surg. 
Journ.,  Oct.  12,  1871. 

It  is  unnecessary  at  this  time  to  commend  the  book, 
except  to  such  as  are  beginners  in  the  study  of  this 
particular  branch  of  surgery.  Every  practical  sur- 
geon in  this  country  and  abroad  knows  of  it  as  a  most 
trustworthy  guide,  and  one  which  they,  in  common 
with  us,  would  unqualifiedly  recommend  as  the  high- 
est authority  in  any  language.—^.  Y.  Med.  Record, 
Oct.  16,  1871. 


28  HENRY  C.  LEA'S  PUBLICATIONS — (Surgery). 

&RICHSEN  (JOHN  E.), 

*-^  Professor  of  Surgery  in  University  College,  London,  etc. 

THE  SCIENCE  AND  ART  OF  SURGERY;  being  a  Treatise  on  Sur- 

gical  Injuries,  Diseases,  and  Operations.  Revised  by  the  author  from  the  Sixth  and 
enlarged  English  Edition.  Illustrated  by  over  seven  hundred  engravings  on  wood.  In 
two  large  and  beautiful  octavo  volumes  of  over  1700  pages,  cloth,  $9  00  ;  leather,  $11  00. 
(Lately  Issued.) 

Author's  Preface  to  the  New  American  Edition. 

"  The  favorable  reception  with  which  the  '  Science  and  Art  of  Surgery'  has  been  honored  by  the 
Surgical  Profession  in  the  United  States  of  America  has  been  not  only  a  source  of  deep  gratifica- 
tion and  of  just  pride  to  me,  but  has  laid  the  foundation  of  many  professional  friendships  that 
are  amongst  the  agreeable  and  valued  recollections  of  my  life. 

"I  have  endeavored  to  make  the  present  edition  of  this  work  more  deserving  than  its  predecessors 
of  the  favor  that  has  been  accorded  to  them.     In  consequence  of  delays  that  have  unavoidably 
occurred  in  the  publication  of  the  Sixth  British  Edition,  time  has  been  afforded  to  me  to  add  to  this 
one  several  paragraphs  which  I  trust  will  be  found  to  increase  the  practical  value  of  the  work." 
LONDON,  Oct.  1S72. 

On  no  former  edition  of  this  work  has  the  author  bestowed  more  pains  to  render  it  a  complete  and 
satisfactory  exposition  of  British  Surgery  in  its  modern  aspects.  Every  portion  has  been  sedu- 
lously revised,  and  a  large  number  of  new  illustrations  have  been  introduced.  In  addition  to  the 
materinl  thus  added  to  the  English  edition,  the  author  has  furnished  for  the  American  edition  such 
material  as  has  accumulated  since  the  passage  of  the  sheets  through  the  press  in  London,  so  that 
the  work  as  now  presented  to  the  American  profession,  contains  his  latest  views  and  experience. 

The  increase  in  the  size  of  the  work  has  seemed  to  render  necessary  its  division  into  two  vol- 
umes. Great  care  has  been  exercised  in  its  typographical  execution,  and  it  is  confidently  pre- 
sented as  in  every  respect  worthy  to  maintain  the  high  reputation  which  has  rendered  it  a  stand- 
ard authority  on  this  department  of  medical  science. 

These  are  only  a  few  of  the  points  in  which  the  states  in  his  preface,  they  are  not  confined  to  any  one 
present  edition  of  Mr.  Erichsen's  work  surpasses  its  j  portion,  but  are  distributed  generally  through  the 
predecessors.  Throughout  there  is  evidence  of  a  !  subjects  of  which  the  work  treats.  Certainly  one  of 
laborious  care  and  solicitude  in  seizing  the  passing:  the  most  valuable  sections  of  the  book  seems  to  us  to 
knowledge  of  the  day,  which  reflects  the  greatest  bo  that  which  treats  of  the  diseases  of  the  arteries 
credit  on  the  author,  and  much  enhances  the  value  and  the  operative  proceedings  which  they  necessitate 
of  his  work.  We  can  only  admire  the  industry  which  In  few  text-books  is  so  much  careful  I/ arranged  in- 
has  enabled  Mr.  Erichsen  thus  to  succeed,  amid  the  formation  collected. — London  Med.  Times  and  Gaz., 
distractions  of  active  practice,  in  producing  emphatic-  !  Oct.  26,  1872. 

ally  THE  book  of  reference  and  study  for  British  prac-  I  The  entire  work  complete,  as  the  great  English 
titioners  of  surgery.—  London  Lancet,  Oct.  26,  1872.  !  treatise  on  Surgery  of  our  own  time,  is,  we  can  assure 
Considerable  changes  have  been  made  in  this  edi-  our  readers,  equally  well  adapted  for  the  most  junior 
lion,  and  nearly  a  hundred  new  illustrations  have  student,  and,  as  a  book  of  reference,  for  the  advanced 
been  added.  It  is  difficult  in  a  small  compass  to  point  practitioner. — Dublin  Quarterly  Journal. 
out  the  alterations  and  additions;  for,  as  the  author  I 


D 


RUITT  (EGBERT),  M.R.C.S.,  frc. 

THE  PRINCIPLES  AND  PRACTICE  OF  MODERN  SURGERY. 

A  new  and  revised  American,  from  the  eighth  enlarged  and  improved  London  edition.  Illus- 
trated with  four  hundred  and  thirty -two  wood  engravings.  In  one  very  handsome  octavo 
volume,  of  nearly  700  large  and  closely  printed  pages,  cloth,  $4  00;  leather,  $5  00. 

practice  of  surgery  are  treated,  and  so  clearly  and 


All  that  the  surgical  student  or  practitioner  could 
desire. — Dublin  Quarterly  Journal. 

It  is  a  most  admirable  book.  We  do  not  know 
when  we  have  examined  one  with  more  pleasure. — 
Boston  Med.  and  Surg.  Journal. 

In  Mr.  Druitt's  book,  though  containing  only  some 
seven  hundred  pages,  both  the  principles  and  the 


perspicuously,  as  to  elucidate  every  important  topic. 
We  have  examined  the  book  most  thoroughly,  and 
can  say  that  this  success  is  well  merited.  His  book, 
moreover,  possesses  the  inestimable  advantages  of 
having  the  subjects  perfectly  well  arranged  and  clas- 
sified, and  of  being  written  in  a  style  at  once  clear 
and  succinct. — Am.  Journal  of  Med.  Sciences. 


ASHTON  (T.  /.). 
ON  THE   DISEASES,  INJURIES,  AND  MALFORMATIONS   OP 

THE  RECTUM  AND  ANUS ;  with  remarks  on  Habitual  Constipation.  Second  American, 
from  the  fourth  and  enlarged  London  edition.  With  handsome  illustrations.  In  one  very 
beautifully  printed  octavo  volume  of  about  300  pages,  cloth,  $3  25. 


T>1GELOW  (HENRY  J.),  M.D., 

-*-*  Professor  of  Surgery  in  the  Massachusetts  Med.  College. 

ON   THE   MECHANISM   OF    DISLOCATION  AND  FRACTURE 

OF  THE  HIP.     With  the  Reduction  of  the  Dislocation  by  the  Flexion  Method.     With 
numerous  original  illustrations.      In  one  very  handsome  octavo  volume.      Cloth,  $2  50. 

LA  WSON  (GEORGE),  F.  R.  C.  S.,  EngL, 
Assistant  Surgeon  to  the  Royal  London  Ophthalmic  Hospital,  Moorflelds,  Ac. 

INJURIES  OF  THE  EYE,  ORBIT,  AND  EYELIDS:  their  Imme- 
diate and  Remote  Effects.  With  about  one  hundred  illustrations.  In  one  very  hand- 
some octavo  volume,  cloth,  $3  50. 

It  is  an  admirable  practical  book  in  the  highest  and  best  sense  of  the  phrase.— London  Medical  Times 
•and  Gazette,  May  18,  1867. 


HENRY  C.  LEA'S  PUBLICATIONS — (Surgery). 


29 


J3RYANT  (THOMAS],  F.R.C.S., 

•£•*  Surgeon  to  Guy's  Hospital. 

THE   PRACTICE    OF    SURGERY.     With  over  Five  Hundred  En- 

gravings  on  Wood.     In  one  large  and  very  handsome  octavo  volume  of  nearly  1000  pages, 
cloth,  $6  25 ;  leather,  raised  bands,  $7  25.     (Lately  Pubiisked.) 


Again,  the  author  gives  us  his  own  practice,  his 
own  beliefs,  and  illustrates  by  his  own  cases,  or  those 
treated  in  Guy's  Hospital.  This  feature  adds  joint 
emphasis,  and  a  solidity  to  his  statements  that  inspire 
confidence.  One  feels  himself  almost  by  the  side  of 
the  surgeon,  seeing  his  work  aud  hearing  his  living 
words.  The  views,  etc.,  of  other  surgeons  are  con- 
sidered calmly  and  fairly,  but  Mr.  Bryant's  are 
adopted.  Thus  the  work  is  not  a  compilation  of 
other  writings;  it  is  not  an  encyclopaedia,  but  the 
plain  statements,  on  practical  points,  of  a  man  who 
has  lived  and  breathed  and  had  his  being  in  the 
richest  surgical  experience.  The  whole  profession 
owe  a  debt  of  gratitude  to  Mr.  Bryant,  for  his  work 
in  their  behalf.  We  are  confident  that  the  American 
profession  will  give  substantial  testimonial  of  their 
feelings  towards  both  author  and  publisher,  by 
speedily  exhausting  this  edition.  We  cordially  and 
heartily  commend  it  to  our  friends,  aud  think  that 
no  live'surgeou  can  afford  to  be  without  it  — Detroit 
Review  of  Med.  and  Pharmacy,  August,  1873. 

As  a  manual  of  the  practice  of  surgery  for  the  use 
of  the  student,  we  do  not  hesitate  to  pronounce  Mr. 
Bryant's  book  a  first-rate  work.  Mr.  Bryant  has  a 
g'.,,d  deal  of  the  dogmatic  energy  which  goes  with 
die  clear,  pronounced  opinions  of  a  man  whose  re- 
flections aud  experience  have  moulded  a  character 
uot  wanting  in  firmness  aud  decision.  At  the  same 
time  he  teaches  withythe  enthusiasm  of  one  who  has 
faith  in  his  teaching  ;\he  speaks  as  one  having  au- 
thority, and  herein  lies  the  charm  and  excellence  of 
his  work.  He  states  the  opinions  of  others  freely 


and  fairly,  yet  it  is  no  mere  compilation.  The  book 
combines  much  of  the  merit  of  the  manual  with  the 
merit  of  the  monograph.  One  may  recognize  in 
almost  every  chapter  of  the  ninety-four  of  which  the 
work  is  made  up  the  acuteness  of  a  surgeon  who  has 
seen  much,  and  observed  closely,  and  who  gives  forth 
the  results  of  actual  experience.  In  conclusion  we 
repeat  what  we  stated  at  first,  that  Mr.  Bryant's  book 
is  one  which  we  can  conscientiously  recommend  both 
to  practitioners  and  students  as  an  admirable  work. 
— Dublin  Journ.  of  Med.  Science,  August,  1873. 

Mr.  Bryant  has  long  been  known  to  the  reading 
portion  of  the  profession  as  an  able,  clear,  and  graphic 
writer  upon  surgical  subjects.  The  volume  before 
us  is  one  eminently  upon  the  practice  of  surgery  and 
not  one  which  treats  at  length  on  surgical  pathology, 
though  the  views  that  are  entertained  upon  tnis  sub- 
ject are  sufficiently  interspersed  through  the  work 
for  all  practical  purposes.  As  a  text-book  we  cheer- 
fully recommend  it,  feeling  convinced  that,  from  the 
subject-matter,  and  the  concise  and  true  way  Mr. 
Bryant  deals  with  his  subject,  it  will  prove  a  for- 
midable rival  among  the  numerous  surgical  text- 
books which  are  offered  to  the  student. — N.  Y.  Med. 
Record,  June,  1S73. 

This  is,  as  the  preface  states,  an  entirely  new  book, 
and  contains  in  a  moderately  condensed  form  all  the 
surgical  information  necessary  to  a  general  practi- 
tioner. It  is  written  in  a  spirit  consistent  with  the 
present  improved  standard  of  medical  and  surgical 
science. — American  Journal  of  Obstetrics,  August, 
1873. 


\XTELL8  (J.  SOELBERG), 

Professor  of  Ophthalmology  in  King's  College  Hospital,  &c. 

A  TREATISE  ON  DISEASES  OF  THE  EYE.      Second  American, 

from  the  Third  and  Revised  Lpndon  Edition,  with  additions;  illustrated  with  numerous 
engravings  on  wood,  and  six  colored  plates.  Together  with  selections  from  the  Test-types 
of  Jaeger  and  Snellen.  In  one  large  and  very  handsome  octavo  volume  of  nearly  800 
pages  ;  cloth,  $5  00  ;  leather,  $6  00.  (Lately  Published.) 

The  continued  demand  for  this  work,  both  iu  England  and  this  country,  is  sufficient  evidence 
that  the  author  has  succeeded  in  his  effort  to  supply  within  a  reasonable  compass  n  full  practical 
digest  of  ophthalmology  in  its  most  modern  aspects,  while  the  call  for  repeated  editions  has  en- 
abled him  in  his  revisions  to  maintain  its  position  abreast  of  the  most  recent  investigations  and 
improvements.  In  again  reprinting  it,  every  effort  has  been  made  to  adapt  it  thoroughly  to  the 
wants  of  the  American  practitioner.  Such  additions  as  seemed  desirable  have  been  introduced 
by  the  editor,  Dr.  I.  Minis  Hays,  and  the  number  of  illustrations  has  been  largely  increased.  The 
importance  of  test-types  as  an  aid  to  diagnosis  is  so  universally  acknowledged  at  the  present  day 
that  it  seemed  essential  to  the  completeness  of  the  work  that  they  should  be  added,  and  as  the 
author  recommends  the  use  of  those  both  of  Jaeger  and  of  Snellen  for  different  purposes,  selec- 
tions have  been  made  from  each,  so  that  the  practitioner  may  have  at  command  all  the  assist- 
ance necessary.  Although  enlarged  by  one  hundred  pages,  it  has  been  retained  at  the  former 
very  moderate  price,  rendering  it  one  of  the  cheapest  volumes  before  the  profession. 
A  few  notices  of  the  previous  edition  are  subjoined. 

On  examining  it  carefully,  one  is  not  at  all  sur-    lucid  and  flowing,  therein  differing  materially  from 
priced  that  it  should  meet  with   universal  favor.     It  \  some  of  the  translations  of  Continental  writers  on  this 


-,  iu  fact,  a  comprehensive  and  thoroughly  practical 
treatise  011  diseases  of  the  eye,  setting  forth  the  prac- 
tice of  the  leading  oculists  of  Europe  and  America, 
a  u  d  giving  the  author's  own  opinions  aud  preferences, 
which  are  quite  decided  and  worthy  of  high  consid- 
eration. The  third  English  edition,  from  which  this 
i.-j  taken,  having  been  revised  by  the  author,  com- 
prises a  notice  of  all  the  more  recent  advances  made 
in  ophthalmic  science.  The  style  of  the  writer  is 


subject  that  are  in  the  market.  Special  paius  are 
taken  to  explain,  at  length,  those  subjects  which  are 
particularly  difficult  of  comprehension  to  the  begin- 
ner, as  the  use  of  the  ophthalmoscope,  the  interpre- 
tation of  its  images,  etc.  The  book  is  profusely  and 
ably  illustrated,  and  at  the  end  are  to  be  found  16 
excellent  colored  ophthalmoscopic  figures,  which  are 
copies  of  some  of  the  plates  of  Liebreich's  admirable 
atlas.— Kansas  City  Med.  Journ.,  June,  1874. 


r  A  URENCE  (JOHN  Z.),  F.  R.  C.  S., 

Editor  of  the  Ophthalmic  Review,  &c. 

A  HANDY-BOOK  OF   OPHTHALMIC   SURGERY,  for  the  use  of 

Practitioners.     Second  Edition,  revised  and  enlarged.     With  numerous  illustrations, 
one  very  handsome  octavo  volume,  cloth,  $3  00. 


In 


For  those,  however,  who  must  assume  the  care  of 
diseases  and  injuries  of  the  eye,  and  who  are  too 
much  pressed  for  time  to  study  the  classic  works  on 
the  subject,  or  those  recently  published  by  Stellwag, 
Wells,  Bader,  aud  others,  Mr.  Laurence  will  prove  a 
safe  and  trustworthy  guide.  He  has  described  in  thib 


editiou  those  novelties  which  have  secured  the  confi- 
dence of  the  profession  since  the  appearance  of  his 
last.  The  volume  has  been  considerably  enlarged 
and  improved  by  the  revision  and  additions  of  its 
author,  expressly  for  the  American  edition. — Am. 
Journ.  Med.  Sciences,  Jan.  1870. 


30  HENRY  C.  LEA'S  PUBLICATIONS—  (Surgery,  &c.). 

THOMPSON  (SIR  HENR  F), 

J-  Surgeon  and  Professor  of  Clinical  Surgery  to  University  College  Hospital. 

LECTURES  ON  DISEASES  OF  THE  URINARY  ORGANS.   With 

illustrations  on  wood.     Second  American  from  the  Third  English  Edition.     In  one  neat 

octavo  volume.     Cloth,  $2  25.     (Now  Ready.) 

My  aim  has  been  to  produce  in  the  smallest  possible  compass  an  epitome  of  practical  knowl- 
edge concerning  the  nature  and  treatment  of  the  diseases  which  form  the  subject  of  the  work  ; 
and  I  venture  to  believe  that  my  intention  has  been  more  fully  realized  in  this  volume  than  in 
either  of  its  predecessors.  —  Authors  Preface. 

•D7  THE  SAME  AUTHOR. 

ON  THE  PATHOLOGY  AND  TREATMENT  OF  STRICTURE  OF 

THE  URETHRA  AND  URINARY  FISTULA.     With  plates  and  wood-cuts.     From  the 
third  and  revised  English  edition.    In  one  very  handsome  octavo  volume,  cloth,  $3  50. 
(Lately  Published.) 
T>Y  THE  SAME  AUTHOR.     (Just  Issued.) 

THE  DISEASES   OF   THE   PROSTATE,  THEIR   PATHOLOGY 

AND  TREATMENT.  Fourth  Edition,  Revised.  In  one  very  handsome  octavo  volume  of 
355  pages,  with  thirteen  plates,  plain  and  colored,  and  illustrations  on  wood.  Cloth,  $3  75. 

/TAYLOR  (ALFRED  £.),  M.D., 

Lecturer  on  Med.  Jurisp.  and  Chemistry  in  Guy^s  Hospital 

MEDICAL  JURISPRUDENCE.     Seventh  American  Edition.     Edited 

by  JOHN  J.  REESE,  M.D.,  Prcf.  of  Med.  Jurisp.  in  the  Univ.  of  Penn.  In  one  large 
octavo  volume  of  nearly  900  pages.  Cloth,  $5  00;  leather,  $6  00.  (Just  Issued.) 

In  preparing  for  the  press  this  seventh  American  edition  of  the  "  Manual  of  Medical  Jurispru- 
dence" the  editor  has,  through  the  courtesy  of  Dr.  Taylor,  enjoyed  the  very  great  advantage  of 
consulting  the  sheets  of  the  new  edition  of  the  author's  larger  work,  "  The  Principles  and  Prac- 
tice of  Medical  Jurisprudence,"  which  is  now  ready  for  publication  in  London.  This  has  enabled 
him  to  introduce  the  author's  latest  views  upon  the  topics  discussed,  which  are  believed  to  bring 
the  work  fully  up  to  the  present  time. 

The  notes  of  the  former  editor,  Dr.  Hartshorne,  as  also  the  numerous  valuable  references  to 
American  practice  and  decisions  by  his  successor,  Mr.  Penrose,  have  been  retained,  with  but  few 
slight  exceptions  ;  they  will  be  found  inclosed  in  brackets,  distinguished  by  the  letters  (H.)  and 
(P.).  The  additions  made  by  the  present  editor,  from  the  material  at  his  command,  amount  to 
about  one  hundred  pages;  and  his  own  notes  are  designated  by  the  letter  (R.). 

Several  subjects,  not  treated  of  in  the  former  edition,  have  been  noticed  in  the  present  one, 
and  the  work,  it  is  hoped,  will  be  found  to  merit  a  continuance  of  the  confidence  which  it  has  so 
long  enjoyed  as  a  standard  authority. 

1D¥  THE  SAME  AUTHOR.     (Now  Ready.) 

THE  PRINCIPLES  AND  PRACTICE  OF  MEDICAL  JURISPRU- 

DENCE. Second  Edition,  Revised,  with  numerous  Illustrations.  In  two  large  octavo 
volumes,  cloth,  $10  00;  leather,  $12  00. 

This  great  work  is  now  recognized  in  England  as  the  fullest  and  most  authoritative  treatise  on 
every  department  of  its  important  subject.  In  laying  it.  in  its  improved  form,  before  the  Ameri- 
can profession,  the  publisher  trusts  that  it  will  assume  the  same  position  in  this  country. 

jgF  THE  SAME  AUTHOR.     New  Edition—  Nearly  Ready. 

POISONS  IN  RELATION  TO  MEDICAL  JURISPRUDENCE  AND 

MEDICINE.     Third  American,  from  the  Third  and  Revised  English  Edition.     In  one 

large  octavo  volume  of  850  pages. 

This  work,  which  has  been  so  long  recognized  as  a  leading  authority  on  its  important  subject, 
has  received  a  very  thorough  revision  at  the  hands  of  the  author,  and  may  be  regarded  as  a 
new  book  rather  than  as  a  mere  revision.  He  has  sought  to  bring  it  on  all  points  to  a  level 
with  the  advanced  science  of  the  day;  many  portions  have  been  rewritten,  much  that  was  of 
minor  importance  has  been  omitted,  and  every  effort  made  to  condense  a  complete  view  of  the 
subject  within  the  limits  of  a  single  volume.  Dr.  Taylor's  position  as  an  expert  has  brought 
him  into  connection  with  nearly  all  important  cases  in  England  for  many  years.  He  thus  speaks 
with  an  authority  that  few  other  living  men  possess,  while  his  intimate  acquaintance  with  the 
literature  of  toxicology  on  both  sides  of  the  Atlantic,  renders  his  work  equally  adapted  as  a 
text-book  in  this  country  as  in  Great  Britain. 


Poisons.  —  Absorption  and  Elimination  —  Detection  —  Action  —  Influence  of  Habit  —  Classifica- 
tion of  Poisons  —  Evidence  of  Poisoning  —  Diseases  resembling  Poisoning  —  Inspection  of  the  Dead 
Body  —  Objects  of  Chemical  Analysis  —  Moral  and  Circumstantial  Evidence  in  Poisoning,  Ac.  &c. 

Irritant  Poisons.  —  Mineral  Irritants  —  Acid  Poisons  —  Alkaline  Poisons  —  Non-Metallic  Irri- 
tants —  Metallic  Irritants  —  Vegetable  Irritants  —  Animal  Irritants. 

Neurotic  Poisons.  —  Cerebral  or  Narcotic  Poisons  —  Spinal  Poisons  —  Cerebro-Spinal  Poisons  — 
Cerebro-Cardiac  Poisons. 


HENRY  C.  LEA'S  PUBLICATIONS — (Psychological  Medicine,  &c.).      31 


WUKE  (DANIEL  HACK],  M.D., 

JL  Joint  author  of  "  The  Manual  of  Psychological  Medicine,"  &c. 

ILLUSTRATIONS  OF  THE  INFLUENCE  OF  THE  MIND  UPON 

THE  BODY  IN  HEALTH  AND  DISEASE.      Designed  to  illustrate  the  Action  of  the 
Imagination.     In  one  handsome  octavo  volume  of  416  pages,  cloth,  $3  25.     (Just  Issued.) 
The  object  of  the  author  in  this  work  has  been  to  show  not  only  the  effect  of  the  mind  in  caus- 
ing and  intensifying  disease,  but  also  its  curative  influence,  and  the  use  which  may  be  made  of 
the  imagination  and  the  emotions  as  therapeutic  agents.     Scattered  facts  bearing  upon  this  sub- 
ject have  long  been  familiar  to  the  profession,  but  no  attempt  has  hitherto  been  made  to  collect 
and  systematize  them  so  as  to  render  them  available  to  the  practitioner,  by  establishing  the  seve- 
ral phenomena  upon  a  scientific  basis.     In  the  endeavor  thus  to  convert  to  the  use  of  legitimate 
medicine  the  means  which  have  been  employed  so  successfully  in  many  systems  of  quackery,  the 
author  has  produced  a  work  of  the  highest  freshness  and  interest  as  well  as  of  permanent  value. 


ftLANDFORD  (G.  FIELDING],  M.  D.,  F.  R.  C  P., 

Lecturer  on  Psychological  Medicine  at  the  School  of  St.  George's  Hospital,  &c. 

INSANITY  AND  ITS  TREATMENT:   Lectures  on  the  Treatment, 

Medical  and  Legal,  of  Insane  Patients.  With  a  Summary  of  the  Laws  in  force  in  the 
United  States  on  the  Confinement  of  the  Insane.  By  ISAAC  RAY,  M.  D.  In  one  very 
handsome  octavo  volume  of  471  pages;  cloth,  $3  25. 

This  volume  is  presented  to  meet  the  want,  so  frequently  expressed,  of  a  comprehensive  trea- 
tise, in  moderate  compass,  on  the  pathology,  diagnosis,  and  treatment  of  insanity.  To  render  it  of 
more  value  to  the  practitioner  in  this  country,  Dr.  Ray  has  added  an  appendix  which  affords  in- 
formation, not  elsewhere  to  be  found  in  so  accessible  a  form,  to  physicians  who  may  at  any  moment 
b«  called  upon  to  take  action  in  relation  to  patients. 

It  satisfies  a  want  which  must  have  been  sorely  j  actually  seen  in  practice  and  the  appropriate  treat 
felt  by  the  busy  general  practitioners  of  this  country. 
It  takes  the  form  of  a  manual  of  clinical  description 
of  the  various  forms  of  insanity,  with  a  description 
of  the  mode  of  examining  persons  suspected  of  in- 
aanity.  We  call  particular  attention  to  this  feature 
of  the  book,  as  giving  it  a  unique  value  to  the  gene- 
ral practitioner.  If  we  pass  from  theoretical  conside- 
rations to  descriptions  of  the  varieties  of  insanity  as 


ment  for  them,  we  find  in  Dr.  Blandford's  work 
considerable  advance  over  previous  writings  on  the 
subject.  His  pictures  of  the  various  forms  of  mental 
disease  are  so  clear  and  good  that  no  reader  can  fail 
to  be  struck  with  their  superiority  to  those  given  in 
ordinary  manuals  in  the  English  language  or  (so  far 
as  our  own  reading  extends)  in  any  other.—  London 
Practitioner,  Feb.  1871. 


w- 


'INSLOW  (FORBES],  M.D.,  D.C.L.,  frc. 

ON  OBSCURE  DISEASES  OF  THE  BRAIN  AND  DISORDERS 

OF  THE  MIND;  their  incipient  Symptoms,  Pathology,  Diagnosis,  Treatment,  and  Pro- 
phylaxis. Second  American,  from  the  third  and  revised  English  edition.  In  one  handsome 
octavo  volume  of  nearly  600  pages,  cloth,  $4  25. 


T  EA  (HENRY  (7.). 
•^SUPERSTITION    AND    FORCE:    ESSAYS    ON    THE   WAGER   OF 

LAW,  THE  WAGER  OF  BATTLE,  THE  ORDEAL,  AND  TORTURE.  Second  Edition, 
Enlarged.  In  one  handsome  volume  royal  12mo.  of  nearly  500  pages;  cloth,  $2  75. 
(Lately  Published.) 

We  know  of  no  single  work  which  contains,  in  so  i  interesting  phases  of  human  society  and  progress.  .  . 
•mall  a  compass,  so  much  illustrative  of  the  strangest  The  fulness  and  breadth  with  which  he  has  carried 
operations  of  the  human  mind.  Foot-notes  give  the  out  his  comparative  survey  of  this  repulsive  field  of 
authority  for  each  statement,  showing  vast  research  history  [Torture],  are  such  as  to  preclude  our  doing 
and  wonderful  industry.  We  advise  our  confreres  j  justice  to  the  work  within  our  present  limits.  But 
to  read  this  book  and  ponder  its  teachings. — Chicago  \  here,  as  throughout  the  volume,  there  will  be  found 
Mvd.  Journal,  Aug.  1870.  a  w 


As  a  work  of  curious  inquiry  on  certain  outlying 
points  of  obsolete  law,  "Superstition  and  Force"  is 
one  of  the  most  remarkable  books  we  have  met  with. 
—London  Athenceum,  Nor.  3,  1866. 

He  has  thrown  a  great  deal  of  light  upon  what  must 
be  regarded  as  one  of  the  most  instructive  as  well  as 


wealth  of  illustration  and  a  critical  grasp  of  the 
philosophical  import  of  facts  which  will  render  Mi. 
Lea's  labors  of  sterling  value  to  the  historical  stu- 
dent.— London  Saturday  Review,  Oct.  8,  1870. 

As  a  book  of  ready  reference  on  the  subject,  it  is  of 
the  highest  value. —  Westminster  Review,  Oct.  1867. 


I  THE  SAME  AUTHOR.    (Lately  Published.) 

STUDIES  IN  CHURCH  HISTORY— THE  RISE  OF  THE  TEM- 
PORAL POWER— BENEFIT  OF  CLERGY— EXCOMMUNICATION.  In  one  large  royal 
12mo.  volume  of  516  pp.  cloth,  $2  75. 

literary  phenomenon  that  the  head  of  one  of  the  first 
American  houses  is  also  the  writer  of  some  of  its  most 
original  books. — London  Athenceum,  Jan.  7,  1871. 

Mr.  Lea  has  done  great  honor  to  himself  and  this 
country  by  the  admirable  works  he  has  written  on 
ecclesiologicaland  cognate  subjects.  We  have  already 
had  occasion  to  commend  his  "Superstition  and 
Force"  and  his  "History  of  Sacerdotal  Celibacy." 
The  present  volume  is  fully  as  admirable  in  its  me- 
thod of  dealing  with  topics  and  in  the  thoroughness — 
a  quality  so  frequently  lacking  in  American  authors — 
with  which  they  are  investigated. — N.  ¥.  Journal  of 
Psychol.  Medicine,  July,  1870. 


The  story  was  never  told  more  calmly  or  with 
greater  learning  or  wiser  thought.  We  doubt,  indeed, 
If  any  other  study  of  this  field  can  be  compared  with 
this  for  clearness,  accuracy,  and  power.  —  Chicago 
Examiner,  Dec.  1870. 

Mr.  Lea's  latest  work,  "Studies  in  Church  History," 
fully  sustains  the  promise  of  the  first.  It  deals  with 
cnree  subjects — the  Temporal  Power,  Benefit  of 
Clergy,  and  Excommunication,  the  record  of  which 
has  a  peculiar  importance  for  the  English  student,  and 
is  a  chapter  on  Ancient  Law  likely  to  be  regarded  as 
final.  We  can  hardly  pass  from  our  mention  of  such 
works  as  these — with  which  that  on  "Sacerdotal 
Celibacy"  should  be  included — without  noting  the 


HENRY  C.  LEA'S  PUBLICATIONS. 


INDEX    TO    CATALOGUE. 


American  Journal  of  the  Medical  Sciences 
Abstract,  Half-Yearly,  of  the  Med.  Sciences 
Anatomical  Atlas,  by  Smith  and  Homer       . 
Anderson  on  Diseases  of  the  Skin          . 
Ashton  on  the  Rectum  and  Anus  .        .        . 


PAGE 

.      1 
.      3 
.      6 
.     20 
.28 
Attfleld's  Chemistry      ......     10 

Ashwell  on  Diseases  of  Females  .        .        .        .23 

Ashhurst's  Surgery          ......     27 

Barnes  on  Diseases  of  Women       .        .        .        .23 

Bellamy's  Surgical  Anatomy         ....       7 

Bryant's  Practical  Surgery    .....     29 

Bloxam's  Chemistry        •        .....     11 

Blandford  on  Insanity     ......     31 

Basham  on  Renal  Diseases     .....     IS 

Brinton  on  the  Stomach          .....     16 

Bigelo-w  on  the  Hip          ....  .28 

Barlow's  Practice  of  Medicine       .        .         .       .     14 

Bowman's  (John  E.)  Practical  Chemistry    .        .     11 
Bowman's  (John  E.)  Medical  Chemistry      .        .     II 
Bumstead  on  Venereal    ......     19 

Bumstead  and  Cullerier's  Atlas  of  Venereal        .    19 
Carpenter's  Human  Physiology    ....       8 

Carpenter's  Comparative  Physiology  ...       8 
Carpenter  on  the  Use  and  Abuse  of  Alcohol         .     13 
Carson's  Synopsis  of  Materia  Medica    .        .        .13 
Chambers  on  Diet  and  Regimen     .        .        .        .16 

Chambers's  Restorative  Medicine  .        .  16 

Christison  and  Griffith's  Dispensatory          .        '     13 
Churchill's  System  of  Midwifery  .        .  [     25 

Churchill  on  Puerperal  Fever        .        .        .        '23 
Condie  on  Diseases  of  Children     .        .        .        '     21 
Cooper's  (B.  B.)  Lectures  on  Surgery    .  '26 

Cullerier's  Atlas  of  Venereal  Diseases          .        '     19 
Cyclopedia  of  Practical  Medicine  .        .  *     15 

Dalton's  Human  Physiology  .  9 

Davis'  Clinical  Lectures  •     14 

De  Jongh  on  Cod-Liver  Oil     .        .        .        .        •     13 

Dewees  on  Diseases  of  Females     .        .        .        '23 
Dewees  on  Diseases  of  Children    .        .        .        -20 
Druitt's  Modern  Surgery  •    28 

Dunglison's  Medical  Dictionary    ...»      4 
Dunglison's  Human  Physiology  9 

Dunglison  on  New  Remedies         .        .        .        -13 
Ellis's  Medical  Formulary,  by  Smith   .        .        •     13 
Erichsen's  System  of  Surgery        .        .        .        •     28 
Fenwick's  Diagnosis        .....         •     14 

Flint  on  Respiratory  Organs  .....     17 

Flint  on  the  Heart  .         .        .  .        ,        -17 

Flint's  Practice  of  Medicine  .        .        .        .        .15 

Flint's  Essays  ......        -15 

Flint  on  Phthisis      .......     17 

Fownes's  Elementary  Chemistry  .        .        .        -     10 
Fox  on  Diseases  of  the  Stomach    .        .        .        •     17 
Fnlleron   the  Lungs,  &c  .....        •     17 

Green's  Pathology  and  Morbid  Anatomy     .        •    14 
Gibson's  Surgery     ......        -26 

G  luge's  Pathological  Histology,  by  Leidy    .        .     14 
Galloway's  Qualitative  Analysis  .  .        .     10 

Gray's  Anatomy      .......      6 

Griffith's  (R.  E.)  Universal  Formulary          .        .     13 
Gross  on  Foreign  Bodies  in  Air-Passages      .        .     26 
Gross's  Principles  and  Practice  of  Surgery  .        .     26 
Guersant  on  Surgical  Diseases  of  Children  .        .     20 
Hamilton  on  Dislocations  and  Fractures      .        .     27 
Hartshorne's  Essentials  of  Medicine    .        .        .16 
Hartshorne's  Conspectus  of  the  Medical  Sciences      5 
Hartshorne's  Anatomy  and  Physiology       .        .      7 
Heath's  Practical  Anatomy    .....       7 

Hoblyn's  Medical  Dictionary        ....      4 

Hodge  on  Women    .......    23 

Hodge's  Obstetrics  .......     24 

Hodges'  Practical  Dissections        ....       6 

Holland's  Medical  Notes  and  Reflections      .        .     14 
Homer's  Anatomy  and  Histology        ...      6 
Hudson  on  Fevers  ......     18 

Hill  on  Venereal  Diseases      .....     19 

Hillier's  Handbook  of  Skin  Diseases  .        .     20 

Jones  and  Sieveking's  Pathological  Anatomy     .    14 
Jones  (C.  Handfield)  on  Nervous  Disorders        .     18 


PAGB 

8 

.11 
.31 
.     31 
18 

.18 
.    25 


Kirkes'  Physiology 

Knapp's  Chemical  Technology     .        . 

Lea's  Superstition  and  Force         .         . 

Lea's  Studies  in  Church  History    .. 

Lee  on  Syphilis 

Lincoln  on  Electro-Therapeutics    .        . 

Leishman's  Midwifery     .... 

La  Roche  on  Yellow  Fever     .....     14 

La  Roche  on  Pneumonia,  &c.         .        .        .        .17 

Laurence  and  Moon's  Ophthalmic  Surgery   .        .     29 
Lawson  on  the  Eye          ......     28 

Laycock  on  Medical  Observation  .        .        .        .14 

Lehmann's  Physiological  Chemistry,  2  vols.        .      9 
Lehmann's  Chemical  Physiology  ....<> 

Ludlow's  Manual  of  Examinations       ...       6 
Lyons  on  Fever        .......     18 

Maclise's  Surgical  Anatomy  .....      7 

Marshall's  Physiology    ......       8 

Medical  News  and  Library    .....      2 

Meigs's  Lectures  on  Diseases  of  Women       .        .     23 
Meigs  on  Puerperal  Fever      .....     23 

Miller's  Practice  of  Surgery  .....     26 

Miller's  Principles  of  Surgery       .        .        .        .26 

Montgomery  on  Pregnancy    .....     25 

NeilL  and  Smith's  Compendium  of  Med.  Science  .      fi 
Neligan's  Atlas  of  Diseases  of  the  Skin         .        .     20 
Neligan  on  Diseases  of  the  Skin    .        ...    2 

Obstetrical  Journal         ......     22 

Odling's  Practical  Chemistry        ....     10 

Pavy  on  Digestion          ......    16 

Pavy  on  Food  ....... 

Parrish'  s  Practical  Pharmacy        ....     12 

Pirrie's  System  of  Surgery     .        .        .  .27 

Pereira's  Mat.  Medica  and  Therapeutics,  abridged    1  3 
Quain  and  Sharpey's  Anatomy,  by  Leidy    . 
Roberts  on  Urinary  Diseases  .....     1 

Ramsbotham  on  Parturition  .....     26 

Rigby's  Midwifery  .......     26 

Royle's  Materia  Medica  and  Therapeutics    .        .     13 
Swayne's  Obstetric  Aphorisms      .         ...     2 

Sargent's  Minor  Surgery         .....     26 

Sharpey  and  Quain's  Anatomy,  by  Leidy    . 

Skey's  Operative  Surgery       .....     26 

Slade  on  Diphtheria        ......     18 

S^nith  (J.L.)  on  Children        .....     2] 

Smith  (H.  H.)  and  Homer's  Anatomical  Atlas      . 
Smith  (Edward)  on  Consumption  .        .        .        .17 

Smith  on  Wasting  Diseases  *.  Children         .        .     21 
Still's  Therapeutics        ......     12 

Sturges  on  Clinical  Medicine          .        .        .        .14 

Stokes  on  Fever       .......     14 

Tanner's  Manual  of  Clinical  Medicine  ...      6 
Tanner  on  Pregnancy     .  ...     24 

Taylor's  Medical  Jurisprudence     .        .        .        .30 

Taylor's  Principles  and  Practice  of  Med   Jurisp      • 
Taylor  on  Poisons   .......     3G 

Tuke  on  the  Influence  of  the  Mind        .        .        .31 
Thomas  on  Diseases  of  Females    .        .        .        .22 

Thompson  on  Urinary  Organs        .        .        .        .30 

Thompson  on  Stricture    ......     30 

Thompson  on  the  Prostate      .....     30 

Todd  on  Acute  Diseases  ......     14 

Walshe  on  the  Heart      ......     17 

Watson's  Practice  of  Physic  .....     15 

Wells  on  the  Eye    .......    29 

West  on  Diseases  of  Females         ...  23 

West  on  Diseases  of  Children        ...  21 

West  on  Nervous  Disorders  of  Children       .  21 

What  to  Observe  in  Medical  Cases        .        .  14 

Williams  on  Consumption     ....  17 

Wilson  s  Human  Anatomy    ....  7 

Wilson  on  Diseases  of  the  Skin     ...  20 

Wilson's  Plates  on  Diseases  of  the  Skin       .  20 

Wilson's  Handbook  of  Cutaneous  Medicine  20 

Winslow  on  Brain  and  Mind          ...  31 

Wohler's  Organic  Chemistry         ...  11 

Winckel  on  Childbed      ......      4 

Zeissl  on  Venereal  .......     19 


For  "THE  OBSTETRICAL  JOURNAL,"  FIVE  DOLLARS  a  year,  see  p.  22. 


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